1. 20 Sep, 2019 1 commit
    • Seth Brenith's avatar
      [tools] Use instance types of known Maps in v8_debug_helper · 1d3c4975
      Seth Brenith authored
      If we can read an object's Map pointer but not any data from the Map
      itself, we may still be able to accurately describe the object's type if
      the Map pointer matches one of the known Maps from the snapshot.
      GetObjectProperties uses that data in one of two ways:
      - If it is sure that the Map pointer matches a known Map, then it uses
        the type from that Map and continues as if it read the type normally.
      - If the Map pointer is at the right offset within a heap page to match
        a known Map, but the caller didn't provide the addresses of the first
        pages in Map space or read-only space, then the type of that Map is
        just a guess and gets returned in a separate array. This gives the
        caller the opportunity to present guessed types to the user, and
        perhaps call again using the guessed type as the type hint.
      
      Bug: v8:9376
      Change-Id: I187f67b77e76699863a14534a9d635b79f654124
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1787986
      Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
      Reviewed-by: 's avatarJakob Gruber <jgruber@chromium.org>
      Reviewed-by: 's avatarMichael Achenbach <machenbach@chromium.org>
      Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#63908}
      1d3c4975
  2. 09 Sep, 2019 1 commit
  3. 31 Jul, 2019 1 commit
    • Seth Brenith's avatar
      Reland "Add postmortem debugging helper library" · 0921e8f2
      Seth Brenith authored
      This is a reland of 517ab73f
      
      Updates since original: now compressed pointers passed to the function
      GetObjectProperties are required to be sign-extended. Previously, the
      function allowed zero-extended values, but that led to ambiguity on
      pointers like 0x88044919: is it compressed or is the heap range actually
      centered on 0x100000000?
      
      Original change's description:
      > Add postmortem debugging helper library
      >
      > This change begins to implement the functionality described in
      > https://docs.google.com/document/d/1evHnb1uLlSbvHAAsmOXyc25x3uh1DjgNa8u1RHvwVhk/edit#
      > for investigating V8 state in crash dumps.
      >
      > This change adds a new library, v8_debug_helper, for providing platform-
      > agnostic assistance with postmortem debugging. This library can be used
      > by extensions built for debuggers such as WinDbg or lldb. Its public API
      > is described by debug-helper.h; currently the only method it exposes is
      > GetObjectProperties, but we'd like to add more functionality over time.
      > The API surface is restricted to plain C-style structs and pointers, so
      > that it's easy to link from a debugger extension built with a different
      > toolchain.
      >
      > This change also adds a new cctest file to exercise some basic
      > interaction with the new library.
      >
      > The API function GetObjectProperties takes an object pointer (which
      > could be compressed, or weak, or a SMI), and returns a string
      > description of the object and a list of properties the object contains.
      > For now, the list of properties is entirely based on Torque object
      > definitions, but we expect to add custom properties in future updates so
      > that it can be easier to make sense of complex data structures such as
      > dictionaries.
      >
      > GetObjectProperties does several things that are intended to generate
      > somewhat useful results even in cases where memory may be corrupt or
      > unavailable:
      > - The caller may optionally provide a type string which will be used if
      >   the memory for the object's Map is inaccessible.
      > - All object pointers are compared against the list of known objects
      >   generated by mkgrokdump. The caller may optionally provide the
      >   pointers for the first pages of various heap spaces, to avoid spurious
      >   matches. If those pointers are not provided, then any matches are
      >   prefixed with "maybe" in the resulting description string, such as
      >   "maybe UndefinedValue (0x4288000341 <Oddball>)".
      >
      > Bug: v8:9376
      >
      > Change-Id: Iebf3cc2dea3133c7811bcefcdf38d9458b02fded
      > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1628012
      > Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
      > Reviewed-by: Yang Guo <yangguo@chromium.org>
      > Reviewed-by: Michael Stanton <mvstanton@chromium.org>
      > Cr-Commit-Position: refs/heads/master@{#62882}
      
      Bug: v8:9376
      Change-Id: I866a1cc9d4c34bfe10c7b98462451fe69763cf3f
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1717090Reviewed-by: 's avatarMichael Achenbach <machenbach@chromium.org>
      Reviewed-by: 's avatarMichael Stanton <mvstanton@chromium.org>
      Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
      Cr-Commit-Position: refs/heads/master@{#63008}
      0921e8f2
  4. 24 Jul, 2019 1 commit
    • Zhi An Ng's avatar
      Revert "Add postmortem debugging helper library" · 6747e3a1
      Zhi An Ng authored
      This reverts commit 517ab73f.
      
      Reason for revert: Test failures https://bugs.chromium.org/p/v8/issues/detail?id=9538
      
      Original change's description:
      > Add postmortem debugging helper library
      > 
      > This change begins to implement the functionality described in
      > https://docs.google.com/document/d/1evHnb1uLlSbvHAAsmOXyc25x3uh1DjgNa8u1RHvwVhk/edit#
      > for investigating V8 state in crash dumps.
      > 
      > This change adds a new library, v8_debug_helper, for providing platform-
      > agnostic assistance with postmortem debugging. This library can be used
      > by extensions built for debuggers such as WinDbg or lldb. Its public API
      > is described by debug-helper.h; currently the only method it exposes is
      > GetObjectProperties, but we'd like to add more functionality over time.
      > The API surface is restricted to plain C-style structs and pointers, so
      > that it's easy to link from a debugger extension built with a different
      > toolchain.
      > 
      > This change also adds a new cctest file to exercise some basic
      > interaction with the new library.
      > 
      > The API function GetObjectProperties takes an object pointer (which
      > could be compressed, or weak, or a SMI), and returns a string
      > description of the object and a list of properties the object contains.
      > For now, the list of properties is entirely based on Torque object
      > definitions, but we expect to add custom properties in future updates so
      > that it can be easier to make sense of complex data structures such as
      > dictionaries.
      > 
      > GetObjectProperties does several things that are intended to generate
      > somewhat useful results even in cases where memory may be corrupt or
      > unavailable:
      > - The caller may optionally provide a type string which will be used if
      >   the memory for the object's Map is inaccessible.
      > - All object pointers are compared against the list of known objects
      >   generated by mkgrokdump. The caller may optionally provide the
      >   pointers for the first pages of various heap spaces, to avoid spurious
      >   matches. If those pointers are not provided, then any matches are
      >   prefixed with "maybe" in the resulting description string, such as
      >   "maybe UndefinedValue (0x4288000341 <Oddball>)".
      > 
      > Bug: v8:9376
      > 
      > Change-Id: Iebf3cc2dea3133c7811bcefcdf38d9458b02fded
      > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1628012
      > Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
      > Reviewed-by: Yang Guo <yangguo@chromium.org>
      > Reviewed-by: Michael Stanton <mvstanton@chromium.org>
      > Cr-Commit-Position: refs/heads/master@{#62882}
      
      TBR=yangguo@chromium.org,mvstanton@chromium.org,jgruber@chromium.org,tebbi@chromium.org,seth.brenith@microsoft.com
      
      Change-Id: Ia078f2e8d101d2375b5db88021b2d65d28f1b075
      No-Presubmit: true
      No-Tree-Checks: true
      No-Try: true
      Bug: v8:9376
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1716033Reviewed-by: 's avatarLeszek Swirski <leszeks@chromium.org>
      Commit-Queue: Zhi An Ng <zhin@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#62899}
      6747e3a1
  5. 23 Jul, 2019 1 commit
    • Seth Brenith's avatar
      Add postmortem debugging helper library · 517ab73f
      Seth Brenith authored
      This change begins to implement the functionality described in
      https://docs.google.com/document/d/1evHnb1uLlSbvHAAsmOXyc25x3uh1DjgNa8u1RHvwVhk/edit#
      for investigating V8 state in crash dumps.
      
      This change adds a new library, v8_debug_helper, for providing platform-
      agnostic assistance with postmortem debugging. This library can be used
      by extensions built for debuggers such as WinDbg or lldb. Its public API
      is described by debug-helper.h; currently the only method it exposes is
      GetObjectProperties, but we'd like to add more functionality over time.
      The API surface is restricted to plain C-style structs and pointers, so
      that it's easy to link from a debugger extension built with a different
      toolchain.
      
      This change also adds a new cctest file to exercise some basic
      interaction with the new library.
      
      The API function GetObjectProperties takes an object pointer (which
      could be compressed, or weak, or a SMI), and returns a string
      description of the object and a list of properties the object contains.
      For now, the list of properties is entirely based on Torque object
      definitions, but we expect to add custom properties in future updates so
      that it can be easier to make sense of complex data structures such as
      dictionaries.
      
      GetObjectProperties does several things that are intended to generate
      somewhat useful results even in cases where memory may be corrupt or
      unavailable:
      - The caller may optionally provide a type string which will be used if
        the memory for the object's Map is inaccessible.
      - All object pointers are compared against the list of known objects
        generated by mkgrokdump. The caller may optionally provide the
        pointers for the first pages of various heap spaces, to avoid spurious
        matches. If those pointers are not provided, then any matches are
        prefixed with "maybe" in the resulting description string, such as
        "maybe UndefinedValue (0x4288000341 <Oddball>)".
      
      Bug: v8:9376
      
      Change-Id: Iebf3cc2dea3133c7811bcefcdf38d9458b02fded
      Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1628012
      Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
      Reviewed-by: 's avatarYang Guo <yangguo@chromium.org>
      Reviewed-by: 's avatarMichael Stanton <mvstanton@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#62882}
      517ab73f