mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-24 14:59:03 +00:00
42a3bb729a
It's now possible to use execve() when the parent process isn't built by cosmo. In such cases, the current process will kill all threads and then linger around, waiting for the newly created process to die, and then we propagate its exit code to the parent. This should help bazel and others Allocating private anonymous memory is now 5x faster on Windows. This is thanks to VirtualAlloc() which is faster than the file mapping APIs. The fork() function also now goes 30% faster, since we are able to avoid the VirtualProtect() calls on mappings in most cases now. Fixes #1253
109 lines
4.9 KiB
C
109 lines
4.9 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 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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#define ShouldUseMsabiAttribute() 1
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#include "ape/sections.internal.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/intrin/asmflag.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/nt/enum/pageflags.h"
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#include "libc/nt/memory.h"
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#include "libc/nt/runtime.h"
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#include "libc/nt/thunk/msabi.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/nr.h"
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#include "libc/sysv/consts/prot.h"
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__msabi extern typeof(VirtualProtectEx) *const __imp_VirtualProtectEx;
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__funline void __morph_mprotect(void *addr, size_t size, int prot, int ntprot) {
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#ifdef __x86_64__
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bool cf;
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int ax, dx;
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uint32_t op;
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if (!IsWindows()) {
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asm volatile(CFLAG_ASM("clc\n\t"
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"syscall")
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: CFLAG_CONSTRAINT(cf), "=a"(ax), "=d"(dx)
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: "1"(__NR_mprotect), "D"(addr), "S"(size), "2"(prot)
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: "rcx", "r8", "r9", "r10", "r11", "memory");
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#ifndef NDEBUG
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if (cf)
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ax = -ax;
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if (ax == -EPERM) {
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kprintf("error: need pledge(prot_exec) permission to code morph\n");
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}
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if (ax < 0) {
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kprintf("error: __morph_mprotect(%p, %#zx, %d) failed: errno=%d\n", addr,
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size, prot, -ax);
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}
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#endif
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} else {
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__imp_VirtualProtectEx(GetCurrentProcess(), addr, size, ntprot, &op);
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}
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#elif defined(__aarch64__)
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register long r0 asm("x0") = (long)addr;
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register long r1 asm("x1") = (long)size;
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register long r2 asm("x2") = (long)prot;
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register long r8 asm("x8") = (long)__NR_mprotect;
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register long r16 asm("x16") = (long)__NR_mprotect;
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asm volatile("svc\t0"
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: "+r"(r0)
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: "r"(r1), "r"(r2), "r"(r8), "r"(r16)
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: "memory");
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#endif
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}
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/**
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* Begins code morphing executable.
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*
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* The following example
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*
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* #include <cosmo.h>
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* #include <stdlib.h>
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*
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* privileged int main() { // privileged code is unmodifiable
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* ShowCrashReports(); // print report if trapped
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* __morph_begin(0); // make executable code R+W
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* *(char *)exit = 0xCC; // turn exit() into an INT3 trap
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* __morph_end(); // make executable code R+X
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* exit(0); // won't actually exit
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* }
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*
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* shows how the exit() function can be recompiled at runtime to become
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* an int3 (x86-64) debugger trap. What makes it tricky is Cosmopolitan
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* maintains a R^X invariant, in order to support OpenBSD. So when code
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* wants to modify some part of the executable image in memory the vast
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* majority of the code stops being executable during that time, unless
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* it's been linked into a special privileged section of the binary. It
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* is only possible to code morph from privileged functions. Privileged
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* functions are also only allowed to call other privileged functions.
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*/
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privileged void __morph_begin(void) {
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__morph_mprotect(__executable_start, __privileged_start - __executable_start,
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PROT_READ | PROT_WRITE, kNtPageWritecopy);
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}
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/**
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* Finishes code morphing executable.
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*/
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privileged void __morph_end(void) {
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__morph_mprotect(__executable_start, __privileged_start - __executable_start,
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PROT_READ | PROT_EXEC, kNtPageExecuteRead);
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}
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