Revert of Non-SFI mode: Add Linux asynchronous signal support

src/nonsfi/linux/irt_signal_handling.c

Index: src/nonsfi/linux/irt_signal_handling.c
diff --git a/src/nonsfi/linux/irt_signal_handling.c b/src/nonsfi/linux/irt_signal_handling.c
deleted file mode 100644
index 9edd3754c84b3953d30b29561a23632b44eff2d5..0000000000000000000000000000000000000000
--- a/src/nonsfi/linux/irt_signal_handling.c
+++ /dev/null
@@ -1,513 +0,0 @@
-/*
- * Copyright (c) 2015 The Native Client Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include <errno.h>
-#include <pthread.h>
-#include <signal.h>
-#include <stdint.h>
-#include <string.h>
-#include <unistd.h>
-
-#include "native_client/src/include/elf_constants.h"
-#include "native_client/src/include/nacl/nacl_exception.h"
-#include "native_client/src/include/nacl_macros.h"
-#include "native_client/src/nonsfi/linux/irt_signal_handling.h"
-#include "native_client/src/nonsfi/linux/linux_sys_private.h"
-#include "native_client/src/nonsfi/linux/linux_syscall_defines.h"
-#include "native_client/src/nonsfi/linux/linux_syscall_structs.h"
-#include "native_client/src/public/linux_syscalls/sys/syscall.h"
-#include "native_client/src/public/nonsfi/irt_signal_handling.h"
-#include "native_client/src/untrusted/irt/irt.h"
-
-typedef struct compat_sigaltstack {
-  uint32_t ss_sp;
-  int32_t ss_flags;
-  uint32_t ss_size;
-} linux_stack_t;
-
-#if defined(__i386__)
-
-/* From linux/arch/x86/include/uapi/asm/sigcontext32.h */
-struct sigcontext_ia32 {
-  uint16_t gs, __gsh;
-  uint16_t fs, __fsh;
-  uint16_t es, __esh;
-  uint16_t ds, __dsh;
-  uint32_t di;
-  uint32_t si;
-  uint32_t bp;
-  uint32_t sp;
-  uint32_t bx;
-  uint32_t dx;
-  uint32_t cx;
-  uint32_t ax;
-  uint32_t trapno;
-  uint32_t err;
-  uint32_t ip;
-  uint16_t cs, __csh;
-  uint32_t flags;
-  uint32_t sp_at_signal;
-  uint16_t ss, __ssh;
-  uint32_t fpstate;
-  uint32_t oldmask;
-  uint32_t cr2;
-};
-
-typedef struct sigcontext_ia32 linux_mcontext_t;
-
-#elif defined(__arm__)
-
-/* From linux/arch/arm/include/uapi/asm/sigcontext.h */
-struct sigcontext_arm {
-  uint32_t trap_no;
-  uint32_t error_code;
-  uint32_t oldmask;
-  uint32_t arm_r0;
-  uint32_t arm_r1;
-  uint32_t arm_r2;
-  uint32_t arm_r3;
-  uint32_t arm_r4;
-  uint32_t arm_r5;
-  uint32_t arm_r6;
-  uint32_t arm_r7;
-  uint32_t arm_r8;
-  uint32_t arm_r9;
-  uint32_t arm_r10;
-  uint32_t arm_r11;  /* fp */
-  uint32_t arm_r12;  /* ip */
-  uint32_t arm_sp;
-  uint32_t arm_lr;
-  uint32_t arm_pc;
-  uint32_t arm_cpsr;
-  uint32_t fault_address;
-};
-
-typedef struct sigcontext_arm linux_mcontext_t;
-
-#else
-#error "unsupported architecture"
-#endif
-
-/* From linux/arch/arm/include/asm/ucontext.h */
-struct linux_ucontext_t {
-  uint32_t uc_flags;
-  uint32_t uc_link;
-  linux_stack_t uc_stack;
-  linux_mcontext_t uc_mcontext;
-  linux_sigset_t uc_sigmask;
-  /* More data follows which we don't care about. */
-};
-
-/*
- * Crash signals to handle.  The differences from SFI NaCl are that
- * NonSFI NaCl does not use NACL_THREAD_SUSPEND_SIGNAL (==SIGUSR1),
- */
-static const int kSignals[] = {
-  LINUX_SIGSTKFLT,
-  LINUX_SIGINT, LINUX_SIGQUIT, LINUX_SIGILL, LINUX_SIGTRAP, LINUX_SIGBUS,
-  LINUX_SIGFPE, LINUX_SIGSEGV,
-  /* Handle SIGABRT in case someone sends it asynchronously using kill(). */
-  LINUX_SIGABRT,
-};
-
-static pthread_mutex_t g_mutex = PTHREAD_MUTEX_INITIALIZER;
-static NaClExceptionHandler g_signal_handler_function_pointer = NULL;
-static NaClExceptionHandler g_exception_handler_function_pointer = NULL;
-static int g_signal_handler_initialized = 0;
-static int g_tgid = 0;
-static int g_main_tid;
-
-struct NonSfiExceptionFrame {
-  struct NaClExceptionContext context;
-  struct NaClExceptionPortableContext portable;
-};
-
-static void machine_context_to_register(const linux_mcontext_t *mctx,
-                                        NaClUserRegisterState *dest) {
-#if defined(__i386__)
-#define COPY_REG(A) dest->e##A = mctx->A
-  COPY_REG(ax);
-  COPY_REG(cx);
-  COPY_REG(dx);
-  COPY_REG(bx);
-  COPY_REG(bp);
-  COPY_REG(si);
-  COPY_REG(di);
-#undef COPY_REG
-  dest->stack_ptr = mctx->sp;
-  dest->prog_ctr = mctx->ip;
-  dest->flags = mctx->flags;
-#elif defined(__arm__)
-#define COPY_REG(A) dest->A = mctx->arm_##A
-  COPY_REG(r0);
-  COPY_REG(r1);
-  COPY_REG(r2);
-  COPY_REG(r3);
-  COPY_REG(r4);
-  COPY_REG(r5);
-  COPY_REG(r6);
-  COPY_REG(r7);
-  COPY_REG(r8);
-  COPY_REG(r9);
-  COPY_REG(r10);
-  COPY_REG(r11);
-  COPY_REG(r12);
-#undef COPY_REG
-  dest->stack_ptr = mctx->arm_sp;
-  dest->lr = mctx->arm_lr;
-  dest->prog_ctr = mctx->arm_pc;
-  dest->cpsr = mctx->arm_cpsr;
-#else
-# error Unsupported architecture
-#endif
-}
-
-static void nonsfi_exception_frame_from_signal_context(
-    struct NonSfiExceptionFrame *frame,
-    const void *raw_ctx) {
-  const struct linux_ucontext_t *uctx = (struct linux_ucontext_t *) raw_ctx;
-  const linux_mcontext_t *mctx = &uctx->uc_mcontext;
-  frame->context.size = (((uintptr_t) (&frame->portable + 1))
-                         - (uintptr_t) &frame->context);
-  frame->context.portable_context_offset = ((uintptr_t) &frame->portable
-                                            - (uintptr_t) &frame->context);
-  frame->context.portable_context_size = sizeof(frame->portable);
-  frame->context.regs_size = sizeof(frame->context.regs);
-
-  memset(frame->context.reserved, 0, sizeof(frame->context.reserved));
-  machine_context_to_register(mctx, &frame->context.regs);
-  frame->portable.prog_ctr = frame->context.regs.prog_ctr;
-  frame->portable.stack_ptr = frame->context.regs.stack_ptr;
-
-#if defined(__i386__)
-  frame->context.arch = EM_386;
-  frame->portable.frame_ptr = frame->context.regs.ebp;
-#elif defined(__arm__)
-  frame->context.arch = EM_ARM;
-  /* R11 is frame pointer in ARM mode, R8 is frame pointer in thumb mode. */
-  frame->portable.frame_ptr = frame->context.regs.r11;
-#else
-# error Unsupported architecture
-#endif
-}
-
-/* A replacement of sigreturn. It does not restore the signal mask. */
-static void __attribute__((noreturn))
-nonsfi_restore_context(const linux_mcontext_t *mctx) {
-
-#if defined(__i386__)
-
-#define OFFSET(name) \
-  [name] "i" (offsetof(linux_mcontext_t, name))
-#define RESTORE_SEGMENT(name) \
-  "mov %c[" #name "](%%eax), %%" #name "\n"
-#define RESTORE(name) \
-  "movl %c[" #name "](%%eax), %%e" #name "\n"
-
-  __asm__ __volatile__(
-      /* Restore floating-point environment */
-      "mov %c[fpstate](%%eax), %%ecx\n"
-      "fldenv (%%ecx)\n"
-
-      /* Restore all segment registers */
-      RESTORE_SEGMENT(gs)
-      RESTORE_SEGMENT(fs)
-      RESTORE_SEGMENT(es)
-      RESTORE_SEGMENT(ds)
-
-      /*
-       * Restore most of the other registers.
-       */
-      RESTORE(di)
-      RESTORE(si)
-      RESTORE(bp)
-      RESTORE(bx)
-
-      /*
-       * Prepare the last registers. eip *must* be one slot above the original
-       * stack, since that is the only way eip and esp can be simultaneously
-       * restored. Here, we are using ecx as the pseudo stack pointer, and edx
-       * as a scratch register. Once the stack is laid out the way we want it to
-       * be, restore edx and eax last.
-       */
-      "mov %c[sp](%%eax), %%ecx\n"
-      "mov %c[ip](%%eax), %%edx\n"
-      "mov %%edx, -4(%%ecx)\n"
-      "mov %c[flags](%%eax), %%edx\n"
-      "mov %%edx, -8(%%ecx)\n"
-      "mov %c[cx](%%eax), %%edx\n"
-      "mov %%edx, -12(%%ecx)\n"
-      RESTORE(dx)
-      RESTORE(ax)
-      "lea -12(%%ecx), %%esp\n"
-
-      /*
-       * Finally pop ecx off the stack, restore the processor flags, and return
-       * to simultaneously restore esp and eip.
-       */
-      "pop %%ecx\n"
-      "popf\n"
-      "ret\n"
-      :
-      : "a" (mctx),
-        OFFSET(gs),
-        OFFSET(fs),
-        OFFSET(es),
-        OFFSET(ds),
-        OFFSET(di),
-        OFFSET(si),
-        OFFSET(bp),
-        OFFSET(sp),
-        OFFSET(bx),
-        OFFSET(dx),
-        OFFSET(cx),
-        OFFSET(ax),
-        OFFSET(ip),
-        OFFSET(flags),
-        OFFSET(fpstate)
-  );
-
-#undef OFFSET
-#undef RESTORE
-#undef RESTORE_SEGMENT
-
-#elif defined(__arm__)
-
-#define OFFSET(name) \
-  [name] "I" (offsetof(linux_mcontext_t, arm_ ## name) - \
-              offsetof(linux_mcontext_t, arm_r0))
-
-  register uint32_t a14 __asm__("r14") = (uint32_t) &mctx->arm_r0;
-
-  __asm__ __volatile__(
-      /* Restore flags */
-      "ldr r0, [r14, %[cpsr]]\n"
-      "msr APSR_nzcvqg, r0\n"
-
-      /*
-       * Restore general-purpose registers.
-       * This code does not use the simpler 'ldmia r14, {r0-pc}' since using
-       * ldmia with either sp or with both lr and pc is deprecated.
-       */
-      "ldmia r14, {r0-r10}\n"
-
-      /*
-       * Copy r11, r12, lr, and pc just before the original sp.
-       * r12 will work as a temporary sp. r11 will be the scratch register, and
-       * will be restored just before moving sp.
-       */
-      "ldr r12, [r14, %[sp]]\n"
-
-      "ldr r11, [r14, %[pc]]\n"
-      "stmdb r12!, {r11}\n"
-      "ldr r11, [r14, %[lr]]\n"
-      "stmdb r12!, {r11}\n"
-      "ldr r11, [r14, %[r12]]\n"
-      "stmdb r12!, {r11}\n"
-      "ldr r11, [r14, %[r11]]\n"
-      "mov sp, r12\n"
-
-      /*
-       * Restore r12, lr, and pc. sp will point to the correct location once
-       * we're done.
-       */
-      "pop {r12, lr}\n"
-      "pop {pc}\n"
-      :
-      : "r" (a14),
-        OFFSET(cpsr),
-        OFFSET(r11),
-        OFFSET(r12),
-        OFFSET(sp),
-        OFFSET(lr),
-        OFFSET(pc)
-  );
-
-#undef OFFSET
-
-#else
-# error Unsupported architecture
-#endif
-
-  /* Should never reach this. */
-  __builtin_trap();
-}
-
-static __attribute__((noreturn))
-void restore_context(void *raw_ctx) {
-  const struct linux_ucontext_t *uctx = (struct linux_ucontext_t *) raw_ctx;
-  const linux_mcontext_t *mctx = &uctx->uc_mcontext;
-  nonsfi_restore_context(mctx);
-}
-
-/* Signal handlers, responsible for calling the registered handlers. */
-static void exception_catch(int sig, linux_siginfo_t *info, void *uc) {
-  if (g_exception_handler_function_pointer) {
-    struct NonSfiExceptionFrame exception_frame;
-    nonsfi_exception_frame_from_signal_context(&exception_frame, uc);
-    g_exception_handler_function_pointer(&exception_frame.context);
-  }
-  _exit(-sig);
-}
-
-static void signal_catch(int sig, linux_siginfo_t *info, void *uc) {
-  if (g_signal_handler_function_pointer) {
-    struct NonSfiExceptionFrame exception_frame;
-    nonsfi_exception_frame_from_signal_context(&exception_frame, uc);
-    g_signal_handler_function_pointer(&exception_frame.context);
-  }
-  restore_context(uc);
-}
-
-static void nonsfi_install_exception_handler_locked() {
-  struct linux_sigaction sa;
-  unsigned int a;
-
-  memset(&sa, 0, sizeof(sa));
-  sa.sa_sigaction = exception_catch;
-  sa.sa_flags = LINUX_SA_SIGINFO | LINUX_SA_ONSTACK;
-
-  /*
-   * Reuse the sigemptyset/sigaddset for the first 32 bits of the
-   * sigmask. Works on little endian systems only.
-   */
-  sigset_t *mask = (sigset_t*)&sa.sa_mask;
-  sigemptyset(mask);
-
-  /* Mask all signals we catch to prevent re-entry. */
-  for (a = 0; a < NACL_ARRAY_SIZE(kSignals); a++) {
-    sigaddset(mask, kSignals[a]);
-  }
-
-  /* Install all handlers. */
-  for (a = 0; a < NACL_ARRAY_SIZE(kSignals); a++) {
-    if (linux_sigaction(kSignals[a], &sa, NULL) != 0)
-      abort();
-  }
-}
-
-static void nonsfi_install_signal_handler_locked() {
-  struct linux_sigaction sa;
-
-  memset(&sa, 0, sizeof(sa));
-  sa.sa_sigaction = signal_catch;
-
-  /*
-   * User signal handler can be recursively interrupted to avoid having
-   * to allow sigreturn/sigprocmask.
-   */
-  sa.sa_flags = LINUX_SA_SIGINFO | LINUX_SA_NODEFER | LINUX_SA_RESTART;
-  sigset_t *mask = (sigset_t*)&sa.sa_mask;
-  sigemptyset(mask);
-
-  /*
-   * Install a single handler.  Multiple signals can be multiplexed in
-   * userspace.
-   */
-  if (linux_sigaction(LINUX_SIGUSR1, &sa, NULL) != 0)
-    abort();
-}
-
-static void nonsfi_initialize_signal_handler_locked() {
-  if (g_signal_handler_initialized)
-    return;
-  pid_t tgid = getpid();
-  if (tgid == -1)
-    abort();
-  pid_t main_tid = syscall(__NR_gettid);
-  if (main_tid == -1)
-    abort();
-  nonsfi_install_exception_handler_locked();
-  nonsfi_install_signal_handler_locked();
-  g_tgid = tgid;
-  g_main_tid = main_tid;
-  g_signal_handler_initialized = 1;
-}
-
-/*
- * Initialize signal handlers before entering sandbox.
- */
-void nonsfi_initialize_signal_handler() {
-  if (pthread_mutex_lock(&g_mutex) != 0)
-    abort();
-  nonsfi_initialize_signal_handler_locked();
-  if (pthread_mutex_unlock(&g_mutex) != 0)
-    abort();
-}
-
-int nacl_exception_get_and_set_handler(NaClExceptionHandler handler,
-                                       NaClExceptionHandler *old_handler) {
-  if (pthread_mutex_lock(&g_mutex) != 0)
-    abort();
-  nonsfi_initialize_signal_handler_locked();
-  if (old_handler)
-    *old_handler = g_exception_handler_function_pointer;
-  g_exception_handler_function_pointer = handler;
-  if (pthread_mutex_unlock(&g_mutex) != 0)
-    abort();
-  return 0;
-}
-
-int nacl_exception_set_handler(NaClExceptionHandler handler) {
-  return nacl_exception_get_and_set_handler(handler, NULL);
-}
-
-int nacl_exception_clear_flag(void) {
-  /*
-   * Unblock signals, useful for unit testing and continuing to
-   * process after fatal signal.
-   */
-
-  /* Allocate the 8 bytes of signal mask. */
-  linux_sigset_t mask;
-
-  /*
-   * sigemptyset will only clear first 4 bytes of sigset_t, and
-   * compat_sigset_t has 8 bytes, clear with memset.
-   */
-  memset(&mask, 0, sizeof(mask));
-
-  /*
-   * Hack to be able to reuse sigset_t utilities from newlib for the
-   * first lower 4 bytes of the signal, works because we are all
-   * little endians.
-   */
-  sigset_t *maskptr = (sigset_t *) &mask;
-  sigemptyset(maskptr);
-  for (int a = 0; a < NACL_ARRAY_SIZE(kSignals); a++) {
-    if (sigaddset(maskptr, kSignals[a]) != 0)
-      abort();
-  }
-  if (linux_sigprocmask(LINUX_SIG_UNBLOCK, &mask, NULL) != 0)
-    abort();
-
-  return 0;
-}
-
-int nacl_exception_set_stack(void *p, size_t s) {
-  /* Not implemented yet. */
-  return ENOSYS;
-}
-
-int nacl_async_signal_set_handler(NaClIrtAsyncSignalHandler handler) {
-  if (pthread_mutex_lock(&g_mutex) != 0)
-    abort();
-  nonsfi_initialize_signal_handler_locked();
-  g_signal_handler_function_pointer = handler;
-  if (pthread_mutex_unlock(&g_mutex) != 0)
-    abort();
-  return 0;
-}
-
-int nacl_async_signal_send_async_signal(nacl_irt_tid_t tid) {
-  if (!g_signal_handler_initialized)
-    return ESRCH;
-  if (tid == 0)
-    tid = g_main_tid;
-  if (linux_tgkill(g_tgid, tid, LINUX_SIGUSR1) == -1)
-    return errno;
-  return 0;
-}