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selftests/bpf: Convert ctx tests from ASM to C

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Convert existing tests from ASM to C, in prep for future changes to add
more comprehensive tests.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260406194403.1649608-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi
2026-04-06 21:43:57 +02:00
committed by Alexei Starovoitov
parent f25777056e
commit 02f500ce01
2 changed files with 35 additions and 45 deletions
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2
tools/testing/selftests/bpf/prog_tests/verifier.c
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@@ -175,7 +175,7 @@ void test_verifier_cgroup_skb(void) { RUN(verifier_cgroup_skb); }
void test_verifier_cgroup_storage(void) { RUN(verifier_cgroup_storage); }
void test_verifier_const(void) { RUN(verifier_const); }
void test_verifier_const_or(void) { RUN(verifier_const_or); }
void test_verifier_ctx(void) { RUN(verifier_ctx); }
void test_verifier_ctx(void) { RUN_TESTS(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_default_trusted_ptr(void) { RUN_TESTS(verifier_default_trusted_ptr); }

78
tools/testing/selftests/bpf/progs/verifier_ctx.c
View File

@@ -295,68 +295,58 @@ padding_access("sk_reuseport", sk_reuseport_md, hash, 4);
SEC("syscall")
__description("syscall: write to ctx with fixed offset")
__success
__naked void syscall_ctx_fixed_off_write(void)
int syscall_ctx_fixed_off_write(void *ctx)
{
asm volatile (" \
r0 = 0; \
*(u32*)(r1 + 0) = r0; \
r1 += 4; \
*(u32*)(r1 + 0) = r0; \
exit; \
" ::: __clobber_all);
char *p = ctx;
*(__u32 *)p = 0;
*(__u32 *)(p + 4) = 0;
return 0;
}
/*
* Test that program types without convert_ctx_access can dereference
* their ctx pointer after adding a fixed offset. Variable and negative
* offsets should still be rejected.
* For non-syscall program types without convert_ctx_access, direct ctx
* dereference is still allowed after adding a fixed offset, while variable
* and negative direct accesses reject.
*
* Passing ctx as a helper or kfunc memory argument is only permitted for
* syscall programs, so the helper and kfunc cases below validate rejection
* for non-syscall ctx pointers at fixed, variable, and zero-sized accesses.
*/
#define no_rewrite_ctx_access(type, name, off, ld_op) \
#define no_rewrite_ctx_access(type, name, off, load_t) \
SEC(type) \
__description(type ": read ctx at fixed offset") \
__success \
__naked void no_rewrite_##name##_fixed(void) \
int no_rewrite_##name##_fixed(void *ctx) \
{ \
asm volatile (" \
r1 += %[__off]; \
r0 = *(" #ld_op " *)(r1 + 0); \
r0 = 0; \
exit;" \
: \
: __imm_const(__off, off) \
: __clobber_all); \
char *p = ctx; \
volatile load_t val; \
\
val = *(load_t *)(p + off); \
(void)val; \
return 0; \
} \
SEC(type) \
__description(type ": reject variable offset ctx access") \
__failure __msg("variable ctx access var_off=") \
__naked void no_rewrite_##name##_var(void) \
int no_rewrite_##name##_var(void *ctx) \
{ \
asm volatile (" \
r6 = r1; \
call %[bpf_get_prandom_u32]; \
r1 = r6; \
r0 &= 4; \
r1 += r0; \
r0 = *(" #ld_op " *)(r1 + 0); \
r0 = 0; \
exit;" \
: \
: __imm(bpf_get_prandom_u32) \
: __clobber_all); \
__u64 off_var = bpf_get_prandom_u32(); \
char *p = ctx; \
\
off_var &= 4; \
p += off_var; \
return *(load_t *)p; \
} \
SEC(type) \
__description(type ": reject negative offset ctx access") \
__failure __msg("negative offset ctx ptr") \
__naked void no_rewrite_##name##_neg(void) \
__failure __msg("invalid bpf_context access") \
int no_rewrite_##name##_neg(void *ctx) \
{ \
asm volatile (" \
r1 += %[__neg_off]; \
r0 = *(" #ld_op " *)(r1 + 0); \
r0 = 0; \
exit;" \
: \
: __imm_const(__neg_off, -(off)) \
: __clobber_all); \
char *p = ctx; \
\
p -= 612; \
return *(load_t *)p; \
}
no_rewrite_ctx_access("kprobe", kprobe, 8, u64);