From 0314e1e1ef21112f22a8a7853666680e9a9846cf Mon Sep 17 00:00:00 2001
From: Frederic Riss <friss@apple.com>
Date: Mon, 1 Feb 2016 03:44:22 +0000
Subject: [PATCH] [dsymutil] Support scattered relocs.

Although it seems like clang will never emit scattered relocations in
the debug information (at least I couldn't find a way), we have too
support them for the benefit of other compilers.
As clang doesn't generate them, the included testcase was produced
from hacked up assembly.

llvm-svn: 259339
---
 .../tools/dsymutil/ARM/dummy-debug-map.map    |  15 ++
 llvm/test/tools/dsymutil/ARM/scattered.c      |  12 ++
 .../tools/dsymutil/Inputs/scattered-reloc/1.o | Bin 0 -> 1528 bytes
 .../tools/dsymutil/Inputs/scattered-reloc/1.s | 186 ++++++++++++++++++
 llvm/tools/dsymutil/DwarfLinker.cpp           |  17 +-
 5 files changed, 228 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/tools/dsymutil/ARM/dummy-debug-map.map
 create mode 100644 llvm/test/tools/dsymutil/ARM/scattered.c
 create mode 100644 llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.o
 create mode 100644 llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.s

diff --git a/llvm/test/tools/dsymutil/ARM/dummy-debug-map.map b/llvm/test/tools/dsymutil/ARM/dummy-debug-map.map
new file mode 100644
index 000000000000..aa69aeafedb1
--- /dev/null
+++ b/llvm/test/tools/dsymutil/ARM/dummy-debug-map.map
@@ -0,0 +1,15 @@
+# This is a dummy debug map used for some tests where the contents of the
+# map are just an implementation detail. The tests wanting to use that file
+# should put all there object files in an explicitely named sub-directory
+# of Inputs, and they should be named 1.o, 2.o, ...
+# As not finding an object file or symbols isn't a fatal error for dsymutil,
+# you can extend this file with as much object files and symbols as needed.
+
+---
+triple:          'thumbv7-apple-darwin'
+objects:
+  - filename: 1.o
+    symbols:
+      - { sym: _bar, objAddr: 0x0, binAddr: 0x10000, size: 0x10 }
+...
+
diff --git a/llvm/test/tools/dsymutil/ARM/scattered.c b/llvm/test/tools/dsymutil/ARM/scattered.c
new file mode 100644
index 000000000000..c84a602063f1
--- /dev/null
+++ b/llvm/test/tools/dsymutil/ARM/scattered.c
@@ -0,0 +1,12 @@
+RUN: llvm-dsymutil -y %p/dummy-debug-map.map -oso-prepend-path %p/../Inputs/scattered-reloc/ -f -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+// See Inputs/scattered-reloc/scattered.s to see how this test
+// actually works. 
+int bar = 42;
+
+CHECK: DW_TAG_variable
+CHECK-NOT: DW_TAG
+CHECK: DW_AT_name{{.*}}"bar"
+CHECK-NOT: DW_TAG
+CHECK: DW_AT_location{{.*}}<0x05> 03 10 00 01 00 
+
diff --git a/llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.o b/llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.o
new file mode 100644
index 0000000000000000000000000000000000000000..df5cc9bd3e0bc7e25f3cef8b29f52940cc82e8a8
GIT binary patch
literal 1528
zcmbVM%Wl(95FN*HcsLD3Wr2i*45U(vP}<TWQ9#g0EtDOCNU*!uuBp-{j^(%&?6T}f
zuwVhZE?Dysd;uGzvP5DH5^#<k=ix*lVx;5inLBfG=H7`v|NQ>DC?aP74afs!KCHw)
z*6}{Z-XeJed0bCnpP1?9DHVCIqkfT6wXGMmzMsCaK4YEKS8B(O?9>xcYO`9a_I<vw
zoE*8~aL)sW=N#;+b`-`ja6GR*ec0P){XJlFR7a08<!H3ru^bz5RHQQnhwV6_cNq6F
zq=OtcfN41D{;L*$GTTc7vD?6LSH~A4xj%$PdI@cR*K3b*yhk$aWQtyzwi`>y>L3S3
z;vXD#5HvjH+fB+C>E#1ryq9kibtD`uXD_~(td6g!F9TO_4jCIbj{zNl?PfU)G(wK8
zDLA4x!Ps6F!SM(j^@$wGoHpvdN3B^M0XR4xA183kV}F*#k|eRoi@*t7l*<pSr?HyA
z6JXG|PyCNvN0HmWKv{=g*siyHYqhdoS+*9U@W9`<Zr)m7U0GR_wrfX`7kWDtSC*n?
zAdVeM-H${&ug#a{481g4xKzTdu8CfHJolh@$GmIi&Wh+|1n!$Ab*}-*<>h0!MY-0M
zyu=-DF9VvU89L8G=O4nr5N$uJZl_Ih<p+<J#0v5Ir<X@251A~CUyh^0wG3rz|G)<M
zr^zAz1t!AyebuCZ)sTFAJ?NryWKsw9GnZX)5Mc{IPOjpqX}?M{Y&PiviGzpCT(t9!
OD-+J8Q?GdPB7Xr*+oAga

literal 0
HcmV?d00001

diff --git a/llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.s b/llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.s
new file mode 100644
index 000000000000..c4d3781d435c
--- /dev/null
+++ b/llvm/test/tools/dsymutil/Inputs/scattered-reloc/1.s
@@ -0,0 +1,186 @@
+# This assembly file was generated from the following trivial C code:
+# $ cat scattered.c 
+# int bar = 42;
+# $ clang -S -arch armv7 -g scattered.c
+# $ clang -c -o 1.o scattered.s
+#
+# Then I edited the debug info bellow to change the DW_AT_location of the bar
+# variable from '.long _bar' to '.long _bar + 16' in order to generate a
+# scattered reloc (I do not think LLVM will generate scattered relocs in
+# debug info by itself).
+
+	.section	__TEXT,__text,regular,pure_instructions
+	.ios_version_min 5, 0
+	.syntax unified
+	.file	1 "scattered.c"
+	.section	__DATA,__data
+	.globl	_bar                    @ @bar
+	.p2align	2
+_bar:
+	.long	42                      @ 0x2a
+
+	.section	__DWARF,__debug_str,regular,debug
+Linfo_string:
+	.asciz	"clang version 3.9.0 (trunk 259311)" @ string offset=0
+	.asciz	"scattered.c"           @ string offset=35
+	.asciz	"/tmp"                  @ string offset=47
+	.asciz	"bar"                   @ string offset=52
+	.asciz	"int"                   @ string offset=56
+	.section	__DWARF,__debug_loc,regular,debug
+Lsection_debug_loc:
+	.section	__DWARF,__debug_abbrev,regular,debug
+Lsection_abbrev:
+	.byte	1                       @ Abbreviation Code
+	.byte	17                      @ DW_TAG_compile_unit
+	.byte	1                       @ DW_CHILDREN_yes
+	.byte	37                      @ DW_AT_producer
+	.byte	14                      @ DW_FORM_strp
+	.byte	19                      @ DW_AT_language
+	.byte	5                       @ DW_FORM_data2
+	.byte	3                       @ DW_AT_name
+	.byte	14                      @ DW_FORM_strp
+	.byte	16                      @ DW_AT_stmt_list
+	.byte	6                       @ DW_FORM_data4
+	.byte	27                      @ DW_AT_comp_dir
+	.byte	14                      @ DW_FORM_strp
+	.byte	0                       @ EOM(1)
+	.byte	0                       @ EOM(2)
+	.byte	2                       @ Abbreviation Code
+	.byte	52                      @ DW_TAG_variable
+	.byte	0                       @ DW_CHILDREN_no
+	.byte	3                       @ DW_AT_name
+	.byte	14                      @ DW_FORM_strp
+	.byte	73                      @ DW_AT_type
+	.byte	19                      @ DW_FORM_ref4
+	.byte	63                      @ DW_AT_external
+	.byte	12                      @ DW_FORM_flag
+	.byte	58                      @ DW_AT_decl_file
+	.byte	11                      @ DW_FORM_data1
+	.byte	59                      @ DW_AT_decl_line
+	.byte	11                      @ DW_FORM_data1
+	.byte	2                       @ DW_AT_location
+	.byte	10                      @ DW_FORM_block1
+	.byte	0                       @ EOM(1)
+	.byte	0                       @ EOM(2)
+	.byte	3                       @ Abbreviation Code
+	.byte	36                      @ DW_TAG_base_type
+	.byte	0                       @ DW_CHILDREN_no
+	.byte	3                       @ DW_AT_name
+	.byte	14                      @ DW_FORM_strp
+	.byte	62                      @ DW_AT_encoding
+	.byte	11                      @ DW_FORM_data1
+	.byte	11                      @ DW_AT_byte_size
+	.byte	11                      @ DW_FORM_data1
+	.byte	0                       @ EOM(1)
+	.byte	0                       @ EOM(2)
+	.byte	0                       @ EOM(3)
+	.section	__DWARF,__debug_info,regular,debug
+Lsection_info:
+Lcu_begin0:
+	.long	52                      @ Length of Unit
+	.short	2                       @ DWARF version number
+Lset0 = Lsection_abbrev-Lsection_abbrev @ Offset Into Abbrev. Section
+	.long	Lset0
+	.byte	4                       @ Address Size (in bytes)
+	.byte	1                       @ Abbrev [1] 0xb:0x2d DW_TAG_compile_unit
+	.long	0                       @ DW_AT_producer
+	.short	12                      @ DW_AT_language
+	.long	35                      @ DW_AT_name
+Lset1 = Lline_table_start0-Lsection_line @ DW_AT_stmt_list
+	.long	Lset1
+	.long	47                      @ DW_AT_comp_dir
+	.byte	2                       @ Abbrev [2] 0x1e:0x12 DW_TAG_variable
+	.long	52                      @ DW_AT_name
+	.long	48                      @ DW_AT_type
+	.byte	1                       @ DW_AT_external
+	.byte	1                       @ DW_AT_decl_file
+	.byte	1                       @ DW_AT_decl_line
+	.byte	5                       @ DW_AT_location
+	.byte	3
+	.long	_bar + 16
+	.byte	3                       @ Abbrev [3] 0x30:0x7 DW_TAG_base_type
+	.long	56                      @ DW_AT_name
+	.byte	5                       @ DW_AT_encoding
+	.byte	4                       @ DW_AT_byte_size
+	.byte	0                       @ End Of Children Mark
+	.section	__DWARF,__debug_ranges,regular,debug
+Ldebug_range:
+	.section	__DWARF,__debug_macinfo,regular,debug
+	.byte	0                       @ End Of Macro List Mark
+	.section	__DWARF,__apple_names,regular,debug
+Lnames_begin:
+	.long	1212240712              @ Header Magic
+	.short	1                       @ Header Version
+	.short	0                       @ Header Hash Function
+	.long	1                       @ Header Bucket Count
+	.long	1                       @ Header Hash Count
+	.long	12                      @ Header Data Length
+	.long	0                       @ HeaderData Die Offset Base
+	.long	1                       @ HeaderData Atom Count
+	.short	1                       @ DW_ATOM_die_offset
+	.short	6                       @ DW_FORM_data4
+	.long	0                       @ Bucket 0
+	.long	193487034               @ Hash in Bucket 0
+	.long	LNames0-Lnames_begin    @ Offset in Bucket 0
+LNames0:
+	.long	52                      @ bar
+	.long	1                       @ Num DIEs
+	.long	30
+	.long	0
+	.section	__DWARF,__apple_objc,regular,debug
+Lobjc_begin:
+	.long	1212240712              @ Header Magic
+	.short	1                       @ Header Version
+	.short	0                       @ Header Hash Function
+	.long	1                       @ Header Bucket Count
+	.long	0                       @ Header Hash Count
+	.long	12                      @ Header Data Length
+	.long	0                       @ HeaderData Die Offset Base
+	.long	1                       @ HeaderData Atom Count
+	.short	1                       @ DW_ATOM_die_offset
+	.short	6                       @ DW_FORM_data4
+	.long	-1                      @ Bucket 0
+	.section	__DWARF,__apple_namespac,regular,debug
+Lnamespac_begin:
+	.long	1212240712              @ Header Magic
+	.short	1                       @ Header Version
+	.short	0                       @ Header Hash Function
+	.long	1                       @ Header Bucket Count
+	.long	0                       @ Header Hash Count
+	.long	12                      @ Header Data Length
+	.long	0                       @ HeaderData Die Offset Base
+	.long	1                       @ HeaderData Atom Count
+	.short	1                       @ DW_ATOM_die_offset
+	.short	6                       @ DW_FORM_data4
+	.long	-1                      @ Bucket 0
+	.section	__DWARF,__apple_types,regular,debug
+Ltypes_begin:
+	.long	1212240712              @ Header Magic
+	.short	1                       @ Header Version
+	.short	0                       @ Header Hash Function
+	.long	1                       @ Header Bucket Count
+	.long	1                       @ Header Hash Count
+	.long	20                      @ Header Data Length
+	.long	0                       @ HeaderData Die Offset Base
+	.long	3                       @ HeaderData Atom Count
+	.short	1                       @ DW_ATOM_die_offset
+	.short	6                       @ DW_FORM_data4
+	.short	3                       @ DW_ATOM_die_tag
+	.short	5                       @ DW_FORM_data2
+	.short	4                       @ DW_ATOM_type_flags
+	.short	11                      @ DW_FORM_data1
+	.long	0                       @ Bucket 0
+	.long	193495088               @ Hash in Bucket 0
+	.long	Ltypes0-Ltypes_begin    @ Offset in Bucket 0
+Ltypes0:
+	.long	56                      @ int
+	.long	1                       @ Num DIEs
+	.long	48
+	.short	36
+	.byte	0
+	.long	0
+
+.subsections_via_symbols
+	.section	__DWARF,__debug_line,regular,debug
+Lsection_line:
+Lline_table_start0:
diff --git a/llvm/tools/dsymutil/DwarfLinker.cpp b/llvm/tools/dsymutil/DwarfLinker.cpp
index fe971e996078..1cabc9a66c3f 100644
--- a/llvm/tools/dsymutil/DwarfLinker.cpp
+++ b/llvm/tools/dsymutil/DwarfLinker.cpp
@@ -1898,6 +1898,19 @@ findValidRelocsMachO(const object::SectionRef &Section,
     uint32_t Offset = Offset64;
     // Mach-o uses REL relocations, the addend is at the relocation offset.
     uint64_t Addend = Data.getUnsigned(&Offset, RelocSize);
+    uint64_t SymAddress;
+    int64_t SymOffset;
+
+    if (Obj.isRelocationScattered(MachOReloc)) {
+      // The address of the base symbol for scattered relocations is
+      // stored in the reloc itself. The actual addend will store the
+      // base address plus the offset.
+      SymAddress = Obj.getScatteredRelocationValue(MachOReloc);
+      SymOffset = int64_t(Addend) - SymAddress;
+    } else {
+      SymAddress = Addend;
+      SymOffset = 0;
+    }
 
     auto Sym = Reloc.getSymbol();
     if (Sym != Obj.symbol_end()) {
@@ -1908,11 +1921,11 @@ findValidRelocsMachO(const object::SectionRef &Section,
       }
       if (const auto *Mapping = DMO.lookupSymbol(*SymbolName))
         ValidRelocs.emplace_back(Offset64, RelocSize, Addend, Mapping);
-    } else if (const auto *Mapping = DMO.lookupObjectAddress(Addend)) {
+    } else if (const auto *Mapping = DMO.lookupObjectAddress(SymAddress)) {
       // Do not store the addend. The addend was the address of the
       // symbol in the object file, the address in the binary that is
       // stored in the debug map doesn't need to be offseted.
-      ValidRelocs.emplace_back(Offset64, RelocSize, 0, Mapping);
+      ValidRelocs.emplace_back(Offset64, RelocSize, SymOffset, Mapping);
     }
   }
 }