[llvm] 8545093 - [obj2yaml] Emit ProgramHeader.Offset
Job Noorman via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 25 01:22:03 PDT 2023
Author: Job Noorman
Date: 2023-09-25T10:21:53+02:00
New Revision: 8545093715c4efcfe7069aa29e9372d32f9c7b36
URL: https://github.com/llvm/llvm-project/commit/8545093715c4efcfe7069aa29e9372d32f9c7b36
DIFF: https://github.com/llvm/llvm-project/commit/8545093715c4efcfe7069aa29e9372d32f9c7b36.diff
LOG: [obj2yaml] Emit ProgramHeader.Offset
Currently, obj2yaml doesn't emit the offset of program headers, leaving
it to yaml2obj to calculate offsets based on `FirstSec` and `LastSec`.
This causes an obj2yaml->yaml2obj round trip to often produce an ELF
file that is not equivalent to the original, especially since it seems
common to have program headers at offset 0 whose first section starts at
a higher address. Besides being non-equivalent, the produced ELF files
also do not seem to work propery and readelf complains about them.
Taking a simple hello world program in C, compiled using either GCC or
Clang, the original ELF file has the following program headers (only
showing some relevant ones):
```
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000000040 0x0000000000000040
0x00000000000002d8 0x00000000000002d8 R 0x8
INTERP 0x0000000000000318 0x0000000000000318 0x0000000000000318
0x000000000000001c 0x000000000000001c R 0x1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000630 0x0000000000000630 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000000161 0x0000000000000161 R E 0x1000
...
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.gnu.property .note.gnu.build-id .note.ABI-tag .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt
03 .init .plt .text .fini
...
```
While this is the result of an obj2yaml->yaml2obj round trip:
```
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000000 0x0000000000000040 0x0000000000000040
0x0000000000000000 0x0000000000000000 R 0x8
readelf: Error: the PHDR segment is not covered by a LOAD segment
INTERP 0x0000000000000318 0x0000000000000318 0x0000000000000318
0x000000000000001c 0x000000000000001c R 0x1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000318 0x0000000000000000 0x0000000000000000
0x0000000000000318 0x0000000000000318 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000000161 0x0000000000000161 R E 0x1000
...
Section to Segment mapping:
Segment Sections...
00
01 .interp
02
03 .init .plt .text .fini
...
```
Note that the offset of segment 2 changed from 0x0 to 0x318. This has
two effects:
- readelf complains "Error: the PHDR segment is not covered by a LOAD
segment" since PHDR was originally covered by segment 2 but not
anymore;
- Segment 2 effectively became empty according to the section to segment
mapping.
I addition to these, the output doesn't correctly execute anymore,
crashing with a "SIGSEGV (Address boundary error)".
This patch fixes the difference in program header layout after a round
trip by explicitly emitting offsets.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D145555
Added:
Modified:
llvm/test/Object/obj2yaml.test
llvm/test/tools/obj2yaml/ELF/program-headers.yaml
llvm/tools/obj2yaml/elf2yaml.cpp
Removed:
################################################################################
diff --git a/llvm/test/Object/obj2yaml.test b/llvm/test/Object/obj2yaml.test
index f07172595173fb8..dea9cf41eab5496 100644
--- a/llvm/test/Object/obj2yaml.test
+++ b/llvm/test/Object/obj2yaml.test
@@ -711,12 +711,14 @@ FileHeader:
# ELF-AVR-NEXT: FirstSec: .text
# ELF-AVR-NEXT: LastSec: .text
# ELF-AVR-NEXT: Align: 0x2
+# ELF-AVR-NEXT: Offset: 0x74
# ELF-AVR-NEXT: - Type: PT_LOAD
# ELF-AVR-NEXT: Flags: [ PF_W, PF_R ]
# ELF-AVR-NEXT: FirstSec: .data
# ELF-AVR-NEXT: LastSec: .data
# ELF-AVR-NEXT: VAddr: 0x800060
# ELF-AVR-NEXT: PAddr: 0x4
+# ELF-AVR-NEXT: Offset: 0x78
# ELF-AVR-NEXT: Sections:
# ELF-AVR-NEXT: - Name: .text
# ELF-AVR-NEXT: Type: SHT_PROGBITS
diff --git a/llvm/test/tools/obj2yaml/ELF/program-headers.yaml b/llvm/test/tools/obj2yaml/ELF/program-headers.yaml
index e9c12a21a0bc6f8..1d620d54019ba5d 100644
--- a/llvm/test/tools/obj2yaml/ELF/program-headers.yaml
+++ b/llvm/test/tools/obj2yaml/ELF/program-headers.yaml
@@ -42,48 +42,57 @@
# YAML-NEXT: FirstSec: .hash
# YAML-NEXT: LastSec: .dynstr
# YAML-NEXT: Align: 0x1000
+# YAML-NEXT: Offset: 0x0
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_X, PF_R ]
# YAML-NEXT: FirstSec: .foo
# YAML-NEXT: LastSec: .zed
# YAML-NEXT: VAddr: 0x1000
# YAML-NEXT: Align: 0x1000
+# YAML-NEXT: Offset: 0x281
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_R ]
# YAML-NEXT: FirstSec: '.foo (1)'
# YAML-NEXT: LastSec: .baz
# YAML-NEXT: VAddr: 0x2000
# YAML-NEXT: Align: 0x1000
+# YAML-NEXT: Offset: 0x291
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_W, PF_R ]
# YAML-NEXT: FirstSec: .dynamic
# YAML-NEXT: LastSec: .dynamic.tail
# YAML-NEXT: VAddr: 0x3EF0
# YAML-NEXT: Align: 0x1000
+# YAML-NEXT: Offset: 0x29A
# YAML-NEXT: - Type: PT_DYNAMIC
# YAML-NEXT: Flags: [ PF_W, PF_R ]
# YAML-NEXT: FirstSec: .dynamic
# YAML-NEXT: LastSec: .dynamic
# YAML-NEXT: VAddr: 0x3EF0
# YAML-NEXT: Align: 0x8
+# YAML-NEXT: Offset: 0x29A
# YAML-NEXT: - Type: PT_GNU_RELRO
# YAML-NEXT: Flags: [ PF_R ]
# YAML-NEXT: FirstSec: .dynamic
# YAML-NEXT: LastSec: .dynamic
# YAML-NEXT: VAddr: 0x3EF0
+# YAML-NEXT: Offset: 0x29A
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_R ]
# YAML-NEXT: VAddr: 0x4000
+# YAML-NEXT: Offset: 0x0
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_R ]
# YAML-NEXT: FirstSec: .gnu.hash
# YAML-NEXT: LastSec: .gnu.hash
# YAML-NEXT: VAddr: 0x1A0
+# YAML-NEXT: Offset: 0x248
# YAML-NEXT: - Type: PT_LOAD
# YAML-NEXT: Flags: [ PF_R ]
# YAML-NEXT: FirstSec: .gnu.hash
# YAML-NEXT: LastSec: .gnu.hash
# YAML-NEXT: VAddr: 0x1A0
+# YAML-NEXT: Offset: 0x248
# YAML-NEXT: Sections:
--- !ELF
@@ -233,21 +242,25 @@ DynamicSymbols: []
# EMPTY-NEXT: LastSec: .empty.tls.end
# EMPTY-NEXT: VAddr: 0x1000
# EMPTY-NEXT: Align: 0x1000
+# EMPTY-NEXT: Offset: 0x120
# EMPTY-NEXT: - Type: PT_TLS
# EMPTY-NEXT: Flags: [ PF_W, PF_R ]
# EMPTY-NEXT: FirstSec: .empty.tls.start
# EMPTY-NEXT: LastSec: .empty.tls.start
# EMPTY-NEXT: VAddr: 0x1000
+# EMPTY-NEXT: Offset: 0x120
# EMPTY-NEXT: - Type: PT_TLS
# EMPTY-NEXT: Flags: [ PF_W, PF_R ]
# EMPTY-NEXT: FirstSec: .empty.tls.middle
# EMPTY-NEXT: LastSec: .empty.tls.middle
# EMPTY-NEXT: VAddr: 0x1100
+# EMPTY-NEXT: Offset: 0x220
# EMPTY-NEXT: - Type: PT_TLS
# EMPTY-NEXT: Flags: [ PF_W, PF_R ]
# EMPTY-NEXT: FirstSec: .empty.tls.end
# EMPTY-NEXT: LastSec: .empty.tls.end
# EMPTY-NEXT: VAddr: 0x1200
+# EMPTY-NEXT: Offset: 0x320
# EMPTY-NEXT: Sections:
--- !ELF
@@ -322,6 +335,7 @@ Sections:
# MISALIGNED-YAML-NEXT: LastSec: .foo
# MISALIGNED-YAML-NEXT: VAddr: 0x1000
# MISALIGNED-YAML-NEXT: Align: 0x1000
+# MISALIGNED-YAML-NEXT: Offset: 0x77
# MISALIGNED-YAML-NEXT: Sections:
--- !ELF
@@ -354,18 +368,22 @@ Sections:
# NON-ALLOC-NEXT: Flags: [ PF_R ]
# NON-ALLOC-NEXT: FirstSec: .alloc.1
# NON-ALLOC-NEXT: LastSec: .non-alloc.1
+# NON-ALLOC-NEXT: Offset: 0x120
# NON-ALLOC-NEXT: - Type: PT_LOAD
# NON-ALLOC-NEXT: Flags: [ PF_R ]
# NON-ALLOC-NEXT: FirstSec: .alloc.1
# NON-ALLOC-NEXT: LastSec: .non-alloc.1
+# NON-ALLOC-NEXT: Offset: 0x120
# NON-ALLOC-NEXT: - Type: PT_LOAD
# NON-ALLOC-NEXT: Flags: [ PF_R ]
# NON-ALLOC-NEXT: FirstSec: .alloc.2
# NON-ALLOC-NEXT: LastSec: .alloc.2
+# NON-ALLOC-NEXT: Offset: 0x230
# NON-ALLOC-NEXT: - Type: PT_LOAD
# NON-ALLOC-NEXT: Flags: [ PF_R ]
# NON-ALLOC-NEXT: FirstSec: .alloc.1
# NON-ALLOC-NEXT: LastSec: .alloc.2
+# NON-ALLOC-NEXT: Offset: 0x120
# NON-ALLOC-NEXT: Sections:
--- !ELF
@@ -418,23 +436,28 @@ Sections:
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .bss
# NOBITS-NEXT: LastSec: .bss
+# NOBITS-NEXT: Offset: 0x159
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .data.1
# NOBITS-NEXT: LastSec: .bss
+# NOBITS-NEXT: Offset: 0x158
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .data.1
# NOBITS-NEXT: LastSec: .data.2
+# NOBITS-NEXT: Offset: 0x158
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .bss
# NOBITS-NEXT: LastSec: .data.2
+# NOBITS-NEXT: Offset: 0x159
# NOBITS-NEXT: - Type: PT_LOAD
# NOBITS-NEXT: Flags: [ PF_W, PF_R ]
# NOBITS-NEXT: FirstSec: .foo.bss
# NOBITS-NEXT: LastSec: .bar.bss
# NOBITS-NEXT: VAddr: 0x200000000
+# NOBITS-NEXT: Offset: 0x15A
# NOBITS-NEXT: Sections:
--- !ELF
@@ -581,6 +604,7 @@ Sections:
# ZERO-SIZE-NEXT: FirstSec: .empty.bar1
# ZERO-SIZE-NEXT: LastSec: .empty.bar2
# ZERO-SIZE-NEXT: VAddr: 0x2000
+# ZERO-SIZE-NEXT: Offset: 0x78
# ZERO-SIZE-NEXT: Sections:
--- !ELF
diff --git a/llvm/tools/obj2yaml/elf2yaml.cpp b/llvm/tools/obj2yaml/elf2yaml.cpp
index 40f6d5217949bcf..7c4a8853ee2d301 100644
--- a/llvm/tools/obj2yaml/elf2yaml.cpp
+++ b/llvm/tools/obj2yaml/elf2yaml.cpp
@@ -484,6 +484,7 @@ ELFDumper<ELFT>::dumpProgramHeaders(
PH.Flags = Phdr.p_flags;
PH.VAddr = Phdr.p_vaddr;
PH.PAddr = Phdr.p_paddr;
+ PH.Offset = Phdr.p_offset;
// yaml2obj sets the alignment of a segment to 1 by default.
// We do not print the default alignment to reduce noise in the output.
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