This drops all of the return address rewriting kludges. The only
remaining hack is the jump out of a call stack while adjusting the
stack pointer.
Signed-off-by: Sergey Bugaev <buga...@gmail.com>
---
sysdeps/mach/hurd/dl-sysdep.c | 4 +-
sysdeps/mach/hurd/dl-sysdep.h | 4 +
sysdeps/mach/hurd/i386/dl-machine.h | 7 -
sysdeps/mach/hurd/i386/init-first.c | 193 +++++++++-------------------
4 files changed, 68 insertions(+), 140 deletions(-)
delete mode 100644 sysdeps/mach/hurd/i386/dl-machine.h
diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c
index 9e591708..a2115f6e 100644
--- a/sysdeps/mach/hurd/dl-sysdep.c
+++ b/sysdeps/mach/hurd/dl-sysdep.c
@@ -207,6 +207,8 @@ _dl_sysdep_start (void **start_argptr,
}
}
+ _dl_init_first (argdata);
+
{
extern void _dl_start_user (void);
/* Unwind the stack to ARGDATA and simulate a return from _dl_start
@@ -793,7 +795,7 @@ _dl_show_auxv (void)
void weak_function
-_dl_init_first (int argc, ...)
+_dl_init_first (void *p)
{
/* This no-op definition only gets used if libc is not linked in. */
}
diff --git a/sysdeps/mach/hurd/dl-sysdep.h b/sysdeps/mach/hurd/dl-sysdep.h
index 3baf56b7..fa35a71c 100644
--- a/sysdeps/mach/hurd/dl-sysdep.h
+++ b/sysdeps/mach/hurd/dl-sysdep.h
@@ -22,3 +22,7 @@
(open, mmap, etc). */
#define RTLD_PRIVATE_ERRNO 0
+
+#ifndef __ASSEMBLER__
+void _dl_init_first (void *data);
+#endif
diff --git a/sysdeps/mach/hurd/i386/dl-machine.h
b/sysdeps/mach/hurd/i386/dl-machine.h
deleted file mode 100644
index 40f2ff29..00000000
--- a/sysdeps/mach/hurd/i386/dl-machine.h
+++ /dev/null
@@ -1,7 +0,0 @@
-/* Dynamic linker magic for Hurd/i386.
- This file just gets us a call to _dl_first_init inserted
- into the asm in sysdeps/i386/dl-machine.h that contains
- the initializer code. */
-
-#define RTLD_START_SPECIAL_INIT "call _dl_init_first@PLT; movl (%esp), %edx"
-#include_next "dl-machine.h"
diff --git a/sysdeps/mach/hurd/i386/init-first.c
b/sysdeps/mach/hurd/i386/init-first.c
index a558da16..05424563 100644
--- a/sysdeps/mach/hurd/i386/init-first.c
+++ b/sysdeps/mach/hurd/i386/init-first.c
@@ -22,10 +22,9 @@
#include <unistd.h>
#include <string.h>
#include <sysdep.h>
+#include <dl-sysdep.h>
#include <set-hooks.h>
#include "hurdstartup.h"
-#include "hurdmalloc.h" /* XXX */
-#include "../locale/localeinfo.h"
#include <ldsodefs.h>
#include <fpu_control.h>
@@ -87,68 +86,13 @@ posixland_init (int argc, char **argv, char **envp)
__init_misc (argc, argv, envp);
}
-
static void
-init1 (int argc, char *arg0, ...)
+init (void **data)
{
- char **argv = &arg0;
- char **envp = &argv[argc + 1];
- struct hurd_startup_data *d;
-
- while (*envp)
- ++envp;
- d = (void *) ++envp;
-
- if ((void *) d == argv[0])
- {
- /* No Hurd data block to process. */
-#ifndef SHARED
- __libc_enable_secure = 0;
-#endif
- return;
- }
-
-#ifndef SHARED
- __libc_enable_secure = d->flags & EXEC_SECURE;
-#endif
-
- _hurd_init_dtable = d->dtable;
- _hurd_init_dtablesize = d->dtablesize;
-
- {
- /* Check if the stack we are now on is different from
- the one described by _hurd_stack_{base,size}. */
-
- char dummy;
- const vm_address_t newsp = (vm_address_t) &dummy;
-
- if (d->stack_size != 0 && (newsp < d->stack_base
- || newsp - d->stack_base > d->stack_size))
- /* The new stack pointer does not intersect with the
- stack the exec server set up for us, so free that stack. */
- __vm_deallocate (__mach_task_self (), d->stack_base, d->stack_size);
- }
-
- if (d->portarray || d->intarray)
- /* Initialize library data structures, start signal processing, etc. */
- _hurd_init (d->flags, argv,
- d->portarray, d->portarraysize,
- d->intarray, d->intarraysize);
-}
-
-
-static inline void
-init (int *data)
-{
- /* data is the address of the argc parameter to _dl_init_first or
- doinit1 in _hurd_stack_setup, so the array subscripts are
- undefined. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (10, "-Warray-bounds");
-
- int argc = *data;
+ int argc = (int) *data;
char **argv = (void *) (data + 1);
char **envp = &argv[argc + 1];
+ struct hurd_startup_data *d;
/* Since the cthreads initialization code uses malloc, and the
malloc initialization code needs to get at the environment, make
@@ -157,18 +101,18 @@ init (int *data)
stored. */
__environ = envp;
-#ifndef SHARED
- struct hurd_startup_data *d;
-
while (*envp)
++envp;
d = (void *) ++envp;
+#ifndef SHARED
+
/* If we are the bootstrap task started by the kernel,
then after the environment pointers there is no Hurd
data block; the argument strings start there. */
if ((void *) d == argv[0] || d->phdr == 0)
{
+ __libc_enable_secure = 0;
/* With a new enough linker (binutils-2.23 or better),
the magic __ehdr_start symbol will be available and
__libc_start_main will have done this that way already. */
@@ -186,51 +130,25 @@ init (int *data)
}
else
{
+ __libc_enable_secure = d->flags & EXEC_SECURE;
_dl_phdr = (ElfW(Phdr) *) d->phdr;
_dl_phnum = d->phdrsz / sizeof (ElfW(Phdr));
assert (d->phdrsz % sizeof (ElfW(Phdr)) == 0);
}
#endif
- /* Call `init1' (above) with the user code as the return address, and the
- argument data immediately above that on the stack. */
-
- void *usercode, **ret_address;
-
- void call_init1 (void);
-
- /* The argument data is just above the stack frame we will unwind by
- returning. Mutate our own return address to run the code below. */
- /* 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. */
- ret_address = (void **) __builtin_frame_address (0) + 1;
- usercode = *ret_address;
- /* GCC 4.4.6 also wants us to force loading USERCODE already here. */
- asm volatile ("# %0" : : "X" (usercode));
- *ret_address = &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));
-
- DIAG_POP_NEEDS_COMMENT; /* -Warray-bounds. */
-}
-
-/* These bits of inline assembler used to be located inside `init'.
- However they were optimized away by gcc 2.95. */
+ if ((void *) d == argv[0])
+ return;
-/* The return address of `init' above, was redirected to here, so at
- this point our stack is unwound and callers' registers restored.
- Only %ecx and %eax are call-clobbered and thus still have the
- values we set just above. We have stashed in %eax the user code
- return address. Push it on the top of the stack so it acts as
- init1's return address, and then jump there. */
-asm ("call_init1:\n"
- " push %eax\n"
- " jmp *%ecx\n");
+ _hurd_init_dtable = d->dtable;
+ _hurd_init_dtablesize = d->dtablesize;
+ if (d->portarray || d->intarray)
+ /* Initialize library data structures, start signal processing, etc. */
+ _hurd_init (d->flags, argv,
+ d->portarray, d->portarraysize,
+ d->intarray, d->intarraysize);
+}
/* Do the first essential initializations that must precede all else. */
static inline void
@@ -242,7 +160,7 @@ first_init (void)
#ifndef SHARED
/* In the static case, we need to set up TLS early so that the stack
protection guard can be read at gs:0x14 by the gcc-generated snippets. */
- _hurd_tls_init(&__init1_tcbhead);
+ _hurd_tls_init (&__init1_tcbhead);
asm ("movw %%gs,%w0" : "=m" (__init1_desc));
#endif
@@ -252,21 +170,15 @@ first_init (void)
#ifdef SHARED
/* This function is called specially by the dynamic linker to do early
initialization of the shared C library before normal initializers
- expecting a Posixoid environment can run. It gets called with the
- stack set up just as the user will see it, so it can switch stacks. */
+ expecting a Posixoid environment can run. */
void
-_dl_init_first (int argc, ...)
+_dl_init_first (void *data)
{
first_init ();
-
- /* If we use ``__builtin_frame_address (0) + 2'' here, GCC gets confused. */
- init (&argc);
+ init (data);
}
-#endif
-
-#ifdef SHARED
/* The regular posixland initialization is what goes into libc's
normal initializer. */
/* NOTE! The linker notices the magical name `_init' and sets the DT_INIT
@@ -280,9 +192,10 @@ __libc_init_first (int argc, char **argv, char **envp)
{
/* Everything was done in the shared library initializer, _init. */
}
-#else
-strong_alias (posixland_init, __libc_init_first);
+#else /* SHARED */
+
+strong_alias (posixland_init, __libc_init_first);
/* XXX This is all a crock and I am not happy with it.
This poorly-named function is called by static-start.S,
@@ -291,32 +204,48 @@ void
inhibit_stack_protector
_hurd_stack_setup (void)
{
- intptr_t caller = (intptr_t) __builtin_return_address (0);
+ /* This is the very first C code that runs in a statically linked
+ executable -- calling this function is the first thing that _start in
+ static-start.S does. Once this function returns, the unusual way that it
+ does (see below), _start jumps to _start1, the regular start-up code.
+
+ _start1 expects the arguments, environment, and a Hurd data block to be
+ located at the top of the stack. The data may already be located there,
+ or we may need to receive it from the exec server. */
+ void *caller = __builtin_extract_return_addr (__builtin_return_address (0));
+ /* If the arguments and environment are already located on the stack, this is
+ where they are, just above our call frame. Note that this may not be a
+ valid pointer in case we're supposed to receive the arguments from the
exec
+ server, so we can not dereference it yet. */
+ void **p = (void **) __builtin_frame_address (0) + 2;
+
+ /* Init the essential things. */
+ first_init ();
void doinit (intptr_t *data)
{
- /* This function gets called with the argument data at TOS. */
- void doinit1 (int argc, ...)
- {
- /* 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. */
- *--data = caller;
+ init ((void **) data);
asm volatile ("movl %0, %%esp\n" /* Switch to new outermost stack. */
- "movl $0, %%ebp\n" /* Clear outermost frame pointer. */
- "jmp *%1" : : "r" (data), "r" (&doinit1));
- /* NOTREACHED */
+ "xorl %%ebp, %%ebp\n" /* Clear outermost frame pointer. */
+ "jmp *%1" : : "r" (data), "r" (caller));
+ __builtin_unreachable ();
}
- first_init ();
-
- _hurd_startup ((void **) __builtin_frame_address (0) + 2, &doinit);
+ /* _hurd_startup () will attempt to receive the data block from the exec
+ server; or if that is not possible, will take the data from the pointer
+ we pass it here. The important point here is that the data
+ _hurd_startup () collects may be allocated in its stack frame (with
+ alloca), which is why _hurd_startup () does not return the normal way.
+ Instead, it invokes a callback (which is not expected to return normally
+ either).
+
+ Our callback not only passes the data pointer to init (), but also jumps
+ out of the call stack back to our caller (i.e. to _start1), while setting
+ the stack pointer to the data (which is somewhere on the current stack
+ anyway). This way, _start1 find the data on the top of the stack, just as
+ it expects to. */
+ _hurd_startup (p, &doinit);
+ __builtin_unreachable ();
}
#endif
--
2.39.2
