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//! Backtrace strategy for MSVC `x86_64` and `aarch64` platforms.
//!
//! This module contains the ability to capture a backtrace on MSVC using
//! `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.
#![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;
// Capture the initial context to start walking from.
let mut context = core::mem::zeroed::<MyContext>();
RtlCaptureContext(&mut context.0);
loop {
let ip = context.ip();
// The base address of the module containing the function will be stored here
// when RtlLookupFunctionEntry returns successfully.
let mut base = 0;
let fn_entry = RtlLookupFunctionEntry(ip, &mut base, ptr::null_mut());
if fn_entry.is_null() {
// No function entry could be found - this may indicate a corrupt
// stack or that a binary was unloaded (amongst other issues). Stop
// walking and don't call the callback as we can't be confident in
// this frame or the rest of the stack.
break;
}
let frame = super::Frame {
inner: Frame {
base_address: base as *mut c_void,
ip: ip as *mut c_void,
sp: context.sp() as *mut c_void,
#[cfg(not(target_env = "gnu"))]
inline_context: None,
},
};
// We've loaded all the info about the current frame, so now call the
// callback.
if !cb(&frame) {
// Callback told us to stop, so we're done.
break;
}
// Unwind to the next frame.
let previous_ip = ip;
let previous_sp = context.sp();
let mut handler_data = 0usize;
let mut establisher_frame = 0;
RtlVirtualUnwind(
0,
base,
ip,
fn_entry,
&mut context.0,
ptr::addr_of_mut!(handler_data).cast::<PVOID>(),
&mut establisher_frame,
ptr::null_mut(),
);
// RtlVirtualUnwind indicates the end of the stack in two different ways:
// * On x64, it sets the instruction pointer to 0.
// * On ARM64, it leaves the context unchanged (easiest way to check is
// to see if the instruction and stack pointers are the same).
// If we detect either of these, then unwinding is completed.
let ip = context.ip();
if ip == 0 || (ip == previous_ip && context.sp() == previous_sp) {
break;
}
}
}