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authorThomas Schwinge <thomas@schwinge.name>2012-05-10 13:20:47 -0700
committerRoland McGrath <roland@hack.frob.com>2012-05-10 15:57:23 -0700
commit18bad2ae1bd1797782d51231d24f7b773c2bfff6 (patch)
tree02e995d107df7b992921eb0f9d189e4a074af166
parent5aa3a74a59916b489e9cf7c4dce9eb149e106c6c (diff)
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Hurd: Avoid init-first.c miscompilation.
-rw-r--r--ChangeLog7
-rw-r--r--sysdeps/mach/hurd/i386/init-first.c45
2 files changed, 38 insertions, 14 deletions
diff --git a/ChangeLog b/ChangeLog
index 9e747cddb4b..e3995421a6a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
2012-05-10 Thomas Schwinge <thomas@schwinge.name>
+ * sysdeps/mach/hurd/i386/init-first.c (init): Use
+ __builtin_frame_address instead of making assumptions about the
+ location of the return address relative to DATA. Force early load of
+ the return address.
+ (_dl_init_first, doinit1 in doinit in _hurd_stack_setup): Don't use
+ __builtin_frame_address.
+
dup3 for GNU Hurd.
* include/unistd.h: Declare __dup3 and use libc_hidden_proto on it.
* sysdeps/mach/hurd/dup3.c: New file, copy from dup2.c. Evolve it to
diff --git a/sysdeps/mach/hurd/i386/init-first.c b/sysdeps/mach/hurd/i386/init-first.c
index 4785e8dbec9..f4bf6246804 100644
--- a/sysdeps/mach/hurd/i386/init-first.c
+++ b/sysdeps/mach/hurd/i386/init-first.c
@@ -122,7 +122,7 @@ init1 (int argc, char *arg0, ...)
{
#ifndef SHARED
/* We may need to see our own phdrs, e.g. for TLS setup.
- Try the usual kludge to find the headers without help from
+ Try the usual kludge to find the headers without help from
the exec server. */
extern const void _start;
const ElfW(Ehdr) *const ehdr = &_start;
@@ -225,7 +225,7 @@ init (int *data)
#ifdef SHARED
/* And readjust the dynamic linker's idea of where the argument
- vector lives. */
+ vector lives. */
assert (_dl_argv == argv);
_dl_argv = (void *) (newsp + 1);
#endif
@@ -244,9 +244,16 @@ init (int *data)
/* Push the user code address on the top of the new stack. It will
be the return address for `init1'; we will jump there with NEWSP
as the stack pointer. */
- *--newsp = data[-1];
- ((void **) data)[-1] = switch_stacks;
- /* Force NEWSP into %ecx and &init1 into %eax, which are not restored
+ /* The following expression would typically be written as
+ ``__builtin_return_address (0)''. But, for example, GCC 4.4.6 doesn't
+ recognize that this read operation may alias the following write
+ operation, and thus is free to reorder the two, clobbering the
+ original return address. */
+ *--newsp = *((int *) __builtin_frame_address (0) + 1);
+ /* GCC 4.4.6 also wants us to force loading *NEWSP already here. */
+ asm volatile ("# %0" : : "X" (*newsp));
+ *((void **) __builtin_frame_address (0) + 1) = &switch_stacks;
+ /* Force NEWSP into %eax and &init1 into %ecx, which are not restored
by function return. */
asm volatile ("# a %0 c %1" : : "a" (newsp), "c" (&init1));
}
@@ -273,8 +280,15 @@ init (int *data)
/* The argument data is just above the stack frame we will unwind by
returning. Mutate our own return address to run the code below. */
- usercode = data[-1];
- data[-1] = (int) &call_init1;
+ /* The following expression would typically be written as
+ ``__builtin_return_address (0)''. But, for example, GCC 4.4.6 doesn't
+ recognize that this read operation may alias the following write
+ operation, and thus is free to reorder the two, clobbering the
+ original return address. */
+ usercode = *((int *) __builtin_frame_address (0) + 1);
+ /* GCC 4.4.6 also wants us to force loading USERCODE already here. */
+ asm volatile ("# %0" : : "X" (usercode));
+ *((void **) __builtin_frame_address (0) + 1) = &call_init1;
/* Force USERCODE into %eax and &init1 into %ecx, which are not
restored by function return. */
asm volatile ("# a %0 c %1" : : "a" (usercode), "c" (&init1));
@@ -322,11 +336,12 @@ first_init (void)
stack set up just as the user will see it, so it can switch stacks. */
void
-_dl_init_first (void)
+_dl_init_first (int argc, ...)
{
first_init ();
- init ((int *) __builtin_frame_address (0) + 2);
+ /* If we use ``__builtin_frame_address (0) + 2'' here, GCC gets confused. */
+ init (&argc);
}
#endif
@@ -360,15 +375,17 @@ _hurd_stack_setup (void)
void doinit (intptr_t *data)
{
/* This function gets called with the argument data at TOS. */
- void doinit1 (void)
+ void doinit1 (int argc, ...)
{
- init ((int *) __builtin_frame_address (0) + 2);
+ /* If we use ``__builtin_frame_address (0) + 2'' here, GCC gets
+ confused. */
+ init ((int *) &argc);
}
/* Push the user return address after the argument data, and then
- jump to `doinit1' (above), so it is as if __libc_init_first's
- caller had called `doinit1' with the argument data already on the
- stack. */
+ jump to `doinit1' (above), so it is as if __libc_init_first's
+ caller had called `doinit1' with the argument data already on the
+ stack. */
*--data = caller;
asm volatile ("movl %0, %%esp\n" /* Switch to new outermost stack. */
"movl $0, %%ebp\n" /* Clear outermost frame pointer. */