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selftests/bpf: Test timed may_goto preserves R0-R5

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Add a test that checks R0-R5 are preserved across
arch_bpf_timed_may_goto() calls.

Use bpf_get_prandom_u32() to avoid the verifier removing the checks
via DCE.

Suggested-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20260723-riscv-bpf-timed-may-goto-v5-2-86acb54e5642@kylinos.cn
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
This commit is contained in:
Feng Jiang
2026-07-23 05:41:33 +00:00
committed by Kumar Kartikeya Dwivedi
parent 6ef8ff20c3
commit a0032241aa
1 changed files with 58 additions and 0 deletions
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58
tools/testing/selftests/bpf/progs/verifier_may_goto_1.c
View File

@@ -106,4 +106,62 @@ __naked void may_goto_batch_2(void)
: __clobber_all);
}
/*
* Use bpf_get_prandom_u32() to prevent DCE from removing the checks.
* retval: 0=all ok, 1-6=R0-R5 clobbered.
*/
SEC("syscall")
__description("timed may_goto preserves R0-R5")
__arch_x86_64
__arch_s390x
__arch_arm64
__arch_riscv64
__success
__retval(0)
__naked void timed_may_goto_preserves_regs(void)
{
asm volatile (
"call %[bpf_get_prandom_u32];"
"r6 = r0;"
"r0 = 0x1111;"
"r0 += r6;"
"r1 = 0x2222;"
"r1 += r6;"
"r2 = 0x3333;"
"r2 += r6;"
"r3 = 0x4444;"
"r3 += r6;"
"r4 = 0x5555;"
"r4 += r6;"
"r5 = 0x6666;"
"r5 += r6;"
".8byte %[may_goto];"
".8byte %[loop];"
"r0 -= r6;"
"r1 -= r6;"
"r2 -= r6;"
"r3 -= r6;"
"r4 -= r6;"
"r5 -= r6;"
"if r0 != 0x1111 goto 1f;"
"if r1 != 0x2222 goto 2f;"
"if r2 != 0x3333 goto 3f;"
"if r3 != 0x4444 goto 4f;"
"if r4 != 0x5555 goto 5f;"
"if r5 != 0x6666 goto 6f;"
"r0 = 0;"
"exit;"
"1: r0 = 1; exit;"
"2: r0 = 2; exit;"
"3: r0 = 3; exit;"
"4: r0 = 4; exit;"
"5: r0 = 5; exit;"
"6: r0 = 6; exit;"
:
: __imm(bpf_get_prandom_u32),
__imm_insn(may_goto, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 1, 0)),
__imm_insn(loop, BPF_RAW_INSN(BPF_JMP | BPF_JA, 0, 0, -2, 0))
: __clobber_all);
}
char _license[] SEC("license") = "GPL";