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| author | Jason Wessel <jason.wessel@windriver.com> | 2007-07-02 15:53:44 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-08-04 09:10:25 -0700 |
| commit | bf35c3779ab61aa93e912679d6c30a8b689e443e (patch) | |
| tree | ab099065ce218287602ce255814812143286ab9a | |
| parent | ed9ee0878e14d15d76ee792cac38def9d34f7f68 (diff) | |
| download | linux-stable-bf35c3779ab61aa93e912679d6c30a8b689e443e.tar.gz linux-stable-bf35c3779ab61aa93e912679d6c30a8b689e443e.tar.bz2 linux-stable-bf35c3779ab61aa93e912679d6c30a8b689e443e.zip | |
i386: fix infinite loop with singlestep int80 syscalls
The commit 635cf99a80f4ebee59d70eb64bb85ce829e4591f introduced a
regression. Executing a ptrace single step after certain int80
accesses will infinitely loop and never advance the PC.
The TIF_SINGLESTEP check should be done on the return from the syscall
and not before it.
The new test case is below:
/* 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>
#include <string.h>
static int child, status;
static struct user_regs_struct regs;
static void do_child()
{
char str[80] = "child: int80 test\n";
ptrace(PTRACE_TRACEME, 0, 0, 0);
kill(getpid(), SIGUSR1);
write(fileno(stdout),str,strlen(str));
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 @ %08lx, expected %08lx %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: Jason Wessel <jason.wessel@windriver.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/i386/kernel/entry.S | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index 18bddcb8e9e8..cb1f16c5a045 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -371,10 +371,6 @@ ENTRY(system_call) CFI_ADJUST_CFA_OFFSET 4 SAVE_ALL GET_THREAD_INFO(%ebp) - testl $TF_MASK,PT_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) @@ -389,6 +385,10 @@ syscall_exit: # setting need_resched or sigpending # between sampling and the iret TRACE_IRQS_OFF + testl $TF_MASK,PT_EFLAGS(%esp) # If tracing set singlestep flag on exit + jz no_singlestep + orl $_TIF_SINGLESTEP,TI_flags(%ebp) +no_singlestep: movl TI_flags(%ebp), %ecx testw $_TIF_ALLWORK_MASK, %cx # current->work jne syscall_exit_work |