From cc08d9232c4875a11b9e2a8097e069467d79f31f Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Wed, 16 Apr 2014 17:11:44 -0400
Subject: [PATCH] liblink: add leaf bit to object file format

Without the leaf bit, the linker cannot record
the correct frame size in the symbol table, and
then stack traces get mangled. (Only for ARM.)

Fixes #7338.
Fixes #7347.

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/88550043
---
 src/cmd/ld/pcln.c                   |   7 +++++--
 src/cmd/link/testdata/autosection.6 | Bin 888 -> 889 bytes
 src/cmd/link/testdata/autoweak.6    | Bin 425 -> 426 bytes
 src/cmd/link/testdata/dead.6        | Bin 1054 -> 1060 bytes
 src/cmd/link/testdata/hello.6       | Bin 271 -> 272 bytes
 src/cmd/link/testdata/layout.6      | Bin 429 -> 430 bytes
 src/cmd/link/testdata/pclntab.6     | Bin 4603 -> 4607 bytes
 src/liblink/objfile.c               |   8 +++++++-
 src/pkg/debug/goobj/read.go         |   2 ++
 9 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/cmd/ld/pcln.c b/src/cmd/ld/pcln.c
index bdb139f7a4..b2370f2a91 100644
--- a/src/cmd/ld/pcln.c
+++ b/src/cmd/ld/pcln.c
@@ -112,7 +112,7 @@ pclntab(void)
 {
 	int32 i, nfunc, start, funcstart;
 	LSym *ftab, *s;
-	int32 off, end;
+	int32 off, end, frameptrsize;
 	int64 funcdata_bytes;
 	Pcln *pcln;
 	Pciter it;
@@ -173,7 +173,10 @@ pclntab(void)
 		// when a called function doesn't have argument information.
 		// We need to make sure everything has argument information
 		// and then remove this.
-		off = setuint32(ctxt, ftab, off, ctxt->cursym->locals + PtrSize);
+		frameptrsize = PtrSize;
+		if(ctxt->cursym->leaf)
+			frameptrsize = 0;
+		off = setuint32(ctxt, ftab, off, ctxt->cursym->locals + frameptrsize);
 		
 		if(pcln != &zpcln) {
 			renumberfiles(pcln->file, pcln->nfile, &pcln->pcfile);
diff --git a/src/cmd/link/testdata/autosection.6 b/src/cmd/link/testdata/autosection.6
index 3a2e35a5b227ebca6093cb358a0762e802a51680..f392e416808f3a92e59faf51628911f57b0d4d1f 100644
GIT binary patch
delta 46
zcmeyt_LFUboPvdcWwM2-Wm<BIS*k*KYKnqmL6L%?nS!CQm7$T9p~XbI=#4WTFaZEk
CMGj#A

delta 46
zcmey#_JeJLoPxQ5k)e^PMOu=%k+Fhrex8D3L6L%?iGrcAm63s!so_Ms=#8`PGXVfT
Cdkw(=

diff --git a/src/cmd/link/testdata/autoweak.6 b/src/cmd/link/testdata/autoweak.6
index 1fd54ed7e60d52f1247958df3b85dadb9369d70f..a694e4729180ac7096dcbff6ef9393357b05e2b8 100644
GIT binary patch
delta 46
zcmZ3<yoz~(oPvdcWwM2-Wm<BIS*k*KYKnqmL6L%?nS!CQm7$T9p~XbI=#4W3838lc
B4DA2_

delta 46
zcmZ3*ypnl>oPxQ5k)e^PMOu=%k+Fhrex8D3L6L%?iGrcAm63s!so_Ms=#8@k7y%#-
B3{3z4

diff --git a/src/cmd/link/testdata/dead.6 b/src/cmd/link/testdata/dead.6
index e0cdecea96b934cdb54ef1416a675cd3d4dca273..270416f0b6c6bc5ed628cdbab77cd7bdbdfb6d55 100644
GIT binary patch
delta 66
zcmbQov4mrSoPvdcWwM2-Wm<BIS*k*KYKnqmL6L%?nS!CQm7$T9p~XbItclB`Co?jZ
WO)g_xGFg%-VR8ji?&c><R*V3M;uJyv

delta 66
zcmZ3&F^^+{oPxQ5k)e^PMOu=%k+Fhrex8D3L6L%?iGrcAm63s!so_Mstcfe5CbKY>
WPOf5HJXww@esUdC&gR!lmW%*tbQ87!

diff --git a/src/cmd/link/testdata/hello.6 b/src/cmd/link/testdata/hello.6
index 9ec799b4f39e5c1f2944573a46c7f7a091cbe895..448d40f76b8ecf08d4b0418e17e66c055484e244 100644
GIT binary patch
delta 45
zcmeBYn!q$cPQk*!GTFk^GA%j9EL9;qHATU(ph&^cOu^9D%FxKl&|;!p!o;~n03E~)
A0RR91

delta 45
zcmbQh)Xy|QPQl#3$k52tA}z_>$XLNQKTpB2ph&^cM8VM5%E-XV)NrC*!o>N701BE6
AVE_OC

diff --git a/src/cmd/link/testdata/layout.6 b/src/cmd/link/testdata/layout.6
index c5121ff154a5b12ba4f13ff087a3d8c37ef4f345..56d416a1a0a62316d4c47109bfbd111b6f91d4b0 100644
GIT binary patch
delta 45
zcmZ3>ypDN-oPvdcWwM2-Wm<BIS*k*KYKnqmL6L%?nS!CQm7$T9p~XbIbrWA70stzG
B4l4iv

delta 45
zcmZ3-yq0-_oPxQ5k)e^PMOu=%k+Fhrex8D3L6L%?iGrcAm63s!so_Msbratn1OOLg
B4T}H(

diff --git a/src/cmd/link/testdata/pclntab.6 b/src/cmd/link/testdata/pclntab.6
index 0f7ab6dd78b59ff505d186408427dc18c909d305..91583a3fd471460d06b111a20e87a41207c8ee79 100644
GIT binary patch
delta 62
zcmeyZ{9k#3oPvdcWwM2-Wm<BIS*k*KYKnqmL6L%?nS!CQm7$T9p~XhKRZN?oGYPY9
S{>fg?wz-_|57Xo#!A<~p-xR9=

delta 62
zcmeyb{9Ac~oPxQ5k)e^PMOu=%k+Fhrex8D3L6L%?iGrcAm63s!so_SuRZN>-G6}J6
S{=;6!wz-<`H`C;D!43dhUlbGo

diff --git a/src/liblink/objfile.c b/src/liblink/objfile.c
index b52b29ca59..0c51e795f5 100644
--- a/src/liblink/objfile.c
+++ b/src/liblink/objfile.c
@@ -49,6 +49,7 @@
 //
 //	- args [int]
 //	- locals [int]
+//	- leaf [int]
 //	- nlocal [int]
 //	- local [nlocal automatics]
 //	- pcln [pcln table]
@@ -291,8 +292,11 @@ writesym(Link *ctxt, Biobuf *b, LSym *s)
 		if(s->dupok)
 			Bprint(ctxt->bso, "dupok ");
 		Bprint(ctxt->bso, "size=%lld value=%lld", (vlong)s->size, (vlong)s->value);
-		if(s->type == STEXT)
+		if(s->type == STEXT) {
 			Bprint(ctxt->bso, " args=%#llux locals=%#llux", (uvlong)s->args, (uvlong)s->locals);
+			if(s->leaf)
+				Bprint(ctxt->bso, " leaf");
+		}
 		Bprint(ctxt->bso, "\n");
 		for(p=s->text; p != nil; p = p->link)
 			Bprint(ctxt->bso, "\t%#06ux %P\n", (int)p->pc, p);
@@ -346,6 +350,7 @@ writesym(Link *ctxt, Biobuf *b, LSym *s)
 	if(s->type == STEXT) {
 		wrint(b, s->args);
 		wrint(b, s->locals);
+		wrint(b, s->leaf);
 		n = 0;
 		for(a = s->autom; a != nil; a = a->link)
 			n++;
@@ -566,6 +571,7 @@ readsym(Link *ctxt, Biobuf *f, char *pkg, char *pn)
 	if(s->type == STEXT) {
 		s->args = rdint(f);
 		s->locals = rdint(f);
+		s->leaf = rdint(f);
 		n = rdint(f);
 		for(i=0; i<n; i++) {
 			a = emallocz(sizeof *a);
diff --git a/src/pkg/debug/goobj/read.go b/src/pkg/debug/goobj/read.go
index 8882eae534..c2e6fa0927 100644
--- a/src/pkg/debug/goobj/read.go
+++ b/src/pkg/debug/goobj/read.go
@@ -190,6 +190,7 @@ type Var struct {
 type Func struct {
 	Args     int        // size in bytes of of argument frame: inputs and outputs
 	Frame    int        // size in bytes of local variable frame
+	Leaf     bool       // function omits save of link register (ARM)
 	Var      []Var      // detail about local variables
 	PCSP     Data       // PC → SP offset map
 	PCFile   Data       // PC → file number map (index into File)
@@ -621,6 +622,7 @@ func (r *objReader) parseObject(prefix []byte) error {
 			s.Func = f
 			f.Args = r.readInt()
 			f.Frame = r.readInt()
+			f.Leaf = r.readInt() != 0
 			f.Var = make([]Var, r.readInt())
 			for i := range f.Var {
 				v := &f.Var[i]
-- 
2.50.0