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authorRoland McGrath <roland@gnu.org>2003-09-23 12:06:48 +0000
committerRoland McGrath <roland@gnu.org>2003-09-23 12:06:48 +0000
commitecdeaac05f73c29eca92eecd55ad4fb8513c7771 (patch)
treee0cc585c839b68bc3e698f09d51c1f0b78c3cbef /elf
parent1deb5779e249255d4247529facd65025c1787cd1 (diff)
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2003-09-23 Roland McGrath <roland@redhat.com>
* sysdeps/generic/ldsodefs.h (struct rtld_global): Add _dl_stack_flags and _dl_make_stack_executable_hook. Declare _dl_make_stack_executable. * elf/rtld.c (_rtld_global): Add initializer for _dl_stack_flags. (dl_main): Reset _dl_stack_flags according to PT_GNU_STACK phdr. Initialize _dl_make_stack_executable_hook. * elf/dl-support.c: Define those new variables. (_dl_non_dynamic_init): Scan phdrs for PT_GNU_STACK. (_dl_phdr): Fix type. * elf/dl-load.c (_dl_map_object_from_fd): Grok PT_GNU_STACK phdr and enable execute permission for the stack if necessary. * sysdeps/generic/dl-execstack.c: New file. * elf/Makefile (dl-routines): Add it. * elf/Versions (ld: GLIBC_PRIVATE): Add _dl_make_stack_executable. * sysdeps/unix/sysv/linux/dl-execstack.c: New file.
Diffstat (limited to 'elf')
-rw-r--r--elf/Versions1
-rw-r--r--elf/dl-load.c20
-rw-r--r--elf/dl-support.c19
-rw-r--r--elf/rtld.c11
4 files changed, 50 insertions, 1 deletions
diff --git a/elf/Versions b/elf/Versions
index 7b07999..d3ed536 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -54,5 +54,6 @@ ld {
_rtld_global; _dl_tls_symaddr; _dl_allocate_tls; _dl_deallocate_tls;
_dl_get_tls_static_info; _dl_allocate_tls_init;
_dl_get_origin; _dl_tls_setup; _dl_rtld_di_serinfo;
+ _dl_make_stack_executable;
}
}
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 249ef84..0b6e96f 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -904,6 +904,9 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
}
}
+ /* Presumed absent PT_GNU_STACK. */
+ uint_fast16_t stack_flags = PF_R|PF_W|PF_X;
+
{
/* Scan the program header table, collecting its load commands. */
struct loadcmd
@@ -1058,6 +1061,10 @@ cannot allocate TLS data structures for initial thread");
errstring = N_("cannot handle TLS data");
goto call_lose;
break;
+
+ case PT_GNU_STACK:
+ stack_flags = ph->p_flags;
+ break;
}
if (__builtin_expect (nloadcmds == 0, 0))
@@ -1334,6 +1341,19 @@ cannot allocate TLS data structures for initial thread");
l->l_dev = st.st_dev;
l->l_ino = st.st_ino;
+ if (__builtin_expect ((stack_flags &~ GL(dl_stack_flags)) & PF_X, 0))
+ {
+ /* The stack is presently not executable, but this module
+ requires that it be executable. */
+ errval = (*GL(dl_make_stack_executable_hook)) ();
+ if (errval)
+ {
+ errstring = N_("\
+cannot enable executable stack as shared object requires");
+ goto call_lose;
+ }
+ }
+
/* When we profile the SONAME might be needed for something else but
loading. Add it right away. */
if (__builtin_expect (GL(dl_profile) != NULL, 0)
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 8c58b2b..448f4c6 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -129,6 +129,16 @@ ElfW(Phdr) *_dl_phdr;
size_t _dl_phnum;
unsigned long int _dl_hwcap __attribute__ ((nocommon));
+/* Prevailing state of the stack, PF_X indicating it's executable. */
+ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
+
+/* If loading a shared object requires that we make the stack executable
+ when it was not, we do it by calling this function.
+ It returns an errno code or zero on success. */
+int (*_dl_make_stack_executable_hook) (void) internal_function
+ = _dl_make_stack_executable;
+
+
#ifdef NEED_DL_SYSINFO
/* Needed for improved syscall handling on at least x86/Linux. */
uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
@@ -264,6 +274,15 @@ _dl_non_dynamic_init (void)
/* Now determine the length of the platform string. */
if (_dl_platform != NULL)
_dl_platformlen = strlen (_dl_platform);
+
+ /* Scan for a program header telling us the stack is nonexecutable. */
+ if (_dl_phdr != NULL)
+ for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
+ if (_dl_phdr[i].p_type == PT_GNU_STACK)
+ {
+ _dl_stack_flags = _dl_phdr[i].p_flags;
+ break;
+ }
}
diff --git a/elf/rtld.c b/elf/rtld.c
index 8f9fc7c..c17f621 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -98,6 +98,8 @@ struct rtld_global _rtld_global =
._dl_fpu_control = _FPU_DEFAULT,
._dl_correct_cache_id = _DL_CACHE_DEFAULT_ID,
._dl_hwcap_mask = HWCAP_IMPORTANT,
+ /* Default presumption without further information is executable stack. */
+ ._dl_stack_flags = PF_R|PF_W|PF_X,
#ifdef _LIBC_REENTRANT
._dl_load_lock = _RTLD_LOCK_RECURSIVE_INITIALIZER
#endif
@@ -249,7 +251,7 @@ _dl_start_final (void *arg, struct dl_start_final_info *info)
file access. It will call `dl_main' (below) to do all the real work
of the dynamic linker, and then unwind our frame and run the user
entry point on the same stack we entered on. */
- start_addr = _dl_sysdep_start (arg, &dl_main);
+ start_addr = _dl_sysdep_start (arg, &dl_main);
#ifndef HP_TIMING_NONAVAIL
if (HP_TIMING_AVAIL)
@@ -903,6 +905,9 @@ of this helper program; chances are you did not intend to run this program.\n\
}
break;
#endif
+ case PT_GNU_STACK:
+ GL(dl_stack_flags) = ph->p_flags;
+ break;
}
#ifdef USE_TLS
/* Adjust the address of the TLS initialization image in case
@@ -949,6 +954,10 @@ of this helper program; chances are you did not intend to run this program.\n\
_exit (has_interp ? 0 : 2);
}
+ /* The explicit initialization here is cheaper than processing the reloc
+ in the _rtld_local definition's initializer. */
+ GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
+
if (! rtld_is_main)
/* Initialize the data structures for the search paths for shared
objects. */