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Alastair Houghton
cc0fb6e4da
On Linux, if one thread generates a backtrace while another is busy unmapping a file, the memory map can change after the backtracer's code has read it, which then means that the backtracer can crash attempting to access memory while it is trying to enumerate loaded images. Fix by changing the way we read memory on Linux so that by default, we do so in a failable manner. Fixes #92089 rdar://186982100
58 lines
1.5 KiB
C++
58 lines
1.5 KiB
C++
//===--- SafeReadMemory.cpp - Safe memory reading (POSIX) -------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// Safely read from the current process's memory.
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//
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//===----------------------------------------------------------------------===//
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#include "modules/OS/SafeReadMemory.h"
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#ifdef __linux__
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namespace {
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thread_local struct _swift_read_memory_context ctx;
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void _swift_handle_fault(int sig) {
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(void)sig;
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siglongjmp(ctx.fault_buf, -1);
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}
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}
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extern "C" swift_read_memory_context_t _swift_begin_reading_memory(void)
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{
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if (!ctx.reading) {
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ctx.reading = true;
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struct sigaction sa;
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sigfillset(&sa.sa_mask);
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sa.sa_handler = _swift_handle_fault;
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sa.sa_flags = SA_NODEFER;
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sigaction(SIGSEGV, &sa, &ctx.sa_old_segv);
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sigaction(SIGBUS, &sa, &ctx.sa_old_bus);
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}
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return &ctx;
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}
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extern "C" void _swift_end_reading_memory(swift_read_memory_context_t pctx)
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{
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if (pctx->reading) {
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sigaction(SIGSEGV, &pctx->sa_old_segv, NULL);
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sigaction(SIGBUS, &pctx->sa_old_bus, NULL);
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pctx->reading = false;
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}
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}
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#endif // __linux__
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