[tip:core/objtool] objtool: Implement stack validation 2.0
From: tip-bot for Josh Poimboeuf
Date: Fri Jun 30 2017 - 09:17:30 EST
Commit-ID: baa41469a7b992c1e3db2a39854219cc7442e48f
Gitweb: http://git.kernel.org/tip/baa41469a7b992c1e3db2a39854219cc7442e48f
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Wed, 28 Jun 2017 10:11:07 -0500
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 30 Jun 2017 10:19:19 +0200
objtool: Implement stack validation 2.0
This is a major rewrite of objtool. Instead of only tracking frame
pointer changes, it now tracks all stack-related operations, including
all register saves/restores.
In addition to making stack validation more robust, this also paves the
way for undwarf generation.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: live-patching@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/678bd94c0566c6129bcc376cddb259c4c5633004.1498659915.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
tools/objtool/Documentation/stack-validation.txt | 153 +++--
tools/objtool/Makefile | 2 +-
tools/objtool/arch.h | 64 ++-
tools/objtool/arch/x86/decode.c | 400 ++++++++++++--
tools/objtool/cfi.h | 55 ++
tools/objtool/check.c | 676 ++++++++++++++++++-----
tools/objtool/check.h | 19 +-
tools/objtool/elf.c | 59 +-
tools/objtool/elf.h | 6 +-
tools/objtool/special.c | 6 +-
tools/objtool/warn.h | 10 +
11 files changed, 1130 insertions(+), 320 deletions(-)
diff --git a/tools/objtool/Documentation/stack-validation.txt b/tools/objtool/Documentation/stack-validation.txt
index 55a60d3..17c1195 100644
--- a/tools/objtool/Documentation/stack-validation.txt
+++ b/tools/objtool/Documentation/stack-validation.txt
@@ -127,28 +127,13 @@ b) 100% reliable stack traces for DWARF enabled kernels
c) Higher live patching compatibility rate
- (NOTE: This is not yet implemented)
-
- Currently with CONFIG_LIVEPATCH there's a basic live patching
- framework which is safe for roughly 85-90% of "security" fixes. But
- patches can't have complex features like function dependency or
- prototype changes, or data structure changes.
-
- There's a strong need to support patches which have the more complex
- features so that the patch compatibility rate for security fixes can
- eventually approach something resembling 100%. To achieve that, a
- "consistency model" is needed, which allows tasks to be safely
- transitioned from an unpatched state to a patched state.
-
- One of the key requirements of the currently proposed livepatch
- consistency model [*] is that it needs to walk the stack of each
- sleeping task to determine if it can be transitioned to the patched
- state. If objtool can ensure that stack traces are reliable, this
- consistency model can be used and the live patching compatibility
- rate can be improved significantly.
-
- [*] https://lkml.kernel.org/r/cover.1423499826.git.jpoimboe@xxxxxxxxxx
+ Livepatch has an optional "consistency model", which is needed for
+ more complex patches. In order for the consistency model to work,
+ stack traces need to be reliable (or an unreliable condition needs to
+ be detectable). Objtool makes that possible.
+ For more details, see the livepatch documentation in the Linux kernel
+ source tree at Documentation/livepatch/livepatch.txt.
Rules
-----
@@ -201,80 +186,84 @@ To achieve the validation, objtool enforces the following rules:
return normally.
-Errors in .S files
-------------------
+Objtool warnings
+----------------
-If you're getting an error in a compiled .S file which you don't
-understand, first make sure that the affected code follows the above
-rules.
+For asm files, if you're getting an error which doesn't make sense,
+first make sure that the affected code follows the above rules.
+
+For C files, the common culprits are inline asm statements and calls to
+"noreturn" functions. See below for more details.
+
+Another possible cause for errors in C code is if the Makefile removes
+-fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options.
Here are some examples of common warnings reported by objtool, what
they mean, and suggestions for how to fix them.
-1. asm_file.o: warning: objtool: func()+0x128: call without frame pointer save/setup
+1. file.o: warning: objtool: func()+0x128: call without frame pointer save/setup
The func() function made a function call without first saving and/or
- updating the frame pointer.
-
- If func() is indeed a callable function, add proper frame pointer
- logic using the FRAME_BEGIN and FRAME_END macros. Otherwise, remove
- its ELF function annotation by changing ENDPROC to END.
+ updating the frame pointer, and CONFIG_FRAME_POINTER is enabled.
- If you're getting this error in a .c file, see the "Errors in .c
- files" section.
+ If the error is for an asm file, and func() is indeed a callable
+ function, add proper frame pointer logic using the FRAME_BEGIN and
+ FRAME_END macros. Otherwise, if it's not a callable function, remove
+ its ELF function annotation by changing ENDPROC to END, and instead
+ use the manual CFI hint macros in asm/undwarf.h.
+ If it's a GCC-compiled .c file, the error may be because the function
+ uses an inline asm() statement which has a "call" instruction. An
+ asm() statement with a call instruction must declare the use of the
+ stack pointer in its output operand. For example, on x86_64:
-2. asm_file.o: warning: objtool: .text+0x53: return instruction outside of a callable function
-
- A return instruction was detected, but objtool couldn't find a way
- for a callable function to reach the instruction.
+ register void *__sp asm("rsp");
+ asm volatile("call func" : "+r" (__sp));
- If the return instruction is inside (or reachable from) a callable
- function, the function needs to be annotated with the ENTRY/ENDPROC
- macros.
+ Otherwise the stack frame may not get created before the call.
- If you _really_ need a return instruction outside of a function, and
- are 100% sure that it won't affect stack traces, you can tell
- objtool to ignore it. See the "Adding exceptions" section below.
+2. file.o: warning: objtool: .text+0x53: unreachable instruction
-3. asm_file.o: warning: objtool: func()+0x9: function has unreachable instruction
+ Objtool couldn't find a code path to reach the instruction.
- The instruction lives inside of a callable function, but there's no
- possible control flow path from the beginning of the function to the
- instruction.
+ If the error is for an asm file, and the instruction is inside (or
+ reachable from) a callable function, the function should be annotated
+ with the ENTRY/ENDPROC macros (ENDPROC is the important one).
+ Otherwise, the code should probably be annotated with the CFI hint
+ macros in asm/undwarf.h so objtool and the unwinder can know the
+ stack state associated with the code.
- If the instruction is actually needed, and it's actually in a
- callable function, ensure that its function is properly annotated
- with ENTRY/ENDPROC.
+ If you're 100% sure the code won't affect stack traces, or if you're
+ a just a bad person, you can tell objtool to ignore it. See the
+ "Adding exceptions" section below.
If it's not actually in a callable function (e.g. kernel entry code),
change ENDPROC to END.
-4. asm_file.o: warning: objtool: func(): can't find starting instruction
+4. file.o: warning: objtool: func(): can't find starting instruction
or
- asm_file.o: warning: objtool: func()+0x11dd: can't decode instruction
+ file.o: warning: objtool: func()+0x11dd: can't decode instruction
- Did you put data in a text section? If so, that can confuse
+ Does the file have data in a text section? If so, that can confuse
objtool's instruction decoder. Move the data to a more appropriate
section like .data or .rodata.
-5. asm_file.o: warning: objtool: func()+0x6: kernel entry/exit from callable instruction
-
- This is a kernel entry/exit instruction like sysenter or sysret.
- Such instructions aren't allowed in a callable function, and are most
- likely part of the kernel entry code.
+5. file.o: warning: objtool: func()+0x6: unsupported instruction in callable function
- If the instruction isn't actually in a callable function, change
- ENDPROC to END.
+ This is a kernel entry/exit instruction like sysenter or iret. Such
+ instructions aren't allowed in a callable function, and are most
+ likely part of the kernel entry code. They should usually not have
+ the callable function annotation (ENDPROC) and should always be
+ annotated with the CFI hint macros in asm/undwarf.h.
-6. asm_file.o: warning: objtool: func()+0x26: sibling call from callable instruction with changed frame pointer
+6. file.o: warning: objtool: func()+0x26: sibling call from callable instruction with modified stack frame
- This is a dynamic jump or a jump to an undefined symbol. Stacktool
+ This is a dynamic jump or a jump to an undefined symbol. Objtool
assumed it's a sibling call and detected that the frame pointer
wasn't first restored to its original state.
@@ -282,24 +271,28 @@ they mean, and suggestions for how to fix them.
destination code to the local file.
If the instruction is not actually in a callable function (e.g.
- kernel entry code), change ENDPROC to END.
+ kernel entry code), change ENDPROC to END and annotate manually with
+ the CFI hint macros in asm/undwarf.h.
-7. asm_file: warning: objtool: func()+0x5c: frame pointer state mismatch
+7. file: warning: objtool: func()+0x5c: stack state mismatch
The instruction's frame pointer state is inconsistent, depending on
which execution path was taken to reach the instruction.
- Make sure the function pushes and sets up the frame pointer (for
- x86_64, this means rbp) at the beginning of the function and pops it
- at the end of the function. Also make sure that no other code in the
- function touches the frame pointer.
+ Make sure that, when CONFIG_FRAME_POINTER is enabled, the function
+ pushes and sets up the frame pointer (for x86_64, this means rbp) at
+ the beginning of the function and pops it at the end of the function.
+ Also make sure that no other code in the function touches the frame
+ pointer.
+ Another possibility is that the code has some asm or inline asm which
+ does some unusual things to the stack or the frame pointer. In such
+ cases it's probably appropriate to use the CFI hint macros in
+ asm/undwarf.h.
-Errors in .c files
-------------------
-1. c_file.o: warning: objtool: funcA() falls through to next function funcB()
+8. file.o: warning: objtool: funcA() falls through to next function funcB()
This means that funcA() doesn't end with a return instruction or an
unconditional jump, and that objtool has determined that the function
@@ -318,22 +311,6 @@ Errors in .c files
might be corrupt due to a gcc bug. For more details, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
-2. If you're getting any other objtool error in a compiled .c file, it
- may be because the file uses an asm() statement which has a "call"
- instruction. An asm() statement with a call instruction must declare
- the use of the stack pointer in its output operand. For example, on
- x86_64:
-
- register void *__sp asm("rsp");
- asm volatile("call func" : "+r" (__sp));
-
- Otherwise the stack frame may not get created before the call.
-
-3. Another possible cause for errors in C code is if the Makefile removes
- -fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options.
-
-Also see the above section for .S file errors for more information what
-the individual error messages mean.
If the error doesn't seem to make sense, it could be a bug in objtool.
Feel free to ask the objtool maintainer for help.
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 27e019c..0e2765e 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -25,7 +25,7 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
all: $(OBJTOOL)
INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS += -Wall -Werror $(EXTRA_WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
+CFLAGS += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
LDFLAGS += -lelf $(LIBSUBCMD)
# Allow old libelf to be used:
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index a59e061..21aeca8 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -19,25 +19,63 @@
#define _ARCH_H
#include <stdbool.h>
+#include <linux/list.h>
#include "elf.h"
+#include "cfi.h"
-#define INSN_FP_SAVE 1
-#define INSN_FP_SETUP 2
-#define INSN_FP_RESTORE 3
-#define INSN_JUMP_CONDITIONAL 4
-#define INSN_JUMP_UNCONDITIONAL 5
-#define INSN_JUMP_DYNAMIC 6
-#define INSN_CALL 7
-#define INSN_CALL_DYNAMIC 8
-#define INSN_RETURN 9
-#define INSN_CONTEXT_SWITCH 10
-#define INSN_NOP 11
-#define INSN_OTHER 12
+#define INSN_JUMP_CONDITIONAL 1
+#define INSN_JUMP_UNCONDITIONAL 2
+#define INSN_JUMP_DYNAMIC 3
+#define INSN_CALL 4
+#define INSN_CALL_DYNAMIC 5
+#define INSN_RETURN 6
+#define INSN_CONTEXT_SWITCH 7
+#define INSN_STACK 8
+#define INSN_NOP 9
+#define INSN_OTHER 10
#define INSN_LAST INSN_OTHER
+enum op_dest_type {
+ OP_DEST_REG,
+ OP_DEST_REG_INDIRECT,
+ OP_DEST_MEM,
+ OP_DEST_PUSH,
+ OP_DEST_LEAVE,
+};
+
+struct op_dest {
+ enum op_dest_type type;
+ unsigned char reg;
+ int offset;
+};
+
+enum op_src_type {
+ OP_SRC_REG,
+ OP_SRC_REG_INDIRECT,
+ OP_SRC_CONST,
+ OP_SRC_POP,
+ OP_SRC_ADD,
+ OP_SRC_AND,
+};
+
+struct op_src {
+ enum op_src_type type;
+ unsigned char reg;
+ int offset;
+};
+
+struct stack_op {
+ struct op_dest dest;
+ struct op_src src;
+};
+
+void arch_initial_func_cfi_state(struct cfi_state *state);
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, unsigned char *type,
- unsigned long *displacement);
+ unsigned long *immediate, struct stack_op *op);
+
+bool arch_callee_saved_reg(unsigned char reg);
#endif /* _ARCH_H */
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 6ac99e3..a36c2eb 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -27,6 +27,17 @@
#include "../../arch.h"
#include "../../warn.h"
+static unsigned char op_to_cfi_reg[][2] = {
+ {CFI_AX, CFI_R8},
+ {CFI_CX, CFI_R9},
+ {CFI_DX, CFI_R10},
+ {CFI_BX, CFI_R11},
+ {CFI_SP, CFI_R12},
+ {CFI_BP, CFI_R13},
+ {CFI_SI, CFI_R14},
+ {CFI_DI, CFI_R15},
+};
+
static int is_x86_64(struct elf *elf)
{
switch (elf->ehdr.e_machine) {
@@ -40,24 +51,50 @@ static int is_x86_64(struct elf *elf)
}
}
+bool arch_callee_saved_reg(unsigned char reg)
+{
+ switch (reg) {
+ case CFI_BP:
+ case CFI_BX:
+ case CFI_R12:
+ case CFI_R13:
+ case CFI_R14:
+ case CFI_R15:
+ return true;
+
+ case CFI_AX:
+ case CFI_CX:
+ case CFI_DX:
+ case CFI_SI:
+ case CFI_DI:
+ case CFI_SP:
+ case CFI_R8:
+ case CFI_R9:
+ case CFI_R10:
+ case CFI_R11:
+ case CFI_RA:
+ default:
+ return false;
+ }
+}
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, unsigned char *type,
- unsigned long *immediate)
+ unsigned long *immediate, struct stack_op *op)
{
struct insn insn;
- int x86_64;
- unsigned char op1, op2, ext;
+ int x86_64, sign;
+ unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
+ modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
+ sib = 0;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
return -1;
- insn_init(&insn, (void *)(sec->data + offset), maxlen, x86_64);
+ insn_init(&insn, sec->data->d_buf + offset, maxlen, x86_64);
insn_get_length(&insn);
- insn_get_opcode(&insn);
- insn_get_modrm(&insn);
- insn_get_immediate(&insn);
if (!insn_complete(&insn)) {
WARN_FUNC("can't decode instruction", sec, offset);
@@ -73,67 +110,323 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
op1 = insn.opcode.bytes[0];
op2 = insn.opcode.bytes[1];
+ if (insn.rex_prefix.nbytes) {
+ rex = insn.rex_prefix.bytes[0];
+ rex_w = X86_REX_W(rex) >> 3;
+ rex_r = X86_REX_R(rex) >> 2;
+ rex_b = X86_REX_B(rex);
+ }
+
+ if (insn.modrm.nbytes) {
+ modrm = insn.modrm.bytes[0];
+ modrm_mod = X86_MODRM_MOD(modrm);
+ modrm_reg = X86_MODRM_REG(modrm);
+ modrm_rm = X86_MODRM_RM(modrm);
+ }
+
+ if (insn.sib.nbytes)
+ sib = insn.sib.bytes[0];
+
switch (op1) {
- case 0x55:
- if (!insn.rex_prefix.nbytes)
- /* push rbp */
- *type = INSN_FP_SAVE;
+
+ case 0x1:
+ case 0x29:
+ if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+
+ /* add/sub reg, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_SRC_REG;
+ op->dest.reg = CFI_SP;
+ }
+ break;
+
+ case 0x50 ... 0x57:
+
+ /* push reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+ op->dest.type = OP_DEST_PUSH;
+
break;
- case 0x5d:
- if (!insn.rex_prefix.nbytes)
- /* pop rbp */
- *type = INSN_FP_RESTORE;
+ case 0x58 ... 0x5f:
+
+ /* pop reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+
+ break;
+
+ case 0x68:
+ case 0x6a:
+ /* push immediate */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
break;
case 0x70 ... 0x7f:
*type = INSN_JUMP_CONDITIONAL;
break;
+ case 0x81:
+ case 0x83:
+ if (rex != 0x48)
+ break;
+
+ if (modrm == 0xe4) {
+ /* and imm, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_AND;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.immediate.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (modrm == 0xc4)
+ sign = 1;
+ else if (modrm == 0xec)
+ sign = -1;
+ else
+ break;
+
+ /* add/sub imm, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.immediate.value * sign;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+
case 0x89:
- if (insn.rex_prefix.nbytes == 1 &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0xe5)
- /* mov rsp, rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0xe5) {
+
+ /* mov %rsp, %rbp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = CFI_SP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_BP;
+ break;
+ }
+ /* fallthrough */
+ case 0x88:
+ if (!rex_b &&
+ (modrm_mod == 1 || modrm_mod == 2) && modrm_rm == 5) {
+
+ /* mov reg, disp(%rbp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_BP;
+ op->dest.offset = insn.displacement.value;
+
+ } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
+
+ /* mov reg, disp(%rsp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_SP;
+ op->dest.offset = insn.displacement.value;
+ }
+
+ break;
+
+ case 0x8b:
+ if (rex_w && !rex_b && modrm_mod == 1 && modrm_rm == 5) {
+
+ /* mov disp(%rbp), reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG_INDIRECT;
+ op->src.reg = CFI_BP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+
+ } else if (rex_w && !rex_b && sib == 0x24 &&
+ modrm_mod != 3 && modrm_rm == 4) {
+
+ /* mov disp(%rsp), reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG_INDIRECT;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ }
+
break;
case 0x8d:
- if (insn.rex_prefix.nbytes &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0x2c &&
- insn.sib.nbytes && insn.sib.bytes[0] == 0x24)
- /* lea %(rsp), %rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0x65) {
+
+ /* lea -disp(%rbp), %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_BP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
+ insn.displacement.value == 8) {
+
+ /*
+ * lea 0x8(%rsp), %r10
+ *
+ * Here r10 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R10;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x6c && sib == 0x24 &&
+ insn.displacement.value == 16) {
+
+ /*
+ * lea 0x10(%rsp), %r13
+ *
+ * Here r13 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R13;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x62 &&
+ insn.displacement.value == -8) {
+
+ /*
+ * lea -0x8(%r10), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R10;
+ op->src.offset = -8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x65 &&
+ insn.displacement.value == -16) {
+
+ /*
+ * lea -0x10(%r13), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R13;
+ op->src.offset = -16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ break;
+
+ case 0x8f:
+ /* pop to mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
break;
case 0x90:
*type = INSN_NOP;
break;
+ case 0x9c:
+ /* pushf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ break;
+
+ case 0x9d:
+ /* popf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ break;
+
case 0x0f:
+
if (op2 >= 0x80 && op2 <= 0x8f)
*type = INSN_JUMP_CONDITIONAL;
else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
op2 == 0x35)
+
/* sysenter, sysret */
*type = INSN_CONTEXT_SWITCH;
+
else if (op2 == 0x0d || op2 == 0x1f)
+
/* nopl/nopw */
*type = INSN_NOP;
- else if (op2 == 0x01 && insn.modrm.nbytes &&
- (insn.modrm.bytes[0] == 0xc2 ||
- insn.modrm.bytes[0] == 0xd8))
- /* vmlaunch, vmrun */
- *type = INSN_CONTEXT_SWITCH;
+
+ else if (op2 == 0xa0 || op2 == 0xa8) {
+
+ /* push fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+
+ } else if (op2 == 0xa1 || op2 == 0xa9) {
+
+ /* pop fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ }
break;
- case 0xc9: /* leave */
- *type = INSN_FP_RESTORE;
+ case 0xc9:
+ /*
+ * leave
+ *
+ * equivalent to:
+ * mov bp, sp
+ * pop bp
+ */
+ *type = INSN_STACK;
+ op->dest.type = OP_DEST_LEAVE;
+
break;
- case 0xe3: /* jecxz/jrcxz */
+ case 0xe3:
+ /* jecxz/jrcxz */
*type = INSN_JUMP_CONDITIONAL;
break;
@@ -158,14 +451,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
break;
case 0xff:
- ext = X86_MODRM_REG(insn.modrm.bytes[0]);
- if (ext == 2 || ext == 3)
+ if (modrm_reg == 2 || modrm_reg == 3)
+
*type = INSN_CALL_DYNAMIC;
- else if (ext == 4)
+
+ else if (modrm_reg == 4)
+
*type = INSN_JUMP_DYNAMIC;
- else if (ext == 5) /*jmpf */
+
+ else if (modrm_reg == 5)
+
+ /* jmpf */
*type = INSN_CONTEXT_SWITCH;
+ else if (modrm_reg == 6) {
+
+ /* push from mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ }
+
break;
default:
@@ -176,3 +482,21 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
return 0;
}
+
+void arch_initial_func_cfi_state(struct cfi_state *state)
+{
+ int i;
+
+ for (i = 0; i < CFI_NUM_REGS; i++) {
+ state->regs[i].base = CFI_UNDEFINED;
+ state->regs[i].offset = 0;
+ }
+
+ /* initial CFA (call frame address) */
+ state->cfa.base = CFI_SP;
+ state->cfa.offset = 8;
+
+ /* initial RA (return address) */
+ state->regs[16].base = CFI_CFA;
+ state->regs[16].offset = -8;
+}
diff --git a/tools/objtool/cfi.h b/tools/objtool/cfi.h
new file mode 100644
index 0000000..443ab2c
--- /dev/null
+++ b/tools/objtool/cfi.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _OBJTOOL_CFI_H
+#define _OBJTOOL_CFI_H
+
+#define CFI_UNDEFINED -1
+#define CFI_CFA -2
+#define CFI_SP_INDIRECT -3
+#define CFI_BP_INDIRECT -4
+
+#define CFI_AX 0
+#define CFI_DX 1
+#define CFI_CX 2
+#define CFI_BX 3
+#define CFI_SI 4
+#define CFI_DI 5
+#define CFI_BP 6
+#define CFI_SP 7
+#define CFI_R8 8
+#define CFI_R9 9
+#define CFI_R10 10
+#define CFI_R11 11
+#define CFI_R12 12
+#define CFI_R13 13
+#define CFI_R14 14
+#define CFI_R15 15
+#define CFI_RA 16
+#define CFI_NUM_REGS 17
+
+struct cfi_reg {
+ int base;
+ int offset;
+};
+
+struct cfi_state {
+ struct cfi_reg cfa;
+ struct cfi_reg regs[CFI_NUM_REGS];
+};
+
+#endif /* _OBJTOOL_CFI_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 231a360..2f80aa51 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -27,10 +27,6 @@
#include <linux/hashtable.h>
#include <linux/kernel.h>
-#define STATE_FP_SAVED 0x1
-#define STATE_FP_SETUP 0x2
-#define STATE_FENTRY 0x4
-
struct alternative {
struct list_head list;
struct instruction *insn;
@@ -38,6 +34,7 @@ struct alternative {
const char *objname;
static bool nofp;
+struct cfi_state initial_func_cfi;
static struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset)
@@ -56,7 +53,7 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
{
struct instruction *next = list_next_entry(insn, list);
- if (&next->list == &file->insn_list || next->sec != insn->sec)
+ if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
return NULL;
return next;
@@ -67,7 +64,7 @@ static bool gcov_enabled(struct objtool_file *file)
struct section *sec;
struct symbol *sym;
- list_for_each_entry(sec, &file->elf->sections, list)
+ for_each_sec(file, sec)
list_for_each_entry(sym, &sec->symbol_list, list)
if (!strncmp(sym->name, "__gcov_.", 8))
return true;
@@ -75,9 +72,6 @@ static bool gcov_enabled(struct objtool_file *file)
return false;
}
-#define for_each_insn(file, insn) \
- list_for_each_entry(insn, &file->insn_list, list)
-
#define func_for_each_insn(file, func, insn) \
for (insn = find_insn(file, func->sec, func->offset); \
insn && &insn->list != &file->insn_list && \
@@ -94,6 +88,9 @@ static bool gcov_enabled(struct objtool_file *file)
#define sec_for_each_insn_from(file, insn) \
for (; insn; insn = next_insn_same_sec(file, insn))
+#define sec_for_each_insn_continue(file, insn) \
+ for (insn = next_insn_same_sec(file, insn); insn; \
+ insn = next_insn_same_sec(file, insn))
/*
* Check if the function has been manually whitelisted with the
@@ -103,7 +100,6 @@ static bool gcov_enabled(struct objtool_file *file)
static bool ignore_func(struct objtool_file *file, struct symbol *func)
{
struct rela *rela;
- struct instruction *insn;
/* check for STACK_FRAME_NON_STANDARD */
if (file->whitelist && file->whitelist->rela)
@@ -116,11 +112,6 @@ static bool ignore_func(struct objtool_file *file, struct symbol *func)
return true;
}
- /* check if it has a context switching instruction */
- func_for_each_insn(file, func, insn)
- if (insn->type == INSN_CONTEXT_SWITCH)
- return true;
-
return false;
}
@@ -234,6 +225,17 @@ static int dead_end_function(struct objtool_file *file, struct symbol *func)
return __dead_end_function(file, func, 0);
}
+static void clear_insn_state(struct insn_state *state)
+{
+ int i;
+
+ memset(state, 0, sizeof(*state));
+ state->cfa.base = CFI_UNDEFINED;
+ for (i = 0; i < CFI_NUM_REGS; i++)
+ state->regs[i].base = CFI_UNDEFINED;
+ state->drap_reg = CFI_UNDEFINED;
+}
+
/*
* Call the arch-specific instruction decoder for all the instructions and add
* them to the global instruction list.
@@ -246,23 +248,29 @@ static int decode_instructions(struct objtool_file *file)
struct instruction *insn;
int ret;
- list_for_each_entry(sec, &file->elf->sections, list) {
+ for_each_sec(file, sec) {
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
continue;
for (offset = 0; offset < sec->len; offset += insn->len) {
insn = malloc(sizeof(*insn));
+ if (!insn) {
+ WARN("malloc failed");
+ return -1;
+ }
memset(insn, 0, sizeof(*insn));
-
INIT_LIST_HEAD(&insn->alts);
+ clear_insn_state(&insn->state);
+
insn->sec = sec;
insn->offset = offset;
ret = arch_decode_instruction(file->elf, sec, offset,
sec->len - offset,
&insn->len, &insn->type,
- &insn->immediate);
+ &insn->immediate,
+ &insn->stack_op);
if (ret)
return ret;
@@ -352,7 +360,7 @@ static void add_ignores(struct objtool_file *file)
struct section *sec;
struct symbol *func;
- list_for_each_entry(sec, &file->elf->sections, list) {
+ for_each_sec(file, sec) {
list_for_each_entry(func, &sec->symbol_list, list) {
if (func->type != STT_FUNC)
continue;
@@ -361,7 +369,7 @@ static void add_ignores(struct objtool_file *file)
continue;
func_for_each_insn(file, func, insn)
- insn->visited = true;
+ insn->ignore = true;
}
}
}
@@ -381,8 +389,7 @@ static int add_jump_destinations(struct objtool_file *file)
insn->type != INSN_JUMP_UNCONDITIONAL)
continue;
- /* skip ignores */
- if (insn->visited)
+ if (insn->ignore)
continue;
rela = find_rela_by_dest_range(insn->sec, insn->offset,
@@ -519,10 +526,13 @@ static int handle_group_alt(struct objtool_file *file,
}
memset(fake_jump, 0, sizeof(*fake_jump));
INIT_LIST_HEAD(&fake_jump->alts);
+ clear_insn_state(&fake_jump->state);
+
fake_jump->sec = special_alt->new_sec;
fake_jump->offset = -1;
fake_jump->type = INSN_JUMP_UNCONDITIONAL;
fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
+ fake_jump->ignore = true;
if (!special_alt->new_len) {
*new_insn = fake_jump;
@@ -844,7 +854,7 @@ static int add_switch_table_alts(struct objtool_file *file)
if (!file->rodata || !file->rodata->rela)
return 0;
- list_for_each_entry(sec, &file->elf->sections, list) {
+ for_each_sec(file, sec) {
list_for_each_entry(func, &sec->symbol_list, list) {
if (func->type != STT_FUNC)
continue;
@@ -901,21 +911,423 @@ static bool is_fentry_call(struct instruction *insn)
return false;
}
-static bool has_modified_stack_frame(struct instruction *insn)
+static bool has_modified_stack_frame(struct insn_state *state)
{
- return (insn->state & STATE_FP_SAVED) ||
- (insn->state & STATE_FP_SETUP);
+ int i;
+
+ if (state->cfa.base != initial_func_cfi.cfa.base ||
+ state->cfa.offset != initial_func_cfi.cfa.offset ||
+ state->stack_size != initial_func_cfi.cfa.offset ||
+ state->drap)
+ return true;
+
+ for (i = 0; i < CFI_NUM_REGS; i++)
+ if (state->regs[i].base != initial_func_cfi.regs[i].base ||
+ state->regs[i].offset != initial_func_cfi.regs[i].offset)
+ return true;
+
+ return false;
+}
+
+static bool has_valid_stack_frame(struct insn_state *state)
+{
+ if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
+ state->regs[CFI_BP].offset == -16)
+ return true;
+
+ if (state->drap && state->regs[CFI_BP].base == CFI_BP)
+ return true;
+
+ return false;
}
-static bool has_valid_stack_frame(struct instruction *insn)
+static void save_reg(struct insn_state *state, unsigned char reg, int base,
+ int offset)
{
- return (insn->state & STATE_FP_SAVED) &&
- (insn->state & STATE_FP_SETUP);
+ if ((arch_callee_saved_reg(reg) ||
+ (state->drap && reg == state->drap_reg)) &&
+ state->regs[reg].base == CFI_UNDEFINED) {
+ state->regs[reg].base = base;
+ state->regs[reg].offset = offset;
+ }
}
-static unsigned int frame_state(unsigned long state)
+static void restore_reg(struct insn_state *state, unsigned char reg)
{
- return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
+ state->regs[reg].base = CFI_UNDEFINED;
+ state->regs[reg].offset = 0;
+}
+
+/*
+ * A note about DRAP stack alignment:
+ *
+ * GCC has the concept of a DRAP register, which is used to help keep track of
+ * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
+ * register. The typical DRAP pattern is:
+ *
+ * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
+ * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
+ * 41 ff 72 f8 pushq -0x8(%r10)
+ * 55 push %rbp
+ * 48 89 e5 mov %rsp,%rbp
+ * (more pushes)
+ * 41 52 push %r10
+ * ...
+ * 41 5a pop %r10
+ * (more pops)
+ * 5d pop %rbp
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * There are some variations in the epilogues, like:
+ *
+ * 5b pop %rbx
+ * 41 5a pop %r10
+ * 41 5c pop %r12
+ * 41 5d pop %r13
+ * 41 5e pop %r14
+ * c9 leaveq
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * and:
+ *
+ * 4c 8b 55 e8 mov -0x18(%rbp),%r10
+ * 48 8b 5d e0 mov -0x20(%rbp),%rbx
+ * 4c 8b 65 f0 mov -0x10(%rbp),%r12
+ * 4c 8b 6d f8 mov -0x8(%rbp),%r13
+ * c9 leaveq
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * Sometimes r13 is used as the DRAP register, in which case it's saved and
+ * restored beforehand:
+ *
+ * 41 55 push %r13
+ * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
+ * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
+ * ...
+ * 49 8d 65 f0 lea -0x10(%r13),%rsp
+ * 41 5d pop %r13
+ * c3 retq
+ */
+static int update_insn_state(struct instruction *insn, struct insn_state *state)
+{
+ struct stack_op *op = &insn->stack_op;
+ struct cfi_reg *cfa = &state->cfa;
+ struct cfi_reg *regs = state->regs;
+
+ /* stack operations don't make sense with an undefined CFA */
+ if (cfa->base == CFI_UNDEFINED) {
+ if (insn->func) {
+ WARN_FUNC("undefined stack state", insn->sec, insn->offset);
+ return -1;
+ }
+ return 0;
+ }
+
+ switch (op->dest.type) {
+
+ case OP_DEST_REG:
+ switch (op->src.type) {
+
+ case OP_SRC_REG:
+ if (cfa->base == op->src.reg && cfa->base == CFI_SP &&
+ op->dest.reg == CFI_BP && regs[CFI_BP].base == CFI_CFA &&
+ regs[CFI_BP].offset == -cfa->offset) {
+
+ /* mov %rsp, %rbp */
+ cfa->base = op->dest.reg;
+ state->bp_scratch = false;
+ } else if (state->drap) {
+
+ /* drap: mov %rsp, %rbp */
+ regs[CFI_BP].base = CFI_BP;
+ regs[CFI_BP].offset = -state->stack_size;
+ state->bp_scratch = false;
+ } else if (!nofp) {
+
+ WARN_FUNC("unknown stack-related register move",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_SRC_ADD:
+ if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
+
+ /* add imm, %rsp */
+ state->stack_size -= op->src.offset;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= op->src.offset;
+ break;
+ }
+
+ if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
+
+ /* lea disp(%rbp), %rsp */
+ state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
+ break;
+ }
+
+ if (op->dest.reg != CFI_BP && op->src.reg == CFI_SP &&
+ cfa->base == CFI_SP) {
+
+ /* drap: lea disp(%rsp), %drap */
+ state->drap_reg = op->dest.reg;
+ break;
+ }
+
+ if (state->drap && op->dest.reg == CFI_SP &&
+ op->src.reg == state->drap_reg) {
+
+ /* drap: lea disp(%drap), %rsp */
+ cfa->base = CFI_SP;
+ cfa->offset = state->stack_size = -op->src.offset;
+ state->drap_reg = CFI_UNDEFINED;
+ state->drap = false;
+ break;
+ }
+
+ if (op->dest.reg == state->cfa.base) {
+ WARN_FUNC("unsupported stack register modification",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_SRC_AND:
+ if (op->dest.reg != CFI_SP ||
+ (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
+ (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
+ WARN_FUNC("unsupported stack pointer realignment",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ if (state->drap_reg != CFI_UNDEFINED) {
+ /* drap: and imm, %rsp */
+ cfa->base = state->drap_reg;
+ cfa->offset = state->stack_size = 0;
+ state->drap = true;
+
+ }
+
+ /*
+ * Older versions of GCC (4.8ish) realign the stack
+ * without DRAP, with a frame pointer.
+ */
+
+ break;
+
+ case OP_SRC_POP:
+ if (!state->drap && op->dest.type == OP_DEST_REG &&
+ op->dest.reg == cfa->base) {
+
+ /* pop %rbp */
+ cfa->base = CFI_SP;
+ }
+
+ if (regs[op->dest.reg].offset == -state->stack_size) {
+
+ if (state->drap && cfa->base == CFI_BP_INDIRECT &&
+ op->dest.type == OP_DEST_REG &&
+ op->dest.reg == state->drap_reg) {
+
+ /* drap: pop %drap */
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ }
+
+ restore_reg(state, op->dest.reg);
+ }
+
+ state->stack_size -= 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= 8;
+
+ break;
+
+ case OP_SRC_REG_INDIRECT:
+ if (state->drap && op->src.reg == CFI_BP &&
+ op->src.offset == regs[op->dest.reg].offset) {
+
+ /* drap: mov disp(%rbp), %reg */
+ if (op->dest.reg == state->drap_reg) {
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ }
+
+ restore_reg(state, op->dest.reg);
+
+ } else if (op->src.reg == cfa->base &&
+ op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
+
+ /* mov disp(%rbp), %reg */
+ /* mov disp(%rsp), %reg */
+ restore_reg(state, op->dest.reg);
+ }
+
+ break;
+
+ default:
+ WARN_FUNC("unknown stack-related instruction",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_DEST_PUSH:
+ state->stack_size += 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset += 8;
+
+ if (op->src.type != OP_SRC_REG)
+ break;
+
+ if (state->drap) {
+ if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
+
+ /* drap: push %drap */
+ cfa->base = CFI_BP_INDIRECT;
+ cfa->offset = -state->stack_size;
+
+ /* save drap so we know when to undefine it */
+ save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
+
+ } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
+
+ /* drap: push %rbp */
+ state->stack_size = 0;
+
+ } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+
+ /* drap: push %reg */
+ save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
+ }
+
+ } else {
+
+ /* push %reg */
+ save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
+ }
+
+ /* detect when asm code uses rbp as a scratch register */
+ if (!nofp && insn->func && op->src.reg == CFI_BP &&
+ cfa->base != CFI_BP)
+ state->bp_scratch = true;
+ break;
+
+ case OP_DEST_REG_INDIRECT:
+
+ if (state->drap) {
+ if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
+
+ /* drap: mov %drap, disp(%rbp) */
+ cfa->base = CFI_BP_INDIRECT;
+ cfa->offset = op->dest.offset;
+
+ /* save drap so we know when to undefine it */
+ save_reg(state, op->src.reg, CFI_CFA, op->dest.offset);
+ }
+
+ else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+
+ /* drap: mov reg, disp(%rbp) */
+ save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
+ }
+
+ } else if (op->dest.reg == cfa->base) {
+
+ /* mov reg, disp(%rbp) */
+ /* mov reg, disp(%rsp) */
+ save_reg(state, op->src.reg, CFI_CFA,
+ op->dest.offset - state->cfa.offset);
+ }
+
+ break;
+
+ case OP_DEST_LEAVE:
+ if ((!state->drap && cfa->base != CFI_BP) ||
+ (state->drap && cfa->base != state->drap_reg)) {
+ WARN_FUNC("leave instruction with modified stack frame",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ /* leave (mov %rbp, %rsp; pop %rbp) */
+
+ state->stack_size = -state->regs[CFI_BP].offset - 8;
+ restore_reg(state, CFI_BP);
+
+ if (!state->drap) {
+ cfa->base = CFI_SP;
+ cfa->offset -= 8;
+ }
+
+ break;
+
+ case OP_DEST_MEM:
+ if (op->src.type != OP_SRC_POP) {
+ WARN_FUNC("unknown stack-related memory operation",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ /* pop mem */
+ state->stack_size -= 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= 8;
+
+ break;
+
+ default:
+ WARN_FUNC("unknown stack-related instruction",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ return 0;
+}
+
+static bool insn_state_match(struct instruction *insn, struct insn_state *state)
+{
+ struct insn_state *state1 = &insn->state, *state2 = state;
+ int i;
+
+ if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
+ WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
+ insn->sec, insn->offset,
+ state1->cfa.base, state1->cfa.offset,
+ state2->cfa.base, state2->cfa.offset);
+
+ } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
+ for (i = 0; i < CFI_NUM_REGS; i++) {
+ if (!memcmp(&state1->regs[i], &state2->regs[i],
+ sizeof(struct cfi_reg)))
+ continue;
+
+ WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
+ insn->sec, insn->offset,
+ i, state1->regs[i].base, state1->regs[i].offset,
+ i, state2->regs[i].base, state2->regs[i].offset);
+ break;
+ }
+
+ } else if (state1->drap != state2->drap ||
+ (state1->drap && state1->drap_reg != state2->drap_reg)) {
+ WARN_FUNC("stack state mismatch: drap1=%d(%d) drap2=%d(%d)",
+ insn->sec, insn->offset,
+ state1->drap, state1->drap_reg,
+ state2->drap, state2->drap_reg);
+
+ } else
+ return true;
+
+ return false;
}
/*
@@ -924,24 +1336,22 @@ static unsigned int frame_state(unsigned long state)
* each instruction and validate all the rules described in
* tools/objtool/Documentation/stack-validation.txt.
*/
-static int validate_branch(struct objtool_file *file,
- struct instruction *first, unsigned char first_state)
+static int validate_branch(struct objtool_file *file, struct instruction *first,
+ struct insn_state state)
{
struct alternative *alt;
struct instruction *insn;
struct section *sec;
struct symbol *func = NULL;
- unsigned char state;
int ret;
insn = first;
sec = insn->sec;
- state = first_state;
if (insn->alt_group && list_empty(&insn->alts)) {
WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
sec, insn->offset);
- return 1;
+ return -1;
}
while (1) {
@@ -951,23 +1361,21 @@ static int validate_branch(struct objtool_file *file,
func->name, insn->func->name);
return 1;
}
-
- func = insn->func;
}
+ func = insn->func;
+
if (insn->visited) {
- if (frame_state(insn->state) != frame_state(state)) {
- WARN_FUNC("frame pointer state mismatch",
- sec, insn->offset);
+ if (!!insn_state_match(insn, &state))
return 1;
- }
return 0;
}
- insn->visited = true;
insn->state = state;
+ insn->visited = true;
+
list_for_each_entry(alt, &insn->alts, list) {
ret = validate_branch(file, alt->insn, state);
if (ret)
@@ -976,50 +1384,24 @@ static int validate_branch(struct objtool_file *file,
switch (insn->type) {
- case INSN_FP_SAVE:
- if (!nofp) {
- if (state & STATE_FP_SAVED) {
- WARN_FUNC("duplicate frame pointer save",
- sec, insn->offset);
- return 1;
- }
- state |= STATE_FP_SAVED;
- }
- break;
-
- case INSN_FP_SETUP:
- if (!nofp) {
- if (state & STATE_FP_SETUP) {
- WARN_FUNC("duplicate frame pointer setup",
- sec, insn->offset);
- return 1;
- }
- state |= STATE_FP_SETUP;
- }
- break;
-
- case INSN_FP_RESTORE:
- if (!nofp) {
- if (has_valid_stack_frame(insn))
- state &= ~STATE_FP_SETUP;
-
- state &= ~STATE_FP_SAVED;
- }
- break;
-
case INSN_RETURN:
- if (!nofp && has_modified_stack_frame(insn)) {
- WARN_FUNC("return without frame pointer restore",
+ if (func && has_modified_stack_frame(&state)) {
+ WARN_FUNC("return with modified stack frame",
sec, insn->offset);
return 1;
}
+
+ if (state.bp_scratch) {
+ WARN("%s uses BP as a scratch register",
+ insn->func->name);
+ return 1;
+ }
+
return 0;
case INSN_CALL:
- if (is_fentry_call(insn)) {
- state |= STATE_FENTRY;
+ if (is_fentry_call(insn))
break;
- }
ret = dead_end_function(file, insn->call_dest);
if (ret == 1)
@@ -1029,7 +1411,7 @@ static int validate_branch(struct objtool_file *file,
/* fallthrough */
case INSN_CALL_DYNAMIC:
- if (!nofp && !has_valid_stack_frame(insn)) {
+ if (!nofp && func && !has_valid_stack_frame(&state)) {
WARN_FUNC("call without frame pointer save/setup",
sec, insn->offset);
return 1;
@@ -1043,8 +1425,8 @@ static int validate_branch(struct objtool_file *file,
state);
if (ret)
return 1;
- } else if (has_modified_stack_frame(insn)) {
- WARN_FUNC("sibling call from callable instruction with changed frame pointer",
+ } else if (func && has_modified_stack_frame(&state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
sec, insn->offset);
return 1;
} /* else it's a sibling call */
@@ -1055,15 +1437,29 @@ static int validate_branch(struct objtool_file *file,
break;
case INSN_JUMP_DYNAMIC:
- if (list_empty(&insn->alts) &&
- has_modified_stack_frame(insn)) {
- WARN_FUNC("sibling call from callable instruction with changed frame pointer",
+ if (func && list_empty(&insn->alts) &&
+ has_modified_stack_frame(&state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
sec, insn->offset);
return 1;
}
return 0;
+ case INSN_CONTEXT_SWITCH:
+ if (func) {
+ WARN_FUNC("unsupported instruction in callable function",
+ sec, insn->offset);
+ return 1;
+ }
+ return 0;
+
+ case INSN_STACK:
+ if (update_insn_state(insn, &state))
+ return -1;
+
+ break;
+
default:
break;
}
@@ -1094,12 +1490,18 @@ static bool is_ubsan_insn(struct instruction *insn)
"__ubsan_handle_builtin_unreachable"));
}
-static bool ignore_unreachable_insn(struct symbol *func,
- struct instruction *insn)
+static bool ignore_unreachable_insn(struct instruction *insn)
{
int i;
- if (insn->type == INSN_NOP)
+ if (insn->ignore || insn->type == INSN_NOP)
+ return true;
+
+ /*
+ * Ignore any unused exceptions. This can happen when a whitelisted
+ * function has an exception table entry.
+ */
+ if (!strcmp(insn->sec->name, ".fixup"))
return true;
/*
@@ -1108,6 +1510,8 @@ static bool ignore_unreachable_insn(struct symbol *func,
*
* End the search at 5 instructions to avoid going into the weeds.
*/
+ if (!insn->func)
+ return false;
for (i = 0; i < 5; i++) {
if (is_kasan_insn(insn) || is_ubsan_insn(insn))
@@ -1118,7 +1522,7 @@ static bool ignore_unreachable_insn(struct symbol *func,
continue;
}
- if (insn->offset + insn->len >= func->offset + func->len)
+ if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
break;
insn = list_next_entry(insn, list);
}
@@ -1131,73 +1535,58 @@ static int validate_functions(struct objtool_file *file)
struct section *sec;
struct symbol *func;
struct instruction *insn;
+ struct insn_state state;
int ret, warnings = 0;
- list_for_each_entry(sec, &file->elf->sections, list) {
+ clear_insn_state(&state);
+
+ state.cfa = initial_func_cfi.cfa;
+ memcpy(&state.regs, &initial_func_cfi.regs,
+ CFI_NUM_REGS * sizeof(struct cfi_reg));
+ state.stack_size = initial_func_cfi.cfa.offset;
+
+ for_each_sec(file, sec) {
list_for_each_entry(func, &sec->symbol_list, list) {
if (func->type != STT_FUNC)
continue;
insn = find_insn(file, sec, func->offset);
- if (!insn)
+ if (!insn || insn->ignore)
continue;
- ret = validate_branch(file, insn, 0);
+ ret = validate_branch(file, insn, state);
warnings += ret;
}
}
- list_for_each_entry(sec, &file->elf->sections, list) {
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- func_for_each_insn(file, func, insn) {
- if (insn->visited)
- continue;
-
- insn->visited = true;
-
- if (file->ignore_unreachables || warnings ||
- ignore_unreachable_insn(func, insn))
- continue;
-
- /*
- * gcov produces a lot of unreachable
- * instructions. If we get an unreachable
- * warning and the file has gcov enabled, just
- * ignore it, and all other such warnings for
- * the file.
- */
- if (!file->ignore_unreachables &&
- gcov_enabled(file)) {
- file->ignore_unreachables = true;
- continue;
- }
-
- WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
- warnings++;
- }
- }
- }
-
return warnings;
}
-static int validate_uncallable_instructions(struct objtool_file *file)
+static int validate_reachable_instructions(struct objtool_file *file)
{
struct instruction *insn;
- int warnings = 0;
+
+ if (file->ignore_unreachables)
+ return 0;
for_each_insn(file, insn) {
- if (!insn->visited && insn->type == INSN_RETURN) {
- WARN_FUNC("return instruction outside of a callable function",
- insn->sec, insn->offset);
- warnings++;
- }
+ if (insn->visited || ignore_unreachable_insn(insn))
+ continue;
+
+ /*
+ * gcov produces a lot of unreachable instructions. If we get
+ * an unreachable warning and the file has gcov enabled, just
+ * ignore it, and all other such warnings for the file. Do
+ * this here because this is an expensive function.
+ */
+ if (gcov_enabled(file))
+ return 0;
+
+ WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
+ return 1;
}
- return warnings;
+ return 0;
}
static void cleanup(struct objtool_file *file)
@@ -1226,10 +1615,8 @@ int check(const char *_objname, bool _nofp)
nofp = _nofp;
file.elf = elf_open(objname);
- if (!file.elf) {
- fprintf(stderr, "error reading elf file %s\n", objname);
+ if (!file.elf)
return 1;
- }
INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
@@ -1238,21 +1625,28 @@ int check(const char *_objname, bool _nofp)
file.ignore_unreachables = false;
file.c_file = find_section_by_name(file.elf, ".comment");
+ arch_initial_func_cfi_state(&initial_func_cfi);
+
ret = decode_sections(&file);
if (ret < 0)
goto out;
warnings += ret;
- ret = validate_functions(&file);
- if (ret < 0)
+ if (list_empty(&file.insn_list))
goto out;
- warnings += ret;
- ret = validate_uncallable_instructions(&file);
+ ret = validate_functions(&file);
if (ret < 0)
goto out;
warnings += ret;
+ if (!warnings) {
+ ret = validate_reachable_instructions(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+ }
+
out:
cleanup(&file);
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index c0d2fde..da85f5b 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -20,22 +20,34 @@
#include <stdbool.h>
#include "elf.h"
+#include "cfi.h"
#include "arch.h"
#include <linux/hashtable.h>
+struct insn_state {
+ struct cfi_reg cfa;
+ struct cfi_reg regs[CFI_NUM_REGS];
+ int stack_size;
+ bool bp_scratch;
+ bool drap;
+ int drap_reg;
+};
+
struct instruction {
struct list_head list;
struct hlist_node hash;
struct section *sec;
unsigned long offset;
- unsigned int len, state;
+ unsigned int len;
unsigned char type;
unsigned long immediate;
- bool alt_group, visited, dead_end;
+ bool alt_group, visited, dead_end, ignore;
struct symbol *call_dest;
struct instruction *jump_dest;
struct list_head alts;
struct symbol *func;
+ struct stack_op stack_op;
+ struct insn_state state;
};
struct objtool_file {
@@ -48,4 +60,7 @@ struct objtool_file {
int check(const char *objname, bool nofp);
+#define for_each_insn(file, insn) \
+ list_for_each_entry(insn, &file->insn_list, list)
+
#endif /* _CHECK_H */
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index d897702..1a7e8aa 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -37,6 +37,9 @@
#define ELF_C_READ_MMAP ELF_C_READ
#endif
+#define WARN_ELF(format, ...) \
+ WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
struct section *find_section_by_name(struct elf *elf, const char *name)
{
struct section *sec;
@@ -139,12 +142,12 @@ static int read_sections(struct elf *elf)
int i;
if (elf_getshdrnum(elf->elf, §ions_nr)) {
- perror("elf_getshdrnum");
+ WARN_ELF("elf_getshdrnum");
return -1;
}
if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
- perror("elf_getshdrstrndx");
+ WARN_ELF("elf_getshdrstrndx");
return -1;
}
@@ -165,37 +168,36 @@ static int read_sections(struct elf *elf)
s = elf_getscn(elf->elf, i);
if (!s) {
- perror("elf_getscn");
+ WARN_ELF("elf_getscn");
return -1;
}
sec->idx = elf_ndxscn(s);
if (!gelf_getshdr(s, &sec->sh)) {
- perror("gelf_getshdr");
+ WARN_ELF("gelf_getshdr");
return -1;
}
sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
if (!sec->name) {
- perror("elf_strptr");
+ WARN_ELF("elf_strptr");
return -1;
}
- sec->elf_data = elf_getdata(s, NULL);
- if (!sec->elf_data) {
- perror("elf_getdata");
+ sec->data = elf_getdata(s, NULL);
+ if (!sec->data) {
+ WARN_ELF("elf_getdata");
return -1;
}
- if (sec->elf_data->d_off != 0 ||
- sec->elf_data->d_size != sec->sh.sh_size) {
+ if (sec->data->d_off != 0 ||
+ sec->data->d_size != sec->sh.sh_size) {
WARN("unexpected data attributes for %s", sec->name);
return -1;
}
- sec->data = (unsigned long)sec->elf_data->d_buf;
- sec->len = sec->elf_data->d_size;
+ sec->len = sec->data->d_size;
}
/* sanity check, one more call to elf_nextscn() should return NULL */
@@ -232,15 +234,15 @@ static int read_symbols(struct elf *elf)
sym->idx = i;
- if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
- perror("gelf_getsym");
+ if (!gelf_getsym(symtab->data, i, &sym->sym)) {
+ WARN_ELF("gelf_getsym");
goto err;
}
sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
sym->sym.st_name);
if (!sym->name) {
- perror("elf_strptr");
+ WARN_ELF("elf_strptr");
goto err;
}
@@ -322,8 +324,8 @@ static int read_relas(struct elf *elf)
}
memset(rela, 0, sizeof(*rela));
- if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
- perror("gelf_getrela");
+ if (!gelf_getrela(sec->data, i, &rela->rela)) {
+ WARN_ELF("gelf_getrela");
return -1;
}
@@ -362,12 +364,6 @@ struct elf *elf_open(const char *name)
INIT_LIST_HEAD(&elf->sections);
- elf->name = strdup(name);
- if (!elf->name) {
- perror("strdup");
- goto err;
- }
-
elf->fd = open(name, O_RDONLY);
if (elf->fd == -1) {
perror("open");
@@ -376,12 +372,12 @@ struct elf *elf_open(const char *name)
elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
if (!elf->elf) {
- perror("elf_begin");
+ WARN_ELF("elf_begin");
goto err;
}
if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
- perror("gelf_getehdr");
+ WARN_ELF("gelf_getehdr");
goto err;
}
@@ -407,6 +403,12 @@ void elf_close(struct elf *elf)
struct symbol *sym, *tmpsym;
struct rela *rela, *tmprela;
+ if (elf->elf)
+ elf_end(elf->elf);
+
+ if (elf->fd > 0)
+ close(elf->fd);
+
list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
list_del(&sym->list);
@@ -421,11 +423,6 @@ void elf_close(struct elf *elf)
list_del(&sec->list);
free(sec);
}
- if (elf->name)
- free(elf->name);
- if (elf->fd > 0)
- close(elf->fd);
- if (elf->elf)
- elf_end(elf->elf);
+
free(elf);
}
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 731973e..343968b 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -37,10 +37,9 @@ struct section {
DECLARE_HASHTABLE(rela_hash, 16);
struct section *base, *rela;
struct symbol *sym;
- Elf_Data *elf_data;
+ Elf_Data *data;
char *name;
int idx;
- unsigned long data;
unsigned int len;
};
@@ -86,6 +85,7 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
struct symbol *find_containing_func(struct section *sec, unsigned long offset);
void elf_close(struct elf *elf);
-
+#define for_each_sec(file, sec) \
+ list_for_each_entry(sec, &file->elf->sections, list)
#endif /* _OBJTOOL_ELF_H */
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index bff8abb..84f001d 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -91,16 +91,16 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
alt->jump_or_nop = entry->jump_or_nop;
if (alt->group) {
- alt->orig_len = *(unsigned char *)(sec->data + offset +
+ alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->orig_len);
- alt->new_len = *(unsigned char *)(sec->data + offset +
+ alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->new_len);
}
if (entry->feature) {
unsigned short feature;
- feature = *(unsigned short *)(sec->data + offset +
+ feature = *(unsigned short *)(sec->data->d_buf + offset +
entry->feature);
/*
diff --git a/tools/objtool/warn.h b/tools/objtool/warn.h
index ac7e075..afd9f7a 100644
--- a/tools/objtool/warn.h
+++ b/tools/objtool/warn.h
@@ -18,6 +18,13 @@
#ifndef _WARN_H
#define _WARN_H
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "elf.h"
+
extern const char *objname;
static inline char *offstr(struct section *sec, unsigned long offset)
@@ -57,4 +64,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
free(_str); \
})
+#define WARN_ELF(format, ...) \
+ WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
#endif /* _WARN_H */