selftests/bpf: Mark uprobe trigger functions with nocf_check attribute

olsajiri · anakryiko · commit af8d27bf15c8 · 2024-03-22T10:01:17.000-07:00
Some distros seem to enable the -fcf-protection=branch by default, which breaks our setup on first instruction of uprobe trigger functions and place there endbr64 instruction. Marking them with nocf_check attribute to skip that. Ignoring unknown attribute warning in gcc for bench objects, because nocf_check can be used only when -fcf-protection=branch is enabled, otherwise we get a warning and break compilation. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240322134936.1075395-1-jolsa@kernel.org
diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
@@ -58,6 +58,10 @@
 #define noinline
 #endif
 
+#ifndef __nocf_check
+#define __nocf_check __attribute__((nocf_check))
+#endif
+
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #ifndef __same_type
 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
diff --git a/tools/testing/selftests/bpf/benchs/bench_trigger.c b/tools/testing/selftests/bpf/benchs/bench_trigger.c
@@ -9,6 +9,8 @@
 /* adjust slot shift in inc_hits() if changing */
 #define MAX_BUCKETS 256
 
+#pragma GCC diagnostic ignored "-Wattributes"
+
 /* BPF triggering benchmarks */
 static struct trigger_ctx {
 	struct trigger_bench *skel;
@@ -167,7 +169,7 @@ static void trigger_fmodret_setup(void)
  * GCC doesn't generate stack setup preample for these functions due to them
  * having no input arguments and doing nothing in the body.
  */
-__weak void uprobe_target_nop(void)
+__nocf_check __weak void uprobe_target_nop(void)
 {
 	asm volatile ("nop");
 }
@@ -176,7 +178,7 @@ __weak void opaque_noop_func(void)
 {
 }
 
-__weak int uprobe_target_push(void)
+__nocf_check __weak int uprobe_target_push(void)
 {
 	/* overhead of function call is negligible compared to uprobe
 	 * triggering, so this shouldn't affect benchmark results much
@@ -185,7 +187,7 @@ __weak int uprobe_target_push(void)
 	return 1;
 }
 
-__weak void uprobe_target_ret(void)
+__nocf_check __weak void uprobe_target_ret(void)
 {
 	asm volatile ("");
 }

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,8 @@`
`9`	`9`	`/* adjust slot shift in inc_hits() if changing */`
`10`	`10`	`#define MAX_BUCKETS 256`
`11`	`11`
	`12`	`+#pragma GCC diagnostic ignored "-Wattributes"`
	`13`	`+`
`12`	`14`	`/* BPF triggering benchmarks */`
`13`	`15`	`static struct trigger_ctx {`
`14`	`16`	`struct trigger_bench *skel;`
`@@ -167,7 +169,7 @@ static void trigger_fmodret_setup(void)`
`167`	`169`	`* GCC doesn't generate stack setup preample for these functions due to them`
`168`	`170`	`* having no input arguments and doing nothing in the body.`
`169`	`171`	`*/`
`170`		`-__weak void uprobe_target_nop(void)`
	`172`	`+__nocf_check __weak void uprobe_target_nop(void)`
`171`	`173`	`{`
`172`	`174`	`asm volatile ("nop");`
`173`	`175`	`}`
`@@ -176,7 +178,7 @@ __weak void opaque_noop_func(void)`
`176`	`178`	`{`
`177`	`179`	`}`
`178`	`180`
`179`		`-__weak int uprobe_target_push(void)`
	`181`	`+__nocf_check __weak int uprobe_target_push(void)`
`180`	`182`	`{`
`181`	`183`	`/* overhead of function call is negligible compared to uprobe`
`182`	`184`	`* triggering, so this shouldn't affect benchmark results much`
`@@ -185,7 +187,7 @@ __weak int uprobe_target_push(void)`
`185`	`187`	`return 1;`
`186`	`188`	`}`
`187`	`189`
`188`		`-__weak void uprobe_target_ret(void)`
	`190`	`+__nocf_check __weak void uprobe_target_ret(void)`
`189`	`191`	`{`
`190`	`192`	`asm volatile ("");`
`191`	`193`	`}`