From ba54d856a9d8a9c56b87e20c88602b7e3cb568fb Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Tue, 17 Apr 2018 18:11:21 +0200 Subject: x86/fault: Dump user opcode bytes on fatal faults Sometimes it is useful to see which user opcode bytes RIP points to when a fault happens: be it to rule out RIP corruption, to dump info early during boot, when doing core dumps is impossible due to not having a writable filesystem yet. Sometimes it is useful if debugging an issue and one doesn't have access to the executable which caused the fault in order to disassemble it. That last aspect might have some security implications so show_unhandled_signals could be revisited for that or a new config option added. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180417161124.5294-7-bp@alien8.de --- arch/x86/mm/fault.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 73bd8c95ac71..a3fd94eff04d 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -828,6 +828,8 @@ static inline void show_signal_msg(struct pt_regs *regs, unsigned long error_code, unsigned long address, struct task_struct *tsk) { + const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; + if (!unhandled_signal(tsk, SIGSEGV)) return; @@ -835,13 +837,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code, return; printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", - task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, - tsk->comm, task_pid_nr(tsk), address, + loglvl, tsk->comm, task_pid_nr(tsk), address, (void *)regs->ip, (void *)regs->sp, error_code); print_vma_addr(KERN_CONT " in ", regs->ip); printk(KERN_CONT "\n"); + + show_opcodes((u8 *)regs->ip, loglvl); } static void -- cgit v1.2.3