Re: [PATCH 00/16] selftests: vDSO: parse_vdso: Make compatible with nolibc

From: Christophe Leroy
Date: Mon Feb 03 2025 - 06:50:10 EST

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Le 03/02/2025 à 10:05, Thomas Weißschuh a écrit :

For testing the functionality of the vDSO, it is necessary to build
userspace programs for multiple different architectures.
It is additional work to acquire matching userspace cross-compilers with
full C libraries and then building root images out of those.
The kernel tree already contains nolibc, a small, header-only C library.
By using it, it is possible to build userspace programs without any
additional dependencies.
For example the kernel.org crosstools or multi-target clang can be used
to build test programs for a multitude of architectures.
While nolibc is very limited, it is enough for many selftests.
With some minor adjustments it is possible to make parse_vdso.c
compatible with nolibc.
As an example, vdso_standalone_test_x86 is now built from the same C
code as the regular vdso_test_gettimeofday, while still being completely
standalone.

This should probably go through the kselftest tree.

Not sure what are the expectations with this series.

I gave it a try with vdso_test_gettimeofday and get the following:

$ powerpc64-linux-gcc -nostdlib -nostdinc -ffreestanding -fno-asynchronous-unwind-tables -fno-stack-protector -include /home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/nolibc/nolibc.h -I/home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/nolibc/ -isystem /home/chleroy/linux-powerpc/tools/testing/selftests/../../../usr/include -std=gnu99 -O2 -D_GNU_SOURCE= -isystem /home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/uapi vdso_test_gettimeofday.c parse_vdso.c -o /home/chleroy/linux-powerpc/tools/testing/selftests/vDSO/vdso_test_gettimeofday

make: Entering directory '/home/chleroy/linux-powerpc/tools/testing/selftests/vDSO'
powerpc64-linux-gcc -nostdlib -nostdinc -ffreestanding -fno-asynchronous-unwind-tables -fno-stack-protector -include /home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/nolibc/nolibc.h -I/home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/nolibc/ -isystem /home/chleroy/linux-powerpc/tools/testing/selftests/../../../usr/include -std=gnu99 -O2 -D_GNU_SOURCE= -isystem /home/chleroy/linux-powerpc/tools/testing/selftests/../../../tools/include/uapi vdso_test_gettimeofday.c parse_vdso.c -o /home/chleroy/linux-powerpc/tools/testing/selftests/vDSO/vdso_test_gettimeofday
parse_vdso.c:38:34: error: unknown type name 'Elf64_Versym'
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:63:9: note: in expansion of macro 'ELF'
63 | ELF(Versym) *versym;
| ^~~
parse_vdso.c:38:34: error: unknown type name 'Elf64_Verdef'
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:64:9: note: in expansion of macro 'ELF'
64 | ELF(Verdef) *verdef;
| ^~~
parse_vdso.c: In function 'vdso_init_from_sysinfo_ehdr':
parse_vdso.c:38:34: error: 'Elf64_Versym' undeclared (first use in this function); did you mean 'Elf64_Sym'?
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:150:45: note: in expansion of macro 'ELF'
150 | vdso_info.versym = (ELF(Versym) *)
| ^~~
parse_vdso.c:38:34: note: each undeclared identifier is reported only once for each function it appears in
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:150:45: note: in expansion of macro 'ELF'
150 | vdso_info.versym = (ELF(Versym) *)
| ^~~
parse_vdso.c:150:58: error: expected expression before ')' token
150 | vdso_info.versym = (ELF(Versym) *)
| ^
parse_vdso.c:38:34: error: 'Elf64_Verdef' undeclared (first use in this function); did you mean 'Elf64_Word'?
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:155:45: note: in expansion of macro 'ELF'
155 | vdso_info.verdef = (ELF(Verdef) *)
| ^~~
parse_vdso.c:155:58: error: expected expression before ')' token
155 | vdso_info.verdef = (ELF(Verdef) *)
| ^
parse_vdso.c: At top level:
parse_vdso.c:38:34: error: unknown type name 'Elf64_Versym'; did you mean 'Elf64_Sym'?
38 | #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
| ^~~
parse_vdso.c:39:33: note: in expansion of macro 'ELF_BITS_XFORM2'
39 | #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
| ^~~~~~~~~~~~~~~
parse_vdso.c:40:16: note: in expansion of macro 'ELF_BITS_XFORM'
40 | #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
| ^~~~~~~~~~~~~~
parse_vdso.c:177:32: note: in expansion of macro 'ELF'
177 | static bool vdso_match_version(ELF(Versym) ver,
| ^~~
parse_vdso.c: In function 'vdso_sym':
parse_vdso.c:224:25: error: 'STN_UNDEF' undeclared (first use in this function); did you mean 'SHN_UNDEF'?
224 | for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
| ^~~~~~~~~
| SHN_UNDEF
parse_vdso.c:240:25: warning: implicit declaration of function 'vdso_match_version' [-Wimplicit-function-declaration]
240 | && !vdso_match_version(vdso_info.versym[chain],
| ^~~~~~~~~~~~~~~~~~
make: *** [../lib.mk:222: /home/chleroy/linux-powerpc/tools/testing/selftests/vDSO/vdso_test_gettimeofday] Error 1
make: Leaving directory '/home/chleroy/linux-powerpc/tools/testing/selftests/vDSO'

Christophe

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
---
Thomas Weißschuh (16):
MAINTAINERS: Add vDSO selftests
elf, uapi: Add definition for STN_UNDEF
elf, uapi: Add definition for DT_GNU_HASH
elf, uapi: Add definitions for VER_FLG_BASE and VER_FLG_WEAK
elf, uapi: Add type ElfXX_Versym
elf, uapi: Add types ElfXX_Verdef and ElfXX_Veraux
tools/include: Add uapi/linux/elf.h
selftests: Add headers target
selftests: vDSO: vdso_standalone_test_x86: Use vdso_init_form_sysinfo_ehdr
selftests: vDSO: parse_vdso: Drop vdso_init_from_auxv()
selftests: vDSO: parse_vdso: Use UAPI headers instead of libc headers
selftests: vDSO: parse_vdso: Test __SIZEOF_LONG__ instead of ULONG_MAX
selftests: vDSO: parse_vdso: Make compatible with nolibc
selftests: vDSO: vdso_test_gettimeofday: Clean up includes
selftests: vDSO: vdso_test_gettimeofday: Make compatible with nolibc
selftests: vDSO: vdso_standalone_test_x86: Switch to nolibc

MAINTAINERS | 1 +
include/uapi/linux/elf.h | 38 ++
tools/include/uapi/linux/elf.h | 524 +++++++++++++++++++++
tools/testing/selftests/lib.mk | 5 +-
tools/testing/selftests/vDSO/Makefile | 11 +-
tools/testing/selftests/vDSO/parse_vdso.c | 21 +-
tools/testing/selftests/vDSO/parse_vdso.h | 1 -
.../selftests/vDSO/vdso_standalone_test_x86.c | 143 +-----
.../selftests/vDSO/vdso_test_gettimeofday.c | 4 +-
9 files changed, 584 insertions(+), 164 deletions(-)
---
base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
change-id: 20241017-parse_vdso-nolibc-e069baa7ff48

Best regards,

Next message: Christophe Leroy: "[PATCH] powerpc/code-patching: Disable KASAN report during patching via temporary mm"
Previous message: Haakon Bugge: "Re: [RFC PATCH] workqueue: introduce queue_delayed_work_on_offline_safe."
In reply to: Thomas Weißschuh: "[PATCH 16/16] selftests: vDSO: vdso_standalone_test_x86: Switch to nolibc"
Next in thread: Thomas Weißschuh: "Re: [PATCH 00/16] selftests: vDSO: parse_vdso: Make compatible with nolibc"
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