Issue 170720043: code review 170720043: runtime: change top-most return PC from goexit to goexi...

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Issue 170720043: code review 170720043: runtime: change top-most return PC from goexit to goexi... (Closed)

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Created:
9 years, 5 months ago by rsc

Modified:
9 years, 5 months ago

Reviewers:
r

CC:
r, golang-codereviews

Visibility:
Public.

Description

runtime: change top-most return PC from goexit to goexit+PCQuantum If you get a stack of PCs from Callers, it would be expected that every PC is immediately after a call instruction, so to find the line of the call, you look up the line for PC-1. CL 163550043 now explicitly documents that. The most common exception to this is the top-most return PC on the stack, which is the entry address of the runtime.goexit function. Subtracting 1 from that PC will end up in a different function entirely. To remove this special case, make the top-most return PC goexit+PCQuantum and then implement goexit in assembly so that the first instruction can be skipped. Fixes issue 7690.

	Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+27 lines, -5 lines)			Patch
M	src/runtime/asm_386.s	View	1	1 chunk	+6 lines, -0 lines	0 comments	Download
M	src/runtime/asm_amd64.s	View	1	1 chunk	+6 lines, -0 lines	0 comments	Download
M	src/runtime/asm_amd64p32.s	View	1	1 chunk	+6 lines, -0 lines	0 comments	Download
M	src/runtime/asm_arm.s	View	1	1 chunk	+6 lines, -0 lines	0 comments	Download
M	src/runtime/proc.c	View	1	2 chunks	+3 lines, -5 lines	0 comments	Download

Messages

Total messages: 3

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rsc

Hello r (cc: golang-codereviews@googlegroups.com), I'd like you to review this change to https://code.google.com/p/go/

9 years, 5 months ago (2014-10-29 22:07:46 UTC) #1

rsc

9 years, 5 months ago (2014-10-30 00:37:50 UTC) #3

*** Submitted as https://code.google.com/p/go/source/detail?r=6e069930edab ***

runtime: change top-most return PC from goexit to goexit+PCQuantum

If you get a stack of PCs from Callers, it would be expected
that every PC is immediately after a call instruction, so to find
the line of the call, you look up the line for PC-1.
CL 163550043 now explicitly documents that.

The most common exception to this is the top-most return PC
on the stack, which is the entry address of the runtime.goexit
function. Subtracting 1 from that PC will end up in a different
function entirely.

To remove this special case, make the top-most return PC
goexit+PCQuantum and then implement goexit in assembly
so that the first instruction can be skipped.

Fixes issue 7690.

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/170720043

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