Messages in this thread Patch in this message | | | Date | Mon, 12 May 2014 19:08:50 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] 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> --- 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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