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 <o...@redhat.com>
---
arch/x86/kernel/traps.c | 7 ++++---
include/linux/uprobes.h | 4 ++++
kernel/events/uprobes.c | 10 ++++++++++
3 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 73b3ea3..3fdb205 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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;
/*
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index edff2b9..88c3b7e 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -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)
{
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a13251e..3b02c72 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -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.
--
1.5.5.1
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