[webkit-changes] [WebKit/WebKit] a2ce77: Vary whether to left or right align PGM allocations.

[nishajain61]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: a2ce7711e418202bd84ca34e529cad3f9f05850e
      https://github.com/WebKit/WebKit/commit/a2ce7711e418202bd84ca34e529cad3f9f05850e
  Author: Nisha Jain <nisha_jain at apple.com>
  Date:   2024-06-10 (Mon, 10 Jun 2024)

  Changed paths:
    M Source/bmalloc/libpas/src/libpas/pas_probabilistic_guard_malloc_allocator.c
    M Source/bmalloc/libpas/src/libpas/pas_probabilistic_guard_malloc_allocator.h
    M Source/bmalloc/libpas/src/libpas/pas_report_crash.c
    M Source/bmalloc/libpas/src/libpas/pas_report_crash_pgm_report.h
    M Source/bmalloc/libpas/src/libpas/pas_utils.h

  Log Message:
  -----------
  Vary whether to left or right align PGM allocations.
https://bugs.webkit.org/show_bug.cgi?id=266581
rdar://107954062.

Reviewed by David Kilzer.

Large heap PGM allocations are right aligned to catch overflows by default.
Added the left alignment with random decision in order to catch underflows with equal probability.

* Source/bmalloc/libpas/src/libpas/pas_probabilistic_guard_malloc_allocator.c:
(pas_probabilistic_guard_malloc_allocate): Added random decision for left or right alignment.
* Source/bmalloc/libpas/src/libpas/pas_probabilistic_guard_malloc_allocator.h: Added flag in meta data to keep track of alignment for given heap.
/Source/bmalloc/libpas/src/libpas/pas_report_crash.c: Modified the crash reporting based on alignment.
/Source/bmalloc/libpas/src/libpas/pas_report_crash_pgm_report.h: Added alignment info.

Canonical link: https://commits.webkit.org/279892@main



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