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Bug 1730222 - Support PHC on macOS when running on ARM-based machines r=glandium

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This also tightens the check for PHC-type crashes in the exception handler
so that we don't accidentally try to interpret unrelated crash types as
potential PHC ones.

Differential Revision: https://phabricator.services.mozilla.com/D126365
This commit is contained in:
Gabriele Svelto 2021-09-29 07:58:13 +00:00
parent b022ae1fc0
commit 1ea22d4cdd
2 changed files with 21 additions and 9 deletions
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24
memory/replace/phc/PHC.cpp
View File

@ -55,12 +55,16 @@
//
// The basic cost of PHC's operation is as follows.
//
// - The physical memory cost is 64 * 4 KiB = 256 KiB per process (assuming 4
// KiB pages) plus some metadata (including stack traces) for each page.
// - The physical memory cost is 64 pages plus some metadata (including stack
// traces) for each page. This amounts to 256 KiB per process on
// architectures with 4 KiB pages and 1024 KiB on macOS/AArch64 which uses
// 16 KiB pages.
//
// - The virtual memory cost is the physical memory cost plus the guard pages:
// another 64 * 4 KiB = 256 KiB per process. PHC is currently only enabled on
// 64-bit platforms so the impact of the virtual memory usage is negligible.
// another 64 pages. This amounts to another 256 KiB per process on
// architectures with 4 KiB pages and 1024 KiB on macOS/AArch64 which uses
// 16 KiB pages. PHC is currently only enabled on 64-bit platforms so the
// impact of the virtual memory usage is negligible.
//
// - Every allocation requires a size check and a decrement-and-check of an
// atomic counter. When the counter reaches zero a PHC allocation can occur,
@ -283,8 +287,16 @@ using Time = uint64_t; // A moment in time.
using Delay = uint32_t; // A time duration.
// PHC only runs if the page size is 4 KiB; anything more is uncommon and would
// use too much memory. So we hardwire this size.
static const size_t kPageSize = 4096;
// use too much memory. So we hardwire this size for all platforms but macOS
// on ARM processors. For the latter we make an exception because the minimum
// page size supported is 16KiB so there's no way to go below that.
static const size_t kPageSize =
#if defined(XP_MACOSX) && defined(__aarch64__)
16384
#else
4096
#endif
;
// There are two kinds of page.
// - Allocation pages, from which allocations are made.

6
toolkit/crashreporter/breakpad-client/mac/handler/exception_handler.cc
View File

@ -413,10 +413,10 @@ bool ExceptionHandler::WriteMinidumpForChild(mach_port_t child,
}
#ifdef MOZ_PHC
static void GetPHCAddrInfo(int64_t exception_subcode,
static void GetPHCAddrInfo(int exception_type, int64_t exception_subcode,
mozilla::phc::AddrInfo* addr_info) {
// Is this a crash involving a PHC allocation?
if (exception_subcode) {
if (exception_type == EXC_BAD_ACCESS) {
// `exception_subcode` is only non-zero when it's a bad access, in which
// case it holds the address of the bad access.
char* addr = reinterpret_cast<char*>(exception_subcode);
@ -443,7 +443,7 @@ bool ExceptionHandler::WriteMinidumpWithException(
mozilla::phc::AddrInfo addr_info;
#ifdef MOZ_PHC
GetPHCAddrInfo(exception_subcode, &addr_info);
GetPHCAddrInfo(exception_type, exception_subcode, &addr_info);
#endif
if (directCallback_) {