From 635cf99a80f4ebee59d70eb64bb85ce829e4591f Mon Sep 17 00:00:00 2001 From: Chuck Ebbert <76306.1226@compuserve.com> Date: Thu, 23 Mar 2006 02:59:48 -0800 Subject: [PATCH] [PATCH] i386: fix singlestep through an int80 syscall Using PTRACE_SINGLESTEP on a child that does an int80 syscall misses the SIGTRAP that should be delivered upon syscall exit. Fix that by setting TIF_SINGLESTEP when entering the kernel via int80 with TF set. /* Test whether singlestep through an int80 syscall works. */ #define _GNU_SOURCE #include #include #include #include #include #include #include static int child, status; static struct user_regs_struct regs; static void do_child() { ptrace(PTRACE_TRACEME, 0, 0, 0); kill(getpid(), SIGUSR1); asm ("int $0x80" : : "a" (20)); /* getpid */ } static void do_parent() { unsigned long eip, expected = 0; again: waitpid(child, &status, 0); if (WIFEXITED(status) || WIFSIGNALED(status)) return; if (WIFSTOPPED(status)) { ptrace(PTRACE_GETREGS, child, 0, ®s); eip = regs.eip; if (expected) fprintf(stderr, "child stop @ %08x, expected %08x %s\n", eip, expected, eip == expected ? "" : " <== ERROR"); if (*(unsigned short *)eip == 0x80cd) { fprintf(stderr, "int 0x80 at %08x\n", (unsigned int)eip); expected = eip + 2; } else expected = 0; ptrace(PTRACE_SINGLESTEP, child, NULL, NULL); } goto again; } int main(int argc, char * const argv[]) { child = fork(); if (child) do_parent(); else do_child(); return 0; } Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/entry.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index 4d704724b2f5..cfc683f153b9 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -226,6 +226,10 @@ ENTRY(system_call) pushl %eax # save orig_eax SAVE_ALL GET_THREAD_INFO(%ebp) + testl $TF_MASK,EFLAGS(%esp) + jz no_singlestep + orl $_TIF_SINGLESTEP,TI_flags(%ebp) +no_singlestep: # system call tracing in operation / emulation /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */ testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp) -- 2.20.1