From: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Date: Sun, 2 Apr 2023 00:19:37 +0000 (-0400)
Subject: runtime/trace: Fix TestTraceSymbolize on solaris and illumos
X-Git-Tag: go1.21rc1~1044
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=6991f63d9e97b2a76f29170450f40b5ac6bb87f3;p=gostls13.git

runtime/trace: Fix TestTraceSymbolize on solaris and illumos

Fix a regression caused by CL 463835. Unlike most platforms, solaris and
illumos don't use a libc_read_trampoline, so we need to skip one frame
less when using frame pointer unwinding in traceGoSysCall.

The solution is a bit hacky, so it might make sense to implement
gp.syscallbp if this causes more test failures in the future.

Fixes #59350

Change-Id: I0f0b08f36efe8a492eb4a535e752c03636857057
Reviewed-on: https://go-review.googlesource.com/c/go/+/481336
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
---

diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index 81093cc9b9..d174ee2e4a 100644
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -1553,16 +1553,23 @@ func traceGoUnpark(gp *g, skip int) {
 }
 
 func traceGoSysCall() {
-	if tracefpunwindoff() {
-		traceEvent(traceEvGoSysCall, 1)
-	} else {
-		// The default unwinder starts unwinding from gp.syscallsp
-		// which is captured 3 frames above this frame. We could
-		// capture gp.syscallbp to allow frame pointer unwinding to
-		// behave the same, but skipping 3 more frames here is
-		// simpler.
-		traceEvent(traceEvGoSysCall, 4)
-	}
+	var skip int
+	switch {
+	case tracefpunwindoff():
+		// Unwind by skipping 1 frame relative to gp.syscallsp which is captured 3
+		// frames above this frame. For frame pointer unwinding we produce the same
+		// results by hard coding the number of frames in between our caller and the
+		// actual syscall, see cases below.
+		// TODO(felixge): Implement gp.syscallbp to avoid this workaround?
+		skip = 1
+	case GOOS == "solaris" || GOOS == "illumos":
+		// These platforms don't use a libc_read_trampoline.
+		skip = 3
+	default:
+		// Skip the extra trampoline frame used on most systems.
+		skip = 4
+	}
+	traceEvent(traceEvGoSysCall, skip)
 }
 
 func traceGoSysExit(ts int64) {