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authorChuck Ebbert <76306.1226@compuserve.com>2006-03-23 02:59:48 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-23 07:38:05 -0800
commit635cf99a80f4ebee59d70eb64bb85ce829e4591f (patch)
tree6c204f34a959d62852812a85faefec5e5bd81b1f /arch
parentdb753bdfc24c31228996799d508ce3bf7cbe3b99 (diff)
[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 <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/ptrace.h> #include <sys/wait.h> #include <sys/mman.h> #include <asm/user.h> 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, &regs); 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 <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/kernel/entry.S4
1 files changed, 4 insertions, 0 deletions
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)