Commit 5335e318 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Steven Rostedt
Browse files

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 <maz@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: default avatarNathan Chancellor <nathan@kernel.org>
Tested-by: default avatarNathan Chancellor <nathan@kernel.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent b4e07588

kernel/trace/.gitignore

deleted100644 → 0
+0 −1
Original line number Diff line number Diff line 
/undefsyms_base.c

kernel/trace/Makefile

+4 −31
Original line number Diff line number Diff line
@@ -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 <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



# 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 \

kernel/trace/undefsyms_base.c

0 → 100644
+28 −0
Original line number Diff line number Diff line 
// 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 <linux/atomic.h>

#include <linux/string.h>

#include <asm/page.h>



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);

}