[RFC][PATCH 4/4] x86_32: Provide consistent pt_regs

From: Peter Zijlstra
Date: Wed May 08 2019 - 04:13:36 EST

Currently pt_regs on x86_32 has an oddity in that kernel regs
(!user_mode(regs)) are short two entries (esp/ss). This means that any
code trying to use them (typically: regs->sp) needs to jump through
some unfortunate hoops.

Change the entry code to fix this up and create a full pt_regs frame.

This then simplifies:

- ftrace
- kprobes
- stack unwinder
- ptrace
- kdump
- kgdb

Hated-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/entry/entry_32.S | 105 ++++++++++++++++++++++++++++++++++----
arch/x86/include/asm/kexec.h | 17 ------
arch/x86/include/asm/ptrace.h | 17 ------
arch/x86/include/asm/stacktrace.h | 2
arch/x86/kernel/crash.c | 8 --
arch/x86/kernel/ftrace_32.S | 81 ++++++++++++++++-------------
arch/x86/kernel/kgdb.c | 8 --
arch/x86/kernel/kprobes/common.h | 4 -
arch/x86/kernel/kprobes/core.c | 29 ++++------
arch/x86/kernel/kprobes/opt.c | 20 ++++---
arch/x86/kernel/process_32.c | 16 +----
arch/x86/kernel/ptrace.c | 29 ----------
arch/x86/kernel/time.c | 3 -
arch/x86/kernel/unwind_frame.c | 32 +----------
arch/x86/kernel/unwind_orc.c | 2
15 files changed, 181 insertions(+), 192 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -202,9 +202,102 @@
.Lend_\@:
.endm

+#define CS_FROM_ENTRY_STACK (1 << 31)
+#define CS_FROM_USER_CR3 (1 << 30)
+#define CS_FROM_KERNEL (1 << 29)
+
+.macro FIXUP_FRAME
+ /*
+ * The high bits of the CS dword (__csh) are used for CS_FROM_*.
+ * Clear them in case hardware didn't do this for us.
+ */
+ andl $0x0000ffff, 3*4(%esp)
+
+#ifdef CONFIG_VM86
+ testl $X86_EFLAGS_VM, 4*4(%esp)
+ jnz .Lfrom_usermode_no_fixup_\@
+#endif
+ testl $SEGMENT_RPL_MASK, 3*4(%esp)
+ jnz .Lfrom_usermode_no_fixup_\@
+
+ orl $CS_FROM_KERNEL, 3*4(%esp)
+
+ /*
+ * When we're here from kernel mode; the (exception) stack looks like:
+ *
+ * 5*4(%esp) - <previous context>
+ * 4*4(%esp) - flags
+ * 3*4(%esp) - cs
+ * 2*4(%esp) - ip
+ * 1*4(%esp) - orig_eax
+ * 0*4(%esp) - gs / function
+ *
+ * Lets build a 5 entry IRET frame after that, such that struct pt_regs
+ * is complete and in particular regs->sp is correct. This gives us
+ * the original 5 enties as gap:
+ *
+ * 12*4(%esp) - <previous context>
+ * 11*4(%esp) - gap / flags
+ * 10*4(%esp) - gap / cs
+ * 9*4(%esp) - gap / ip
+ * 8*4(%esp) - gap / orig_eax
+ * 7*4(%esp) - gap / gs / function
+ * 6*4(%esp) - ss
+ * 5*4(%esp) - sp
+ * 4*4(%esp) - flags
+ * 3*4(%esp) - cs
+ * 2*4(%esp) - ip
+ * 1*4(%esp) - orig_eax
+ * 0*4(%esp) - gs / function
+ */
+
+ pushl %ss # ss
+ pushl %esp # sp (points at ss)
+ addl $6*4, (%esp) # point sp back at the previous context
+ pushl 6*4(%esp) # flags
+ pushl 6*4(%esp) # cs
+ pushl 6*4(%esp) # ip
+ pushl 6*4(%esp) # orig_eax
+ pushl 6*4(%esp) # gs / function
+.Lfrom_usermode_no_fixup_\@:
+.endm
+
+.macro IRET_FRAME
+ testl $CS_FROM_KERNEL, 1*4(%esp)
+ jz .Lfinished_frame_\@
+
+ /*
+ * Reconstruct the 3 entry IRET frame right after the (modified)
+ * regs->sp without lowering %esp in between, such that an NMI in the
+ * middle doesn't scribble our stack.
+ */
+ pushl %eax
+ pushl %ecx
+ movl 5*4(%esp), %eax # (modified) regs->sp
+
+ movl 4*4(%esp), %ecx # flags
+ movl %ecx, -4(%eax)
+
+ movl 3*4(%esp), %ecx # cs
+ andl $0x0000ffff, %ecx
+ movl %ecx, -8(%eax)
+
+ movl 2*4(%esp), %ecx # ip
+ movl %ecx, -12(%eax)
+
+ movl 1*4(%esp), %ecx # eax
+ movl %ecx, -16(%eax)
+
+ popl %ecx
+ lea -16(%eax), %esp
+ popl %eax
+.Lfinished_frame_\@:
+.endm
+
.macro SAVE_ALL pt_regs_ax=%eax switch_stacks=0
cld
PUSH_GS
+ FIXUP_FRAME
pushl %fs
pushl %es
pushl %ds
@@ -374,9 +467,6 @@
* switch to it before we do any copying.
*/

-#define CS_FROM_ENTRY_STACK (1 << 31)
-#define CS_FROM_USER_CR3 (1 << 30)
-
.macro SWITCH_TO_KERNEL_STACK

ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV
@@ -390,13 +480,6 @@
* that register for the time this macro runs
*/

- /*
- * The high bits of the CS dword (__csh) are used for
- * CS_FROM_ENTRY_STACK and CS_FROM_USER_CR3. Clear them in case
- * hardware didn't do this for us.
- */
- andl $(0x0000ffff), PT_CS(%esp)
-
/* Are we on the entry stack? Bail out if not! */
movl PER_CPU_VAR(cpu_entry_area), %ecx
addl $CPU_ENTRY_AREA_entry_stack + SIZEOF_entry_stack, %ecx
@@ -1006,6 +1089,7 @@ ENTRY(entry_INT80_32)
/* Restore user state */
RESTORE_REGS pop=4 # skip orig_eax/error_code
.Lirq_return:
+ IRET_FRAME
/*
* ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization
* when returning from IPI handler and when returning from
@@ -1356,6 +1440,7 @@ END(page_fault)

common_exception:
/* the function address is in %gs's slot on the stack */
+ FIXUP_FRAME
pushl %fs
pushl %es
pushl %ds
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -71,22 +71,6 @@ struct kimage;
#define KEXEC_BACKUP_SRC_END (640 * 1024UL - 1) /* 640K */

/*
- * CPU does not save ss and sp on stack if execution is already
- * running in kernel mode at the time of NMI occurrence. This code
- * fixes it.
- */
-static inline void crash_fixup_ss_esp(struct pt_regs *newregs,
- struct pt_regs *oldregs)
-{
-#ifdef CONFIG_X86_32
- newregs->sp = (unsigned long)&(oldregs->sp);
- asm volatile("xorl %%eax, %%eax\n\t"
- "movw %%ss, %%ax\n\t"
- :"=a"(newregs->ss));
-#endif
-}
-
-/*
* This function is responsible for capturing register states if coming
* via panic otherwise just fix up the ss and sp if coming via kernel
* mode exception.
@@ -96,7 +80,6 @@ static inline void crash_setup_regs(stru
{
if (oldregs) {
memcpy(newregs, oldregs, sizeof(*newregs));
- crash_fixup_ss_esp(newregs, oldregs);
} else {
#ifdef CONFIG_X86_32
asm volatile("movl %%ebx,%0" : "=m"(newregs->bx));
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -166,14 +166,10 @@ static inline bool user_64bit_mode(struc
#define compat_user_stack_pointer() current_pt_regs()->sp
#endif

-#ifdef CONFIG_X86_32
-extern unsigned long kernel_stack_pointer(struct pt_regs *regs);
-#else
static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
{
return regs->sp;
}
-#endif

#define GET_IP(regs) ((regs)->ip)
#define GET_FP(regs) ((regs)->bp)
@@ -201,14 +197,6 @@ static inline unsigned long regs_get_reg
if (unlikely(offset > MAX_REG_OFFSET))
return 0;
#ifdef CONFIG_X86_32
- /*
- * Traps from the kernel do not save sp and ss.
- * Use the helper function to retrieve sp.
- */
- if (offset == offsetof(struct pt_regs, sp) &&
- regs->cs == __KERNEL_CS)
- return kernel_stack_pointer(regs);
-
/* The selector fields are 16-bit. */
if (offset == offsetof(struct pt_regs, cs) ||
offset == offsetof(struct pt_regs, ss) ||
@@ -234,8 +222,7 @@ static inline unsigned long regs_get_reg
static inline int regs_within_kernel_stack(struct pt_regs *regs,
unsigned long addr)
{
- return ((addr & ~(THREAD_SIZE - 1)) ==
- (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+ return ((addr & ~(THREAD_SIZE - 1)) == (regs->sp & ~(THREAD_SIZE - 1)));
}

/**
@@ -249,7 +236,7 @@ static inline int regs_within_kernel_sta
*/
static inline unsigned long *regs_get_kernel_stack_nth_addr(struct pt_regs *regs, unsigned int n)
{
- unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+ unsigned long *addr = (unsigned long *)regs->sp;

addr += n;
if (regs_within_kernel_stack(regs, (unsigned long)addr))
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -78,7 +78,7 @@ static inline unsigned long *
get_stack_pointer(struct task_struct *task, struct pt_regs *regs)
{
if (regs)
- return (unsigned long *)kernel_stack_pointer(regs);
+ return (unsigned long *)regs->sp;

if (task == current)
return __builtin_frame_address(0);
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -72,14 +72,6 @@ static inline void cpu_crash_vmclear_loa

static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
{
-#ifdef CONFIG_X86_32
- struct pt_regs fixed_regs;
-
- if (!user_mode(regs)) {
- crash_fixup_ss_esp(&fixed_regs, regs);
- regs = &fixed_regs;
- }
-#endif
crash_save_cpu(regs, cpu);

/*
--- a/arch/x86/kernel/ftrace_32.S
+++ b/arch/x86/kernel/ftrace_32.S
@@ -9,6 +9,7 @@
#include <asm/export.h>
#include <asm/ftrace.h>
#include <asm/nospec-branch.h>
+#include <asm/asm-offsets.h>

#ifdef CC_USING_FENTRY
# define function_hook __fentry__
@@ -104,26 +105,38 @@ END(ftrace_caller)

ENTRY(ftrace_regs_caller)
/*
- * i386 does not save SS and ESP when coming from kernel.
- * Instead, to get sp, &regs->sp is used (see ptrace.h).
- * Unfortunately, that means eflags must be at the same location
- * as the current return ip is. We move the return ip into the
- * regs->ip location, and move flags into the return ip location.
+ * We're here from an mcount/fentry CALL, and the stack frame looks like:
+ *
+ * <previous context>
+ * RET-IP
+ *
+ * The purpose of this function is to call out in an emulated INT3
+ * environment with a stack frame like:
+ *
+ * <previous context>
+ * gap / RET-IP
+ * gap
+ * gap
+ * gap
+ * pt_regs
+ *
+ * We do _NOT_ restore: ss, flags, cs, gs, fs, es, ds
*/
- pushl $__KERNEL_CS
- pushl 4(%esp) /* Save the return ip */
- pushl $0 /* Load 0 into orig_ax */
+ subl $3*4, %esp # RET-IP + 3 gaps
+ pushl %ss # ss
+ pushl %esp # points at ss
+ addl $5*4, (%esp) # make it point at <previous context>
+ pushfl # flags
+ pushl $__KERNEL_CS # cs
+ pushl 7*4(%esp) # ip <- RET-IP
+ pushl $0 # orig_eax
+
pushl %gs
pushl %fs
pushl %es
pushl %ds
- pushl %eax
-
- /* Get flags and place them into the return ip slot */
- pushf
- popl %eax
- movl %eax, 8*4(%esp)

+ pushl %eax
pushl %ebp
pushl %edi
pushl %esi
@@ -131,12 +144,13 @@ ENTRY(ftrace_regs_caller)
pushl %ecx
pushl %ebx

- movl 12*4(%esp), %eax /* Load ip (1st parameter) */
- subl $MCOUNT_INSN_SIZE, %eax /* Adjust ip */
+ movl PT_EIP(%esp), %eax # 1st argument: IP
+ subl $MCOUNT_INSN_SIZE, %eax
+
#ifdef CC_USING_FENTRY
- movl 15*4(%esp), %edx /* Load parent ip (2nd parameter) */
+ movl 21*4(%esp), %edx # 2nd argument: parent ip
#else
- movl 0x4(%ebp), %edx /* Load parent ip (2nd parameter) */
+ movl 1*4(%ebp), %edx # 2nd argument: parent ip
#endif

#ifdef CONFIG_FRAME_POINTER
@@ -144,21 +158,22 @@ ENTRY(ftrace_regs_caller)
andl $0x7fffffff, %ebp
#endif

- movl function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
- pushl %esp /* Save pt_regs as 4th parameter */
+ movl function_trace_op, %ecx # 3rd argument: ftrace_pos
+ pushl %esp # 4th argument: pt_regs

GLOBAL(ftrace_regs_call)
call ftrace_stub

- addl $4, %esp /* Skip pt_regs */
+ addl $4, %esp # skip 4th argument

- /* restore flags */
- push 14*4(%esp)
- popf
-
- /* Move return ip back to its original location */
- movl 12*4(%esp), %eax
- movl %eax, 14*4(%esp)
+ /* place IP below the new SP */
+ movl PT_OLDESP(%esp), %eax
+ movl PT_EIP(%esp), %ecx
+ movl %ecx, -4(%eax)
+
+ /* place EAX below that */
+ movl PT_EAX(%esp), %ecx
+ movl %ecx, -8(%eax)

popl %ebx
popl %ecx
@@ -166,16 +181,12 @@ GLOBAL(ftrace_regs_call)
popl %esi
popl %edi
popl %ebp
- popl %eax
- popl %ds
- popl %es
- popl %fs
- popl %gs

- /* use lea to not affect flags */
- lea 3*4(%esp), %esp /* Skip orig_ax, ip and cs */
+ lea -8(%eax), %esp
+ popl %eax

jmp .Lftrace_ret
+
#else /* ! CONFIG_DYNAMIC_FTRACE */

ENTRY(function_hook)
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -127,14 +127,6 @@ char *dbg_get_reg(int regno, void *mem,

#ifdef CONFIG_X86_32
switch (regno) {
- case GDB_SS:
- if (!user_mode(regs))
- *(unsigned long *)mem = __KERNEL_DS;
- break;
- case GDB_SP:
- if (!user_mode(regs))
- *(unsigned long *)mem = kernel_stack_pointer(regs);
- break;
case GDB_GS:
case GDB_FS:
*(unsigned long *)mem = 0xFFFF;
--- a/arch/x86/kernel/kprobes/common.h
+++ b/arch/x86/kernel/kprobes/common.h
@@ -86,8 +86,8 @@
" popl %edi\n" \
" popl %ebp\n" \
" popl %eax\n" \
- /* Skip ds, es, fs, gs, orig_ax, and ip. Note: don't pop cs here*/\
- " addl $24, %esp\n"
+ /* Skip ds, es, fs, gs, orig_ax, ip, and cs. */\
+ " addl $7*4, %esp\n"
#endif

/* Ensure if the instruction can be boostable */
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -69,7 +69,7 @@
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

-#define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
+#define stack_addr(regs) ((unsigned long *)regs->sp)

#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
@@ -731,29 +731,27 @@ asm(
".global kretprobe_trampoline\n"
".type kretprobe_trampoline, @function\n"
"kretprobe_trampoline:\n"
-#ifdef CONFIG_X86_64
/* We don't bother saving the ss register */
+#ifdef CONFIG_X86_64
" pushq %rsp\n"
" pushfq\n"
SAVE_REGS_STRING
" movq %rsp, %rdi\n"
" call trampoline_handler\n"
/* Replace saved sp with true return address. */
- " movq %rax, 152(%rsp)\n"
+ " movq %rax, 19*8(%rsp)\n"
RESTORE_REGS_STRING
" popfq\n"
#else
- " pushf\n"
+ " pushl %esp\n"
+ " pushfl\n"
SAVE_REGS_STRING
" movl %esp, %eax\n"
" call trampoline_handler\n"
- /* Move flags to cs */
- " movl 56(%esp), %edx\n"
- " movl %edx, 52(%esp)\n"
- /* Replace saved flags with true return address. */
- " movl %eax, 56(%esp)\n"
+ /* Replace saved sp with true return address. */
+ " movl %eax, 15*4(%esp)\n"
RESTORE_REGS_STRING
- " popf\n"
+ " popfl\n"
#endif
" ret\n"
".size kretprobe_trampoline, .-kretprobe_trampoline\n"
@@ -794,16 +792,13 @@ static __used void *trampoline_handler(s
INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/* fixup registers */
-#ifdef CONFIG_X86_64
regs->cs = __KERNEL_CS;
- /* On x86-64, we use pt_regs->sp for return address holder. */
- frame_pointer = &regs->sp;
-#else
- regs->cs = __KERNEL_CS | get_kernel_rpl();
+#ifdef CONFIG_X86_32
+ regs->cs |= get_kernel_rpl();
regs->gs = 0;
- /* On x86-32, we use pt_regs->flags for return address holder. */
- frame_pointer = &regs->flags;
#endif
+ /* We use pt_regs->sp for return address holder. */
+ frame_pointer = &regs->sp;
regs->ip = trampoline_address;
regs->orig_ax = ~0UL;

--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -115,14 +115,15 @@ asm (
"optprobe_template_call:\n"
ASM_NOP5
/* Move flags to rsp */
- " movq 144(%rsp), %rdx\n"
- " movq %rdx, 152(%rsp)\n"
+ " movq 18*8(%rsp), %rdx\n"
+ " movq %rdx, 19*8(%rsp)\n"
RESTORE_REGS_STRING
/* Skip flags entry */
" addq $8, %rsp\n"
" popfq\n"
#else /* CONFIG_X86_32 */
- " pushf\n"
+ " pushl %esp\n"
+ " pushfl\n"
SAVE_REGS_STRING
" movl %esp, %edx\n"
".global optprobe_template_val\n"
@@ -131,9 +132,13 @@ asm (
".global optprobe_template_call\n"
"optprobe_template_call:\n"
ASM_NOP5
+ /* Move flags into esp */
+ " movl 14*4(%esp), %edx\n"
+ " movl %edx, 15*4(%esp)\n"
RESTORE_REGS_STRING
- " addl $4, %esp\n" /* skip cs */
- " popf\n"
+ /* Skip flags entry */
+ " addl $4, %esp\n"
+ " popfl\n"
#endif
".global optprobe_template_end\n"
"optprobe_template_end:\n"
@@ -165,10 +170,9 @@ optimized_callback(struct optimized_kpro
} else {
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
/* Save skipped registers */
-#ifdef CONFIG_X86_64
regs->cs = __KERNEL_CS;
-#else
- regs->cs = __KERNEL_CS | get_kernel_rpl();
+#ifdef CONFIG_X86_32
+ regs->cs |= get_kernel_rpl();
regs->gs = 0;
#endif
regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -62,27 +62,21 @@ void __show_regs(struct pt_regs *regs, e
{
unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
unsigned long d0, d1, d2, d3, d6, d7;
- unsigned long sp;
- unsigned short ss, gs;
+ unsigned short gs;

- if (user_mode(regs)) {
- sp = regs->sp;
- ss = regs->ss;
+ if (user_mode(regs))
gs = get_user_gs(regs);
- } else {
- sp = kernel_stack_pointer(regs);
- savesegment(ss, ss);
+ else
savesegment(gs, gs);
- }

show_ip(regs, KERN_DEFAULT);

printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
regs->ax, regs->bx, regs->cx, regs->dx);
printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
- regs->si, regs->di, regs->bp, sp);
+ regs->si, regs->di, regs->bp, regs->sp);
printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
- (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);
+ (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, regs->ss, regs->flags);

if (mode != SHOW_REGS_ALL)
return;
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -153,35 +153,6 @@ static inline bool invalid_selector(u16

#define FLAG_MASK FLAG_MASK_32

-/*
- * X86_32 CPUs don't save ss and esp if the CPU is already in kernel mode
- * when it traps. The previous stack will be directly underneath the saved
- * registers, and 'sp/ss' won't even have been saved. Thus the '&regs->sp'.
- *
- * Now, if the stack is empty, '&regs->sp' is out of range. In this
- * case we try to take the previous stack. To always return a non-null
- * stack pointer we fall back to regs as stack if no previous stack
- * exists.
- *
- * This is valid only for kernel mode traps.
- */
-unsigned long kernel_stack_pointer(struct pt_regs *regs)
-{
- unsigned long context = (unsigned long)regs & ~(THREAD_SIZE - 1);
- unsigned long sp = (unsigned long)&regs->sp;
- u32 *prev_esp;
-
- if (context == (sp & ~(THREAD_SIZE - 1)))
- return sp;
-
- prev_esp = (u32 *)(context);
- if (*prev_esp)
- return (unsigned long)*prev_esp;
-
- return (unsigned long)regs;
-}
-EXPORT_SYMBOL_GPL(kernel_stack_pointer);
-
static unsigned long *pt_regs_access(struct pt_regs *regs, unsigned long regno)
{
BUILD_BUG_ON(offsetof(struct pt_regs, bx) != 0);
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -37,8 +37,7 @@ unsigned long profile_pc(struct pt_regs
#ifdef CONFIG_FRAME_POINTER
return *(unsigned long *)(regs->bp + sizeof(long));
#else
- unsigned long *sp =
- (unsigned long *)kernel_stack_pointer(regs);
+ unsigned long *sp = (unsigned long *)regs->sp;
/*
* Return address is either directly at stack pointer
* or above a saved flags. Eflags has bits 22-31 zero,
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -69,15 +69,6 @@ static void unwind_dump(struct unwind_st
}
}

-static size_t regs_size(struct pt_regs *regs)
-{
- /* x86_32 regs from kernel mode are two words shorter: */
- if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
- return sizeof(*regs) - 2*sizeof(long);
-
- return sizeof(*regs);
-}
-
static bool in_entry_code(unsigned long ip)
{
char *addr = (char *)ip;
@@ -197,12 +188,6 @@ static struct pt_regs *decode_frame_poin
}
#endif

-#ifdef CONFIG_X86_32
-#define KERNEL_REGS_SIZE (sizeof(struct pt_regs) - 2*sizeof(long))
-#else
-#define KERNEL_REGS_SIZE (sizeof(struct pt_regs))
-#endif
-
static bool update_stack_state(struct unwind_state *state,
unsigned long *next_bp)
{
@@ -213,7 +198,7 @@ static bool update_stack_state(struct un
size_t len;

if (state->regs)
- prev_frame_end = (void *)state->regs + regs_size(state->regs);
+ prev_frame_end = (void *)state->regs + sizeof(*state->regs);
else
prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;

@@ -221,7 +206,7 @@ static bool update_stack_state(struct un
regs = decode_frame_pointer(next_bp);
if (regs) {
frame = (unsigned long *)regs;
- len = KERNEL_REGS_SIZE;
+ len = sizeof(*regs);
state->got_irq = true;
} else {
frame = next_bp;
@@ -245,14 +230,6 @@ static bool update_stack_state(struct un
frame < prev_frame_end)
return false;

- /*
- * On 32-bit with user mode regs, make sure the last two regs are safe
- * to access:
- */
- if (IS_ENABLED(CONFIG_X86_32) && regs && user_mode(regs) &&
- !on_stack(info, frame, len + 2*sizeof(long)))
- return false;
-
/* Move state to the next frame: */
if (regs) {
state->regs = regs;
@@ -411,10 +388,9 @@ void __unwind_start(struct unwind_state
* Pretend that the frame is complete and that BP points to it, but save
* the real BP so that we can use it when looking for the next frame.
*/
- if (regs && regs->ip == 0 &&
- (unsigned long *)kernel_stack_pointer(regs) >= first_frame) {
+ if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
state->next_bp = bp;
- bp = ((unsigned long *)kernel_stack_pointer(regs)) - 1;
+ bp = ((unsigned long *)regs->sp) - 1;
}

/* Initialize stack info and make sure the frame data is accessible: */
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -579,7 +579,7 @@ void __unwind_start(struct unwind_state
goto done;

state->ip = regs->ip;
- state->sp = kernel_stack_pointer(regs);
+ state->sp = regs->sp;
state->bp = regs->bp;
state->regs = regs;
state->full_regs = true;