[llvm-readobj] Dump callgraph section info for ELF #157499

Prabhuk · 2025-09-08T15:58:03Z

Introduce a new flag --call-graph-info which outputs callgraph ELF
section information to the console as a text output or as JSON output.

github-actions · 2025-09-08T16:00:45Z

✅ With the latest revision this PR passed the C/C++ code formatter.

Introduce a new flag `--call-graph-info` which outputs callgraph ELF section information to the console as a text output or as JSON output.

…dth size.

…toms out to llvm_unreachable.

llvm/tools/llvm-readobj/ELFDumper.cpp

llvm/test/tools/llvm-readobj/ELF/call-graph-info.test

llvm/tools/llvm-readobj/ELFDumper.cpp

llvm/test/tools/llvm-readobj/ELF/call-graph-info.test

llvm/test/tools/llvm-readobj/ELF/call-graph-info-err-missing-indirect.s

jh7370

Please make sure to update the llvm-readobj and llvm-readelf CommandGuide documents under llvm/docs.

I'm keen to review this, as I've seen several things when skimming I'd like addressed, but don't have time to review it properly this week, due to other reviews and some planned time off.

jh7370 · 2025-11-03T09:34:03Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/Error.h"


I'm surprised some/most/all of these new headers need to be added? Is your IDE adding additional headers unnecessarily?

I think the IDE is adding the corresponding header whenever I initialize a type. Cleaned up the header includes. PTAL.

Error.h is almost certainly not needed explicitly, given Error and Expected are already widely in use. (https://llvm.org/docs/CodingStandards.html#include-as-little-as-possible, specifically the bit about being able to include headers implicitly via other headers).

llvm/tools/llvm-readobj/ELFDumper.cpp

ilovepi

I think this is basically LGTM from me. Lets make sure we wait until @jh7370 weighs in w/ a full review to land though.

Prabhuk · 2025-11-04T23:04:42Z

I think this is basically LGTM from me. Lets make sure we wait until @jh7370 weighs in w/ a full review to land though.

Thank you. I will be adding a few more tests and will wait for @jh7370's review.

llvm/test/tools/llvm-readobj/ELF/call-graph-info-relocatable-obj.test

ilovepi · 2025-11-05T17:10:40Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-callgraph-section.s

+# JSON-NEXT:          "NumDirectCallees": 1,
+# JSON-NEXT:          "DirectCallees": [
+# JSON-NEXT:            {
+# JSON-NEXT:              "Offset": 19


What is Offset here? is it the address? offset from the start of the section?

Offset is pointless actually. It's the offset of the symbol for which we couldn't find corresponding relocation. I removed "offset" and turned it into a warning for this scenario.

jh7370

Sorry for the delay in looking. The CommandGuide docs still haven't been updated. Please update them with the new option.

I've made another pass, but have run out of time to look at everything. Hopefully there's enough here to keep going on.

jh7370 · 2025-11-19T09:05:58Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-callgraph-section.s

@@ -0,0 +1,150 @@
+## Tests --call-graph-info prints information from call graph section.
+
+# REQUIRES: x86-registered-target


Could we convert the test input to use yaml2obj, instead of requiring x86? It looks like the file format is trivial enough that something like a YAML ELF input using ContentArray would be just as descriptive, whilst also allowing more precise control of everything.

llvm/test/tools/llvm-readobj/ELF/call-graph-info-callgraph-section.s

llvm/tools/llvm-readobj/Opts.td

llvm/tools/llvm-readobj/ObjDumper.h

llvm/tools/llvm-readobj/ELFDumper.cpp

jh7370 · 2025-11-19T10:14:51Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+    reportError(createError("No .llvm.callgraph section found."),
+                "Missing section");


https://llvm.org/docs/CodingStandards.html#error-and-warning-messages

Same applies to other error/warning messages.

That being said, we don't tend to emit an error for other options that do similar things, if the respective section doesn't exist.

When a diagnostic message is appropriate, we usually prefer warnings, rather than errors, so that we can continue dumping other requested items, or we emit a warning then try to dump the information we can for the requested section and use placeholder values (e.g. "<?>").

Done. PTAL.

It's definitely not done. There are loads of other diagnostic messages that are using a capital letter, despite the rules described. Please take another look.

jh7370 · 2025-11-19T10:15:58Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+
+  Expected<ArrayRef<uint8_t>> SectionBytesOrErr =
+      Obj.getSectionContents(*CGSection);
+  if (!SectionBytesOrErr) {


https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

Applies in several other places too.

I think I have addressed all the cases. PTAL.

I've highlighted several cases where it's not been addressed. I'd be surprised if I caught them all.

jh7370 · 2025-11-19T10:22:54Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+                    .str());
+  };
+
+  DataExtractor Data(SectionBytesOrErr.get(), Obj.isLE(),


Have you looked into using the DataExtractor::Cursor class? I think that would simplify some of your parsing logic below.

llvm/tools/llvm-readobj/ELFDumper.cpp

…f the output which is not useful.

github-actions · 2025-11-21T03:11:01Z

🐧 Linux x64 Test Results

186436 tests passed
4868 tests skipped

ilovepi · 2025-11-21T17:45:03Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+    SmallVector<uint64_t, 4> IndirectTypeIdsList = SmallVector<uint64_t, 4>(
+        CGInfo.IndirectTypeIDs.begin(), CGInfo.IndirectTypeIDs.end());


Suggested change

SmallVector<uint64_t, 4> IndirectTypeIdsList = SmallVector<uint64_t, 4>(

CGInfo.IndirectTypeIDs.begin(), CGInfo.IndirectTypeIDs.end());

SmallVector<uint64_t, 4> IndirectTypeIdsList(CGInfo.IndirectTypeIDs.begin(), CGInfo.IndirectTypeIDs.end());

Can't recall if you need .begin()/.end() to convert w/ SmallSet, or if there is an overload in ADT.

Alternatively, you can avoid the conversion altogether. Looking at printHexList(), its going to put the items in a SmallVector on its own (

llvm-project/llvm/include/llvm/Support/ScopedPrinter.h

Line 364 in f8a8039

template <typename T> void printHexList(StringRef Label, const T &List) {

). Arguable that there should probably be a specialization for things automatically convertible to ArraryRef that just forwards to printHexListImpl().

ilovepi · 2025-11-21T18:05:01Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-callgraph-section.s

+# JSON:     "CallGraph": [
+# JSON-NEXT:      {
+# JSON-NEXT:        "Function": {
+# JSON-SAME:     warning: '[[FILE]]': unknown relocation at offset 2


Why are we getting this warning here? can we avoid it in this test case, and have specific test cases that should issue the diagnostic? To ensure no warnings occur, you can use the FileCheck --implicit-check-not "warning:".

ilovepi · 2025-11-21T18:06:32Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-err-invalid-flags.s

@@ -0,0 +1,22 @@
+## Tests that --call-graph-info fails if .llvm.callgraph section has invalid


Since you only issue a warning now, the file name should probably get updated.

ilovepi · 2025-11-21T18:07:57Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-err-no-callgraph-section.s

+# RUN: llvm-readelf --elf-output-style=LLVM --call-graph-info %t 2>&1 | FileCheck %s -DFILE=%t
+# RUN: llvm-readelf --elf-output-style=JSON --pretty-print --call-graph-info %t 2>&1 | FileCheck %s -DFILE=%t
+
+# CHECK: warning: 'missing section': No .llvm.callgraph section found.


Update file name to reflect that its no longer an error.

ilovepi · 2025-11-21T18:10:02Z

llvm/test/tools/llvm-readobj/ELF/call-graph-info-relocatable-file.s

+## We do not support GNU format console output for --call-graph-info as it is an LLVM only info.
+# CHECK-NOT: .
+
+# LLVM: 		CallGraph [


Suggested change

# LLVM: CallGraph [

# LLVM: CallGraph [

I think this would align it w/ the one below. Seems less jarring than the current indentation. Could also unindent this more to reflect the actual nesting.

ilovepi · 2025-11-21T18:14:03Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+  SmallVector<std::string> getFunctionNames(uint64_t FuncAddr) {
+    SmallVector<uint32_t> FuncSymIndexes =
+        this->getSymbolIndexesForFunctionAddress(FuncAddr, std::nullopt);
+    SmallVector<std::string> FuncSymNames;


you know the size at this point, so you can use reserve() to avoid extra allocations + copies on push_back when the vector grows.

ilovepi · 2025-11-21T18:28:35Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+                Twine("while reading call graph info's [" + Component +
+                      "] for function at [0x" + FuncPC + "]")


Looking at the def for reportError() in llvm-readobj, I think the Input parameter (2nd param) is typically a file name. Or, at least its getting passed to reportFileError() under the hood, and I don't see anyone passing a string like this into reportError() in the rest of the code.

Maybe the typical pattern is to wrap your error message in another error type?

ilovepi · 2025-11-21T18:29:59Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+    Error CGSectionErr = Error::success();
+    uint8_t FormatVersionNumber = Data.getU8(&Offset, &CGSectionErr);


Is the initialization dead, since getU8() updates it's value?

ilovepi · 2025-11-21T18:30:59Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+      reportError(createError("Unknown format version value [" +
+                              std::to_string(FormatVersionNumber) +
+                              "] in .llvm.callgraph section."),
+                  "unknown value");


Suggested change

"unknown value");

FileStr);

ilovepi · 2025-11-21T18:32:27Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+      reportWarning(std::move(CGSectionErr),
+                    "while reading call graph info's Flags");


I think this needs to wrap the message in an error type. you're passing it in as a filename, from what I can see.

This seems pervasive, throughout the patch.

jh7370

Requesting changes to make it clear there's still plenty of work to be done.

jh7370 · 2025-11-24T08:11:01Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/Error.h"


Error.h is almost certainly not needed explicitly, given Error and Expected are already widely in use. (https://llvm.org/docs/CodingStandards.html#include-as-little-as-possible, specifically the bit about being able to include headers implicitly via other headers).

jh7370 · 2025-11-24T08:11:26Z

llvm/tools/llvm-readobj/ELFDumper.cpp

 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/SystemZ/zOSSupport.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/TargetParser/Triple.h"


Why this include?

jh7370 · 2025-11-24T08:15:53Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+} // namespace callgraph
+
+template <class ELFT> bool ELFDumper<ELFT>::processCallGraphSection() {
+  const Elf_Shdr *CGSection = findSectionByName(".llvm.callgraph");


Is .llvm.callgraph a new section, or a long pre-existing section that we're just gaining functionality to dump now? If it's new, a much-preferred approach would be to give the section a specific type, as type lookup is more appropriate for ELF than name lookup (and much faster, especially in large objects).

jh7370 · 2025-11-24T08:18:32Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+
+  Expected<ArrayRef<uint8_t>> SectionBytesOrErr =
+      Obj.getSectionContents(*CGSection);
+  if (!SectionBytesOrErr) {


Remove braces here.

jh7370 · 2025-11-24T08:20:39Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+      return false;
+    }
+    if (FormatVersionNumber != 0) {
+      reportError(createError("Unknown format version value [" +


This should be a warning and bail out of the dumping, so that other requested llvm-readobj operations can continue.

jh7370 · 2025-11-24T08:21:27Z

llvm/tools/llvm-readobj/ELFDumper.cpp

 }

+template <class ELFT> void LLVMELFDumper<ELFT>::printCallGraphInfo() {
+  if (!this->processCallGraphSection() || this->FuncCGInfos.empty()) {


Unnecessary braces.

jh7370 · 2025-11-24T08:21:43Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+      this->reportUniqueWarning(RelSymOrErr.takeError());
+      return;
+    }
+    if (!RelSymOrErr->Name.empty()) {


Unnecessary braces.

jh7370 · 2025-11-24T08:30:14Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+    reportError(createError("No .llvm.callgraph section found."),
+                "Missing section");


It's definitely not done. There are loads of other diagnostic messages that are using a capital letter, despite the rules described. Please take another look.

jh7370 · 2025-11-24T08:30:58Z

llvm/tools/llvm-readobj/ELFDumper.cpp

+
+  Expected<ArrayRef<uint8_t>> SectionBytesOrErr =
+      Obj.getSectionContents(*CGSection);
+  if (!SectionBytesOrErr) {


I've highlighted several cases where it's not been addressed. I'd be surprised if I caught them all.

Prabhuk mentioned this pull request Sep 9, 2025

[llvm-objdump] Handle .callgraph section #151009

Closed

Prabhuk added 13 commits September 17, 2025 18:59

[llvm-readobj] Dump callgraph section info for ELF

ac4b7bc

Introduce a new flag `--call-graph-info` which outputs callgraph ELF section information to the console as a text output or as JSON output.

Format code

31c4d2b

Implement JSON output for printCallGraph()

4d1a7c7

ELFDumper cleanups

f0810b2

Add readelf callgraph info tests.

5f20b7b

more tests

d991194

Extend tests to json

c2d8d22

Expand all tests to include JSON and LLVM formats.

2874918

Improve tests. Match full lines.

9803c62

Make call graph processing agnostic of target architecture pointer wi…

7285210

…dth size.

Remove unnecessary function returns after reportError calls which bot…

8236798

…toms out to llvm_unreachable.

Formatting fixes.

abe189e

Remove callsites from direct call data.

0b9c46d

Prabhuk force-pushed the readelf_callgraph_info branch from 3499c2d to 0b9c46d Compare September 18, 2025 03:09

Prabhuk added 12 commits September 17, 2025 20:10

Format

5b504fc

Simplify readelf output.

5b6bb00

format

937ff61

Clean up callgraph output

1b86857

Format

7280ff3

Show symbol names.

bdb8683

Format

09d3a87

Make llvm output better.

b851b8d

format source.

fd50ff0

Minor improvements to LLVM output.

ee3a081

Fix tests to match the new output.

3c94a44

Add REQUIRES: x86-registered-target to tests.

026b184

Prabhuk requested review from frobtech and ilovepi September 19, 2025 00:12

ilovepi reviewed Oct 24, 2025

View reviewed changes

Prabhuk added 3 commits October 31, 2025 13:31

Address review comments.

d04fbd0

Function name printing to match stack size printing behavior.

75bffeb

Refactor getCalGraphSection function as suggested in review.

77acb10

ilovepi reviewed Oct 31, 2025

View reviewed changes

jh7370 reviewed Nov 3, 2025

View reviewed changes

Prabhuk added 4 commits November 4, 2025 11:36

Declutter ouput format. Remove GNU output.

246275d

Remove unnecessary header includes.

402c90f

More header include cleanups.

87d3dd8

Rename test files to .S

20ea016

ilovepi approved these changes Nov 4, 2025

View reviewed changes

Prabhuk added 8 commits November 4, 2025 16:21

Fix relocation printing handling.

c5823aa

Remove addend, type and offset info from relocations.

8d3a27c

Fix tests.

aaa2cd4

Fix tests.

afc13ee

Rename files to .s

6e22254

Make relocatable test to be built from YAML.

5b3bff0

Relocatable file tests fixed.

c4ea41d

Nits. Alignment within test files.

53ffcaa

ilovepi reviewed Nov 5, 2025

View reviewed changes

Prabhuk added 2 commits November 5, 2025 11:00

Merge remote-tracking branch 'upstream/main' into readelf_callgraph_info

edc5eaa

Merge branch 'main' into readelf_callgraph_info

14b5cf0

jh7370 reviewed Nov 19, 2025

View reviewed changes

Prabhuk added 3 commits November 20, 2025 17:19

Warn for unknown relocations instead of printing the offset as part o…

b56a17c

…f the output which is not useful.

Address review comments.

ae501fa

Fix messages. Remove unnecessary errors and unused functions.

f454957

ilovepi reviewed Nov 21, 2025

View reviewed changes

jh7370 requested changes Nov 24, 2025

View reviewed changes

		@@ -0,0 +1,150 @@
		## Tests --call-graph-info prints information from call graph section.

		# REQUIRES: x86-registered-target

		reportError(createError("No .llvm.callgraph section found."),
		"Missing section");

		SmallVector<uint64_t, 4> IndirectTypeIdsList = SmallVector<uint64_t, 4>(
		CGInfo.IndirectTypeIDs.begin(), CGInfo.IndirectTypeIDs.end());

		@@ -0,0 +1,22 @@
		## Tests that --call-graph-info fails if .llvm.callgraph section has invalid

		Twine("while reading call graph info's [" + Component +
		"] for function at [0x" + FuncPC + "]")

		Error CGSectionErr = Error::success();
		uint8_t FormatVersionNumber = Data.getU8(&Offset, &CGSectionErr);

		reportWarning(std::move(CGSectionErr),
		"while reading call graph info's Flags");

[llvm-readobj] Dump callgraph section info for ELF #157499

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[llvm-readobj] Dump callgraph section info for ELF #157499

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Prabhuk commented Sep 8, 2025

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github-actions bot commented Nov 21, 2025

🐧 Linux x64 Test Results

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