This reverts commit fee168ce.

Reason for revert: The DCHECK fails when freeing code
(https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/38292/overview),
which means that the current code is not correct. The added DCHECK
makes the bots red though, so the state before this CL was still
better.

Original change's description:
> [wasm] Check correctness of thread-local write protection
>
> We make an undocumented assumption in {CodeSpaceWriteScope} that a
> single thread will only work on one module at a time. If this is
> violated, the thread-local {code_space_write_nesting_level_} would
> prevent the second module from being switched to writable.
>
> This CL adds a second thread local (in debug only) to check that if
> there is already a {CodeSpaceWriteScope} open that it contains the same
> {NativeModule} as any nested scope.
>
> R=​jkummerow@chromium.org
>
> Change-Id: I43fa886d9d0fdf0e1846137dc411745fcca471fa
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3074477
> Commit-Queue: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#76134}

TBR=jkummerow@chromium.org

Change-Id: I5262b0e886f99a64452966345fc084a1ab750459
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3078360Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76146}

pthread_jit_write_protect* functions are only available on arm64 Mac,
not on iOS (which also sets V8_{TARGET_,}OS_MACOSX).
This CL refactors the logic to detect whether pthread_jit_write_protect
and MAP_JIT are available and defines a global preprocessor macro which
can subsequently be used instead of the existing complex condition.

R=jkummerow@chromium.org, mlippautz@chromium.org

Change-Id: I63894f42df35406d6eee90a4ce5070c2fde7b566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3077154Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Auto-Submit: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76143}

We make an undocumented assumption in {CodeSpaceWriteScope} that a
single thread will only work on one module at a time. If this is
violated, the thread-local {code_space_write_nesting_level_} would
prevent the second module from being switched to writable.

This CL adds a second thread local (in debug only) to check that if
there is already a {CodeSpaceWriteScope} open that it contains the same
{NativeModule} as any nested scope.

R=jkummerow@chromium.org

Change-Id: I43fa886d9d0fdf0e1846137dc411745fcca471fa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3074477
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76134}

Since {CodeSpaceWriteScope} is now used from cctests (since
https://crrev.com/c/3024150), its constructor and destructor need to be
exported.

R=jkummerow@chromium.org

Change-Id: I30627d632a9f4e4fde51bcb037bad69ceaedf6fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3038062
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75786}

This removes the low-level {SwitchMemoryPermissionsToWritable()} and
{SwitchMemoryPermissionsToExecutable()} functions. They are only used in
tests and can be replaced by {CodeSpaceWriteScope} objects that we also
use in production.

R=jkummerow@chromium.org

Change-Id: I7ba702c836f3ac2dd7c7a81d6362040b28e8bef4
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3024150
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75739}

We had two implementations of a thread-local counter for the number of
writers: One in {CodeSpaceWriteScope} and one in
{WasmCodeManager::SetThreadWritable}. This CL removes the latter, and
uses the counter in {CodeSpaceWriteScope} for all implementations.

R=jkummerow@chromium.org

Bug: v8:11974
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng
Change-Id: I683131296c6106a2b12986942bb18e6c0e716612
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3024148Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75733}

Merges `NativeModuleModificationScope` (with an implementation using
Intel PKU, if available, and mprotect otherwise) and
`CodeSpaceWriteScope` (for Apple Silicon, where switching to RWX with
mprotect is disallowed anyway, so MAP_JIT and thread-local switching
must be used).

Because `CodeSpaceWriteScope` sounded better (and is shorter), we kept
its name (which unfortunately makes the diff a bit harder to read).

R=clemensb@chromium.org
CC=jkummerow@chromium.org

Bug: v8:11714

Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Change-Id: Ib2a7d18e72797a725ed34b904c70769166d811dd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2972911Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Daniel Lehmann <dlehmann@google.com>
Cr-Commit-Position: refs/heads/master@{#75272}

In an effort to merge `CODE_SPACE_WRITE_SCOPE` and
`NativeModuleModificationScope`, this CL moves the interface and
implementation of the latter into code-space-access.{h,cc}, where the
former already lives. No other changes to the code itself.

R=clemensb@chromium.org
CC=jkummerow@chromium.org

Bug: v8:11714

Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Change-Id: I1aabce26f2033430523a7a3a0a4864e7267bee21
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2972803Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Daniel Lehmann <dlehmann@google.com>
Cr-Commit-Position: refs/heads/master@{#75267}

This will make accidental includes much easier to see and fix. Without
this, you might get compiler or linker errors instead.

R=jkummerow@chromium.org

Bug: v8:11238
Cq-Include-Trybots: luci.v8.try:v8_linux64_no_wasm_compile_rel
Change-Id: I235d779f9c1ed3af5d736f1554ded427935ddc9b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2756531
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73422}

Scopes in V8 are used to guarantee one or more properties during its
lifetimes. If a scope is not named e.g MyClassScope(args) instead of
MyClassScope scope(args) it will get created and automatically destroyed
and therefore, being useless as a scope. This CL would produce a
compiling warning when that happens to ward off this developer error.

Follow-up to ccrev.com/2552415 in which it was introduced and
implemented for Guard classes.

Change-Id: Ifa0fb89cc3d9bdcdee0fd8150a2618af5ef45cbf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2555001
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71425}

Apple's upcoming arm64 devices will prevent rwx access to memory,
but in turn provide a new per-thread way to switch between write
and execute permissions. This patch puts that system to use for
the WebAssembly subsystem.
The approach relies on CodeSpaceWriteScope objects for now. That
isn't optimal for background threads (which could stay in "write"
mode permanently instead of toggling), but its simplicity makes
it a good first step.

Background:
https://developer.apple.com/documentation/apple_silicon/porting_just-in-time_compilers_to_apple_silicon

Bug: chromium:1117591
Change-Id: I3b60f0efd34c0fed924dfc71ee2c7805801c5d42
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2378307
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69791}