Commit 91603353 authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

selftests/bpf: Add tests for s>>=31 and s>>=63 



Add tests for special arithmetic shift right.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Co-developed-by: default avatarPuranjay Mohan <puranjay@kernel.org>
Signed-off-by: default avatarPuranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260112201424.816836-3-puranjay@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent bffacdb8

tools/testing/selftests/bpf/progs/verifier_subreg.c

+85 −0
Original line number Diff line number Diff line
@@ -738,4 +738,89 @@ __naked void ldx_w_zero_extend_check(void) 
	: __clobber_all);

}



SEC("socket")

__success __success_unpriv __retval(0)

__naked void arsh_31_and(void)

{

	/* Below is what LLVM generates in cilium's bpf_wiregard.o */

	asm volatile ("					\

	call %[bpf_get_prandom_u32];			\

	w2 = w0;					\

	w2 s>>= 31;					\

	w2 &= -134; /* w2 becomes 0 or -134 */		\

	if w2 s> -1 goto +2;				\

	/* Branch always taken because w2 = -134 */	\

	if w2 != -136 goto +1;				\

	w0 /= 0;					\

	w0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_get_prandom_u32)

	: __clobber_all);

}



SEC("socket")

__success __success_unpriv __retval(0)

__naked void arsh_63_and(void)

{

	/* Copy of arsh_31 with s/w/r/ */

	asm volatile ("					\

	call %[bpf_get_prandom_u32];			\

	r2 = r0;					\

	r2 <<= 32;					\

	r2 s>>= 63;					\

	r2 &= -134;					\

	if r2 s> -1 goto +2;				\

	/* Branch always taken because w2 = -134 */	\

	if r2 != -136 goto +1;				\

	r0 /= 0;					\

	r0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_get_prandom_u32)

	: __clobber_all);

}



SEC("socket")

__success __success_unpriv __retval(0)

__naked void arsh_31_or(void)

{

	asm volatile ("					\

	call %[bpf_get_prandom_u32];			\

	w2 = w0;					\

	w2 s>>= 31;					\

	w2 |= 134; /* w2 becomes -1 or 134 */		\

	if w2 s> -1 goto +2;				\

	/* Branch always taken because w2 = -1 */	\

	if w2 == -1 goto +1;				\

	w0 /= 0;					\

	w0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_get_prandom_u32)

	: __clobber_all);

}



SEC("socket")

__success __success_unpriv __retval(0)

__naked void arsh_63_or(void)

{

	/* Copy of arsh_31 with s/w/r/ */

	asm volatile ("					\

	call %[bpf_get_prandom_u32];			\

	r2 = r0;					\

	r2 <<= 32;					\

	r2 s>>= 63;					\

	r2 |= 134; /* r2 becomes -1 or 134 */		\

	if r2 s> -1 goto +2;				\

	/* Branch always taken because w2 = -1 */	\

	if r2 == -1 goto +1;				\

	r0 /= 0;					\

	r0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_get_prandom_u32)

	: __clobber_all);

}



char _license[] SEC("license") = "GPL";