[PATCH v2 bpf-next] selftests/bpf: Fix the invalid operand for instruction issue

[PATCH v2 bpf-next] selftests/bpf: Fix the invalid operand for instruction issue

[Feng Yang]

From: Feng Yang <yangfeng@kylinos.cn>

The following issue occurs when compiling with clang version 17.0.6:
progs/compute_live_registers.c:251:3: error: invalid operand for instruction
  251 |                 "r0 = 1;"
      |                 ^
<inline asm>:1:22: note: instantiated into assembly here
    1 |         r0 = 1;r2 = 2;if r1 & 0x7 goto +1;exit;r0 = r2;exit;
      |                             ^
1 error generated.

Use __imm_insn to fix this issue.

Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation")
Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
Changes in v2:
- Use __imm_insn, thanks: Eduard Zingerman.
- Link to v1: https://lore.kernel.org/all/20250827031540.461017-1-yangfeng59949@163.com/
---
 tools/testing/selftests/bpf/progs/compute_live_registers.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/compute_live_registers.c b/tools/testing/selftests/bpf/progs/compute_live_registers.c
index 6884ab99a421..01d73ad76faf 100644
--- a/tools/testing/selftests/bpf/progs/compute_live_registers.c
+++ b/tools/testing/selftests/bpf/progs/compute_live_registers.c
@@ -249,11 +249,13 @@ __naked void if3_jset_bug(void)
 	asm volatile (
 		"r0 = 1;"
 		"r2 = 2;"
-		"if r1 & 0x7 goto +1;"
+		".8byte %[jset];" /* same as 'if r1 & 0x7 goto +1;' */
 		"exit;"
 		"r0 = r2;"
 		"exit;"
-		::: __clobber_all);
+		:
+		: __imm_insn(jset, BPF_JMP_IMM(BPF_JSET, BPF_REG_1, 0x7, 1))
+		: __clobber_all);
 }
 
 SEC("socket")
-- 
2.43.0

Re: [PATCH v2 bpf-next] selftests/bpf: Fix the invalid operand for instruction issue

[Eduard Zingerman]

On Thu, 2025-08-28 at 10:01 +0800, Feng Yang wrote:
> From: Feng Yang <yangfeng@kylinos.cn>
> 
> The following issue occurs when compiling with clang version 17.0.6:
> progs/compute_live_registers.c:251:3: error: invalid operand for instruction
>   251 |                 "r0 = 1;"
>       |                 ^
> <inline asm>:1:22: note: instantiated into assembly here
>     1 |         r0 = 1;r2 = 2;if r1 & 0x7 goto +1;exit;r0 = r2;exit;
>       |                             ^
> 1 error generated.
> 
> Use __imm_insn to fix this issue.
> 
> Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation")
> Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> ---

Hi Feng,

This message felt through cracks a bit.  It's a minor thing, of
course, but there is a legit question of how much backward we'd like
to support clang versions for the test suite.

Could you please provide some detail on your build environment,
why do you want to run the tests with older clang?

[...]

Re: [PATCH v2 bpf-next] selftests/bpf: Fix the invalid operand for instruction issue

[Feng Yang]

On Thu, 04 Sep 2025 08:48:45 -0700 Eduard Zingerman wrote:

> On Thu, 2025-08-28 at 10:01 +0800, Feng Yang wrote:
> > From: Feng Yang <yangfeng@kylinos.cn>
> > 
> > The following issue occurs when compiling with clang version 17.0.6:
> > progs/compute_live_registers.c:251:3: error: invalid operand for instruction
> >   251 |                 "r0 = 1;"
> >       |                 ^
> > <inline asm>:1:22: note: instantiated into assembly here
> >     1 |         r0 = 1;r2 = 2;if r1 & 0x7 goto +1;exit;r0 = r2;exit;
> >       |                             ^
> > 1 error generated.
> > 
> > Use __imm_insn to fix this issue.
> > 
> > Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation")
> > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > ---
> 
> Hi Feng,
> 
> This message felt through cracks a bit.  It's a minor thing, of
> course, but there is a legit question of how much backward we'd like
> to support clang versions for the test suite.
> 
> Could you please provide some detail on your build environment,
> why do you want to run the tests with older clang?

Hi Eduard,

Actually, there is no specific reason to test with an older version of Clang.
It's just that the Clang downloaded from the source is this version,
and installing a newer version by myself would be rather troublesome.

clang version 17.0.6
GNU Make 4.4.1
gcc (GCC) 12.3.1
linux version: 6.6
arch: x86-64