[PATCH bpf-next 2/4] selftests/bpf: convenience macro for use with 'asm volatile' blocks

[Eduard Zingerman <eddyz87@gmail.com>]

A set of macros useful for writing naked BPF functions using inline
assembly. E.g. as follows:

struct map_struct {
	...
} map SEC(".maps");

SEC(...)
__naked int foo_test(void)
{
	asm volatile(
		"r0 = 0;"
		"*(u64*)(r10 - 8) = r0;"
		"r1 = %[map] ll;"
		"r2 = r10;"
		"r2 += -8;"
		"call %[bpf_map_lookup_elem];"
		"r0 = 0;"
		"exit;"
		:
		: __imm(bpf_map_lookup_elem),
		  __imm_addr(map)
		: __clobber_all);
}

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 tools/testing/selftests/bpf/progs/bpf_misc.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index a42363a3fef1..bbf56ad95636 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -8,6 +8,12 @@
 #define __log_level(lvl)	__attribute__((btf_decl_tag("comment:test_log_level="#lvl)))
 #define __test_state_freq	__attribute__((btf_decl_tag("comment:test_state_freq")))
 
+/* Convenience macro for use with 'asm volatile' blocks */
+#define __naked __attribute__((naked))
+#define __clobber_all "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "memory"
+#define __imm(name) [name]"i"(name)
+#define __imm_addr(name) [name]"i"(&name)
+
 #if defined(__TARGET_ARCH_x86)
 #define SYSCALL_WRAPPER 1
 #define SYS_PREFIX "__x64_"
-- 
2.38.2