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6c57d32048
Add _SC_MINSIGSTKSZ for the minimum signal stack size derived from AT_MINSIGSTKSZ, which is the minimum number of bytes of free stack space required in order to gurantee successful, non-nested handling of a single signal whose handler is an empty function, and _SC_SIGSTKSZ which is the suggested minimum number of bytes of stack space required for a signal stack. If AT_MINSIGSTKSZ isn't available, sysconf (_SC_MINSIGSTKSZ) returns MINSIGSTKSZ. On Linux/x86 with XSAVE, the signal frame used by kernel is composed of the following areas and laid out as: ------------------------------ | alignment padding | ------------------------------ | xsave buffer | ------------------------------ | fsave header (32-bit only) | ------------------------------ | siginfo + ucontext | ------------------------------ Compute AT_MINSIGSTKSZ value as size of xsave buffer + size of fsave header (32-bit only) + size of siginfo and ucontext + alignment padding. If _SC_SIGSTKSZ_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are redefined as /* Default stack size for a signal handler: sysconf (SC_SIGSTKSZ). */ # undef SIGSTKSZ # define SIGSTKSZ sysconf (_SC_SIGSTKSZ) /* Minimum stack size for a signal handler: SIGSTKSZ. */ # undef MINSIGSTKSZ # define MINSIGSTKSZ SIGSTKSZ Compilation will fail if the source assumes constant MINSIGSTKSZ or SIGSTKSZ. The reason for not simply increasing the kernel's MINSIGSTKSZ #define (apart from the fact that it is rarely used, due to glibc's shadowing definitions) was that userspace binaries will have baked in the old value of the constant and may be making assumptions about it. For example, the type (char [MINSIGSTKSZ]) changes if this #define changes. This could be a problem if an newly built library tries to memcpy() or dump such an object defined by and old binary. Bounds-checking and the stack sizes passed to things like sigaltstack() and makecontext() could similarly go wrong.
370 lines
11 KiB
C
370 lines
11 KiB
C
/* Operating system support for run-time dynamic linker. Generic Unix version.
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Copyright (C) 1995-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* We conditionalize the whole of this file rather than simply eliding it
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from the static build, because other sysdeps/ versions of this file
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might define things needed by a static build. */
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#ifdef SHARED
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#include <assert.h>
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#include <elf.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <libintl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/mman.h>
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#include <ldsodefs.h>
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#include <_itoa.h>
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#include <fpu_control.h>
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#include <entry.h>
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#include <dl-machine.h>
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#include <dl-procinfo.h>
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#include <dl-osinfo.h>
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#include <libc-internal.h>
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#include <tls.h>
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#include <dl-tunables.h>
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#include <dl-auxv.h>
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extern char **_environ attribute_hidden;
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extern char _end[] attribute_hidden;
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/* Protect SUID program against misuse of file descriptors. */
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extern void __libc_check_standard_fds (void);
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#ifdef NEED_DL_BASE_ADDR
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ElfW(Addr) _dl_base_addr;
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#endif
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int __libc_enable_secure attribute_relro = 0;
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rtld_hidden_data_def (__libc_enable_secure)
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/* This variable contains the lowest stack address ever used. */
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void *__libc_stack_end attribute_relro = NULL;
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rtld_hidden_data_def(__libc_stack_end)
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void *_dl_random attribute_relro = NULL;
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#ifndef DL_FIND_ARG_COMPONENTS
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# define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
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do { \
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void **_tmp; \
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(argc) = *(long int *) cookie; \
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(argv) = (char **) ((long int *) cookie + 1); \
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(envp) = (argv) + (argc) + 1; \
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for (_tmp = (void **) (envp); *_tmp; ++_tmp) \
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continue; \
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(auxp) = (void *) ++_tmp; \
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} while (0)
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#endif
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#ifndef DL_STACK_END
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# define DL_STACK_END(cookie) ((void *) (cookie))
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#endif
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ElfW(Addr)
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_dl_sysdep_start (void **start_argptr,
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void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
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ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
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{
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const ElfW(Phdr) *phdr = NULL;
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ElfW(Word) phnum = 0;
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ElfW(Addr) user_entry;
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ElfW(auxv_t) *av;
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#ifdef HAVE_AUX_SECURE
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# define set_seen(tag) (tag) /* Evaluate for the side effects. */
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# define set_seen_secure() ((void) 0)
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#else
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uid_t uid = 0;
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gid_t gid = 0;
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unsigned int seen = 0;
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# define set_seen_secure() (seen = -1)
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# ifdef HAVE_AUX_XID
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# define set_seen(tag) (tag) /* Evaluate for the side effects. */
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# else
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# define M(type) (1 << (type))
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# define set_seen(tag) seen |= M ((tag)->a_type)
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# endif
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#endif
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#ifdef NEED_DL_SYSINFO
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uintptr_t new_sysinfo = 0;
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#endif
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__libc_stack_end = DL_STACK_END (start_argptr);
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DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, _dl_argv, _environ,
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GLRO(dl_auxv));
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user_entry = (ElfW(Addr)) ENTRY_POINT;
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GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
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/* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
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_Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
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"CONSTANT_MINSIGSTKSZ is constant");
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GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
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for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
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switch (av->a_type)
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{
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case AT_PHDR:
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phdr = (void *) av->a_un.a_val;
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break;
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case AT_PHNUM:
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phnum = av->a_un.a_val;
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break;
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case AT_PAGESZ:
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GLRO(dl_pagesize) = av->a_un.a_val;
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break;
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case AT_ENTRY:
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user_entry = av->a_un.a_val;
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break;
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#ifdef NEED_DL_BASE_ADDR
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case AT_BASE:
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_dl_base_addr = av->a_un.a_val;
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break;
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#endif
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#ifndef HAVE_AUX_SECURE
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case AT_UID:
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case AT_EUID:
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uid ^= av->a_un.a_val;
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break;
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case AT_GID:
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case AT_EGID:
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gid ^= av->a_un.a_val;
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break;
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#endif
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case AT_SECURE:
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#ifndef HAVE_AUX_SECURE
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seen = -1;
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#endif
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__libc_enable_secure = av->a_un.a_val;
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break;
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case AT_PLATFORM:
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GLRO(dl_platform) = (void *) av->a_un.a_val;
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break;
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case AT_HWCAP:
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GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
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break;
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case AT_HWCAP2:
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GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
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break;
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case AT_CLKTCK:
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GLRO(dl_clktck) = av->a_un.a_val;
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break;
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case AT_FPUCW:
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GLRO(dl_fpu_control) = av->a_un.a_val;
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break;
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#ifdef NEED_DL_SYSINFO
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case AT_SYSINFO:
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new_sysinfo = av->a_un.a_val;
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break;
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#endif
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#ifdef NEED_DL_SYSINFO_DSO
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case AT_SYSINFO_EHDR:
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GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
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break;
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#endif
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case AT_RANDOM:
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_dl_random = (void *) av->a_un.a_val;
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break;
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case AT_MINSIGSTKSZ:
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GLRO(dl_minsigstacksize) = av->a_un.a_val;
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break;
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DL_PLATFORM_AUXV
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}
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#ifndef HAVE_AUX_SECURE
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if (seen != -1)
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{
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/* Fill in the values we have not gotten from the kernel through the
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auxiliary vector. */
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# ifndef HAVE_AUX_XID
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# define SEE(UID, var, uid) \
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if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
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SEE (UID, uid, uid);
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SEE (EUID, uid, euid);
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SEE (GID, gid, gid);
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SEE (EGID, gid, egid);
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# endif
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/* If one of the two pairs of IDs does not match this is a setuid
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or setgid run. */
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__libc_enable_secure = uid | gid;
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}
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#endif
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#ifndef HAVE_AUX_PAGESIZE
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if (GLRO(dl_pagesize) == 0)
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GLRO(dl_pagesize) = __getpagesize ();
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#endif
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#ifdef NEED_DL_SYSINFO
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if (new_sysinfo != 0)
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{
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# ifdef NEED_DL_SYSINFO_DSO
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/* Only set the sysinfo value if we also have the vsyscall DSO. */
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if (GLRO(dl_sysinfo_dso) != 0)
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# endif
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GLRO(dl_sysinfo) = new_sysinfo;
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}
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#endif
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__tunables_init (_environ);
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#ifdef DL_SYSDEP_INIT
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DL_SYSDEP_INIT;
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#endif
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#ifdef DL_PLATFORM_INIT
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DL_PLATFORM_INIT;
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#endif
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/* Determine the length of the platform name. */
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if (GLRO(dl_platform) != NULL)
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GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
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if (__sbrk (0) == _end)
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/* The dynamic linker was run as a program, and so the initial break
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starts just after our bss, at &_end. The malloc in dl-minimal.c
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will consume the rest of this page, so tell the kernel to move the
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break up that far. When the user program examines its break, it
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will see this new value and not clobber our data. */
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__sbrk (GLRO(dl_pagesize)
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- ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
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/* If this is a SUID program we make sure that FDs 0, 1, and 2 are
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allocated. If necessary we are doing it ourself. If it is not
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possible we stop the program. */
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if (__builtin_expect (__libc_enable_secure, 0))
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__libc_check_standard_fds ();
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(*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
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return user_entry;
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}
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void
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_dl_sysdep_start_cleanup (void)
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{
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}
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void
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_dl_show_auxv (void)
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{
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char buf[64];
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ElfW(auxv_t) *av;
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/* Terminate string. */
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buf[63] = '\0';
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/* The following code assumes that the AT_* values are encoded
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starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
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close by (otherwise the array will be too large). In case we have
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to support a platform where these requirements are not fulfilled
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some alternative implementation has to be used. */
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for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
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{
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static const struct
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{
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const char label[22];
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enum { unknown = 0, dec, hex, str, ignore } form : 8;
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} auxvars[] =
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{
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[AT_EXECFD - 2] = { "EXECFD: ", dec },
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[AT_EXECFN - 2] = { "EXECFN: ", str },
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[AT_PHDR - 2] = { "PHDR: 0x", hex },
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[AT_PHENT - 2] = { "PHENT: ", dec },
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[AT_PHNUM - 2] = { "PHNUM: ", dec },
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[AT_PAGESZ - 2] = { "PAGESZ: ", dec },
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[AT_BASE - 2] = { "BASE: 0x", hex },
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[AT_FLAGS - 2] = { "FLAGS: 0x", hex },
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[AT_ENTRY - 2] = { "ENTRY: 0x", hex },
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[AT_NOTELF - 2] = { "NOTELF: ", hex },
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[AT_UID - 2] = { "UID: ", dec },
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[AT_EUID - 2] = { "EUID: ", dec },
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[AT_GID - 2] = { "GID: ", dec },
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[AT_EGID - 2] = { "EGID: ", dec },
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[AT_PLATFORM - 2] = { "PLATFORM: ", str },
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[AT_HWCAP - 2] = { "HWCAP: ", hex },
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[AT_CLKTCK - 2] = { "CLKTCK: ", dec },
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[AT_FPUCW - 2] = { "FPUCW: ", hex },
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[AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
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[AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
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[AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
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[AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
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[AT_SECURE - 2] = { "SECURE: ", dec },
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[AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
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[AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
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[AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
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[AT_RANDOM - 2] = { "RANDOM: 0x", hex },
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[AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
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[AT_MINSIGSTKSZ - 2] = { "MINSIGSTKSZ ", dec },
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[AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
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[AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
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[AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
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[AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
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[AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
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[AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
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[AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
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[AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
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};
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unsigned int idx = (unsigned int) (av->a_type - 2);
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if ((unsigned int) av->a_type < 2u
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|| (idx < sizeof (auxvars) / sizeof (auxvars[0])
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&& auxvars[idx].form == ignore))
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continue;
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assert (AT_NULL == 0);
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assert (AT_IGNORE == 1);
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/* Some entries are handled in a special way per platform. */
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if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
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continue;
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if (idx < sizeof (auxvars) / sizeof (auxvars[0])
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&& auxvars[idx].form != unknown)
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{
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const char *val = (char *) av->a_un.a_val;
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if (__builtin_expect (auxvars[idx].form, dec) == dec)
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val = _itoa ((unsigned long int) av->a_un.a_val,
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buf + sizeof buf - 1, 10, 0);
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else if (__builtin_expect (auxvars[idx].form, hex) == hex)
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val = _itoa ((unsigned long int) av->a_un.a_val,
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buf + sizeof buf - 1, 16, 0);
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_dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
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continue;
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}
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/* Unknown value: print a generic line. */
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char buf2[17];
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buf2[sizeof (buf2) - 1] = '\0';
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const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
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buf2 + sizeof buf2 - 1, 16, 0);
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const char *val = _itoa ((unsigned long int) av->a_type,
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buf + sizeof buf - 1, 16, 0);
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_dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
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}
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}
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#endif
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