From: Feng Yang yangfeng@kylinos.cn
The following issue occurs when compiling with clang version 17.0.6, but not with version 18.1.8. Add a version restriction to fix this problem.
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.
Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation") Signed-off-by: Feng Yang yangfeng@kylinos.cn --- tools/testing/selftests/bpf/progs/compute_live_registers.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/compute_live_registers.c b/tools/testing/selftests/bpf/progs/compute_live_registers.c index 6884ab99a421..56aec43f206f 100644 --- a/tools/testing/selftests/bpf/progs/compute_live_registers.c +++ b/tools/testing/selftests/bpf/progs/compute_live_registers.c @@ -240,6 +240,7 @@ __naked void if2(void) ::: __clobber_all); }
+#if __clang_major__ >= 18 /* Verifier misses that r2 is alive if jset is not handled properly */ SEC("socket") __log_level(2) @@ -255,6 +256,7 @@ __naked void if3_jset_bug(void) "exit;" ::: __clobber_all); } +#endif
SEC("socket") __log_level(2)
On Tue, Aug 26, 2025 at 8:16 PM Feng Yang yangfeng59949@163.com wrote:
From: Feng Yang yangfeng@kylinos.cn
The following issue occurs when compiling with clang version 17.0.6, but not with version 18.1.8. Add a version restriction to fix this problem.
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.
and once it compiles what happens next ?
pw-bot: cr
On Wed, 2025-08-27 at 11:15 +0800, Feng Yang wrote:
From: Feng Yang yangfeng@kylinos.cn
The following issue occurs when compiling with clang version 17.0.6, but not with version 18.1.8. Add a version restriction to fix this problem.
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.
Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation") Signed-off-by: Feng Yang yangfeng@kylinos.cn
tools/testing/selftests/bpf/progs/compute_live_registers.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/compute_live_registers.c b/tools/testing/selftests/bpf/progs/compute_live_registers.c index 6884ab99a421..56aec43f206f 100644 --- a/tools/testing/selftests/bpf/progs/compute_live_registers.c +++ b/tools/testing/selftests/bpf/progs/compute_live_registers.c @@ -240,6 +240,7 @@ __naked void if2(void) ::: __clobber_all); } +#if __clang_major__ >= 18
Instead of guarding this with compiler version, could you please use progs/bpf_misc.h:__imm_insn() macro for the jset instruction?
/* Verifier misses that r2 is alive if jset is not handled properly */ SEC("socket") __log_level(2) @@ -255,6 +256,7 @@ __naked void if3_jset_bug(void) "exit;" ::: __clobber_all); } +#endif SEC("socket") __log_level(2)
On Tue, 26 Aug 2025 21:48:43 -0700, Eduard Zingerman eddyz87@gmail.com wrote:
On Wed, 2025-08-27 at 11:15 +0800, Feng Yang wrote:
From: Feng Yang yangfeng@kylinos.cn
The following issue occurs when compiling with clang version 17.0.6, but not with version 18.1.8. Add a version restriction to fix this problem.
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.
Fixes: 4a4b84ba9e453 ("selftests/bpf: verify jset handling in CFG computation") Signed-off-by: Feng Yang yangfeng@kylinos.cn
tools/testing/selftests/bpf/progs/compute_live_registers.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/compute_live_registers.c b/tools/testing/selftests/bpf/progs/compute_live_registers.c index 6884ab99a421..56aec43f206f 100644 --- a/tools/testing/selftests/bpf/progs/compute_live_registers.c +++ b/tools/testing/selftests/bpf/progs/compute_live_registers.c @@ -240,6 +240,7 @@ __naked void if2(void) ::: __clobber_all); } +#if __clang_major__ >= 18
Instead of guarding this with compiler version, could you please use progs/bpf_misc.h:__imm_insn() macro for the jset instruction?
I don't know much about assembly language. Could you tell me if the following changes are correct?
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); }
On Wed, 2025-08-27 at 16:24 +0800, Feng Yang wrote:
[...]
I don't know much about assembly language. Could you tell me if the following changes are correct?
Looks correct, should be similar to verifier_search_pruning.c:short_loop1().
Unfortunately, I'm afraid that the best source for assembly syntax doc are llvm backend tests and sources, e.g.: - https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/BPF/assembl... - https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/BPF/assembl... - https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/BPF/BPFInstrI...
The directives should gas compatible (subset supported by llvm): - https://sourceware.org/binutils/docs/as/8byte.html
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;' */
::: __clobber_all);
:: __imm_insn(jset, BPF_JMP_IMM(BPF_JSET, BPF_REG_1, 0x7, 1)): __clobber_all);}
linux-kselftest-mirror@lists.linaro.org
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Alexei Starovoitov -
Eduard Zingerman -
Feng Yang