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. Also drop the dependency of parse_vdso.c on the elf.h header from libc and only use the one from the kernel's UAPI. While this series is useful on its own now, it will also integrate with the kunit UAPI framework currently under development: https://lore.kernel.org/lkml/20250217-kunit-kselftests-v1-0-42b4524c3b0a@xxxxxxxxxxxxx/ Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx> --- Changes in v2: - Provide a limits.h header in nolibc - Pick up Reviewed-by tags from Kees - Link to v1: https://lore.kernel.org/r/20250203-parse_vdso-nolibc-v1-0-9cb6268d77be@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 tools/nolibc: add limits.h shim header 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: 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/nolibc/Makefile | 1 + tools/include/nolibc/limits.h | 7 + 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 | 19 +- tools/testing/selftests/vDSO/parse_vdso.h | 1 - .../selftests/vDSO/vdso_standalone_test_x86.c | 143 +----- .../selftests/vDSO/vdso_test_gettimeofday.c | 4 +- 11 files changed, 590 insertions(+), 164 deletions(-) --- base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b change-id: 20241017-parse_vdso-nolibc-e069baa7ff48 Best regards, -- Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
