[go] runtime: clear X15 before calling cgocallbackg

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Gopher Robot (Gerrit)

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Apr 24, 2026, 4:25:56 PM (17 hours ago) Apr 24

to Michael Pratt, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Keith Randall, Keith Randall, golang...@luci-project-accounts.iam.gserviceaccount.com, Ariel Otilibili Anieli, golang-co...@googlegroups.com

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Change information

Commit message:

runtime: clear X15 before calling cgocallbackg

CL 765581 uses ABIInternal to call from cgocallback to cgocallbackg.
That CL restores the g to R14, but fails to zero X15 as required by
ABIInternal.

As a result, the undefined value of X15 from C leaks into Go code,
causing all sorts of interesting crashes due to the broken invariant.

For #78934.

Change-Id: I70d131be66e971f7c238d18a84cc44b66a6a6964

Reviewed-on: https://go-review.googlesource.com/c/go/+/770560

Reviewed-by: Keith Randall <k...@google.com>

Reviewed-by: Keith Randall <k...@golang.org>

Auto-Submit: Michael Pratt <mpr...@google.com>

LUCI-TryBot-Result: golang...@luci-project-accounts.iam.gserviceaccount.com <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files:

M src/runtime/asm_amd64.s
M src/runtime/crash_cgo_test.go
A src/runtime/testdata/testprogcgo/callback_amd64.go
A src/runtime/testdata/testprogcgo/goasm/x15_amd64.go
A src/runtime/testdata/testprogcgo/goasm/x15_amd64.s

Change size: M

Delta: 5 files changed, 82 insertions(+), 1 deletion(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +1 by Keith Randall, +2 by Keith Randall
TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com

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