From: Paolo Bonzini Date: Tue, 21 Apr 2026 10:04:55 +0000 (+0100) Subject: tracing: Make undefsyms_base.c a first-class citizen X-Git-Tag: v7.1-rc1~47^2 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=5335e318ad3cf12d905de27e3be4e7fd7b1c6746;p=thirdparty%2Fkernel%2Flinux.git tracing: Make undefsyms_base.c a first-class citizen Linus points out that dumping undefsyms_base.c form the Makefile is rather ugly, and that a much better course of action would be to have this file as a first-class citizen in the git tree. This allows some extra cleanup in the Makefile, and the removal of the .gitignore file in kernel/trace. Cc: Marc Zyngier Cc: Arnd Bergmann Link: https://lore.kernel.org/r/CAHk-=wieqGd_XKpu8UxDoyADZx8TDe8CF3RmkUXt5N_9t5Pf_w@mail.gmail.com Link: https://lore.kernel.org/all/20260421095446.2951646-1-maz@kernel.org/ Link: https://patch.msgid.link/20260421100455.324333-1-pbonzini@redhat.com Reported-by: Linus Torvalds Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Paolo Bonzini Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/.gitignore b/kernel/trace/.gitignore deleted file mode 100644 index 6adbb09d6deb..000000000000 --- a/kernel/trace/.gitignore +++ /dev/null @@ -1 +0,0 @@ -/undefsyms_base.c diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 4d4229e5eec4..1decdce8cbef 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -133,41 +133,14 @@ obj-$(CONFIG_TRACE_REMOTE) += trace_remote.o obj-$(CONFIG_SIMPLE_RING_BUFFER) += simple_ring_buffer.o obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o -# # simple_ring_buffer is used by the pKVM hypervisor which does not have access # to all kernel symbols. Fail the build if forbidden symbols are found. -# -# undefsyms_base generates a set of compiler and tooling-generated symbols that can -# safely be ignored for simple_ring_buffer. -# -filechk_undefsyms_base = \ - echo '$(pound)include '; \ - echo '$(pound)include '; \ - echo '$(pound)include '; \ - echo 'static char page[PAGE_SIZE] __aligned(PAGE_SIZE);'; \ - echo 'void undefsyms_base(void *p, int n);'; \ - echo 'void undefsyms_base(void *p, int n) {'; \ - echo ' char buffer[256] = { 0 };'; \ - echo ' u32 u = 0;'; \ - echo ' memset((char * volatile)page, 8, PAGE_SIZE);'; \ - echo ' memset((char * volatile)buffer, 8, sizeof(buffer));'; \ - echo ' memcpy((void * volatile)p, buffer, sizeof(buffer));'; \ - echo ' cmpxchg((u32 * volatile)&u, 0, 8);'; \ - echo ' WARN_ON(n == 0xdeadbeef);'; \ - echo '}' - -$(obj)/undefsyms_base.c: FORCE - $(call filechk,undefsyms_base) - -clean-files += undefsyms_base.c - -$(obj)/undefsyms_base.o: $(obj)/undefsyms_base.c +# Basic compiler and tooling-generated symbols that can safely be left +# undefined. Ensure KASAN is enabled to avoid logic that may disable +# FORTIFY_SOURCE when KASAN is not enabled. undefsyms_base.o does not +# automatically get KASAN flags because it is not linked into vmlinux. targets += undefsyms_base.o - -# Ensure KASAN is enabled to avoid logic that may disable FORTIFY_SOURCE when -# KASAN is not enabled. undefsyms_base.o does not automatically get KASAN flags -# because it is not linked into vmlinux. KASAN_SANITIZE_undefsyms_base.o := y UNDEFINED_ALLOWLIST = __asan __gcov __kasan __kcsan __hwasan __sancov __sanitizer __tsan __ubsan __x86_indirect_thunk \ diff --git a/kernel/trace/undefsyms_base.c b/kernel/trace/undefsyms_base.c new file mode 100644 index 000000000000..e65baf58e6ff --- /dev/null +++ b/kernel/trace/undefsyms_base.c @@ -0,0 +1,28 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * simple_ring_buffer is used by the pKVM hypervisor which does not have access + * to all kernel symbols. Whatever is undefined when compiling this file is + * compiler and tooling-generated symbols that can safely be ignored for + * simple_ring_buffer. + */ + +#include +#include +#include + +void undefsyms_base(void *p, int n); + +static char page[PAGE_SIZE] __aligned(PAGE_SIZE); + +void undefsyms_base(void *p, int n) +{ + char buffer[256] = { 0 }; + + u32 u = 0; + memset((char * volatile)page, 8, PAGE_SIZE); + memset((char * volatile)buffer, 8, sizeof(buffer)); + memcpy((void * volatile)p, buffer, sizeof(buffer)); + cmpxchg((u32 * volatile)&u, 0, 8); + WARN_ON(n == 0xdeadbeef); +}