From 462e90259af39af9e23c9d919e002913042c2faa Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Mon, 14 Jan 2019 13:47:14 -0800 Subject: [PATCH] runtime: keep FuncForPC from crashing for PCs between functions Reuse the strict mechanism from FileLine for FuncForPC, so we don't crash when asking the pcln table about bad pcs. Fixes #29735 Change-Id: Iaffb32498b8586ecf4eae03823e8aecef841aa68 Reviewed-on: https://go-review.googlesource.com/c/157799 Reviewed-by: Josh Bleecher Snyder Run-TryBot: Josh Bleecher Snyder TryBot-Result: Gobot Gobot --- src/runtime/symtab.go | 20 +++++++++++++++++--- test/fixedbugs/issue29735.go | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 3 deletions(-) create mode 100644 test/fixedbugs/issue29735.go diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go index e7ce3de497..17e342ef69 100644 --- a/src/runtime/symtab.go +++ b/src/runtime/symtab.go @@ -474,7 +474,11 @@ func FuncForPC(pc uintptr) *Func { return nil } if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil { - if ix := pcdatavalue(f, _PCDATA_InlTreeIndex, pc, nil); ix >= 0 { + // Note: strict=false so bad PCs (those between functions) don't crash the runtime. + // We just report the preceeding function in that situation. See issue 29735. + // TODO: Perhaps we should report no function at all in that case. + // The runtime currently doesn't have function end info, alas. + if ix := pcdatavalue1(f, _PCDATA_InlTreeIndex, pc, nil, false); ix >= 0 { inltree := (*[1 << 20]inlinedCall)(inldata) name := funcnameFromNameoff(f, inltree[ix].func_) file, line := funcline(f, pc) @@ -756,12 +760,22 @@ func funcspdelta(f funcInfo, targetpc uintptr, cache *pcvalueCache) int32 { return x } +func pcdatastart(f funcInfo, table int32) int32 { + return *(*int32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4)) +} + func pcdatavalue(f funcInfo, table int32, targetpc uintptr, cache *pcvalueCache) int32 { if table < 0 || table >= f.npcdata { return -1 } - off := *(*int32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4)) - return pcvalue(f, off, targetpc, cache, true) + return pcvalue(f, pcdatastart(f, table), targetpc, cache, true) +} + +func pcdatavalue1(f funcInfo, table int32, targetpc uintptr, cache *pcvalueCache, strict bool) int32 { + if table < 0 || table >= f.npcdata { + return -1 + } + return pcvalue(f, pcdatastart(f, table), targetpc, cache, strict) } func funcdata(f funcInfo, i uint8) unsafe.Pointer { diff --git a/test/fixedbugs/issue29735.go b/test/fixedbugs/issue29735.go new file mode 100644 index 0000000000..7a0381d533 --- /dev/null +++ b/test/fixedbugs/issue29735.go @@ -0,0 +1,33 @@ +// run + +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Make sure FuncForPC won't panic when given a pc which +// lies between two functions. + +package main + +import ( + "runtime" +) + +func main() { + var stack [1]uintptr + runtime.Callers(1, stack[:]) + f() // inlined function, to give main some inlining info + for i := uintptr(0); true; i++ { + f := runtime.FuncForPC(stack[0] + i) + if f.Name() != "main.main" && f.Name() != "main.f" { + // Reached next function successfully. + break + } + } +} + +func f() { + sink = 0 // one instruction which can't be removed +} + +var sink int -- 2.50.0