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https://github.com/jart/cosmopolitan.git
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af7bd80430
This change introduces a new deadlock detector for Cosmo's POSIX threads implementation. Error check mutexes will now track a DAG of nested locks and report EDEADLK when a deadlock is theoretically possible. These will occur rarely, but it's important for production hardening your code. You don't even need to change your mutexes to use the POSIX error check mode because `cosmocc -mdbg` will enable error checking on mutexes by default globally. When cycles are found, an error message showing your demangled symbols describing the strongly connected component are printed and then the SIGTRAP is raised, which means you'll also get a backtrace if you're using ShowCrashReports() too. This new error checker is so low-level and so pure that it's able to verify the relationships of every libc runtime lock, including those locks upon which the mutex implementation depends.
105 lines
3.6 KiB
ArmAsm
105 lines
3.6 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│ vi: set noet ft=asm ts=8 sw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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#include "libc/dce.h"
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nop
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// Invokes deferred function calls.
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//
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// This offers behavior similar to std::unique_ptr. Functions
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// overwrite their return addresses jumping here, and pushing
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// exactly one entry on the shadow stack below. Functions may
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// repeat that process multiple times, in which case the body
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// of this gadget loops and unwinds as a natural consequence.
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//
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// @param rax,rdx,xmm0,xmm1,st0,st1 is return value
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// @see test/libc/runtime/gc_test.c
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.ftrace1
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__gc: .ftrace2
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#ifdef __x86_64__
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mov %gs:0x30,%rcx // __get_tls()
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mov 0x18(%rcx),%rcx // tls::garbages
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decl (%rcx) // --g->i
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mov (%rcx),%r8d // r8 = g->i
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mov 8(%rcx),%r9 // r9 = g->p
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js 9f
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shl $5,%r8
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lea (%r9,%r8),%r8
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mov 8(%r8),%r9
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mov 16(%r8),%rdi
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push 24(%r8)
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push %rbp
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mov %rsp,%rbp
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sub $32,%rsp
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mov %rax,-8(%rbp)
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mov %rdx,-16(%rbp)
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movdqa %xmm0,-32(%rbp)
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call *%r9
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movdqa -32(%rbp),%xmm0
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mov -16(%rbp),%rdx
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mov -8(%rbp),%rax
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leave
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ret
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9: ud2
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nop
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#elif defined(__aarch64__)
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// if this code fails
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// check if CosmoTib's size changed
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sub x8,x28,#1024 // __get_tls()
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ldr x9,[x8,0x18] // tib::garbages
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ldr x10,[x9] // g->i
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ldr x8,[x9,8] // g->p
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sub x10,x10,#1 //
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str x10,[x9] //
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sbfiz x10,x10,5,32 //
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add x8,x8,x10 // g->p+i
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ldr x9,[x8,#8] // g->p[i].fn
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ldr x10,[x8,#16] // g->p[i].arg
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ldr x11,[x8,#24] // g->p[i].ret
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stp x29,x11,[sp,-208]!
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mov x29,sp
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stp x0,x1,[sp,16]
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stp x2,x3,[sp,32]
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stp x4,x5,[sp,48]
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stp x6,x7,[sp,64]
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stp q0,q1,[sp,80]
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stp q2,q3,[sp,112]
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stp q4,q5,[sp,144]
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stp q6,q7,[sp,176]
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mov x0,x10
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blr x9
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ldp q6,q7,[sp,176]
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ldp q4,q5,[sp,144]
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ldp q2,q3,[sp,112]
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ldp q0,q1,[sp,80]
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ldp x6,x7,[sp,64]
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ldp x4,x5,[sp,48]
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ldp x2,x3,[sp,32]
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ldp x0,x1,[sp,16]
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ldp x29,x30,[sp],208
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ret
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#endif /* __x86_64__ */
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.endfn __gc,globl,hidden
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