// Copyright 2014 The Crashpad Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__)
#if defined(__i386__) || defined(__x86_64__)
// namespace crashpad {
// void CaptureContext(x86_thread_state_t* x86_thread_state);
// } // namespace crashpad
#define CAPTURECONTEXT_SYMBOL __ZN8crashpad14CaptureContextEP16x86_thread_state
#elif defined(__aarch64__)
// namespace crashpad {
// void CaptureContext(arm_unified_thread_state_t* arm_unified_thread_state);
// } // namespace crashpad
#define CAPTURECONTEXT_SYMBOL \
__ZN8crashpad14CaptureContextEP24arm_unified_thread_state
#endif
.section __TEXT,__text,regular,pure_instructions
.private_extern CAPTURECONTEXT_SYMBOL
.globl CAPTURECONTEXT_SYMBOL
#if defined(__i386__) || defined(__x86_64__)
.p2align 4, 0x90
#elif defined(__aarch64__)
.p2align 2
#endif
CAPTURECONTEXT_SYMBOL:
#if defined(__i386__)
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset %ebp, -8
movl %esp, %ebp
.cfi_def_cfa_register %ebp
// Note that 16-byte stack alignment is not maintained because this function
// does not call out to any other.
// pushfl first, because some instructions (but probably none used here)
// affect %eflags. %eflags will be in -4(%ebp).
pushfl
// Save the original value of %eax, and use %eax to hold the x86_thread_state*
// argument. The original value of %eax will be in -8(%ebp).
pushl %eax
movl 8(%ebp), %eax
// Initialize the header identifying the x86_thread_state_t structure as
// carrying an x86_thread_state32_t (flavor x86_THREAD_STATE32) of size
// x86_THREAD_STATE32_COUNT 32-bit values.
movl $1, (%eax) // x86_thread_state->tsh.flavor
movl $16, 4(%eax) // x86_thread_state->tsh.count
// General-purpose registers whose values haven’t changed can be captured
// directly.
movl %ebx, 12(%eax) // x86_thread_state->uts.ts32.__ebx
movl %ecx, 16(%eax) // x86_thread_state->uts.ts32.__ecx
movl %edx, 20(%eax) // x86_thread_state->uts.ts32.__edx
movl %edi, 24(%eax) // x86_thread_state->uts.ts32.__edi
movl %esi, 28(%eax) // x86_thread_state->uts.ts32.__esi
// Now that the original value of %edx has been saved, it can be repurposed to
// hold other registers’ values.
// The original %eax was saved on the stack above.
movl -8(%ebp), %edx
movl %edx, 8(%eax) // x86_thread_state->uts.ts32.__eax
// The original %ebp was saved on the stack in this function’s prologue.
movl (%ebp), %edx
movl %edx, 32(%eax) // x86_thread_state->uts.ts32.__ebp
// %esp was saved in %ebp in this function’s prologue, but the caller’s %esp
// is 8 more than this value: 4 for the original %ebp saved on the stack in
// this function’s prologue, and 4 for the return address saved on the stack
// by the call instruction that reached this function.
leal 8(%ebp), %edx
movl %edx, 36(%eax) // x86_thread_state->uts.ts32.__esp
// The original %eflags was saved on the stack above.
movl -4(%ebp), %edx
movl %edx, 44(%eax) // x86_thread_state->uts.ts32.__eflags
// %eip can’t be accessed directly, but the return address saved on the stack
// by the call instruction that reached this function can be used.
movl 4(%ebp), %edx
movl %edx, 48(%eax) // x86_thread_state->uts.ts32.__eip
// The segment registers are 16 bits wide, but x86_thread_state declares them
// as unsigned 32-bit values, so zero the top half.
xorl %edx, %edx
movw %ss, %dx
movl %edx, 40(%eax) // x86_thread_state->uts.ts32.__ss
movw %cs, %dx
movl %edx, 52(%eax) // x86_thread_state->uts.ts32.__cs
movw %ds, %dx
movl %edx, 56(%eax) // x86_thread_state->uts.ts32.__ds
movw %es, %dx
movl %edx, 60(%eax) // x86_thread_state->uts.ts32.__es
movw %fs, %dx
movl %edx, 64(%eax) // x86_thread_state->uts.ts32.__fs
movw %gs, %dx
movl %edx, 68(%eax) // x86_thread_state->uts.ts32.__gs
// Clean up by restoring clobbered registers, even those considered volatile
// by the ABI, so that the captured context represents the state at this
// function’s exit.
movl 20(%eax), %edx // x86_thread_state->uts.ts32.__edx
popl %eax
popfl
popl %ebp
ret
.cfi_endproc
#elif defined(__x86_64__)
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
// Note that 16-byte stack alignment is not maintained because this function
// does not call out to any other.
// pushfq first, because some instructions (but probably none used here)
// affect %rflags. %rflags will be in -8(%rbp).
pushfq
// Initialize the header identifying the x86_thread_state_t structure as
// carrying an x86_thread_state64_t (flavor x86_THREAD_STATE64) of size
// x86_THREAD_STATE64_COUNT 32-bit values.
movl $4, (%rdi) // x86_thread_state->tsh.flavor
movl $42, 4(%rdi) // x86_thread_state->tsh.count
// General-purpose registers whose values haven’t changed can be captured
// directly.
movq %rax, 8(%rdi) // x86_thread_state->uts.ts64.__rax
movq %rbx, 16(%rdi) // x86_thread_state->uts.ts64.__rbx
movq %rcx, 24(%rdi) // x86_thread_state->uts.ts64.__rcx
movq %rdx, 32(%rdi) // x86_thread_state->uts.ts64.__rdx
movq %rsi, 48(%rdi) // x86_thread_state->uts.ts64.__rsi
movq %r8, 72(%rdi) // x86_thread_state->uts.ts64.__r8
movq %r9, 80(%rdi) // x86_thread_state->uts.ts64.__r9
movq %r10, 88(%rdi) // x86_thread_state->uts.ts64.__r10
movq %r11, 96(%rdi) // x86_thread_state->uts.ts64.__r11
movq %r12, 104(%rdi) // x86_thread_state->uts.ts64.__r12
movq %r13, 112(%rdi) // x86_thread_state->uts.ts64.__r13
movq %r14, 120(%rdi) // x86_thread_state->uts.ts64.__r14
movq %r15, 128(%rdi) // x86_thread_state->uts.ts64.__r15
// Because of the calling convention, there’s no way to recover the value of
// the caller’s %rdi as it existed prior to calling this function. This
// function captures a snapshot of the register state at its return, which
// involves %rdi containing a pointer to its first argument. Callers that
// require the value of %rdi prior to calling this function should obtain it
// separately. For example:
// uint64_t rdi;
// asm("movq %%rdi, %0" : "=m"(rdi));
movq %rdi, 40(%rdi) // x86_thread_state->uts.ts64.__rdi
// Now that the original value of %rax has been saved, it can be repurposed to
// hold other registers’ values.
// The original %rbp was saved on the stack in this function’s prologue.
movq (%rbp), %rax
movq %rax, 56(%rdi) // x86_thread_state->uts.ts64.__rbp
// %rsp was saved in %rbp in this function’s prologue, but the caller’s %rsp
// is 16 more than this value: 8 for the original %rbp saved on the stack in
// this function’s prologue, and 8 for the return address saved on the stack
// by the call instruction that reached this function.
leaq 16(%rbp), %rax
movq %rax, 64(%rdi) // x86_thread_state->uts.ts64.__rsp
// %rip can’t be accessed directly, but the return address saved on the stack
// by the call instruction that reached this function can be used.
movq 8(%rbp), %rax
movq %rax, 136(%rdi) // x86_thread_state->uts.ts64.__rip
// The original %rflags was saved on the stack above.
movq -8(%rbp), %rax
movq %rax, 144(%rdi) // x86_thread_state->uts.ts64.__rflags
// The segment registers are 16 bits wide, but x86_thread_state declares them
// as unsigned 64-bit values, so zero the top portion.
xorq %rax, %rax
movw %cs, %ax
movq %rax, 152(%rdi) // x86_thread_state->uts.ts64.__cs
movw %fs, %ax
movq %rax, 160(%rdi) // x86_thread_state->uts.ts64.__fs
movw %gs, %ax
movq %rax, 168(%rdi) // x86_thread_state->uts.ts64.__gs
// Clean up by restoring clobbered registers, even those considered volatile
// by the ABI, so that the captured context represents the state at this
// function’s exit.
movq 8(%rdi), %rax
popfq
popq %rbp
ret
.cfi_endproc
#elif defined(__aarch64__)
.cfi_startproc
// Save general-purpose registers in arm_unified_thread_state->ts_64.__x[0].
// The original x0 can't be recovered.
stp x0, x1, [x0, #0x8]
stp x2, x3, [x0, #0x18]
stp x4, x5, [x0, #0x28]
stp x6, x7, [x0, #0x38]
stp x8, x9, [x0, #0x48]
stp x10, x11, [x0, #0x58]
stp x12, x13, [x0, #0x68]
stp x14, x15, [x0, #0x78]
stp x16, x17, [x0, #0x88]
stp x18, x19, [x0, #0x98]
stp x20, x21, [x0, #0xa8]
stp x22, x23, [x0, #0xb8]
stp x24, x25, [x0, #0xc8]
stp x26, x27, [x0, #0xd8]
// Save the last general-purpose register (x28) and the frame pointer (x29).
stp x28, x29, [x0, #0xe8] // __x[28] and __fp
// Save the link register (x30) and the stack pointer (using x1 as a scratch
// register)
mov x1, sp
stp x30, x1, [x0, #0xf8] // __lr and __sp
// The link register (x30) holds the return address for this function.
// __cpsr should hold current program status register, but nzcv are the only
// bits we know about (saved using x1 as a scratch register). The 64-bit x1
// covers both the 32-bit __cpsr (which receives the nzcv bits) and __pad
// (which will be zeroed).
mrs x1, nzcv
stp x30, x1, [x0, #0x108] // __pc and __cpsr and __pad
// Initialize the header identifying the arm_unified_thread_state structure as
// carrying an arm_thread_state64_t (flavor ARM_THREAD_STATE64) of size
// ARM_THREAD_STATE64_COUNT 32-bit values.
mov x1, #6
movk x1, #68, lsl #32
str x1, [x0, #0x0] // arm_thread_state->ash.flavor and count
// Restore x1 from the saved context.
ldr x1, [x0, #0x10]
// TODO(justincohen): Consider saving floating-point registers into
// arm_neon_state64_t as second parameter, or as a a second function call
// after all of the general-purpose state is captured, or as a new struct that
// has both arm_unified_state_t and arm_neon_state64_t members. That may be
// better than a second parameter (which occupies another register) and better
// than a second function call.
ret
.cfi_endproc
#endif
.subsections_via_symbols
#endif
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