compiler.h: Fix annotation macro misplacement with Clang
authorJosh Poimboeuf <jpoimboe@redhat.com>
Mon, 8 Nov 2021 22:35:59 +0000 (14:35 -0800)
committerJosh Poimboeuf <jpoimboe@redhat.com>
Tue, 21 Dec 2021 23:09:46 +0000 (15:09 -0800)
When building with Clang and CONFIG_TRACE_BRANCH_PROFILING, there are a
lot of unreachable warnings, like:

  arch/x86/kernel/traps.o: warning: objtool: handle_xfd_event()+0x134: unreachable instruction

Without an input to the inline asm, 'volatile' is ignored for some
reason and Clang feels free to move the reachable() annotation away from
its intended location.

Fix that by re-adding the counter value to the inputs.

Fixes: f1069a8756b9 ("compiler.h: Avoid using inline asm operand modifiers")
Fixes: c199f64ff93c ("instrumentation.h: Avoid using inline asm operand modifiers")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/0417e96909b97a406323409210de7bf13df0b170.1636410380.git.jpoimboe@redhat.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Miroslav Benes <mbenes@suse.cz>
include/linux/compiler.h
include/linux/instrumentation.h

index 3d5af56..429dceb 100644 (file)
@@ -121,7 +121,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
        asm volatile(__stringify_label(c) ":\n\t"                       \
                     ".pushsection .discard.reachable\n\t"              \
                     ".long " __stringify_label(c) "b - .\n\t"          \
-                    ".popsection\n\t");                                \
+                    ".popsection\n\t" : : "i" (c));                    \
 })
 #define annotate_reachable() __annotate_reachable(__COUNTER__)
 
@@ -129,7 +129,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
        asm volatile(__stringify_label(c) ":\n\t"                       \
                     ".pushsection .discard.unreachable\n\t"            \
                     ".long " __stringify_label(c) "b - .\n\t"          \
-                    ".popsection\n\t");                                \
+                    ".popsection\n\t" : : "i" (c));                    \
 })
 #define annotate_unreachable() __annotate_unreachable(__COUNTER__)
 
index fa2cd8c..24359b4 100644 (file)
@@ -11,7 +11,7 @@
        asm volatile(__stringify(c) ": nop\n\t"                         \
                     ".pushsection .discard.instr_begin\n\t"            \
                     ".long " __stringify(c) "b - .\n\t"                \
-                    ".popsection\n\t");                                \
+                    ".popsection\n\t" : : "i" (c));                    \
 })
 #define instrumentation_begin() __instrumentation_begin(__COUNTER__)
 
@@ -50,7 +50,7 @@
        asm volatile(__stringify(c) ": nop\n\t"                         \
                     ".pushsection .discard.instr_end\n\t"              \
                     ".long " __stringify(c) "b - .\n\t"                \
-                    ".popsection\n\t");                                \
+                    ".popsection\n\t" : : "i" (c));                    \
 })
 #define instrumentation_end() __instrumentation_end(__COUNTER__)
 #else