From 30a63ecee351c029ea99dce388a5953a150b4e02 Mon Sep 17 00:00:00 2001 From: Lynn Boger Date: Fri, 8 Jun 2018 11:07:18 -0400 Subject: runtime: restore r2 when restoring state from gobuf in gogo on ppc64x When using plugins with goroutines calling cgo, we hit a case where an intermittent SIGSEGV occurs when referencing an address that is based on r2 (TOC address). When the failure can be generated in gdb, the contents of r2 is wrong even though the value in the current stack's slot for r2 is correct. So that means it somehow switched to start running the code in this function without passing through the beginning of the function which had the correct value of r2 and stored it there. It was noted that in runtime.gogo when the state is restored from gobuf, r2 is not restored from its slot on the stack. Adding the instruction to restore r2 prevents the SIGSEGV. This adds a testcase under testplugin which reproduces the problem if the program is run multiple times. The team who reported this problem has verified it fixes the issue on their larger, more complex application. Fixes #25756 Change-Id: I6028b6f1f8775d5c23f4ebb57ae273330a28eb8f Reviewed-on: https://go-review.googlesource.com/117515 Run-TryBot: Lynn Boger Reviewed-by: Ian Lance Taylor TryBot-Result: Gobot Gobot --- src/runtime/asm_ppc64x.s | 1 + 1 file changed, 1 insertion(+) (limited to 'src/runtime') diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s index 93f9110cc0..3708961d76 100644 --- a/src/runtime/asm_ppc64x.s +++ b/src/runtime/asm_ppc64x.s @@ -139,6 +139,7 @@ TEXT runtime·gogo(SB), NOSPLIT, $16-8 MOVD 0(g), R4 MOVD gobuf_sp(R5), R1 MOVD gobuf_lr(R5), R31 + MOVD 24(R1), R2 // restore R2 MOVD R31, LR MOVD gobuf_ret(R5), R3 MOVD gobuf_ctxt(R5), R11 -- cgit v1.3