| /* |
| * Copyright (C) 2013 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include <private/bionic_asm.h> |
| #include <private/bionic_asm_dwarf_exprs.h> |
| |
| // In the signal trampoline frame, rsp points to a ucontext_t struct. |
| |
| // Offsets into struct ucontext_t of uc_mcontext.gregs[x]. |
| #define OFFSET_R8 40 |
| #define OFFSET_R9 48 |
| #define OFFSET_R10 56 |
| #define OFFSET_R11 64 |
| #define OFFSET_R12 72 |
| #define OFFSET_R13 80 |
| #define OFFSET_R14 88 |
| #define OFFSET_R15 96 |
| #define OFFSET_RDI 104 |
| #define OFFSET_RSI 112 |
| #define OFFSET_RBP 120 |
| #define OFFSET_RBX 128 |
| #define OFFSET_RDX 136 |
| #define OFFSET_RAX 144 |
| #define OFFSET_RCX 152 |
| #define OFFSET_RSP 160 |
| #define OFFSET_RIP 168 |
| |
| // Non-standard DWARF constants for the x86-64 registers. |
| #define DW_x86_64_RAX 0 |
| #define DW_x86_64_RDX 1 |
| #define DW_x86_64_RCX 2 |
| #define DW_x86_64_RBX 3 |
| #define DW_x86_64_RSI 4 |
| #define DW_x86_64_RDI 5 |
| #define DW_x86_64_RBP 6 |
| #define DW_x86_64_RSP 7 |
| #define DW_x86_64_R8 8 |
| #define DW_x86_64_R9 9 |
| #define DW_x86_64_R10 10 |
| #define DW_x86_64_R11 11 |
| #define DW_x86_64_R12 12 |
| #define DW_x86_64_R13 13 |
| #define DW_x86_64_R14 14 |
| #define DW_x86_64_R15 15 |
| #define DW_x86_64_RIP 16 |
| |
| // Insert a nop between .cfi_startproc and the trampoline symbol so that unwinders can find the FDE. |
| // A function's last instruction can be a call instruction (e.g. to __cxa_throw), in which case the |
| // return address (e.g. from __cxa_throw to the caller) will be just after the function. This |
| // address may also be the start of the next function, so to avoid ambiguity, unwinders assume that |
| // a return address PC can refer to the address just after a function, but never to the start of a |
| // function. (This is implemented by subtracting 1 from the return address PC before looking it up.) |
| // This is fine for ordinary functions, but breaks on trampolines. Inserting a nop fixes it. |
| // |
| // N.B. Unwinders have two other strategies for recognizing the signal trampoline: |
| // - Read the instructions that the return address PC points at and look for a sigreturn syscall. |
| // (Hence, the instructions must not change at all.) |
| // - Do a symbol table lookup and check that against the PC (e.g. LLDB looks for |
| // __kernel_rt_sigreturn and __restore_rt.) |
| // Either way, the nop is needed to avoid ambiguity if the function before the trampoline could end |
| // with a call. |
| |
| #define RESTORE_GPR(reg) m_cfi_breg_offset DW_x86_64_ ## reg, DW_x86_64_RSP, OFFSET_ ## reg; |
| |
| .text |
| .cfi_startproc |
| .cfi_signal_frame |
| m_cfi_def_cfa_deref DW_x86_64_RSP, OFFSET_RSP |
| RESTORE_GPR(R8) |
| RESTORE_GPR(R9) |
| RESTORE_GPR(R10) |
| RESTORE_GPR(R11) |
| RESTORE_GPR(R12) |
| RESTORE_GPR(R13) |
| RESTORE_GPR(R14) |
| RESTORE_GPR(R15) |
| RESTORE_GPR(RDI) |
| RESTORE_GPR(RSI) |
| RESTORE_GPR(RBP) |
| RESTORE_GPR(RBX) |
| RESTORE_GPR(RDX) |
| RESTORE_GPR(RAX) |
| RESTORE_GPR(RCX) |
| // Restoring RSP is unnecessary as the unwinder simply uses the CFA value. |
| RESTORE_GPR(RIP) |
| nop |
| ENTRY_PRIVATE_NO_DWARF(__restore_rt) |
| mov $__NR_rt_sigreturn, %rax |
| syscall |
| END(__restore_rt) |