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Re: [patch] Fix CLONE_VM vs. TLS [Re: Is CLONE_VM really needed in gdbserver?]
- From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- To: gdb-patches at sourceware dot org
- Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, GDB <gdb at sourceware dot org>
- Date: Fri, 29 Jan 2010 02:26:25 +0100
- Subject: Re: [patch] Fix CLONE_VM vs. TLS [Re: Is CLONE_VM really needed in gdbserver?]
- References: <6dc9ffc81001261551j6221db6v88e96713d6dd9497@mail.gmail.com> <20100127000821.GA29862@caradoc.them.org> <20100127221236.GA4746@host0.dyn.jankratochvil.net> <20100128170103.GA9936@caradoc.them.org>
On Thu, 28 Jan 2010 18:01:07 +0100, Daniel Jacobowitz wrote:
> I don't recommend testing HAVE_FORK; uClibc may provide a dummy fork
> that returns ENOSYS. There's a HAS_NOMMU in linux-low.c that should work.
OK, copied the current usage of HAS_NOMMU.
> For the test case, what defines UCLINUX?
Seen in some Googled source but it is true nobody sets it.
CodeSourcery arm-2009q3-66-arm-uclinuxeabi-i686-pc-linux-gnu.tar.bz2 gcc sets
__uClinux__ although gdb/gdbserver/linux-low.c depends on __UCLIBC__.
CLONE_VM is a kernel feature so gcc should be more appropriate but maybe it
does not matter.
Thanks,
Jan
gdb/gdbserver/
2010-01-29 Jan Kratochvil <jan.kratochvil@redhat.com>
PR libc/11214:
* linux-low.c (linux_tracefork_child) [!(__UCLIBC__ && HAS_NOMMU)]: New.
(linux_test_for_tracefork): Move `stack' into [__UCLIBC__ && HAS_NOMMU].
(linux_test_for_tracefork) [!(__UCLIBC__ && HAS_NOMMU)]: New.
gdb/testsuite/
2010-01-29 Jan Kratochvil <jan.kratochvil@redhat.com>
PR libc/11214:
* gdb.threads/current-lwp-dead.c (fn, main): Move CLONE_VM into
[__uClinux__].
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -2586,6 +2586,14 @@ linux_tracefork_child (void *arg)
{
ptrace (PTRACE_TRACEME, 0, 0, 0);
kill (getpid (), SIGSTOP);
+
+#if !(defined(__UCLIBC__) && defined(HAS_NOMMU))
+
+ if (fork () == 0)
+ linux_tracefork_grandchild (NULL);
+
+#else /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
+
#ifdef __ia64__
__clone2 (linux_tracefork_grandchild, arg, STACK_SIZE,
CLONE_VM | SIGCHLD, NULL);
@@ -2593,6 +2601,9 @@ linux_tracefork_child (void *arg)
clone (linux_tracefork_grandchild, arg + STACK_SIZE,
CLONE_VM | SIGCHLD, NULL);
#endif
+
+#endif /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
+
_exit (0);
}
@@ -2605,18 +2616,31 @@ linux_test_for_tracefork (void)
{
int child_pid, ret, status;
long second_pid;
+#if defined(__UCLIBC__) && defined(HAS_NOMMU)
char *stack = xmalloc (STACK_SIZE * 4);
+#endif /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
linux_supports_tracefork_flag = 0;
+#if !(defined(__UCLIBC__) && defined(HAS_NOMMU))
+
+ child_pid = fork ();
+ if (child_pid == 0)
+ linux_tracefork_child (NULL);
+
+#else /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
+
/* Use CLONE_VM instead of fork, to support uClinux (no MMU). */
#ifdef __ia64__
child_pid = __clone2 (linux_tracefork_child, stack, STACK_SIZE,
CLONE_VM | SIGCHLD, stack + STACK_SIZE * 2);
-#else
+#else /* !__ia64__ */
child_pid = clone (linux_tracefork_child, stack + STACK_SIZE,
CLONE_VM | SIGCHLD, stack + STACK_SIZE * 2);
-#endif
+#endif /* !__ia64__ */
+
+#endif /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
+
if (child_pid == -1)
perror_with_name ("clone");
@@ -2685,7 +2709,9 @@ linux_test_for_tracefork (void)
}
while (WIFSTOPPED (status));
+#if defined(__UCLIBC__) && defined(HAS_NOMMU)
free (stack);
+#endif /* defined(__UCLIBC__) && defined(HAS_NOMMU) */
}
--- a/gdb/testsuite/gdb.threads/current-lwp-dead.c
+++ b/gdb/testsuite/gdb.threads/current-lwp-dead.c
@@ -51,8 +51,11 @@ fn (void *unused)
stack = malloc (STACK_SIZE);
assert (stack != NULL);
- new_pid = clone (fn_return, stack + STACK_SIZE, CLONE_FILES | CLONE_VM, NULL,
- NULL, NULL, NULL);
+ new_pid = clone (fn_return, stack + STACK_SIZE, CLONE_FILES
+#ifdef __uClinux__
+ | CLONE_VM
+#endif /* __uClinux__ */
+ , NULL, NULL, NULL, NULL);
assert (new_pid > 0);
return 0;
@@ -67,8 +70,11 @@ main (int argc, char **argv)
stack = malloc (STACK_SIZE);
assert (stack != NULL);
- new_pid = clone (fn, stack + STACK_SIZE, CLONE_FILES | CLONE_VM, NULL, NULL,
- NULL, NULL);
+ new_pid = clone (fn, stack + STACK_SIZE, CLONE_FILES
+#ifdef __uClinux__
+ | CLONE_VM
+#endif /* __uClinux__ */
+ , NULL, NULL, NULL, NULL);
assert (new_pid > 0);
return 0;