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Date: Tue, 13 May 2014 15:23:32 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
Jim Keniston <jkenisto@...ibm.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, x86@...nel.org,
linux-kernel@...r.kernel.org,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
David Long <dave.long@...aro.org>
Subject: Re: [PATCH 1/1] uprobes/x86: Fix the wrong ->si_addr when xol triggers
a trap
(2014/05/13 2:08), Oleg Nesterov wrote:
> 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@...hat.com>
Looks good to me :)
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Thanks,
> ---
> 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.
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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