From ecdeaac05f73c29eca92eecd55ad4fb8513c7771 Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Tue, 23 Sep 2003 12:06:48 +0000 Subject: 2003-09-23 Roland McGrath * 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. --- elf/Versions | 1 + elf/dl-load.c | 20 ++++++++++++++++++++ elf/dl-support.c | 19 +++++++++++++++++++ elf/rtld.c | 11 ++++++++++- 4 files changed, 50 insertions(+), 1 deletion(-) (limited to 'elf') 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. */ -- cgit v1.2.3