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tracing: Generate undef symbols allowlist for simple_ring_buffer 

Compiler and tooling-generated symbols are difficult to maintain
across all supported architectures. Make the allowlist more robust by
replacing the harcoded list with a mechanism that automatically detects
these symbols.

This mechanism generates a C function designed to trigger common
compiler-inserted symbols.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260316092845.3367411-1-vdonnefort@google.com
[maz: added __msan prefix to allowlist as pointed out by Arnd]
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Vincent Donnefort 2026-03-16 09:28:45 +00:00 committed by Marc Zyngier
parent 9e5dd49de5
commit 1211907ac0
1 changed files with 38 additions and 8 deletions
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46
kernel/trace/Makefile
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@ -136,17 +136,47 @@ 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.
#
UNDEFINED_ALLOWLIST := memset alt_cb_patch_nops __x86 __ubsan __asan __kasan __gcov __aeabi_unwind
UNDEFINED_ALLOWLIST += __stack_chk_fail stackleak_track_stack __ref_stack __sanitizer llvm_gcda llvm_gcov
UNDEFINED_ALLOWLIST += .TOC\. __clear_pages_unrolled __memmove copy_page warn_slowpath_fmt
UNDEFINED_ALLOWLIST += ftrace_likely_update __hwasan_load __hwasan_store __hwasan_tag_memory
UNDEFINED_ALLOWLIST += warn_bogus_irq_restore __stack_chk_guard
UNDEFINED_ALLOWLIST := $(addprefix -e , $(UNDEFINED_ALLOWLIST))
# undefsyms_base generates a set of compiler and tooling-generated symbols that can
# safely be ignored for simple_ring_buffer.
#
filechk_undefsyms_base = \
echo '$(pound)include <linux/atomic.h>'; \
echo '$(pound)include <linux/string.h>'; \
echo '$(pound)include <asm/page.h>'; \
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
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 \
__msan simple_ring_buffer \
$(shell $(NM) -u $(obj)/undefsyms_base.o 2>/dev/null | awk '{print $$2}')
quiet_cmd_check_undefined = NM $<
cmd_check_undefined = test -z "`$(NM) -u $< | grep -v $(UNDEFINED_ALLOWLIST)`"
cmd_check_undefined = test -z "`$(NM) -u $< | grep -v $(addprefix -e , $(UNDEFINED_ALLOWLIST))`"
$(obj)/%.o.checked: $(obj)/%.o FORCE
$(obj)/%.o.checked: $(obj)/%.o $(obj)/undefsyms_base.o FORCE
$(call if_changed,check_undefined)
always-$(CONFIG_SIMPLE_RING_BUFFER) += simple_ring_buffer.o.checked