Re: [PATCH v2 7/7] arm64: uprobes - ARM32 instruction probing
From: Julien Thierry
Date: Thu Sep 27 2018 - 12:18:22 EST
Hi Maciej,
On 26/09/18 13:12, Maciej Slodczyk wrote:
Detect what kind of instruction is being probed and depending on the
result:
- if an A64 instruction handle it the old way, using existing A64
instructions probing code,
- if an A32 instruction decode it and handle using the new code, moved
from 32 bit arm kernel tree.
Signed-off-by: Maciej Slodczyk <m.slodczyk2@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/debug-monitors.c | 8 +++
arch/arm64/kernel/probes/uprobes.c | 111 ++++++++++++++++++++++++++++++++++---
lib/probes/arm/actions-arm.c | 35 ++++++++----
lib/probes/arm/decode-arm.c | 16 +++++-
4 files changed, 148 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 06ca574..ee10c0b 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -366,6 +366,14 @@ int aarch32_break_handler(struct pt_regs *regs)
if (!bp)
return -EFAULT;
+ /*
+ * Since bp != false, a sofware breakpoint instruction is being handled.
+ * If in user mode (compat_user_mode() few lines above),
+ * try to handle it by an uprobe handler, if registered.
+ */
+ if (!brk_handler((unsigned long)pc, BRK64_ESR_UPROBES, regs))
+ return 0;
+
send_user_sigtrap(TRAP_BRKPT);
return 0;
}
diff --git a/arch/arm64/kernel/probes/uprobes.c b/arch/arm64/kernel/probes/uprobes.c
index e7b8912..872c8ec 100644
--- a/arch/arm64/kernel/probes/uprobes.c
+++ b/arch/arm64/kernel/probes/uprobes.c
@@ -11,9 +11,49 @@
#include <asm/cacheflush.h>
#include "decode-insn.h"
+#include "decode.h"
+#include "decode-arm.h"
+#include <../../../arm/include/asm/opcodes.h>
I'm almost positive this is frowned upon. I don't see any headers from
arch/arm every being included in arch/arm64.
#define UPROBE_INV_FAULT_CODE UINT_MAX
+uprobe_opcode_t get_swbp_insn(void)
+{
+ if (is_compat_task())
+ return AARCH32_BREAK_ARM;
+ else
+ return UPROBE_SWBP_INSN;
+}
+
+bool is_swbp_insn(uprobe_opcode_t *insn)
+{
+ return ((__mem_to_opcode_arm(*insn) & 0x0fffffff) ==
+ (AARCH32_BREAK_ARM & 0x0fffffff)) ||
+ *insn == UPROBE_SWBP_INSN;
+}
+
+int set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm,
+ unsigned long vaddr)
+{
+ if (auprobe->arch == UPROBE_AARCH32)
+ return uprobe_write_opcode(auprobe, mm, vaddr,
+ __opcode_to_mem_arm(auprobe->bp_insn));
+ else
+ return uprobe_write_opcode(auprobe, mm, vaddr,
+ UPROBE_SWBP_INSN);
+}
+
+int set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
+ unsigned long vaddr)
+{
+ if (auprobe->arch == UPROBE_AARCH32)
+ return uprobe_write_opcode(auprobe, mm, vaddr,
+ auprobe->orig_insn);
+ else
+ return uprobe_write_opcode(auprobe, mm, vaddr,
+ *(uprobe_opcode_t *)&auprobe->insn);
+}
+
void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
void *src, unsigned long len)
{
@@ -38,16 +78,44 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long addr)
{
probes_opcode_t insn;
+ enum probes_insn retval;
+ unsigned int bpinsn;
- /* TODO: Currently we do not support AARCH32 instruction probing */
- if (mm->context.flags & MMCF_AARCH32)
- return -ENOTSUPP;
- else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
+ insn = *(probes_opcode_t *)(&auprobe->insn[0]);
+
+ if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
return -EINVAL;
- insn = *(probes_opcode_t *)(&auprobe->insn[0]);
+ /* check if AARCH32 */
+ if (is_compat_task()) {
+
+ /* Thumb is not supported yet */
+ if (addr & 0x3)
+ return -EINVAL;
-ENOTSUPP?
Cheers,
Julien
+
+ retval = arm_probes_decode_insn(insn, &auprobe->api, false,
+ uprobes_probes_actions, NULL);
+ auprobe->arch = UPROBE_AARCH32;
+
+ /*
+ * original instruction could have been modified
+ * when preparing for xol on AArch32
+ */
+ auprobe->orig_insn = insn;
+
+ bpinsn = AARCH32_BREAK_ARM & 0x0fffffff;
+ if (insn >= 0xe0000000) /* Unconditional instruction */
+ bpinsn |= 0xe0000000;
+ else /* Copy condition from insn */
+ bpinsn |= insn & 0xf0000000;
+
+ auprobe->bp_insn = bpinsn;
+ } else {
+ retval = arm64_probes_decode_insn(insn, &auprobe->api);
+ auprobe->arch = UPROBE_AARCH64;
+ }
- switch (arm64_probes_decode_insn(insn, &auprobe->api)) {
+ switch (retval) {
case INSN_REJECTED:
return -EINVAL;
@@ -66,6 +134,9 @@ int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
+ if (auprobe->prehandler)
+ auprobe->prehandler(auprobe, &utask->autask, regs);
+
/* Initialize with an invalid fault code to detect if ol insn trapped */
current->thread.fault_code = UPROBE_INV_FAULT_CODE;
@@ -88,6 +159,9 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
user_disable_single_step(current);
+ if (auprobe->posthandler)
+ auprobe->posthandler(auprobe, &utask->autask, regs);
+
return 0;
}
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
@@ -103,10 +177,24 @@ bool arch_uprobe_xol_was_trapped(struct task_struct *t)
return false;
}
+bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ probes_opcode_t insn = *(probes_opcode_t *)(&auprobe->insn[0]);
+ pstate_check_t *check = (*aarch32_opcode_cond_checks[insn >> 28]);
+
+ if (auprobe->arch == UPROBE_AARCH64)
+ return false;
+
+ if (!check(regs->pstate & 0xffffffff)) {
+ instruction_pointer_set(regs, instruction_pointer(regs) + 4);
+ return true;
+ }
+ return false;
+}
+
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
probes_opcode_t insn;
- unsigned long addr;
if (!auprobe->simulate)
return false;
@@ -154,9 +242,14 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
{
unsigned long orig_ret_vaddr;
- orig_ret_vaddr = procedure_link_pointer(regs);
/* Replace the return addr with trampoline addr */
- procedure_link_pointer_set(regs, trampoline_vaddr);
+ if (is_compat_task()) {
+ orig_ret_vaddr = link_register(regs);
+ link_register_set(regs, trampoline_vaddr);
+ } else {
+ orig_ret_vaddr = procedure_link_pointer(regs);
+ procedure_link_pointer_set(regs, trampoline_vaddr);
+ }
return orig_ret_vaddr;
}
diff --git a/lib/probes/arm/actions-arm.c b/lib/probes/arm/actions-arm.c
index 2393573..cee1496 100644
--- a/lib/probes/arm/actions-arm.c
+++ b/lib/probes/arm/actions-arm.c
@@ -15,10 +15,7 @@
#include "decode.h"
#include "decode-arm.h"
-
-#ifdef CONFIG_ARM64
#include <../../../arm/include/asm/opcodes.h>
-#endif /* CONFIG_ARM64 */
static int uprobes_substitute_pc(unsigned long *pinsn, u32 oregs)
{
@@ -75,8 +72,13 @@ static void uprobe_set_pc(struct arch_uprobe *auprobe,
{
u32 pcreg = auprobe->pcreg;
- autask->backup = pt_regs_read_reg(regs, pcreg);
- pt_regs_write_reg(regs, pcreg, instruction_pointer(regs) + 8);
+ if (pcreg == 15) {
+ autask->backup = instruction_pointer(regs);
+ instruction_pointer_set(regs, instruction_pointer(regs) + 8);
+ } else {
+ autask->backup = pt_regs_read_reg(regs, pcreg);
+ pt_regs_write_reg(regs, pcreg, instruction_pointer(regs) + 8);
+ }
}
static void uprobe_unset_pc(struct arch_uprobe *auprobe,
@@ -84,7 +86,10 @@ static void uprobe_unset_pc(struct arch_uprobe *auprobe,
struct pt_regs *regs)
{
/* PC will be taken care of by common code */
- pt_regs_write_reg(regs, auprobe->pcreg, autask->backup);
+ if (auprobe->pcreg == 15)
+ instruction_pointer_set(regs, autask->backup);
+ else
+ pt_regs_write_reg(regs, auprobe->pcreg, autask->backup);
}
static void uprobe_aluwrite_pc(struct arch_uprobe *auprobe,
@@ -93,8 +98,13 @@ static void uprobe_aluwrite_pc(struct arch_uprobe *auprobe,
{
u32 pcreg = auprobe->pcreg;
- alu_write_pc(pt_regs_read_reg(regs, pcreg), regs);
- pt_regs_write_reg(regs, pcreg, autask->backup);
+ if (pcreg == 15) {
+ alu_write_pc(instruction_pointer(regs), regs);
+ instruction_pointer_set(regs, autask->backup);
+ } else {
+ alu_write_pc(pt_regs_read_reg(regs, pcreg), regs);
+ pt_regs_write_reg(regs, pcreg, autask->backup);
+ }
}
static void uprobe_write_pc(struct arch_uprobe *auprobe,
@@ -103,8 +113,13 @@ static void uprobe_write_pc(struct arch_uprobe *auprobe,
{
u32 pcreg = auprobe->pcreg;
- load_write_pc(pt_regs_read_reg(regs, pcreg), regs);
- pt_regs_write_reg(regs, pcreg, autask->backup);
+ if (pcreg == 15) {
+ load_write_pc(instruction_pointer(regs), regs);
+ instruction_pointer_set(regs, autask->backup);
+ } else {
+ load_write_pc(pt_regs_read_reg(regs, pcreg), regs);
+ pt_regs_write_reg(regs, pcreg, autask->backup);
+ }
}
enum probes_insn
diff --git a/lib/probes/arm/decode-arm.c b/lib/probes/arm/decode-arm.c
index 36eb939..2f2a810 100644
--- a/lib/probes/arm/decode-arm.c
+++ b/lib/probes/arm/decode-arm.c
@@ -87,11 +87,18 @@ void __kprobes simulate_blx2bx(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
int rm = insn & 0xf;
- long rmv = pt_regs_read_reg(regs, rm);
+ long rmv;
long cpsr;
+ if (rm == 15)
+ rmv = (long) instruction_pointer(regs);
+ else
+ rmv = pt_regs_read_reg(regs, rm);
+
if (insn & (1 << 5))
- link_register_set(regs, (long) instruction_pointer(regs));
+ link_register_set(regs,
+ (long) instruction_pointer(regs)
+ + ARM_COMPAT_LR_OFFSET);
instruction_pointer_set(regs, rmv & ~0x1);
cpsr = state_register(regs) & ~PSR_T_BIT;
@@ -108,7 +115,10 @@ void __kprobes simulate_mrs(probes_opcode_t insn,
int rd = (insn >> 12) & 0xf;
unsigned long mask = 0xf8ff03df; /* Mask out execution state */
- pt_regs_write_reg(regs, rd, state_register(regs) & mask);
+ if (rd == 15)
+ instruction_pointer_set(regs, state_register(regs) & mask);
+ else
+ pt_regs_write_reg(regs, rd, state_register(regs) & mask);
}
void __kprobes simulate_mov_ipsp(probes_opcode_t insn,
--
Julien Thierry