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-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
-rw-r--r--sysdeps/generic/dl-execstack.c32
-rw-r--r--sysdeps/generic/ldsodefs.h13
-rw-r--r--sysdeps/unix/sysv/linux/dl-execstack.c115
7 files changed, 210 insertions, 1 deletions
diff --git a/elf/Versions b/elf/Versions
index 7b0799958b..d3ed536d0f 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 249ef84639..0b6e96f998 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 8c58b2ba69..448f4c6848 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 8f9fc7c063..c17f621cc9 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. */
diff --git a/sysdeps/generic/dl-execstack.c b/sysdeps/generic/dl-execstack.c
new file mode 100644
index 0000000000..04f87cf519
--- /dev/null
+++ b/sysdeps/generic/dl-execstack.c
@@ -0,0 +1,32 @@
+/* Stack executability handling for GNU dynamic linker. Stub version.
+ Copyright (C) 2003 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <ldsodefs.h>
+#include <errno.h>
+
+/* There is no portable way to know the bounds of the initial thread's stack
+ so as to mprotect it. */
+
+int
+internal_function
+_dl_make_stack_executable (void)
+{
+ return ENOSYS;
+}
+rtld_hidden_def (_dl_make_stack_executable)
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 58dfc15ca3..afb192925a 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -355,6 +355,14 @@ struct rtld_global
EXTERN void (*_dl_rtld_unlock_recursive) (void *);
#endif
+ /* Prevailing state of the stack, PF_X indicating it's executable. */
+ EXTERN ElfW(Word) _dl_stack_flags;
+
+ /* 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. */
+ EXTERN int (*_dl_make_stack_executable_hook) (void) internal_function;
+
/* Keep the conditional TLS members at the end so the layout of the
structure used by !USE_TLS code matches the prefix of the layout in
the USE_TLS rtld. Note that `struct link_map' is conditionally
@@ -438,6 +446,11 @@ extern void **_dl_initial_error_catch_tsd (void) __attribute__ ((const))
attribute_hidden;
#endif
+/* This is the initial value of GL(dl_make_stack_executable_hook).
+ A threads library can change it. */
+extern int _dl_make_stack_executable (void) internal_function;
+rtld_hidden_proto (_dl_make_stack_executable)
+
/* Parameters passed to the dynamic linker. */
extern int _dl_argc attribute_hidden;
extern char **_dl_argv;
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
new file mode 100644
index 0000000000..42300b0f4d
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -0,0 +1,115 @@
+/* Stack executability handling for GNU dynamic linker. Linux version.
+ Copyright (C) 2003 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <ldsodefs.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stackinfo.h>
+
+extern void *__libc_stack_end;
+
+int
+internal_function
+_dl_make_stack_executable (void)
+{
+ if (__libc_stack_end == 0)
+ /* XXX for a DT_NEEDED library that requires the change,
+ this is not initialized yet!
+ */
+ return ENOSYS;
+
+#if _STACK_GROWS_DOWN
+ /* This gives us the highest page that needs to be changed. */
+ uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
+
+ /* There is always a hole in the address space below the bottom of the
+ stack. So when we make an mprotect call that starts below the bottom
+ of the stack, it will include the hole and fail with ENOMEM.
+
+ We start with a random guess at how deep the stack might have gotten
+ so as to have extended the GROWSDOWN mapping to lower pages. */
+
+ size_t size = GL(dl_pagesize) * 8;
+ page = page + GL(dl_pagesize) - size;
+ while (1)
+ {
+ if (__mprotect ((void *) page, size,
+ PROT_READ|PROT_WRITE|PROT_EXEC) == 0)
+ /* We got this chunk changed; loop to do another chunk below. */
+ page -= size;
+ else
+ {
+ if (errno != ENOMEM) /* Unexpected failure mode. */
+ return errno;
+
+ if (size == GL(dl_pagesize))
+ /* We just tried to mprotect the top hole page and failed.
+ We are done. */
+ break;
+
+ /* Our mprotect call failed because it started below the lowest
+ stack page. Try again on just the top half of that region. */
+ size /= 2;
+ page += size;
+ }
+ }
+
+#elif _STACK_GROWS_UP
+
+ /* This gives us the lowest page that needs to be changed. */
+ uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
+
+ /* There is always a hole in the address space above the top of the
+ stack. So when we make an mprotect call that spans past the top
+ of the stack, it will include the hole and fail with ENOMEM.
+
+ We start with a random guess at how deep the stack might have gotten
+ so as to have extended the GROWSUP mapping to higher pages. */
+
+ size_t size = GL(dl_pagesize) * 8;
+ while (1)
+ {
+ if (__mprotect ((void *) page, size,
+ PROT_READ|PROT_WRITE|PROT_EXEC) == 0)
+ /* We got this chunk changed; loop to do another chunk below. */
+ page += size;
+ else
+ {
+ if (errno != ENOMEM) /* Unexpected failure mode. */
+ return errno;
+
+ if (size == GL(dl_pagesize))
+ /* We just tried to mprotect the lowest hole page and failed.
+ We are done. */
+ break;
+
+ /* Our mprotect call failed because it extended past the highest
+ stack page. Try again on just the bottom half of that region. */
+ size /= 2;
+ }
+ }
+
+#else
+# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
+#endif
+
+ return 0;
+}
+rtld_hidden_def (_dl_make_stack_executable)