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1bdda52fe9
This patch moves the vDSO setup from libc to loader code, just after the vDSO link_map setup. For static case the initialization is moved to _dl_non_dynamic_init instead. Instead of using the mangled pointer, the vDSO data is set as attribute_relro (on _rtld_global_ro for shared or _dl_vdso_* for static). It is read-only even with partial relro. It fixes BZ#24967 now that the vDSO pointer is setup earlier than malloc interposition is called. Also, vDSO calls should not be a problem for static dlopen as indicated by BZ#20802. The vDSO pointer would be zero-initialized and the syscall will be issued instead. Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu, powerpc64-linux-gnu, powerpc-linux-gnu, s390x-linux-gnu, sparc64-linux-gnu, and sparcv9-linux-gnu. I also run some tests on mips. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
131 lines
3.8 KiB
C
131 lines
3.8 KiB
C
/* Return backtrace of current program state.
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Copyright (C) 1998-2020 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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#include <execinfo.h>
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#include <stddef.h>
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#include <string.h>
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#include <signal.h>
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#include <libc-vdso.h>
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/* This is the stack layout we see with every stack frame.
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Note that every routine is required by the ABI to lay out the stack
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like this.
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+----------------+ +-----------------+
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%r1 -> | %r1 last frame--------> | %r1 last frame--->... --> NULL
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| | | |
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| (unused) | | return address |
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+----------------+ +-----------------+
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*/
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struct layout
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{
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struct layout *next;
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void *return_address;
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};
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#define SIGNAL_FRAMESIZE 64
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/* Since the signal handler is just like any other function it needs to
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save/restore its LR and it will save it into callers stack frame.
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Since a signal handler doesn't have a caller, the kernel creates a
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dummy frame to make it look like it has a caller. */
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struct signal_frame_32 {
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char dummy[SIGNAL_FRAMESIZE];
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struct sigcontext sctx;
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mcontext_t mctx;
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/* We don't care about the rest, since IP value is at 'mctx' field. */
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};
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static inline bool
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is_sigtramp_address (void *nip)
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{
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#ifdef HAVE_SIGTRAMP_RT32
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if (nip == GLRO (dl_vdso_sigtramp_32))
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return true;
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#endif
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return false;
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}
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struct rt_signal_frame_32 {
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char dummy[SIGNAL_FRAMESIZE + 16];
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siginfo_t info;
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ucontext_t uc;
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/* We don't care about the rest, since IP value is at 'uc' field. */
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};
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static inline bool
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is_sigtramp_address_rt (void * nip)
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{
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#ifdef HAVE_SIGTRAMP_32
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if (nip == GLRO (dl_vdso_sigtramp_rt32))
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return true;
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#endif
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return false;
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}
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int
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__backtrace (void **array, int size)
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{
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struct layout *current;
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int count;
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/* Force gcc to spill LR. */
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asm volatile ("" : "=l"(current));
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/* Get the address on top-of-stack. */
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asm volatile ("lwz %0,0(1)" : "=r"(current));
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for ( count = 0;
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current != NULL && count < size;
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current = current->next, count++)
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{
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gregset_t *gregset = NULL;
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array[count] = current->return_address;
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/* Check if the symbol is the signal trampoline and get the interrupted
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* symbol address from the trampoline saved area. */
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if (is_sigtramp_address (current->return_address))
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{
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struct signal_frame_32 *sigframe =
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(struct signal_frame_32*) current;
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gregset = &sigframe->mctx.gregs;
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}
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else if (is_sigtramp_address_rt (current->return_address))
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{
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struct rt_signal_frame_32 *sigframe =
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(struct rt_signal_frame_32*) current;
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gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs;
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}
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if (gregset)
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{
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array[++count] = (void*)((*gregset)[PT_NIP]);
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current = (void*)((*gregset)[PT_R1]);
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}
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}
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/* It's possible the second-last stack frame can't return
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(that is, it's __libc_start_main), in which case
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the CRT startup code will have set its LR to 'NULL'. */
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if (count > 0 && array[count-1] == NULL)
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count--;
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return count;
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}
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weak_alias (__backtrace, backtrace)
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libc_hidden_def (__backtrace)
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