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x86/stackframe/32: Provide consistent pt_regs

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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 various trampolines in ftrace and kprobes, the
stack unwinder, ptrace, kdump and kgdb.

Much thanks to Josh for help with the cleanups!

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2019-05-07 23:25:54 +02:00
committed by Ingo Molnar
parent ea1ed38dba
commit 3c88c692c2
15 changed files with 177 additions and 190 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
arch/x86/include/asm/kexec.h
View File

@@ -70,22 +70,6 @@ struct kimage;
#define KEXEC_BACKUP_SRC_START (0UL)
#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
@@ -96,7 +80,6 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
{
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));

17
arch/x86/include/asm/ptrace.h
View File

@@ -166,14 +166,10 @@ static inline bool user_64bit_mode(struct pt_regs *regs)
#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_register(struct pt_regs *regs,
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_register(struct pt_regs *regs,
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_stack(struct pt_regs *regs,
*/
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))

2
arch/x86/include/asm/stacktrace.h
View File

@@ -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);