Fangrui Song MaskRay

Published to https://maskray.me/blog/2024-01-23-riscv-tlsdesc-works

Patch musl

--- c/arch/riscv64/reloc.h
+++ i/arch/riscv64/reloc.h
@@ -17,6 +17,7 @@
 #define REL_DTPMOD      R_RISCV_TLS_DTPMOD64
 #define REL_DTPOFF      R_RISCV_TLS_DTPREL64
 #define REL_TPOFF       R_RISCV_TLS_TPREL64

AddressSanitizer (ASan) is a compiler technology that checks addressability-related memory errors with some add-on checks. It consists of two parts: compiler instrumentation and runtime library. To put it in the simplest way,

The compiler instruments global variables, stack frames, and heap allocations to track shadow memory.
The compiler instruments memory access instructions to check shadow memory.
In case of an error, the inserted code calls a callback (implemented in the runtime library) to report an error with a stack trace. Normally the program will exit after the error message is printed.

Clang 3.1 implemented AddressSanitizer in 2011. GCC 4.8 integrated AddressSanitizer in 2012. MSVC (starting in Visual Studio 2019 version 16.9) added /INFERASANLIBS.

theme: ./theme class: text-center highlighter: shiki lineNumbers: false drawings: persist: false css: unocss routerMode: hash title: Optimize lld/ELF

glibc functions perform stack unwinding mainly in two places, pthread_exit/pthread_cancel, and backtrace-family functions.

`pthread_exit`/`pthread_cancel`.

Here is a C++ program that calls pthread_exit. Shall the destructors ~A and ~B be called?

#include <pthread.h>
#include <stdio.h>

void foo() { pthread_exit(NULL); }

In the kernel source directory, run

make O=/tmp/linux/arm64 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j60 defconfig all

Then create an Alpine aarch64 image following https://hackmd.io/@starnight/Run_Alpine_on_QEMU_aarch64_Virtual_Machine

wget https://dl-cdn.alpinelinux.org/alpine/latest-stable/releases/aarch64/netboot/vmlinuz-lts https://dl-cdn.alpinelinux.org/alpine/latest-stable/releases/aarch64/netboot/config-lts

	PATH=/tmp/Rel/bin:$PATH
	cat > switch.cc <<e
	#define DO A(0) A(1) A(2) A(3) A(4) A(5) A(6) A(7) A(8) A(9) A(10) A(11) A(12) A(13)
	#define A(i) void bar##i();
	DO
	#undef A
	void ext();
	void foo(int i) {
	switch (i) {
	#define A(i) case i: bar##i(); break;

	#
	# Automatically generated file; DO NOT EDIT.
	# Linux/x86 6.7.0 Kernel Configuration
	#
	CONFIG_CC_VERSION_TEXT="gcc (Debian 13.2.0-5) 13.2.0"
	CONFIG_CC_IS_GCC=y
	CONFIG_GCC_VERSION=130200
	CONFIG_CLANG_VERSION=0
	CONFIG_AS_IS_GNU=y
	CONFIG_AS_VERSION=24100

	https://reviews.llvm.org/D1 Abandoned Test klimek
	https://reviews.llvm.org/D6 Abandoned Update all diagnostic messages in DiagnosticSemaKinds.td to use the new diffing format for types. rtrieu
	https://reviews.llvm.org/D7 Abandoned test dblaikie
	https://reviews.llvm.org/D9 Abandoned Test for playing around with emails klimek
	https://reviews.llvm.org/D10 Abandoned A new test revision for funz klimek
	https://reviews.llvm.org/D11 Abandoned Let's try again klimek
	https://reviews.llvm.org/D12 Abandoned And yet another test klimek
	https://reviews.llvm.org/D13 Abandoned test klimek
	https://reviews.llvm.org/D14 Abandoned Test test klimek
	https://reviews.llvm.org/D16 Abandoned Big test klimek

	#!/bin/zsh
	CC=/tmp/Rel/bin/clang
	if [[ -n $1 ]]; then
	update=1
	echo updated
	else
	update=
	fi

	[[ ! -e a.cc ]] && echo 'void bar(char *); void foo() { char a[200]; bar(a); }' > a.cc

	#!/usr/bin/env python3
	import re, subprocess, sys

	def main():
	for line in open(sys.argv[1]).readlines():
	line = line.strip()
	m = re.match(r'Clang :: (.*)', line)
	if not m: continue
	name = m.group(1)
	print(name)

Fangrui Song MaskRay

pthread_exit/pthread_cancel.

`pthread_exit`/`pthread_cancel`.