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[llvm-objcopy]Don't implicitly strip sections in segments

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This patch changes llvm-objcopy's behaviour to not strip sections that
are in segments, if they otherwise would be due to a stripping operation
(--strip-all, --strip-sections, --strip-non-alloc). This preserves the
segment contents. It does not change the behaviour of --strip-all-gnu
(although we could choose to do so), because GNU objcopy's behaviour in
this case seems to be to strip the section, nor does it prevent removing
of sections in segments with --remove-section (if a user REALLY wants to
remove a section, we should probably let them, although I could be
persuaded that warning might be appropriate). Tests have been added to
show this latter behaviour.

This fixes https://bugs.llvm.org/show_bug.cgi?id=41006.

Reviewed by: grimar, rupprecht, jakehehrlich

Differential Revision: https://reviews.llvm.org/D59293

This is a reland of r356129, attempting to fix greendragon failures
due to a suspected compatibility issue with od on the greendragon bots
versus other versions.

llvm-svn: 356136
This commit is contained in:
James Henderson 2019-03-14 11:47:41 +00:00
parent 4a0b23b067
commit f563d45752
8 changed files with 112 additions and 21 deletions
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47
test/tools/llvm-objcopy/ELF/remove-section-in-segment.test Normal file
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@ -0,0 +1,47 @@
# Show that --remove-section removes sections in segments.
# RUN: yaml2obj %s -o %t
# Validate the offsets for the later parts of the test.
# RUN: llvm-objcopy %t %t.copy
# Skip to the start of the sections, which should be immediately after the
# program header table (i.e. sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) == 120).
# RUN: od -t x1 -N 16 -j 120 %t.copy | FileCheck %s --check-prefix=COPY
# COPY: 11 22 33 44 55 66 77 88
# RUN: llvm-objcopy --remove-section non_alloc %t %t.nonalloc
# RUN: llvm-readelf --sections %t.nonalloc | FileCheck %s --check-prefix=NONALLOC-SHDRS
# RUN: od -t x1 -N 16 -j 120 %t.nonalloc | FileCheck %s --check-prefix=NONALLOC-BYTES
# NONALLOC-SHDRS-NOT: non_alloc
# NONALLOC-BYTES: 11 22 33 44 00 00 00 00
# RUN: llvm-objcopy --remove-section shf_alloc %t %t.alloc
# RUN: llvm-readelf --sections %t.alloc | FileCheck %s --check-prefix=ALLOC-SHDRS
# RUN: od -t x1 -N 16 -j 120 %t.alloc | FileCheck %s --check-prefix=ALLOC-BYTES
# ALLOC-SHDRS-NOT: shf_alloc
# ALLOC-BYTES: 00 00 00 00 55 66 77 88
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_EXEC
Machine: EM_X86_64
Sections:
- Name: shf_alloc
Type: SHT_PROGBITS
Flags: [SHF_ALLOC]
Content: '11223344'
- Name: non_alloc
Type: SHT_PROGBITS
Flags: []
Content: '55667788'
ProgramHeaders:
# Use an arbitrary segment type to show that the segment type is unimportant.
- Type: 0x61234567
Sections:
- Section: shf_alloc
- Section: non_alloc

19
test/tools/llvm-objcopy/ELF/strip-all-gnu.test
View File

@ -1,10 +1,15 @@
# RUN: yaml2obj %s > %t
# RUN: cp %t %t1
# RUN: llvm-objcopy --strip-all-gnu %t %t2
# RUN: llvm-strip --strip-all-gnu %t -o %t3
# RUN: llvm-readobj --file-headers --sections %t2 | FileCheck %s
# RUN: cmp %t2 %t3
# Show that the debug section in a segment was removed, to match GNU.
# First validate that the offset in use is correct.
# RUN: llvm-objcopy %t %t4
# RUN: od -t x1 -N 4 -j 120 %t4 | FileCheck %s --check-prefix=COPY-BYTES
# RUN: od -t x1 -N 4 -j 120 %t2 | FileCheck %s --check-prefix=STRIP-BYTES
!ELF
FileHeader:
Class: ELFCLASS64
@ -12,6 +17,10 @@ FileHeader:
Type: ET_REL
Machine: EM_X86_64
Sections:
- Name: .debug_in_segment
Type: SHT_PROGBITS
Flags: [ ]
Content: "deadbeef"
- Name: .dynstr
Type: SHT_STRTAB
Flags: [ SHF_ALLOC ]
@ -45,6 +54,11 @@ Sections:
- Name: .rela.text
Type: SHT_RELA
Info: .text
ProgramHeaders:
# Use an arbitrary segment type to show that the segment type is unimportant.
- Type: 0x61234567
Sections:
- Section: .debug_in_segment
# CHECK: SectionHeaderCount: 8
@ -55,3 +69,6 @@ Sections:
# CHECK: Name: .comment
# CHECK: Name: .random_section_name
# CHECK: Name: .shstrtab
# COPY-BYTES: de ad be ef
# STRIP-BYTES: 00 00 00 00

12
test/tools/llvm-objcopy/ELF/strip-all.test
View File

@ -57,6 +57,10 @@ FileHeader:
Type: ET_REL
Machine: EM_X86_64
Sections:
- Name: non_alloc_in_segment
Type: SHT_PROGBITS
Flags: [ ]
Size: 4
- Name: .bss
Type: SHT_NOBITS
Flags: [ SHF_ALLOC ]
@ -68,9 +72,15 @@ Sections:
Flags: [ ]
- Name: .gnu.warning.foo
Type: SHT_PROGBITS
ProgramHeaders:
# Use an arbitrary segment type to show that the segment type is unimportant.
- Type: 0x61234567
Sections:
- Section: non_alloc_in_segment
# CHECK: SectionHeaderCount: 5
# CHECK: SectionHeaderCount: 6
# CHECK: Name: non_alloc_in_segment
# CHECK: Name: .bss
# CHECK: Name: .text
# CHECK: Name: .gnu.warning.foo

12
test/tools/llvm-objcopy/ELF/strip-non-alloc.test
View File

@ -9,6 +9,10 @@ FileHeader:
Type: ET_REL
Machine: EM_X86_64
Sections:
- Name: non_alloc_in_segment
Type: SHT_PROGBITS
Flags: [ ]
Size: 4
- Name: .bss
Type: SHT_NOBITS
Flags: [ SHF_ALLOC ]
@ -18,9 +22,15 @@ Sections:
- Name: .blarg
Type: SHT_PROGBITS
Flags: [ ]
ProgramHeaders:
# Use an arbitrary segment type to show that the segment type is unimportant.
- Type: 0x61234567
Sections:
- Section: non_alloc_in_segment
# CHECK: SectionHeaderCount: 4
# CHECK: SectionHeaderCount: 5
# CHECK: Name: non_alloc_in_segment
# CHECK: Name: .bss
# CHECK: Name: .text
# CHECK: Name: .shstrtab

11
test/tools/llvm-objcopy/ELF/strip-sections.test
View File

@ -15,13 +15,18 @@ Sections:
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
AddressAlign: 0x0000000000001000
Content: "DEADBEEF"
- Name: .non_alloc_in_segment
Type: SHT_PROGBITS
Flags: [ ]
Content: "CAFEBABE"
ProgramHeaders:
- Type: PT_LOAD
Flags: [ PF_X, PF_R ]
Sections:
- Section: .text
- Section: .non_alloc_in_segment
#DATA: 0010000 de ad be ef
#DATA: 0010000 de ad be ef ca fe ba be
#CHECK: ElfHeader {
#CHECK-NEXT: Ident {
@ -55,8 +60,8 @@ ProgramHeaders:
#CHECK-NEXT: Offset: 0x1000
#CHECK-NEXT: VirtualAddress: 0x0
#CHECK-NEXT: PhysicalAddress: 0x0
#CHECK-NEXT: FileSize: 4
#CHECK-NEXT: MemSize: 4
#CHECK-NEXT: FileSize: 8
#CHECK-NEXT: MemSize: 8
#CHECK-NEXT: Flags [ (0x5)
#CHECK-NEXT: PF_R (0x4)
#CHECK-NEXT: PF_X (0x1)

6
tools/llvm-objcopy/ELF/ELFObjcopy.cpp
View File

@ -403,7 +403,7 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj,
if (Config.StripSections) {
RemovePred = [RemovePred](const SectionBase &Sec) {
return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
return RemovePred(Sec) || Sec.ParentSegment == nullptr;
};
}
@ -419,7 +419,7 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj,
return true;
if (&Sec == Obj.SectionNames)
return false;
return (Sec.Flags & SHF_ALLOC) == 0;
return (Sec.Flags & SHF_ALLOC) == 0 && Sec.ParentSegment == nullptr;
};
if (Config.StripAll)
@ -430,6 +430,8 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj,
return false;
if (StringRef(Sec.Name).startswith(".gnu.warning"))
return false;
if (Sec.ParentSegment != nullptr)
return false;
return (Sec.Flags & SHF_ALLOC) == 0;
};

19
tools/llvm-objcopy/ObjcopyOpts.td
View File

@ -103,10 +103,9 @@ defm set_section_flags
"rom, share, contents, merge, strings.">,
MetaVarName<"section=flag1[,flag2,...]">;
def strip_all
: Flag<["-", "--"], "strip-all">,
HelpText<
"Remove non-allocated sections other than .gnu.warning* sections">;
def strip_all : Flag<["-", "--"], "strip-all">,
HelpText<"Remove non-allocated sections outside segments. "
".gnu.warning* sections are not removed">;
def S : Flag<["-"], "S">, Alias<strip_all>;
def strip_all_gnu : Flag<["-", "--"], "strip-all-gnu">,
HelpText<"Compatible with GNU objcopy's --strip-all">;
@ -116,13 +115,15 @@ def g : Flag<["-"], "g">, Alias<strip_debug>,
HelpText<"Alias for --strip-debug">;
def strip_dwo : Flag<["-", "--"], "strip-dwo">,
HelpText<"Remove all DWARF .dwo sections from file">;
def strip_sections : Flag<["-", "--"], "strip-sections">,
HelpText<"Remove all section headers">;
def strip_non_alloc : Flag<["-", "--"], "strip-non-alloc">,
HelpText<"Remove all non-allocated sections">;
def strip_sections
: Flag<["-", "--"], "strip-sections">,
HelpText<"Remove all section headers and all sections not in segments">;
def strip_non_alloc
: Flag<["-", "--"], "strip-non-alloc">,
HelpText<"Remove all non-allocated sections outside segments">;
def strip_unneeded : Flag<["-", "--"], "strip-unneeded">,
HelpText<"Remove all symbols not needed by relocations">;
defm strip_unneeded_symbol
defm strip_unneeded_symbol
: Eq<"strip-unneeded-symbol",
"Remove symbol <symbol> if it is not needed by relocations">,
MetaVarName<"symbol">;

7
tools/llvm-objcopy/StripOpts.td
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@ -31,10 +31,9 @@ def preserve_dates : Flag<["-", "--"], "preserve-dates">,
HelpText<"Preserve access and modification timestamps">;
def p : Flag<["-"], "p">, Alias<preserve_dates>;
def strip_all
: Flag<["-", "--"], "strip-all">,
HelpText<
"Remove non-allocated sections other than .gnu.warning* sections">;
def strip_all : Flag<["-", "--"], "strip-all">,
HelpText<"Remove non-allocated sections outside segments. "
".gnu.warning* sections are not removed">;
def s : Flag<["-"], "s">, Alias<strip_all>;
def strip_all_gnu : Flag<["-", "--"], "strip-all-gnu">,