i#1973 musl: fix build on musl libc #7168

ziyao233 · 2024-12-23T19:59:26Z

This pull request allows DynamoRIO and all the tests to be built on musl libc,

Introduce MUSL macro and detect for musl libc in CMakeLists.txt
Add necessary macro and typedefs in core/unix/include/siginfo.h
Fix compilation of vendored elfutils
Temporarily use STDOUT/STDERR_FILENO when we need the underlying fds of
stdout/stderr and suppress warnings for musl's opaque FILE type
Adjust linux.signal* tests to stay compatible with musl's SIGRTMAX, which is
actually a function call, instead of a constant value

Tested on Alpine Linux, half of the tests are passed and it's possible to run
some applications (busybox, mutt and telegram-desktop) and some simple clients
(bbsize).

Issue: #1973

This introduces the MUSL macro.

bits/wordsize.h is a glibc-specific header, on musl __WORD_SIZE is defined as LONG_BIT. This is okay since Linux kernel assumes the size of long is equal to a machine word.

The pre-defined config.h is adjusted to match musl's features. We also to build and link lib/error.c to provide functions for error message handling.

As DynamoRIO enables -Werror by default, such warnings will prevent a warning-aware build. Since we also issue a warnings during start up, Let's remove it.

GCC on Alpine Linux enables "-Wtrampolines" by default, breaking the test. Since Alpine is the most widely-used musl-based distribution, it's worth to work around this: let's defaults to -Wno-trampoline on musl systems.

Some glibc-specific APIs are used in the test, we need to port them to musl.

DynamoRIO defines REG_* macros for compatibility with old clients, which conflict with signal.h on musl. Use of pragma push_macro/pop_macro to avoid messing musl's header up.

ziyao233 · 2024-12-23T21:57:45Z

@derekbruening thanks for your review

abhinav92003 · 2024-12-26T15:42:57Z

@derekbruening thanks for your review

If this PR is ready for review, please add a reviewer from the "Reviewers" list on the top-right1.

ziyao233 · 2024-12-26T16:02:35Z

@derekbruening thanks for your review

If this PR is ready for review, please add a reviewer from the "Reviewers" list on the top-right1.

I have no write access to the repository, thus cannot require a reviewer :/
It's ready for review and I'll be thankful if you could give me a helpful hand.

CMakeLists.txt

derekbruening · 2025-01-02T23:19:38Z

CMakeLists.txt

+  if (NOT LDD)
+    message(STATUS "Unable to find ldd: assume glibc")
+  else ()
+    execute_process(COMMAND ${LDD}


Does the build host ldd on the path always correspond with the build toolchain in use and the target? Any cross-compilation concerns?

Does the build host ldd on the path always correspond with the build toolchain in use and the target?

Sure not.

Any cross-compilation concerns?

I don't know a better way to detect musl in cmake. but following strategy may be appropriate,

When building natively, check ldd and examine whether it's musl libc.

When cross compiling, always assume glibc.

Provide an extra build argument to force a musl build.

Then native builds and cross ones targeting glibc will go smoothly, which covers most cases. Those who crosscompile for musl should know what they're doing (and read the doc).

What do you think of it?

suite/tests/CMakeLists.txt

suite/tests/linux/signal-base.h

derekbruening · 2025-01-02T23:41:54Z

suite/tests/linux/signal-base.h

@@ -182,7 +168,28 @@ static void
    }
 #endif

-    default: assert(0);
+    default:
+        /* i#1973: SIGRTMAX is a macro over function call, rather a constant on


A function call into libc.so? While that may work in this test, that will break core DR where libdynamorio.so cannot import from libc. All core DR uses need to be replaced with something that does not need libc code at runtime. There is a build-time check for such imports: CMake_readelf.cmake check_deps. Is that check running in your build (maybe it gets disabled if it can't find readelf or sthg)? Does it pass?

A function call into libc.so? While that may work in this test, that will break core DR where libdynamorio.so cannot import from libc. All core DR uses need to be replaced with something that does not need libc code at runtime.

I understand dr cannot rely on any libc functions, but __SIGRTMAX seems unrelated to this: All results of git grep SIGRTMAX are in suite/tests/linux/signal-base.h, thus I think there's no reference to it in the core DR.

There is a build-time check for such imports: CMake_readelf.cmake check_deps. Is that check running in your build (maybe it gets disabled if it can't find readelf or sthg)? Does it pass?

Have checked my generated build.ninja, it did run and pass :)

CMakeLists.txt

derekbruening · 2025-01-02T23:45:28Z

core/unix/os.c

@@ -6418,7 +6418,6 @@ set_stdfile_fileno(stdfile_t **stdfile, file_t old_fd, file_t file_no)
    (*stdfile)->STDFILE_FILENO = file_no;
 #    endif
 #else
-#    warning stdfile_t is opaque; DynamoRIO will not set fds of libc FILEs.


We try to separate the build system from the target runtime system: but here it seems they are tied together so a glibc build will fail when trying to use a musl libc library with a tool run on a musl system; and this musl build will fail on a glibc system even though the musl build would be able to work if it had dynamic discovery of the libc type. Add a XXX comment on that possibility? Likely not worth effort to implement at this point.

What do you think of adding

XXX: Discover libc type at runtime and use appropriate stdfile_t variant

at top of set_stdfile_fileno()?

ziyao233 · 2025-01-11T19:01:06Z

btw, may I have write access to the repository? I'm an intern of ISCAS and will continue working on riscv and musl port for DR, the access will help a lot (like adding an appropriate reviewer)

ziyao233 added 12 commits December 23, 2024 19:24

detect musl libc in CMakeLists.txt

23b83b3

This introduces the MUSL macro.

handle musl case in core/unix/include/siginfo.h

d5b9e0b

bits/wordsize.h is a glibc-specific header, on musl __WORD_SIZE is defined as LONG_BIT. This is okay since Linux kernel assumes the size of long is equal to a machine word.

fix vendor elfutils build on musl

bed2443

The pre-defined config.h is adjusted to match musl's features. We also to build and link lib/error.c to provide functions for error message handling.

remove redundant warnings in core/unix/os.c

ec30b58

As DynamoRIO enables -Werror by default, such warnings will prevent a warning-aware build. Since we also issue a warnings during start up, Let's remove it.

fix test security-linux/trampolines on Alpine Linux

6fcfa2b

GCC on Alpine Linux enables "-Wtrampolines" by default, breaking the test. Since Alpine is the most widely-used musl-based distribution, it's worth to work around this: let's defaults to -Wno-trampoline on musl systems.

disable test client.file_io on musl

0c8fc71

Some glibc-specific APIs are used in the test, we need to port them to musl.

workaround naming conflicts on musl

3f57b66

DynamoRIO defines REG_* macros for compatibility with old clients, which conflict with signal.h on musl. Use of pragma push_macro/pop_macro to avoid messing musl's header up.

fix linux.signal* tests on musl libc

0ae1cbf

fix suite/tests/tools.c on musl

05b5c20

fix indentation

733aa8c

fix style

400105e

fix style in signal-base.h

7aaaba7

ksco requested review from derekbruening and abhinav92003 December 26, 2024 16:56

derekbruening approved these changes Jan 2, 2025

View reviewed changes

ziyao233 changed the title ~~I#1973: fix build on musl libc~~ i#1973: fix build on musl libc Jan 11, 2025

ziyao233 changed the title ~~i#1973: fix build on musl libc~~ i#1973 musl: fix build on musl libc Jan 11, 2025

ziyao233 added 2 commits January 11, 2025 18:34

misc style fixes

ab7c054

Define __SIGRTMAX for all systems missing it

8b45b7d

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i#1973 musl: fix build on musl libc #7168

i#1973 musl: fix build on musl libc #7168

ziyao233 commented Dec 23, 2024

ziyao233 commented Dec 23, 2024

abhinav92003 commented Dec 26, 2024

ziyao233 commented Dec 26, 2024

derekbruening Jan 2, 2025

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i#1973 musl: fix build on musl libc #7168

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i#1973 musl: fix build on musl libc #7168

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