kernel/linux.git/tools/testing/selftests/rseq/rseq.c, branch v6.18.21

rseq/selftests: Use weak symbol reference, not definition, to link with glibc

2025-09-13T17:51:59+00:00

Add "extern" to the glibc-defined weak rseq symbols to convert the rseq selftest's usage from weak symbol definitions to weak symbol _references_. Effectively re-defining the glibc symbols wreaks havoc when building with -fno-common, e.g. generates segfaults when running multi-threaded programs, as dynamically linked applications end up with multiple versions of the symbols. Building with -fcommon, which until recently has the been the default for GCC and clang, papers over the bug by allowing the linker to resolve the weak/tentative definition to glibc's "real" definition. Note, the symbol itself (or rather its address), not the value of the symbol, is set to 0/NULL for unresolved weak symbol references, as the symbol doesn't exist and thus can't have a value. Check for a NULL rseq size pointer to handle the scenario where the test is statically linked against a libc that doesn't support rseq in any capacity. Fixes: 3bcbc20942db ("selftests/rseq: Play nice with binaries statically linked against glibc 2.35+") Reported-by: Thomas Gleixner Suggested-by: Florian Weimer Signed-off-by: Sean Christopherson Signed-off-by: Thomas Gleixner Reviewed-by: Mathieu Desnoyers Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/all/87frdoybk4.ffs@tglx

rseq/selftests: Fix namespace collision with rseq UAPI header

2025-03-19T20:26:24+00:00

When the rseq UAPI header is included, 'union rseq' clashes with 'struct rseq'. It's not the case in the rseq selftests but it does break the KVM selftests that also include this file. Rename 'union rseq' to 'union rseq_tls' to fix this. Fixes: e6644c967d3c ("rseq/selftests: Ensure the rseq ABI TLS is actually 1024 bytes") Reported-by: Mark Brown Signed-off-by: Michael Jeanson Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Link: https://lore.kernel.org/r/20250319202144.1141542-1-mjeanson@efficios.com

rseq/selftests: Ensure the rseq ABI TLS is actually 1024 bytes

2025-03-12T12:19:47+00:00

Adding the aligned(1024) attribute to the definition of __rseq_abi did not increase its size to 1024, for this attribute to impact the size of __rseq_abi it would need to be added to the declaration of 'struct rseq_abi'. We only want to increase the size of the TLS allocation to ensure registration will succeed with future extended ABI. Use a union with a dummy member to ensure we allocate 1024 bytes. Signed-off-by: Michael Jeanson Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Link: https://lore.kernel.org/r/20250311192222.323453-1-mjeanson@efficios.com

selftests/rseq: Add rseq syscall errors test

2025-02-22T13:13:45+00:00

This test adds coverage of expected errors during rseq registration and unregistration, it disables glibc integration and will thus always exercise the rseq syscall explictly. Signed-off-by: Michael Jeanson Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Cc: Shuah Khan Link: https://lore.kernel.org/r/20250121213402.1754762-1-mjeanson@efficios.com

selftests/rseq: Fix handling of glibc without rseq support

2025-01-15T17:54:48+00:00

When porting librseq commit: commit c7b45750fa85 ("Adapt to glibc __rseq_size feature detection") from librseq to the kernel selftests, the following line was missed at the end of rseq_init(): rseq_size = get_rseq_kernel_feature_size(); which effectively leaves rseq_size initialized to -1U when glibc does not have rseq support. glibc supports rseq from version 2.35 onwards. In a following librseq commit commit c67d198627c2 ("Only set 'rseq_size' on first thread registration") to mimic the libc behavior, a new approach is taken: don't set the feature size in 'rseq_size' until at least one thread has successfully registered. This allows using 'rseq_size' in fast-paths to test for both registration status and available features. The caveat is that on libc either all threads are registered or none are, while with bare librseq it is the responsability of the user to register all threads using rseq. This combines the changes from the following librseq git commits: commit c7b45750fa85 ("Adapt to glibc __rseq_size feature detection") commit c67d198627c2 ("Only set 'rseq_size' on first thread registration") Fixes: a0cc649353bb ("selftests/rseq: Fix mm_cid test failure") Reported-by: Raghavendra Rao Ananta Signed-off-by: Mathieu Desnoyers Cc: Raghavendra Rao Ananta Cc: Shuah Khan Cc: Peter Zijlstra Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Carlos O'Donell Cc: Florian Weimer Cc: Michael Jeanson Cc: linux-kselftest@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Shuah Khan

selftests/rseq: Fix mm_cid test failure

2024-10-11T21:05:05+00:00

Adapt the rseq.c/rseq.h code to follow GNU C library changes introduced by: glibc commit 2e456ccf0c34 ("Linux: Make __rseq_size useful for feature detection (bug 31965)") Without this fix, rseq selftests for mm_cid fail: ./run_param_test.sh Default parameters Running test spinlock Running compare-twice test spinlock Running mm_cid test spinlock Error: cpu id getter unavailable Fixes: 18c2355838e7 ("selftests/rseq: Implement rseq mm_cid field support") Signed-off-by: Mathieu Desnoyers Cc: Peter Zijlstra CC: Boqun Feng CC: "Paul E. McKenney" Cc: Shuah Khan CC: Carlos O'Donell CC: Florian Weimer CC: linux-kselftest@vger.kernel.org CC: stable@vger.kernel.org Signed-off-by: Shuah Khan

selftests/rseq: Fix build with undefined __weak

2023-08-04T22:10:29+00:00

Commit 3bcbc20942db ("selftests/rseq: Play nice with binaries statically linked against glibc 2.35+") which is now in Linus' tree introduced uses of __weak but did nothing to ensure that a definition is provided for it resulting in build failures for the rseq tests: rseq.c:41:1: error: unknown type name '__weak' __weak ptrdiff_t __rseq_offset; ^ rseq.c:41:17: error: expected ';' after top level declarator __weak ptrdiff_t __rseq_offset; ^ ; rseq.c:42:1: error: unknown type name '__weak' __weak unsigned int __rseq_size; ^ rseq.c:43:1: error: unknown type name '__weak' __weak unsigned int __rseq_flags; Fix this by using the definition from tools/include compiler.h. Fixes: 3bcbc20942db ("selftests/rseq: Play nice with binaries statically linked against glibc 2.35+") Signed-off-by: Mark Brown Message-Id: <20230804-kselftest-rseq-build-v1-1-015830b66aa9@kernel.org> Signed-off-by: Paolo Bonzini

selftests/rseq: Play nice with binaries statically linked against glibc 2.35+

2023-07-29T15:05:28+00:00

To allow running rseq and KVM's rseq selftests as statically linked binaries, initialize the various "trampoline" pointers to point directly at the expect glibc symbols, and skip the dlysm() lookups if the rseq size is non-zero, i.e. the binary is statically linked *and* the libc registered its own rseq. Define weak versions of the symbols so as not to break linking against libc versions that don't support rseq in any capacity. The KVM selftests in particular are often statically linked so that they can be run on targets with very limited runtime environments, i.e. test machines. Fixes: 233e667e1ae3 ("selftests/rseq: Uplift rseq selftests for compatibility with glibc-2.35") Cc: Aaron Lewis Cc: kvm@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20230721223352.2333911-1-seanjc@google.com> Signed-off-by: Paolo Bonzini

selftests/rseq: Implement rseq numa node id field selftest

2022-12-27T11:52:11+00:00

Test the NUMA node id extension rseq field. Compare it against the value returned by the getcpu(2) system call while pinned on a specific core. Signed-off-by: Mathieu Desnoyers Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20221122203932.231377-7-mathieu.desnoyers@efficios.com

selftests/rseq: Use ELF auxiliary vector for extensible rseq

2022-12-27T11:52:11+00:00

Use the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE to detect the RSEQ features supported by the kernel. Signed-off-by: Mathieu Desnoyers Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20221122203932.231377-6-mathieu.desnoyers@efficios.com