109 lines
2.5 KiB
C++
109 lines
2.5 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#include <RB_INC_EXECINFO_H
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#include <RB_INC_SYS_MMAN_H
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#if defined(__GNUC__) && defined(HAVE_EXECINFO_H)
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#define IRCD_BACKTRACE_SUPPORT
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#endif
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#if defined(IRCD_BACKTRACE_SUPPORT) && defined(HAVE_SYS_MMAN_H) && !defined(__clang__)
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#define IRCD_BACKTRACE_GLIBC_WORKAROUND
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#endif
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#if defined(IRCD_BACKTRACE_GLIBC_WORKAROUND)
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// The problem here is that backtrace(3) performs checks against this value
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// which is not correct for our own allocated `ircd::ctx` stacks. To workaround
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// this we neutralize the value before calling backtrace(3) and restore it
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// afterward. While this symbol is extern accessible, the page its on is
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// write-protected at some point, so we have to re-allow writing to it here.
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//
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// sysdeps/i386/backtrace.c | elf/dl-support.c
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// > This is a global variable set at program start time. It marks the
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// > highest used stack address.
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//
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extern void *
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__libc_stack_end;
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void
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__attribute__((constructor))
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ircd_backtrace_allow_libc_fix()
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{
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static const auto &prot
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{
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PROT_READ | PROT_WRITE
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};
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const auto &addr
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{
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uintptr_t(&__libc_stack_end) & ~(getpagesize() - 1UL)
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};
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ircd::syscall(::mprotect, (void *)addr, sizeof(__libc_stack_end), prot);
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}
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#endif defined(IRCD_BACKTRACE_GLIBC_WORKAROUND)
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//
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// backtrace::backtrace
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//
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namespace ircd
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{
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static thread_local std::array<const void *, 512> backtrace_buffer;
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}
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ircd::backtrace::backtrace()
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:backtrace
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{
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backtrace_buffer.data(),
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backtrace_buffer.size()
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}
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{
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}
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ircd::backtrace::backtrace(const mutable_buffer &buf)
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:backtrace
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{
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reinterpret_cast<const void **>
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(
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const_cast<const char **>
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(
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std::addressof(data(buf))
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)
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),
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buffer::size(buf) / sizeof(void *)
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}
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{
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}
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ircd::backtrace::backtrace(const void **const &array,
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const size_t &count)
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:array
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{
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array
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}
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,count
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{
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0UL
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}
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{
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#if defined(IRCD_BACKTRACE_GLIBC_WORKAROUND)
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const scope_restore stack_check_workaround
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{
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__libc_stack_end, reinterpret_cast<void *>(uintptr_t(-1UL))
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};
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#endif
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#if defined(IRCD_BACKTRACE_SUPPORT)
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this->count = ::backtrace(const_cast<void **>(this->array), count);
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#endif
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}
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