On 4/2/24 4:26 PM, Andrii Nakryiko wrote:
On Tue, Apr 2, 2024 at 3:50 PM Andrii Nakryiko <andrii@xxxxxxxxxx> wrote:
Add selftests validating that BPF verifier handles precision marking
for SCALAR registers derived from r10 (fp) register correctly.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
.../bpf/progs/verifier_subprog_precision.c | 86 +++++++++++++++++++
1 file changed, 86 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
index 6f5d19665cf6..e1a8f107f0a7 100644
--- a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
@@ -76,6 +76,92 @@ __naked int subprog_result_precise(void)
);
}
+__naked __noinline __used
+static unsigned long fp_leaking_subprog()
+{
+ asm volatile (
+ "r0 = (s8)r10;"
Our CI's clang doesn't like this instruction. I guess I'll have to
encode it in binary form :(
This patch disappeared from CI so I am not able to check the result.
But I tried with the following small example.
$ cat t.c
__attribute__((naked)) unsigned long t(void)
{
asm volatile("r0 = (s8)r10;"
"exit;"
);
}
$ clang --target=bpf -O2 -mcpu=v2 -g -c t.c && llvm-objdump -d t.o
t.o: file format elf64-bpf
Disassembly of section .text:
0000000000000000 <t>:
0: bf a0 08 00 00 00 00 00 r0 = (s8)r10
1: 95 00 00 00 00 00 00 00 exit
-mcpu=v3/v4 has the same result.
Not sure what clang complains.
+ "exit;"
+ );
+}
+
[...]
