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https://github.com/jart/cosmopolitan.git
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2278327eba
This change makes some miracle modifications to the System Five system call support, which lets us have safe, correct, and atomic handling of thread cancellations. It all turned out to be cheaper than anticipated because it wasn't necessary to modify the system call veneers. We were able to encode the cancellability of each system call into the magnums found in libc/sysv/syscalls.sh. Since cancellations are so waq, we are also supporting a lovely Musl Libc mask feature for raising ECANCELED.
241 lines
8.8 KiB
C
241 lines
8.8 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 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/calls/calls.h"
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#include "libc/calls/struct/rusage.h"
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#include "libc/calls/struct/sigaction.h"
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#include "libc/calls/struct/siginfo.h"
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#include "libc/calls/struct/sigset.h"
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#include "libc/calls/struct/sigset.internal.h"
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#include "libc/calls/syscall_support-sysv.internal.h"
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#include "libc/calls/ucontext.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/nexgen32e/nexgen32e.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/sa.h"
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#include "libc/sysv/consts/sig.h"
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#include "libc/sysv/consts/uc.h"
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#include "libc/testlib/testlib.h"
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#include "third_party/xed/x86.h"
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struct sigaction oldsa;
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volatile bool gotsigint;
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void SetUpOnce(void) {
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ASSERT_SYS(0, 0, pledge("stdio rpath proc", 0));
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}
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void OnSigInt(int sig) {
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CheckStackIsAligned();
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gotsigint = true;
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}
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void SetUp(void) {
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gotsigint = false;
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}
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////////////////////////////////////////////////////////////////////////////////
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// test raise()
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TEST(sigaction, raise) {
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struct sigaction saint = {.sa_handler = OnSigInt};
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EXPECT_SYS(0, 0, sigaction(SIGINT, &saint, &oldsa));
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ASSERT_FALSE(gotsigint);
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EXPECT_NE(-1, raise(SIGINT));
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ASSERT_TRUE(gotsigint);
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EXPECT_SYS(0, 0, sigaction(SIGINT, &oldsa, NULL));
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}
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////////////////////////////////////////////////////////////////////////////////
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// test kill()
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TEST(sigaction, testPingPongParentChildWithSigint) {
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int pid, status;
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sigset_t blockint, oldmask;
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struct sigaction oldint;
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struct sigaction ignoreint = {.sa_handler = SIG_IGN};
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struct sigaction catchint = {.sa_handler = OnSigInt};
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if (IsWindows()) {
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// this works if it's run by itself on the command prompt. but it
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// doesn't currently work if it's launched as a subprocess of some
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// kind of runner. todo(fixme!)
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return;
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}
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EXPECT_SYS(0, 0, sigemptyset(&blockint));
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EXPECT_SYS(0, 0, sigaddset(&blockint, SIGINT));
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EXPECT_SYS(0, 0, sigprocmask(SIG_BLOCK, &blockint, &oldmask));
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EXPECT_SYS(0, 0, sigaction(SIGINT, &catchint, &oldint));
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ASSERT_NE(-1, (pid = fork()));
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if (!pid) {
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// ping
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EXPECT_SYS(0, 0, kill(getppid(), SIGINT));
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EXPECT_FALSE(gotsigint);
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// pong
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EXPECT_SYS(0, 0, sigaction(SIGINT, &catchint, 0));
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EXPECT_SYS(EINTR, -1, sigsuspend(0));
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EXPECT_TRUE(gotsigint);
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_exit(0);
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}
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// pong
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EXPECT_FALSE(gotsigint);
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EXPECT_SYS(0, 0, sigaction(SIGINT, &catchint, 0));
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EXPECT_SYS(EINTR, -1, sigsuspend(0));
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EXPECT_TRUE(gotsigint);
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// ping
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EXPECT_SYS(0, 0, sigaction(SIGINT, &ignoreint, 0));
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EXPECT_SYS(0, 0, kill(pid, SIGINT));
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// cleanup
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EXPECT_NE(-1, wait4(pid, &status, 0, 0));
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EXPECT_EQ(1, WIFEXITED(status));
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EXPECT_EQ(0, WEXITSTATUS(status));
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EXPECT_EQ(0, WTERMSIG(status));
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EXPECT_SYS(0, 0, sigaction(SIGINT, &oldint, 0));
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EXPECT_SYS(0, 0, sigprocmask(SIG_BLOCK, &oldmask, 0));
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}
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////////////////////////////////////////////////////////////////////////////////
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// test int3 crash
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// we expect this to be recoverable by default
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volatile int trapeax;
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void OnTrap(int sig, struct siginfo *si, void *vctx) {
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struct ucontext *ctx = vctx;
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CheckStackIsAligned();
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trapeax = ctx->uc_mcontext.rax;
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}
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TEST(sigaction, debugBreak_handlerCanReadCpuState) {
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struct sigaction saint = {.sa_sigaction = OnTrap, .sa_flags = SA_SIGINFO};
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EXPECT_NE(-1, sigaction(SIGTRAP, &saint, &oldsa));
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asm("int3" : /* no outputs */ : "a"(0x31337));
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EXPECT_EQ(0x31337, trapeax);
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EXPECT_SYS(0, 0, sigaction(SIGTRAP, &oldsa, NULL));
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}
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////////////////////////////////////////////////////////////////////////////////
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// test fpu crash (unrecoverable)
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// test signal handler can modify cpu registers (now it's recoverable!)
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void SkipOverFaultingInstruction(struct ucontext *ctx) {
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CheckStackIsAligned();
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struct XedDecodedInst xedd;
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xed_decoded_inst_zero_set_mode(&xedd, XED_MACHINE_MODE_LONG_64);
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xed_instruction_length_decode(&xedd, (void *)ctx->uc_mcontext.rip, 15);
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ctx->uc_mcontext.rip += xedd.length;
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}
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void OnFpe(int sig, struct siginfo *si, void *vctx) {
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struct ucontext *ctx = vctx;
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CheckStackIsAligned();
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SkipOverFaultingInstruction(ctx);
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ctx->uc_mcontext.rax = 42;
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ctx->uc_mcontext.rdx = 0;
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}
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noubsan void ubsanTrumpsSystemsEngineering(void) {
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struct sigaction saint = {.sa_sigaction = OnFpe, .sa_flags = SA_SIGINFO};
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EXPECT_SYS(0, 0, sigaction(SIGFPE, &saint, &oldsa));
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volatile long x = 0;
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EXPECT_EQ(42, 666 / x); /* systems engineering trumps math */
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EXPECT_SYS(0, 0, sigaction(SIGFPE, &oldsa, NULL));
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}
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TEST(sigaction, sigFpe_handlerCanEditProcessStateAndRecoverExecution) {
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ubsanTrumpsSystemsEngineering();
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}
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static unsigned OnSignalCnt = 0;
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void OnSignal(int sig, siginfo_t *si, void *ctx) {
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OnSignalCnt++;
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}
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TEST(sigaction, ignoringSignalDiscardsSignal) {
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struct sigaction sa = {.sa_sigaction = OnSignal, .sa_flags = SA_SIGINFO};
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ASSERT_EQ(0, sigaction(SIGUSR1, &sa, NULL));
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sigset_t blocked;
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sigemptyset(&blocked);
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sigaddset(&blocked, SIGUSR1);
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ASSERT_EQ(0, sigprocmask(SIG_SETMASK, &blocked, NULL));
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ASSERT_EQ(0, raise(SIGUSR1));
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ASSERT_NE(SIG_ERR, signal(SIGUSR1, SIG_IGN));
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ASSERT_EQ(0, sigaction(SIGUSR1, &sa, NULL));
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ASSERT_EQ(0, sigprocmask(SIG_UNBLOCK, &blocked, NULL));
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EXPECT_EQ(0, OnSignalCnt);
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}
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TEST(sigaction, autoZombieSlayer) {
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if (IsWindows()) return;
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int pid;
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struct sigaction sa;
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// make sure we're starting in expected state
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ASSERT_SYS(0, 0, sigaction(SIGCHLD, 0, &sa));
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ASSERT_EQ(SIG_DFL, sa.sa_handler);
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// verify child becomes zombie
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ASSERT_NE(-1, (pid = fork()));
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if (!pid) _Exit(0);
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ASSERT_SYS(0, pid, wait(0));
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// enable automatic zombie slayer
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sa.sa_handler = SIG_IGN;
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sa.sa_flags = SA_NOCLDWAIT; // seems to be optional
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sigemptyset(&sa.sa_mask);
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ASSERT_SYS(0, 0, sigaction(SIGCHLD, &sa, &sa));
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// verify it works
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ASSERT_NE(-1, (pid = fork()));
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if (!pid) _Exit(0);
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// XXX: WSL does the wrong thing here.
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if (IsWsl1()) usleep(10);
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ASSERT_SYS(ECHILD, -1, wait(0));
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// clean up
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ASSERT_SYS(0, 0, sigaction(SIGCHLD, &sa, 0));
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}
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TEST(sigaction, enosys_returnsErrnoRatherThanSigsysByDefault) {
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if (IsTiny()) return; // systemfive.S disables the fix w/ tiny
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if (IsOpenbsd()) return; // TODO: Why does OpenBSD raise SIGABRT?
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ASSERT_SYS(ENOSYS, -1, sys_bogus());
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}
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sig_atomic_t gotusr1;
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void OnSigMask(int sig, struct siginfo *si, void *ctx) {
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ucontext_t *uc = ctx;
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sigaddset(&uc->uc_sigmask, sig);
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gotusr1 = true;
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}
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TEST(uc_sigmask, signalHandlerCanChangeSignalMaskOfTrappedThread) {
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if (IsWindows()) return; // TODO(jart): uc_sigmask support on windows
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sigset_t want, got;
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struct sigaction oldsa;
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struct sigaction sa = {.sa_sigaction = OnSigMask, .sa_flags = SA_SIGINFO};
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sigemptyset(&want);
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ASSERT_SYS(0, 0, sigprocmask(SIG_SETMASK, &want, 0));
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ASSERT_SYS(0, 0, sigaction(SIGUSR1, &sa, &oldsa));
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ASSERT_SYS(0, 0, raise(SIGUSR1));
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ASSERT_TRUE(gotusr1);
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ASSERT_SYS(0, 0, sigprocmask(SIG_SETMASK, 0, &got));
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sigaddset(&want, SIGUSR1);
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ASSERT_STREQ(DescribeSigset(0, &want), DescribeSigset(0, &got));
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ASSERT_SYS(0, 0, sigaction(SIGUSR1, &oldsa, 0));
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sigdelset(&want, SIGUSR1);
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ASSERT_SYS(0, 0, sigprocmask(SIG_SETMASK, &want, 0));
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}
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