1. 19 May, 2022 1 commit
  2. 28 Apr, 2022 1 commit
    • Igor Sheludko's avatar
      Reland "[rwx][mac] Support fast W^X permission switching on Apple Silicon (M1)" · 449ece38
      Igor Sheludko authored
      This is a reland of commit 9d31f866
      There were issues with --future flag implications on M1.
      
      Original change's description:
      > [rwx][mac] Support fast W^X permission switching on Apple Silicon (M1)
      >
      > ... for V8 code space. The feature is currently disabled.
      >
      > In order to use fast W^X permission switching we must allocate
      > executable pages with readable writable executable permissions (RWX).
      > However, MacOS on ARM64 ("Apple M1"/Apple Silicon) prohibits further
      > permission changing of RWX memory pages. This means that the code page
      > headers must be allocated with RWX permissions too because otherwise
      > it wouldn't be possible to allocate a large code page over the freed
      > regular code page and vice versa.
      >
      > When enabled, the new machinery works as follows:
      >
      > 1) when memory region is reserved for allocating executable pages, the
      >    whole region is committed with RWX permissions and then decommitted,
      > 2) since reconfiguration of RWX page permissions is not allowed on
      >    MacOS on ARM64 ("Apple M1"/Apple Silicon), there must be no attempts
      >    to change them,
      > 3) the request to set RWX permissions in the executable page region
      >    just recommits the pages without changing permissions (see (1), they
      >    were already allocated as RWX and then discarded),
      > 4) in order to make executable pages inaccessible one must use
      >    OS::DiscardSystemPages() instead of OS::DecommitPages() or
      >    setting permissions to kNoAccess because the latter two are not
      >    allowed by the MacOS (see (2)).
      > 5) since code space page headers are allocated as RWX pages it's also
      >    necessary to switch between W^X modes when updating the data in the
      >    page headers (i.e. when marking, updating stats, wiring pages in
      >    lists, etc.). The new CodePageHeaderModificationScope class is used
      >    in the respective places. On unrelated configurations it's a no-op.
      >
      > The fast permission switching can't be used for V8 configuration with
      > enabled pointer compression and disabled external code space because
      > a) the pointer compression cage has to be reserved with MAP_JIT flag
      >    which is too expensive,
      > b) in case of shared pointer compression cage if the code range will
      >    be deleted while the cage is still alive then attempt to configure
      >    permissions of pages that were previously set to RWX will fail.
      >
      > This also CL extends the unmapper unit tests with permissions tracking
      > for discarded pages.
      >
      > Bug: v8:12797
      > Change-Id: Idb28cbc481306477589eee9962d2e75167d87c61
      > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3579303
      > Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
      > Reviewed-by: Clemens Backes <clemensb@chromium.org>
      > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
      > Commit-Queue: Igor Sheludko <ishell@chromium.org>
      > Cr-Commit-Position: refs/heads/main@{#80238}
      
      Bug: v8:12797
      Change-Id: I0fe86666f31bad37d7074e217555c95900d2afba
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3610433Reviewed-by: 's avatarNico Hartmann <nicohartmann@chromium.org>
      Reviewed-by: 's avatarMichael Lippautz <mlippautz@chromium.org>
      Commit-Queue: Igor Sheludko <ishell@chromium.org>
      Reviewed-by: 's avatarClemens Backes <clemensb@chromium.org>
      Cr-Commit-Position: refs/heads/main@{#80259}
      449ece38
  3. 27 Apr, 2022 2 commits
    • Adam Klein's avatar
      Revert "[rwx][mac] Support fast W^X permission switching on Apple Silicon (M1)" · 10807c9f
      Adam Klein authored
      This reverts commit 9d31f866.
      
      Reason for revert: crashes on Mac/arm64 bots:
      https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Mac%20-%20arm64%20-%20debug/5923/overview
      
      Original change's description:
      > [rwx][mac] Support fast W^X permission switching on Apple Silicon (M1)
      >
      > ... for V8 code space. The feature is currently disabled.
      >
      > In order to use fast W^X permission switching we must allocate
      > executable pages with readable writable executable permissions (RWX).
      > However, MacOS on ARM64 ("Apple M1"/Apple Silicon) prohibits further
      > permission changing of RWX memory pages. This means that the code page
      > headers must be allocated with RWX permissions too because otherwise
      > it wouldn't be possible to allocate a large code page over the freed
      > regular code page and vice versa.
      >
      > When enabled, the new machinery works as follows:
      >
      > 1) when memory region is reserved for allocating executable pages, the
      >    whole region is committed with RWX permissions and then decommitted,
      > 2) since reconfiguration of RWX page permissions is not allowed on
      >    MacOS on ARM64 ("Apple M1"/Apple Silicon), there must be no attempts
      >    to change them,
      > 3) the request to set RWX permissions in the executable page region
      >    just recommits the pages without changing permissions (see (1), they
      >    were already allocated as RWX and then discarded),
      > 4) in order to make executable pages inaccessible one must use
      >    OS::DiscardSystemPages() instead of OS::DecommitPages() or
      >    setting permissions to kNoAccess because the latter two are not
      >    allowed by the MacOS (see (2)).
      > 5) since code space page headers are allocated as RWX pages it's also
      >    necessary to switch between W^X modes when updating the data in the
      >    page headers (i.e. when marking, updating stats, wiring pages in
      >    lists, etc.). The new CodePageHeaderModificationScope class is used
      >    in the respective places. On unrelated configurations it's a no-op.
      >
      > The fast permission switching can't be used for V8 configuration with
      > enabled pointer compression and disabled external code space because
      > a) the pointer compression cage has to be reserved with MAP_JIT flag
      >    which is too expensive,
      > b) in case of shared pointer compression cage if the code range will
      >    be deleted while the cage is still alive then attempt to configure
      >    permissions of pages that were previously set to RWX will fail.
      >
      > This also CL extends the unmapper unit tests with permissions tracking
      > for discarded pages.
      >
      > Bug: v8:12797
      > Change-Id: Idb28cbc481306477589eee9962d2e75167d87c61
      > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3579303
      > Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
      > Reviewed-by: Clemens Backes <clemensb@chromium.org>
      > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
      > Commit-Queue: Igor Sheludko <ishell@chromium.org>
      > Cr-Commit-Position: refs/heads/main@{#80238}
      
      Bug: v8:12797
      Change-Id: Ic07948e036db36326d464a2a901d052aa060a406
      No-Presubmit: true
      No-Tree-Checks: true
      No-Try: true
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3611665
      Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
      Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
      Auto-Submit: Adam Klein <adamk@chromium.org>
      Cr-Commit-Position: refs/heads/main@{#80239}
      10807c9f
    • Igor Sheludko's avatar
      [rwx][mac] Support fast W^X permission switching on Apple Silicon (M1) · 9d31f866
      Igor Sheludko authored
      ... for V8 code space. The feature is currently disabled.
      
      In order to use fast W^X permission switching we must allocate
      executable pages with readable writable executable permissions (RWX).
      However, MacOS on ARM64 ("Apple M1"/Apple Silicon) prohibits further
      permission changing of RWX memory pages. This means that the code page
      headers must be allocated with RWX permissions too because otherwise
      it wouldn't be possible to allocate a large code page over the freed
      regular code page and vice versa.
      
      When enabled, the new machinery works as follows:
      
      1) when memory region is reserved for allocating executable pages, the
         whole region is committed with RWX permissions and then decommitted,
      2) since reconfiguration of RWX page permissions is not allowed on
         MacOS on ARM64 ("Apple M1"/Apple Silicon), there must be no attempts
         to change them,
      3) the request to set RWX permissions in the executable page region
         just recommits the pages without changing permissions (see (1), they
         were already allocated as RWX and then discarded),
      4) in order to make executable pages inaccessible one must use
         OS::DiscardSystemPages() instead of OS::DecommitPages() or
         setting permissions to kNoAccess because the latter two are not
         allowed by the MacOS (see (2)).
      5) since code space page headers are allocated as RWX pages it's also
         necessary to switch between W^X modes when updating the data in the
         page headers (i.e. when marking, updating stats, wiring pages in
         lists, etc.). The new CodePageHeaderModificationScope class is used
         in the respective places. On unrelated configurations it's a no-op.
      
      The fast permission switching can't be used for V8 configuration with
      enabled pointer compression and disabled external code space because
      a) the pointer compression cage has to be reserved with MAP_JIT flag
         which is too expensive,
      b) in case of shared pointer compression cage if the code range will
         be deleted while the cage is still alive then attempt to configure
         permissions of pages that were previously set to RWX will fail.
      
      This also CL extends the unmapper unit tests with permissions tracking
      for discarded pages.
      
      Bug: v8:12797
      Change-Id: Idb28cbc481306477589eee9962d2e75167d87c61
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3579303Reviewed-by: 's avatarNico Hartmann <nicohartmann@chromium.org>
      Reviewed-by: 's avatarClemens Backes <clemensb@chromium.org>
      Reviewed-by: 's avatarMichael Lippautz <mlippautz@chromium.org>
      Commit-Queue: Igor Sheludko <ishell@chromium.org>
      Cr-Commit-Position: refs/heads/main@{#80238}
      9d31f866
  4. 19 Apr, 2022 1 commit
  5. 18 Apr, 2022 1 commit
    • Deepti Gandluri's avatar
      Revert "[rwx][mac] Introduce RwxMemoryWriteScope" · e73757be
      Deepti Gandluri authored
      This reverts commit 4d8e1846.
      
      Reason for revert: Blocks V8 roll, crbug.com/1316800
      
      Original change's description:
      > [rwx][mac] Introduce RwxMemoryWriteScope
      >
      > ... as a single bottleneck that encapsulates the semantics and
      > implementation of fast per-thread W^X permission switching supported
      > by Apple Silicon (arm64 M1).
      > On other architectures this class is a no-op.
      >
      > Bug: v8:12797
      > Change-Id: Ica842ff9f843e20b7f61fd7e80591e7a1fd29771
      > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3586986
      > Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
      > Commit-Queue: Igor Sheludko <ishell@chromium.org>
      > Cr-Commit-Position: refs/heads/main@{#79994}
      
      Bug: v8:12797
      Change-Id: I81792567839e72b4147d009c0845b0c0de003eb0
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3590752
      Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
      Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
      Owners-Override: Deepti Gandluri <gdeepti@chromium.org>
      Cr-Commit-Position: refs/heads/main@{#80007}
      e73757be
  6. 14 Apr, 2022 1 commit