Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[llvm-objdump] Print out xcoff load section of xcoff object file with option private-headers #121226

Open
wants to merge 3 commits into
base: main
Choose a base branch
from
Open

[llvm-objdump] Print out xcoff load section of xcoff object file with option private-headers #121226

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
cb20a6e
[llvm-objdump] Print out xcoff file header for xcoff object file with…
diggerlin Dec 27, 2024
dce5109
minor change
diggerlin Dec 27, 2024
2ecfb53
add warnning test scenario
diggerlin Jan 14, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
83 changes: 83 additions & 0 deletions llvm/test/tools/llvm-objdump/XCOFF/private-headers-option.test
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,83 @@
## Test the --private-headers option for the loader section of XCOFF object files.

# RUN: yaml2obj --docnum=1 %s -o %t_xcoff32.o
# RUN: yaml2obj --docnum=2 %s -o %t_xcoff64.o
# RUN: llvm-objdump --private-headers %t_xcoff32.o |\
# RUN: FileCheck %s --check-prefixes=CHECK32 --match-full-lines
# RUN: llvm-objdump --private-headers %t_xcoff64.o |\
# RUN: FileCheck %s --check-prefixes=CHECK64 --match-full-lines

--- !XCOFF
FileHeader:
MagicNumber: 0x1DF
Sections:
- Name: .loader
Flags: [ STYP_LOADER ]
SectionData: "0000000100000003000000050000016D00000001000000A40000001800000211"
## ^------- -Version=1
## ^------- -NumberOfSymbolEntries=3
## ^------- -NumberOfRelocationEntries=5
## ^------- -LengthOfImportFileIDStringTable=365
## ^------- -NumberOfImportFileIDs=1
## ^------- -OffsetToImportFileIDs=0xA4
## ^------- -LengthOfStringTable=24
## ^------- -OffsetToStringTable=0x211


--- !XCOFF
FileHeader:
MagicNumber: 0x1F7
Sections:
- Name: .loader
Flags: [ STYP_LOADER ]
SectionData: "0000000200000003000000050000016D000000010000002300000000000000D0000000000000023D00000000000000380000000000000080"
## ^------- -Version=2
## ^------- -NumberOfSymbolEntries=3
## ^------- -NumberOfRelocationEntries=5
## ^------- -LengthOfImportFileIDStringTable=365
## ^------- -NumberOfImportFileIDs=1
## ^------- --LengthOfStringTable=0x23
## ^--------------- -OffsetToImportFileIDs=0xD0
## ^--------------- -OffsetToStringTable=0x23D
## ^-------------- -OffsetToSymbolTable=0x38
## ^--------------- -OffsetToRelocationEntries=0x80

# CHECK32: ---File Header:
# CHECK32-NEXT: Magic: 0x1df
# CHECK32-NEXT: NumberOfSections: 1
# CHECK32-NEXT: Timestamp: None (0)
# CHECK32-NEXT: SymbolTableOffset: 0x0
# CHECK32-NEXT: SymbolTableEntries: 0
# CHECK32-NEXT: OptionalHeaderSize: 0x0
# CHECK32-NEXT: Flags: 0x0

# CHECK32: ---Loader Section Header:
# CHECK32-NEXT: Version: 1
# CHECK32-NEXT: NumberOfSymbolEntries: 3
# CHECK32-NEXT: NumberOfRelocationEntries: 5
# CHECK32-NEXT: LengthOfImportFileIDStringTable: 365
# CHECK32-NEXT: NumberOfImportFileIDs: 1
# CHECK32-NEXT: OffsetToImportFileIDs: 0xa4
# CHECK32-NEXT: LengthOfStringTable: 24
# CHECK32-NEXT: OffsetToStringTable: 0x211

# CHECK64: ---File Header:
# CHECK64-NEXT: Magic: 0x1f7
# CHECK64-NEXT: NumberOfSections: 1
# CHECK64-NEXT: Timestamp: None (0)
# CHECK64-NEXT: SymbolTableOffset: 0x0
# CHECK64-NEXT: SymbolTableEntries: 0
# CHECK64-NEXT: OptionalHeaderSize: 0x0
# CHECK64-NEXT: Flags: 0x0

# CHECK64: ---Loader Section Header:
# CHECK64-NEXT: Version: 2
# CHECK64-NEXT: NumberOfSymbolEntries: 3
# CHECK64-NEXT: NumberOfRelocationEntries: 5
# CHECK64-NEXT: LengthOfImportFileIDStringTable: 365
# CHECK64-NEXT: NumberOfImportFileIDs: 1
# CHECK64-NEXT: OffsetToImportFileIDs: 0xd0
# CHECK64-NEXT: LengthOfStringTable: 35
# CHECK64-NEXT: OffsetToStringTable: 0x23d
# CHECK64-NEXT: OffsetToSymbolTable 0x38
# CHECK64-NEXT: OffsetToRelocationEntries 0x80
41 changes: 41 additions & 0 deletions llvm/tools/llvm-objdump/XCOFFDump.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@ class XCOFFDumper : public objdump::Dumper {
void printPrivateHeaders() override;
void printFileHeader();
void printAuxiliaryHeader();
void printLoaderSectionHeader();
void printAuxiliaryHeader(const XCOFFAuxiliaryHeader32 *AuxHeader);
void printAuxiliaryHeader(const XCOFFAuxiliaryHeader64 *AuxHeader);
template <typename AuxHeaderMemberType, typename XCOFFAuxiliaryHeader>
Expand All @@ -66,6 +67,7 @@ class XCOFFDumper : public objdump::Dumper {
void XCOFFDumper::printPrivateHeaders() {
printFileHeader();
printAuxiliaryHeader();
printLoaderSectionHeader();
}

FormattedString XCOFFDumper::formatName(StringRef Name) {
Expand Down Expand Up @@ -262,6 +264,45 @@ void XCOFFDumper::printAuxiliaryHeader(
AuxSize, *AuxHeader);
}

void XCOFFDumper::printLoaderSectionHeader() {
Expected<uintptr_t> LoaderSectionAddrOrError =
Obj.getSectionFileOffsetToRawData(XCOFF::STYP_LOADER);
if (!LoaderSectionAddrOrError) {
reportUniqueWarning(LoaderSectionAddrOrError.takeError());
jh7370 marked this conversation as resolved.
Show resolved Hide resolved
return;
}
uintptr_t LoaderSectionAddr = LoaderSectionAddrOrError.get();

if (LoaderSectionAddr == 0)
return;

auto PrintLoadSecHeaderCommon = [&](const auto *LDHeader) {
printNumber("Version:", LDHeader->Version);
printNumber("NumberOfSymbolEntries:", LDHeader->NumberOfSymTabEnt);
printNumber("NumberOfRelocationEntries:", LDHeader->NumberOfRelTabEnt);
printNumber("LengthOfImportFileIDStringTable:",
LDHeader->LengthOfImpidStrTbl);
printNumber("NumberOfImportFileIDs:", LDHeader->NumberOfImpid);
printHex("OffsetToImportFileIDs:", LDHeader->OffsetToImpid);
printNumber("LengthOfStringTable:", LDHeader->LengthOfStrTbl);
printHex("OffsetToStringTable:", LDHeader->OffsetToStrTbl);
};

Width = 35;
outs() << "\n---Loader Section Header:\n";
if (Obj.is64Bit()) {
const LoaderSectionHeader64 *LoaderSec64 =
reinterpret_cast<const LoaderSectionHeader64 *>(LoaderSectionAddr);
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is there a risk that the data won't be aligned in memory, such that on some architectures, reading the data will cause a failure?

Copy link
Contributor Author

@diggerlin diggerlin Jan 14, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

If I understand your question correctly. I wrote following test case and run , it do not crash. it looks the PowerPC do not need to be alignment on the memory in when reading the data.

bash> cat test.cpp
unsigned int var =10;
int main() {
 char *cvar = reinterpret_cast<char *>(&var)+1;

 int *us = reinterpret_cast<int *>(cvar);
 (*us)++;
 return *us;
}

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, I think you understood the question correctly, but you've missed the fact that this code could be run on non-PowerPC architectures, which is where my concern lies. See issues like #95811 for examples.

In this case, perhaps we should check that LoaderSectionAddr is appropriately aligned and emit an error if it isn't. Alternatively, we can simply do a memcpy of the raw data into a local copy of LoaderSectionHeader[64|32], so that the data is guaranteed to be aligned. I think either approach is valid, since it's probably a requirement (either explicitly, or indirectly implied by other aspects of the spec) of the XCOFF spec that LoaderSectionAddr is aligned.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think it only happen when compile with option -mstrict-align on the AArch64, I do not think llvm compile the llvm-objdump with option -mstrict-align.

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I've seen issues fixed in LLVM because of alignment problems, flagged by build bots. The issue I filed was just one possible example. Another example: 8fbe1e7.

Copy link
Contributor Author

@diggerlin diggerlin Jan 16, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There is a lot of reinterpret_cast or static_cast in the XCOFFObjectFile.cpp/Archive.cpp etc. it will have the same problem if there is.
I think if we want to fix the problem we need to have underlying API to deal with the problem for whole the llvm in a separate patch instead of using memcpy one by one.

PrintLoadSecHeaderCommon(LoaderSec64);
printHex("OffsetToSymbolTable", LoaderSec64->OffsetToSymTbl);
printHex("OffsetToRelocationEntries", LoaderSec64->OffsetToRelEnt);
} else {
const LoaderSectionHeader32 *LoaderSec32 =
reinterpret_cast<const LoaderSectionHeader32 *>(LoaderSectionAddr);
PrintLoadSecHeaderCommon(LoaderSec32);
}
}

void XCOFFDumper::printFileHeader() {
Width = 20;
outs() << "\n---File Header:\n";
Expand Down
Loading