1700869 - Add `JS::ProfilingFrameIterator::getCppEntryRegisters()` to retrieve registers needed to resume stack-walking

Status: RESOLVED FIXED

(Core :: Gecko Profiler, task, P2)

Description

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

This bug will focus on the initial implementation of JS::ProfilingFrameIterator::getCppEntryRegisters(), doing nothing on all platforms, except on x64 to start with (as this will be the first platform where stack walkers will be updated).

Comment 1

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1700869 - JS::ProfilingFrameIterator::getCppEntryRegisters() skeleton - r?jandem

getCppEntryRegisters() for JIT frames delegates to jit::JitRuntime::getCppEntryRegisters(), which retrieves important state registers pointing at the native caller.

For now implementations on all platforms do nothing. They will be implemented in subsequent patches and bugs, to be used with modified stack walkers, so that they may resume sampling past JIT frames -- see main bug 1635987.

Comment 2

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1700869 - Add struct EnterJITStack in Trampoline-x64.cpp - r?jandem

EnterJITStack reflects the native entry stack.

Depends on D109696

Comment 3

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1700869 - Implement JitRuntime::getCppEntryRegisters() on x64 - r?jandem

From a frame pointer, getCppEntryRegisters() can use the descriptor in CommonFrameLayout, first to verify that it's a CppToJit frame, and then to find the EnterJITStackEntry, in which the native call registers can be retrieved.

Depends on D109697

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bd43525ba2fc
JS::ProfilingFrameIterator::getCppEntryRegisters() skeleton - r=jandem
https://hg.mozilla.org/integration/autoland/rev/9245b486d243
Add struct EnterJITStack in Trampoline-x64.cpp - r=jandem
https://hg.mozilla.org/integration/autoland/rev/7dcf53ec0e8f
Implement JitRuntime::getCppEntryRegisters() on x64 - r=jandem

Comment 5

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/bd43525ba2fc
https://hg.mozilla.org/mozilla-central/rev/9245b486d243
https://hg.mozilla.org/mozilla-central/rev/7dcf53ec0e8f