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SubjectRe: [PATCH] x86_64: make traps on 'iret' be debuggable in user space
> thanks, applied. I suppose you have a testcase for this that we could try?

This should exit 0 and show "wait status 0xb7f", and does on i386.
On 2.6.24 it exits 1 and shows "wait status 0xb".

Note, on the current tree before [PATCH] x86_64: fix iret exception recovery
that I also posted today, this will instead produce pathological weirdness
probably with a quick crash or silent reboot, from running with the wrong GS.


#define _GNU_SOURCE
#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/wait.h>
#include <stddef.h>
#include <sys/ptrace.h>
#include <asm/ptrace.h>
#include <asm/user.h>

static pid_t child;

static void
cleanup (void)
if (child != 0)
kill (child, SIGKILL);

static void
handler_fail (int signo)
cleanup ();

signal (SIGABRT, SIG_DFL);
abort ();

int main (void)
long l;
int status, i;
pid_t pid;
long cs;

setbuf (stdout, NULL);
atexit (cleanup);
signal (SIGABRT, handler_fail);
signal (SIGINT, handler_fail);
signal (SIGALRM, handler_fail);
alarm (10);

signal (SIGUSR1, SIG_IGN);
signal (SIGUSR2, SIG_IGN);

child = fork ();
switch (child)
case -1:
assert_perror (errno);
assert (0);
case 0:
l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
assert (l == 0);
i = raise (SIGUSR1);
assert (i == 0);
assert (0);

pid = waitpid (child, &status, 0);
assert (pid == child);
assert (WIFSTOPPED (status));
assert (WSTOPSIG (status) == SIGUSR1);

cs = 0xFFFF;

l = ptrace (PTRACE_POKEUSER, child,
(void *) offsetof (struct user_regs_struct, cs), (void *) cs);
assert (l == 0);

l = ptrace (PTRACE_CONT, child, NULL, NULL);
assert (l == 0);

pid = waitpid (child, &status, 0);
assert (pid == child);

printf ("wait status %#x\n", status);

return WIFSTOPPED (status) ? 0 : 1;

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