From 5f2f83047126f1cb2986d142d2e76e1fa3cef3f0 Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Thu, 12 Mar 2026 11:35:35 +0000 Subject: tracing: Update undefined symbols allow list for simple_ring_buffer Undefined symbols are not allowed for simple_ring_buffer.c. But some compiler emitted symbols are missing in the allowlist. Update it. Reported-by: Nathan Chancellor Signed-off-by: Vincent Donnefort Fixes: a717943d8ecc ("tracing: Check for undefined symbols in simple_ring_buffer") Closes: https://lore.kernel.org/all/20260311221816.GA316631@ax162/ Acked-by: Steven Rostedt (Google) Link: https://patch.msgid.link/20260312113535.2213350-1-vdonnefort@google.com Signed-off-by: Marc Zyngier --- kernel/trace/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/trace/Makefile') diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 3182e1bc1cf7..3cc490aadc99 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -137,7 +137,8 @@ obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o # 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 +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 := $(addprefix -e , $(UNDEFINED_ALLOWLIST)) quiet_cmd_check_undefined = NM $< -- cgit v1.2.3 From 7e4b6c94300e355a72670c5b896ccc26ac312c63 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 12 Mar 2026 13:35:43 +0100 Subject: tracing: add more symbols to whitelist Randconfig builds show a number of cryptic build errors from hitting undefined symbols in simple_ring_buffer.o: make[7]: *** [/home/arnd/arm-soc/kernel/trace/Makefile:147: kernel/trace/simple_ring_buffer.o.checked] Error 1 These happen with CONFIG_TRACE_BRANCH_PROFILING, CONFIG_KASAN_HW_TAGS, CONFIG_STACKPROTECTOR, CONFIG_DEBUG_IRQFLAGS and indirectly from WARN_ON(). Add exceptions for each one that I have hit so far on arm64, x86_64 and arm randconfig builds. Other architectures likely hit additional ones, so it would be nice to produce a little more verbose output that include the name of the missing symbols directly. Fixes: a717943d8ecc ("tracing: Check for undefined symbols in simple_ring_buffer") Signed-off-by: Arnd Bergmann Link: https://patch.msgid.link/20260312123601.625063-2-arnd@kernel.org Signed-off-by: Marc Zyngier --- kernel/trace/Makefile | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/trace/Makefile') diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 3cc490aadc99..beb15936829d 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -1,4 +1,4 @@ -# SPDX-License-Identifier: GPL-2.0 + # Do not instrument the tracer itself: @@ -139,6 +139,8 @@ obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o 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)) quiet_cmd_check_undefined = NM $< -- cgit v1.2.3 From 1211907ac0b5f35e5720620c50b7ca3c72d81f7e Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Mon, 16 Mar 2026 09:28:45 +0000 Subject: tracing: Generate undef symbols allowlist for simple_ring_buffer Compiler and tooling-generated symbols are difficult to maintain across all supported architectures. Make the allowlist more robust by replacing the harcoded list with a mechanism that automatically detects these symbols. This mechanism generates a C function designed to trigger common compiler-inserted symbols. Signed-off-by: Vincent Donnefort Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Acked-by: Steven Rostedt (Google) Tested-by: Arnd Bergmann Link: https://patch.msgid.link/20260316092845.3367411-1-vdonnefort@google.com [maz: added __msan prefix to allowlist as pointed out by Arnd] Signed-off-by: Marc Zyngier --- kernel/trace/Makefile | 46 ++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 38 insertions(+), 8 deletions(-) (limited to 'kernel/trace/Makefile') diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index beb15936829d..26f3d61e900d 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -136,17 +136,47 @@ obj-$(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 '; \ + 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 + +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 -- cgit v1.2.3 From d7729643942325933508274f0392b749ca74f7cc Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 17 Mar 2026 19:42:52 +0000 Subject: tracing: Restore accidentally removed SPDX tag Restore the SPDX tag that was accidentally dropped. Fixes: 7e4b6c94300e3 ("tracing: add more symbols to whitelist") Reported-by: Nathan Chancellor Cc: Arnd Bergmann Cc: Vincent Donnefort Cc: Steven Rostedt Reviewed-by: Steven Rostedt (Google) Link: https://patch.msgid.link/20260317194252.1890568-1-maz@kernel.org Signed-off-by: Marc Zyngier --- kernel/trace/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/trace/Makefile') diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 26f3d61e900d..c5e14ffd36ee 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -1,4 +1,4 @@ - +# SPDX-License-Identifier: GPL-2.0 # Do not instrument the tracer itself: -- cgit v1.2.3 From 58b4bd18390ec3118d8577e19bdee0d01d40c31e Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Fri, 20 Mar 2026 14:29:33 -0700 Subject: tracing: Adjust cmd_check_undefined to show unexpected undefined symbols When the check_undefined command in kernel/trace/Makefile fails, there is no output, making it hard to understand why the build failed. Capture the output of the $(NM) + grep command and print it when failing to make it clearer what the problem is. Fixes: a717943d8ecc ("tracing: Check for undefined symbols in simple_ring_buffer") Signed-off-by: Nathan Chancellor Reviewed-by: Vincent Donnefort Acked-by: Arnd Bergmann Link: https://patch.msgid.link/20260320-cmd_check_undefined-verbose-v1-1-54fc5b061f94@kernel.org Signed-off-by: Marc Zyngier --- kernel/trace/Makefile | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'kernel/trace/Makefile') diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index c5e14ffd36ee..d662c1a64cd5 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -174,7 +174,13 @@ UNDEFINED_ALLOWLIST = __asan __gcov __kasan __kcsan __hwasan __sancov __sanitize $(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 $(addprefix -e , $(UNDEFINED_ALLOWLIST))`" + cmd_check_undefined = \ + undefsyms=$$($(NM) -u $< | grep -v $(addprefix -e , $(UNDEFINED_ALLOWLIST)) || true); \ + if [ -n "$$undefsyms" ]; then \ + echo "Unexpected symbols in $<:" >&2; \ + echo "$$undefsyms" >&2; \ + false; \ + fi $(obj)/%.o.checked: $(obj)/%.o $(obj)/undefsyms_base.o FORCE $(call if_changed,check_undefined) -- cgit v1.2.3