linux-kernel - [PATCH 2/3] [v2] kmsan: disable ftrace in kmsan core code

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Date:   Wed, 15 Feb 2023 14:00:57 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>,
        Marco Elver <elver@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] [v2] kmsan: disable ftrace in kmsan core code

From: Arnd Bergmann <arnd@...db.de>

objtool warns about some suspicous code inside of kmsan:

vmlinux.o: warning: objtool: __msan_metadata_ptr_for_load_n+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_store_n+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_load_1+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_store_1+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_load_2+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_store_2+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_load_4+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_store_4+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_load_8+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_metadata_ptr_for_store_8+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_instrument_asm_store+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_chain_origin+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_poison_alloca+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_warning+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: __msan_get_context_state+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: kmsan_copy_to_user+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: kmsan_unpoison_memory+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: kmsan_unpoison_entry_regs+0x4: call to __fentry__() with UACCESS enabled
vmlinux.o: warning: objtool: kmsan_report+0x4: call to __fentry__() with UACCESS enabled

The Makefile contained a line to turn off ftrace for the entire directory,
but this does not work. Replace it with individual lines, matching the
approach in kasan.

Fixes: f80be4571b19 ("kmsan: add KMSAN runtime core")
Acked-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: remove the old "CFLAGS_REMOVE.o = $(CC_FLAGS_FTRACE)" line
---
 mm/kmsan/Makefile | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/kmsan/Makefile b/mm/kmsan/Makefile
index 98eab2856626..91cfdde642d1 100644
--- a/mm/kmsan/Makefile
+++ b/mm/kmsan/Makefile
@@ -14,7 +14,13 @@ CC_FLAGS_KMSAN_RUNTIME := -fno-stack-protector
 CC_FLAGS_KMSAN_RUNTIME += $(call cc-option,-fno-conserve-stack)
 CC_FLAGS_KMSAN_RUNTIME += -DDISABLE_BRANCH_PROFILING
 
-CFLAGS_REMOVE.o = $(CC_FLAGS_FTRACE)
+# Disable ftrace to avoid recursion.
+CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_hooks.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_init.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_instrumentation.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_shadow.o = $(CC_FLAGS_FTRACE)
 
 CFLAGS_core.o := $(CC_FLAGS_KMSAN_RUNTIME)
 CFLAGS_hooks.o := $(CC_FLAGS_KMSAN_RUNTIME)
-- 
2.39.1