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25123a1c5c
This patch adds a field to ucontext_t to save shadow stack: 1. getcontext and swapcontext are updated to save the caller's shadow stack pointer and return addresses. 2. setcontext and swapcontext are updated to restore shadow stack and jump to new context directly. 3. makecontext is updated to allocate a new shadow stack and set the caller's return address to __start_context. Since makecontext allocates a new shadow stack when making a new context and kernel allocates a new shadow stack for clone/fork/vfork syscalls, we track the current shadow stack base. In setcontext and swapcontext, if the target shadow stack base is the same as the current shadow stack base, we unwind the shadow stack. Otherwise it is a stack switch and we look for a restore token. We enable shadow stack at run-time only if program and all used shared objects, including dlopened ones, are shadow stack enabled, which means that they must be compiled with GCC 8 or above and glibc 2.28 or above. We need to save and restore shadow stack only if shadow stack is enabled. When caller of getcontext, setcontext, swapcontext and makecontext is compiled with smaller ucontext_t, shadow stack won't be enabled at run-time. We check if shadow stack is enabled before accessing the extended field in ucontext_t. Reviewed-by: Carlos O'Donell <carlos@redhat.com> * sysdeps/unix/sysv/linux/x86/sys/ucontext.h (ucontext_t): Add __ssp. * sysdeps/unix/sysv/linux/x86_64/__start_context.S: Include <asm/prctl.h> and "ucontext_i.h" when shadow stack is enabled. (__push___start_context): New. * sysdeps/unix/sysv/linux/x86_64/getcontext.S: Include <asm/prctl.h>. (__getcontext): Record the current shadow stack base. Save the caller's shadow stack pointer and base. * sysdeps/unix/sysv/linux/x86_64/makecontext.c: Include <pthread.h>, <libc-pointer-arith.h> and <sys/prctl.h>. (__push___start_context): New prototype. (__makecontext): Call __push___start_context to allocate a new shadow stack, push __start_context onto the new stack as well as the new shadow stack. * sysdeps/unix/sysv/linux/x86_64/setcontext.S: Include <asm/prctl.h>. (__setcontext): Restore the target shadow stack. * sysdeps/unix/sysv/linux/x86_64/swapcontext.S: Include <asm/prctl.h>. (__swapcontext): Record the current shadow stack base. Save the caller's shadow stack pointer and base. Restore the target shadow stack. * sysdeps/unix/sysv/linux/x86_64/sysdep.h (STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT): New. * sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym (oSSP): New.
138 lines
3.7 KiB
ArmAsm
138 lines
3.7 KiB
ArmAsm
/* Save current context.
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Copyright (C) 2002-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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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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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <asm/prctl.h>
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#include "ucontext_i.h"
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/* int __getcontext (ucontext_t *ucp)
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Saves the machine context in UCP such that when it is activated,
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it appears as if __getcontext() returned again.
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This implementation is intended to be used for *synchronous* context
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switches only. Therefore, it does not have to save anything
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other than the PRESERVED state. */
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ENTRY(__getcontext)
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/* Save the preserved registers, the registers used for passing
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args, and the return address. */
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movq %rbx, oRBX(%rdi)
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movq %rbp, oRBP(%rdi)
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movq %r12, oR12(%rdi)
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movq %r13, oR13(%rdi)
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movq %r14, oR14(%rdi)
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movq %r15, oR15(%rdi)
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movq %rdi, oRDI(%rdi)
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movq %rsi, oRSI(%rdi)
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movq %rdx, oRDX(%rdi)
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movq %rcx, oRCX(%rdi)
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movq %r8, oR8(%rdi)
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movq %r9, oR9(%rdi)
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movq (%rsp), %rcx
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movq %rcx, oRIP(%rdi)
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leaq 8(%rsp), %rcx /* Exclude the return address. */
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movq %rcx, oRSP(%rdi)
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#if SHSTK_ENABLED
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/* Check if shadow stack is enabled. */
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testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
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jz L(no_shstk)
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/* Save RDI in RDX which won't be clobbered by syscall. */
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movq %rdi, %rdx
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xorl %eax, %eax
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cmpq %fs:SSP_BASE_OFFSET, %rax
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jnz L(shadow_stack_bound_recorded)
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/* Get the base address and size of the default shadow stack
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which must be the current shadow stack since nothing has
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been recorded yet. */
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sub $24, %RSP_LP
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mov %RSP_LP, %RSI_LP
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movl $ARCH_CET_STATUS, %edi
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movl $__NR_arch_prctl, %eax
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syscall
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testq %rax, %rax
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jz L(continue_no_err)
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/* This should never happen. */
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hlt
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L(continue_no_err):
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/* Record the base of the current shadow stack. */
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movq 8(%rsp), %rax
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movq %rax, %fs:SSP_BASE_OFFSET
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add $24, %RSP_LP
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/* Restore RDI. */
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movq %rdx, %rdi
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L(shadow_stack_bound_recorded):
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/* Get the current shadow stack pointer. */
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rdsspq %rax
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/* NB: Save the caller's shadow stack so that we can jump back
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to the caller directly. */
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addq $8, %rax
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movq %rax, oSSP(%rdx)
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/* Save the current shadow stack base in ucontext. */
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movq %fs:SSP_BASE_OFFSET, %rax
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movq %rax, (oSSP + 8)(%rdi)
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L(no_shstk):
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#endif
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/* We have separate floating-point register content memory on the
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stack. We use the __fpregs_mem block in the context. Set the
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links up correctly. */
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leaq oFPREGSMEM(%rdi), %rcx
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movq %rcx, oFPREGS(%rdi)
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/* Save the floating-point environment. */
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fnstenv (%rcx)
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fldenv (%rcx)
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stmxcsr oMXCSR(%rdi)
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/* Save the current signal mask with
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rt_sigprocmask (SIG_BLOCK, NULL, set,_NSIG/8). */
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leaq oSIGMASK(%rdi), %rdx
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xorl %esi,%esi
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#if SIG_BLOCK == 0
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xorl %edi, %edi
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#else
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movl $SIG_BLOCK, %edi
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#endif
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movl $_NSIG8,%r10d
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movl $__NR_rt_sigprocmask, %eax
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syscall
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cmpq $-4095, %rax /* Check %rax for error. */
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jae SYSCALL_ERROR_LABEL /* Jump to error handler if error. */
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/* All done, return 0 for success. */
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xorl %eax, %eax
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ret
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PSEUDO_END(__getcontext)
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weak_alias (__getcontext, getcontext)
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