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//! Backtrace strategy for MSVC platforms.
//!
//! This module contains the ability to capture a backtrace on MSVC using one
//! of three possible methods. For `x86_64` and `aarch64`, we use `RtlVirtualUnwind`
//! to walk the stack one frame at a time. This function is much faster than using
//! `dbghelp!StackWalk*` because it does not load debug info to report inlined frames.
//! We still report inlined frames during symbolization by consulting the appropriate
//! `dbghelp` functions.
//!
//! For all other platforms, primarily `i686`, the `StackWalkEx` function is used if
//! possible, but not all systems have that. Failing that the `StackWalk64` function
//! is used instead. Note that `StackWalkEx` is favored because it handles debuginfo
//! internally and returns inline frame information.
//!
//! Note that all dbghelp support is loaded dynamically, see `src/dbghelp.rs`
//! for more information about that.
#![allow(bad_style)]
use super::super::windows::*;
use core::ffi::c_void;
#[derive(Clone, Copy)]
pub struct Frame {
base_address: *mut c_void,
ip: *mut c_void,
sp: *mut c_void,
#[cfg(not(target_env = "gnu"))]
inline_context: Option<DWORD>,
}
// we're just sending around raw pointers and reading them, never interpreting
// them so this should be safe to both send and share across threads.
unsafe impl Send for Frame {}
unsafe impl Sync for Frame {}
impl Frame {
pub fn ip(&self) -> *mut c_void {
self.ip
}
pub fn sp(&self) -> *mut c_void {
self.sp
}
pub fn symbol_address(&self) -> *mut c_void {
self.ip
}
pub fn module_base_address(&self) -> Option<*mut c_void> {
Some(self.base_address)
}
#[cfg(not(target_env = "gnu"))]
pub fn inline_context(&self) -> Option<DWORD> {
self.inline_context
}
}
#[repr(C, align(16))] // required by `CONTEXT`, is a FIXME in winapi right now
struct MyContext(CONTEXT);
#[cfg(any(target_arch = "x86_64", target_arch = "arm64ec"))]
impl MyContext {
#[inline(always)]
fn ip(&self) -> DWORD64 {
self.0.Rip
}
#[inline(always)]
fn sp(&self) -> DWORD64 {
self.0.Rsp
}
}
#[cfg(target_arch = "aarch64")]
impl MyContext {
#[inline(always)]
fn ip(&self) -> DWORD64 {
self.0.Pc
}
#[inline(always)]
fn sp(&self) -> DWORD64 {
self.0.Sp
}
}
#[cfg(any(
target_arch = "x86_64",
target_arch = "aarch64",
target_arch = "arm64ec"
))]
#[inline(always)]
pub unsafe fn trace(cb: &mut dyn FnMut(&super::Frame) -> bool) {
use core::ptr;
let mut context = core::mem::zeroed::<MyContext>();
RtlCaptureContext(&mut context.0);
// Call `RtlVirtualUnwind` to find the previous stack frame, walking until we hit ip = 0.
while context.ip() != 0 {
let mut base = 0;
let fn_entry = RtlLookupFunctionEntry(context.ip(), &mut base, ptr::null_mut());
if fn_entry.is_null() {
break;
}
let frame = super::Frame {
inner: Frame {
base_address: fn_entry.cast::<c_void>(),
ip: context.ip() as *mut c_void,
sp: context.sp() as *mut c_void,
#[cfg(not(target_env = "gnu"))]
inline_context: None,
},
};
if !cb(&frame) {
break;
}
let mut handler_data = 0usize;
let mut establisher_frame = 0;
RtlVirtualUnwind(
0,
base,
context.ip(),
fn_entry,
&mut context.0,
ptr::addr_of_mut!(handler_data).cast::<PVOID>(),
&mut establisher_frame,
ptr::null_mut(),
);
}
}