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uprobes/x86: Fix the wrong ->si_addr when xol triggers a trap

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If the probed insn triggers a trap, ->si_addr = regs->ip is technically
correct, but this is not what the signal handler wants; we need to pass
the address of the probed insn, not the address of xol slot.

Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change
fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in
uprobes.h uses a macro to avoid include hell and ensure that it can be
compiled even if an architecture doesn't define instruction_pointer().

Test-case:

	#include <signal.h>
	#include <stdio.h>
	#include <unistd.h>

	extern void probe_div(void);

	void sigh(int sig, siginfo_t *info, void *c)
	{
		int passed = (info->si_addr == probe_div);
		printf(passed ? "PASS\n" : "FAIL\n");
		_exit(!passed);
	}

	int main(void)
	{
		struct sigaction sa = {
			.sa_sigaction	= sigh,
			.sa_flags	= SA_SIGINFO,
		};

		sigaction(SIGFPE, &sa, NULL);

		asm (
			"xor %ecx,%ecx\n"
			".globl probe_div; probe_div:\n"
			"idiv %ecx\n"
		);

		return 0;
	}

it fails if probe_div() is probed.

Note: show_unhandled_signals users should probably use this helper too,
but we need to cleanup them first.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
This commit is contained in:
Oleg Nesterov 2014-05-12 18:24:45 +02:00
parent 0eb14833d5
commit b02ef20a9f
3 changed files with 18 additions and 3 deletions
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7
arch/x86/kernel/traps.c
View File

@ -23,6 +23,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/errno.h>
@ -148,11 +149,11 @@ static siginfo_t *fill_trap_info(struct pt_regs *regs, int signr, int trapnr,
case X86_TRAP_DE:
sicode = FPE_INTDIV;
siaddr = regs->ip;
siaddr = uprobe_get_trap_addr(regs);
break;
case X86_TRAP_UD:
sicode = ILL_ILLOPN;
siaddr = regs->ip;
siaddr = uprobe_get_trap_addr(regs);
break;
case X86_TRAP_AC:
sicode = BUS_ADRALN;
@ -531,7 +532,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
task->thread.error_code = error_code;
info.si_signo = SIGFPE;
info.si_errno = 0;
info.si_addr = (void __user *)regs->ip;
info.si_addr = (void __user *)uprobe_get_trap_addr(regs);
if (trapnr == X86_TRAP_MF) {
unsigned short cwd, swd;
/*

4
include/linux/uprobes.h
View File

@ -102,6 +102,7 @@ extern int __weak set_orig_insn(struct arch_uprobe *aup, struct mm_struct *mm, u
extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
extern bool __weak is_trap_insn(uprobe_opcode_t *insn);
extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs);
extern int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t);
extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
@ -130,6 +131,9 @@ extern bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *r
#else /* !CONFIG_UPROBES */
struct uprobes_state {
};
#define uprobe_get_trap_addr(regs) instruction_pointer(regs)
static inline int
uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{

10
kernel/events/uprobes.c
View File

@ -1351,6 +1351,16 @@ unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
}
unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (unlikely(utask && utask->active_uprobe))
return utask->vaddr;
return instruction_pointer(regs);
}
/*
* Called with no locks held.
* Called in context of a exiting or a exec-ing thread.