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bpf: Inline bpf_iter_num_next() kfunc

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bpf_iter_num_next() runs on every bpf_for() iteration, so inlining it
drops a call from the loop body. R1 points to the iterator; the returned
pointer to s->cur is R1 itself, since s->cur is first.

s->cur and s->end are int, so the kfunc's s->cur + 1 >= s->end is a
signed 32-bit compare and the inlined code needs no sign extension.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260804134601.2305303-4-puranjay@kernel.org
This commit is contained in:
Puranjay Mohan 2026-08-04 06:45:55 -07:00 committed by Andrii Nakryiko
parent f8f2b567d5
commit e933477048
1 changed files with 17 additions and 0 deletions
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17
kernel/bpf/verifier.c
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@ -20030,6 +20030,23 @@ int bpf_fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
insn_buf[i++] = BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 0);
insn_buf[i++] = BPF_MOV64_IMM(BPF_REG_0, -E2BIG);
*cnt = i;
} else if (desc->func_id == special_kfunc_list[KF_bpf_iter_num_next]) {
/* inline bpf_iter_num_next(&it); R1=&it, returns &s->cur or NULL */
int i = 0;
/* r0 = s->cur + 1; if ((s32)r0 >= s->end) goto done; */
insn_buf[i++] = BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0);
insn_buf[i++] = BPF_ALU32_IMM(BPF_ADD, BPF_REG_0, 1);
insn_buf[i++] = BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 4);
insn_buf[i++] = BPF_JMP32_REG(BPF_JSGE, BPF_REG_0, BPF_REG_2, 3);
/* s->cur = r0; return &s->cur; */
insn_buf[i++] = BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0, 0);
insn_buf[i++] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);
insn_buf[i++] = BPF_JMP_A(2);
/* done: s->cur = s->end = 0; return NULL; */
insn_buf[i++] = BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 0);
insn_buf[i++] = BPF_MOV64_IMM(BPF_REG_0, 0);
*cnt = i;
}
if (env->insn_aux_data[insn_idx].arg_prog) {