[RFC,bpf-next,02/11] selftests/bpf: tests for opt_hard_wire_dead_code_branches()

Commit Message

Eduard Zingerman Nov. 7, 2024, 5:50 p.m. UTC

As opt_hard_wire_dead_code_branches() was changed to react to
accumulated branch prediction flags for conditional jumps,
add tests for various possible predictions.

Signed-off-by: Eduard Zingerman <[e-mail]>
---
 .../selftests/bpf/prog_tests/verifier.c       |  2 +
 .../selftests/bpf/progs/verifier_dead_code.c  | 63 +++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_dead_code.c

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 75f7a2ce334b..efd42c07f58a 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -26,6 +26,7 @@ 
 #include "verifier_ctx.skel.h"
 #include "verifier_ctx_sk_msg.skel.h"
 #include "verifier_d_path.skel.h"
+#include "verifier_dead_code.skel.h"
 #include "verifier_direct_packet_access.skel.h"
 #include "verifier_direct_stack_access_wraparound.skel.h"
 #include "verifier_div0.skel.h"
@@ -154,6 +155,7 @@  void test_verifier_const_or(void)             { RUN(verifier_const_or); }
 void test_verifier_ctx(void)                  { RUN(verifier_ctx); }
 void test_verifier_ctx_sk_msg(void)           { RUN(verifier_ctx_sk_msg); }
 void test_verifier_d_path(void)               { RUN(verifier_d_path); }
+void test_verifier_dead_code(void)            { RUN(verifier_dead_code); }
 void test_verifier_direct_packet_access(void) { RUN(verifier_direct_packet_access); }
 void test_verifier_direct_stack_access_wraparound(void) { RUN(verifier_direct_stack_access_wraparound); }
 void test_verifier_div0(void)                 { RUN(verifier_div0); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_dead_code.c b/tools/testing/selftests/bpf/progs/verifier_dead_code.c
new file mode 100644
index 000000000000..b2eed6be0d42
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_dead_code.c
@@ -0,0 +1,63 @@ 
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+SEC("socket")
+__xlated("0: r1 = 1")
+__xlated("1: r0 = 42")
+__xlated("2: r0 = 24")
+__xlated("3: exit")
+__success
+__retval(24)
+__naked void cond_always_false(void)
+{
+	asm volatile (
+		"r1 = 1;"
+		"r0 = 42;"
+		"if r1 != 1 goto +1;"
+		"r0 = 24;"
+		"exit;"
+		::: __clobber_all
+	);
+}
+
+SEC("socket")
+__xlated("0: r1 = 2")
+__xlated("1: r0 = 42")
+__xlated("2: exit")
+__success
+__retval(42)
+__naked void cond_always_true(void)
+{
+	asm volatile (
+		"r1 = 2;"
+		"r0 = 42;"
+		"if r1 != 1 goto +1;"
+		"r0 = 24;"
+		"exit;"
+		::: __clobber_all
+	);
+}
+
+SEC("socket")
+__xlated("0: call")
+__xlated("1: r1 = r0")
+__xlated("2: r0 = 42")
+__xlated("3: if r1 != 0x1 goto pc+1")
+__xlated("4: r0 = 24")
+__xlated("5: exit")
+__success
+__naked void cond_unknown(void)
+{
+	asm volatile (
+		"call %[bpf_get_prandom_u32];"
+		"r1 = r0;"
+		"r0 = 42;"
+		"if r1 != 1 goto +1;"
+		"r0 = 24;"
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32)
+		: __clobber_all
+	);
+}