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Hurd: Avoid init-first.c miscompilation.

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Thomas Schwinge 2012-05-10 13:20:47 -07:00 committed by Roland McGrath
parent 5aa3a74a59
commit 18bad2ae1b
2 changed files with 38 additions and 14 deletions
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7
ChangeLog
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@ -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

35
sysdeps/mach/hurd/i386/init-first.c
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@ -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
@ -360,9 +375,11 @@ _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