[PATCH bpf-next v1 1/7] selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX

[PATCH bpf-next v1 1/7] selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX

[Vineet Gupta]

Commit 7cd1f73b37ea ("selftests/bpf: Fix build of callx tests with GCC")
gated the callx progs on __clang__. GCC had indirect call support which was
recently refurbished along with a __BPF_FEATURE_CALLX macro [1], so gate
on that as well so once this GCC is released, the tests start passing.

Put the arch and compiler conditions in a CAN_USE_CALLX macro in
bpf_misc.h, and use it all the test programs.

While at it, mark the placeholder programs left for unsupported
toolchains and arches with __skip(), so they report SKIP rather than OK.

[1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=ffe3ead4a8ad704b557b0cfa4f823df647c65a0d

Measured on bpf-next with a stock bpf-gcc that defines
__BPF_FEATURE_CALLX, test_progs before and after: 76 subtests run that
previously did not exist in the report, 75 OK and one @unpriv SKIP,
with no failures.  The two dummy placeholders retire and
callx_rodata_lskel goes SKIP -> OK.

Signed-off-by: Vineet Gupta <vineet.gupta@linux.dev>
---
 .../testing/selftests/bpf/prog_tests/callx_rodata_lskel.c  | 2 +-
 tools/testing/selftests/bpf/progs/bpf_misc.h               | 7 +++++++
 tools/testing/selftests/bpf/progs/callx_rodata.c           | 4 ++--
 tools/testing/selftests/bpf/progs/verifier_callx.c         | 5 ++---
 tools/testing/selftests/bpf/progs/verifier_callx_rodata.c  | 5 ++---
 5 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/callx_rodata_lskel.c b/tools/testing/selftests/bpf/prog_tests/callx_rodata_lskel.c
index f6ef67c3141e..acd821fb568f 100644
--- a/tools/testing/selftests/bpf/prog_tests/callx_rodata_lskel.c
+++ b/tools/testing/selftests/bpf/prog_tests/callx_rodata_lskel.c
@@ -36,7 +36,7 @@ static void __test_callx_rodata_lskel(void)
 	if (!ASSERT_OK_PTR(skel, "open"))
 		return;
 
-	/* gcc doesn't support indirect calls */
+	/* toolchain or JIT can't do callx */
 	if (skel->rodata->skip) {
 		test__skip();
 		goto out;
diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index d7f706c3bc4a..1b264480e128 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -295,6 +295,13 @@
 #define CAN_USE_LOAD_ACQ_STORE_REL
 #endif
 
+/* clang always emits callx, gcc only when it defines __BPF_FEATURE_CALLX */
+#if (defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86) ||	\
+     (defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) &&		\
+	(defined(__clang__) || defined(__BPF_FEATURE_CALLX))
+#define CAN_USE_CALLX
+#endif
+
 #if defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86)
 #define SPEC_V1
 #endif
diff --git a/tools/testing/selftests/bpf/progs/callx_rodata.c b/tools/testing/selftests/bpf/progs/callx_rodata.c
index e3f8335f80f8..8c28f01b7113 100644
--- a/tools/testing/selftests/bpf/progs/callx_rodata.c
+++ b/tools/testing/selftests/bpf/progs/callx_rodata.c
@@ -4,13 +4,14 @@
 #include <stdbool.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
 
 /* set by user space before the programs are loaded, it's in .rodata too */
 const volatile int bias = 1;
 
 int op_idx;
 
-#ifdef __clang__
+#ifdef CAN_USE_CALLX
 
 const volatile bool skip = false;
 
@@ -48,7 +49,6 @@ int both_ops(void *ctx)
 
 #else
 
-/* gcc doesn't support indirect calls */
 const volatile bool skip = true;
 
 SEC("socket")
diff --git a/tools/testing/selftests/bpf/progs/verifier_callx.c b/tools/testing/selftests/bpf/progs/verifier_callx.c
index 7e59188d9fca..a87e2a85f43d 100644
--- a/tools/testing/selftests/bpf/progs/verifier_callx.c
+++ b/tools/testing/selftests/bpf/progs/verifier_callx.c
@@ -6,9 +6,7 @@
 #include "bpf_misc.h"
 #include "../../../include/linux/filter.h"
 
-/* gcc doesn't support indirect calls */
-#if defined(__clang__) && (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
-    (defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64))
+#ifdef CAN_USE_CALLX
 
 #define CALLX_INSN(DST, SRC, OFF, IMM) \
 	BPF_RAW_INSN(BPF_JMP | BPF_CALL | BPF_X, DST, SRC, OFF, IMM)
@@ -1075,6 +1073,7 @@ int callx_c_ops_on_stack(void *ctx)
 #else
 
 SEC("socket")
+__skip("callx needs x86/arm64 JIT and compiler support")
 __success
 int dummy(void *ctx)
 {
diff --git a/tools/testing/selftests/bpf/progs/verifier_callx_rodata.c b/tools/testing/selftests/bpf/progs/verifier_callx_rodata.c
index 6cf58ca9ac5b..29bc2f78315d 100644
--- a/tools/testing/selftests/bpf/progs/verifier_callx_rodata.c
+++ b/tools/testing/selftests/bpf/progs/verifier_callx_rodata.c
@@ -6,9 +6,7 @@
 #include "bpf_misc.h"
 #include "../../../include/linux/filter.h"
 
-/* gcc doesn't support indirect calls */
-#if defined(__clang__) && (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
-    (defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64))
+#ifdef CAN_USE_CALLX
 
 /*
  * Read-only data with pointers to functions, where the compiler puts tables
@@ -892,6 +890,7 @@ int callx_c_packed_struct(void *ctx)
 #else
 
 SEC("socket")
+__skip("callx needs x86/arm64 JIT and compiler support")
 __success
 int dummy(void *ctx)
 {
-- 
2.53.0-Meta

Re: [PATCH bpf-next v1 1/7] selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 2372 bytes --]

> selftests/bpf: Build callx tests with GCC that defines __BPF_FEATURE_CALLX

TL;DR: Nit only: the new __skip() reason in the callx selftests omits riscv64,
though riscv64 is supported, so a riscv64 build with a GCC lacking callx
prints a misleading skip message.

> diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
> --- a/tools/testing/selftests/bpf/progs/bpf_misc.h
> +++ b/tools/testing/selftests/bpf/progs/bpf_misc.h

[ ... ]

> @@ -295,6 +295,13 @@
>  #define CAN_USE_LOAD_ACQ_STORE_REL
>  #endif
>
> +/* clang always emits callx, gcc only when it defines __BPF_FEATURE_CALLX */
> +#if (defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86) ||	\
> +     (defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) &&		\
> +	(defined(__clang__) || defined(__BPF_FEATURE_CALLX))
> +#define CAN_USE_CALLX
> +#endif
> +

[ ... ]

> diff --git a/tools/testing/selftests/bpf/progs/verifier_callx.c b/tools/testing/selftests/bpf/progs/verifier_callx.c
> --- a/tools/testing/selftests/bpf/progs/verifier_callx.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_callx.c

[ ... ]

> @@ -1075,6 +1073,7 @@ int callx_c_ops_on_stack(void *ctx)
>  #else
>
>  SEC("socket")
> +__skip("callx needs x86/arm64 JIT and compiler support")
>  __success
>  int dummy(void *ctx)
>  {

this isn't a bug, but the skip reason leaves out riscv64, even though the
CAN_USE_CALLX macro above accepts it.

The same string is added to the dummy() program in
verifier_callx_rodata.c.  The riscv64 JIT implements bpf_jit_supports_callx(),
and commit 530dfafc6107 ("selftests/bpf: Enable callx related testcases for
RV64") turned these tests on for RV64.

On a riscv64 build with a bpf-gcc that does not define __BPF_FEATURE_CALLX,
the arch supports callx and only the compiler lacks it, yet run_subtest()
prints:

  run_subtest:SKIP: callx needs x86/arm64 JIT and compiler support

That reads as though riscv64 itself were unsupported.

Could the reason say x86/arm64/riscv64, or leave the arch list out (for
example "toolchain or JIT can't do callx", as the new comment in
callx_rodata_lskel.c does)?


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/40608355234