[PATCH bpf-next 1/3] bpf,s390: introduce emit_store_stack_imm64() for trampoline

Menglong Dong
2026-02-23T08:40:43Z

Introduce a helper to store 64-bit immediate on the trampoline stack with
a help of a register.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
arch/s390/net/bpf_jit_comp.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 579461d471bb..763d2491dfa3 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -2506,6 +2506,13 @@ static void load_imm64(struct bpf_jit *jit, int dst_reg, u64 val)
EMIT6_IMM(0xc00d0000, dst_reg, val);
}

+static void emit_store_stack_imm64(struct bpf_jit *jit, int tmp_reg, int stack_off, u64 imm)
+{
+ load_imm64(jit, tmp_reg, imm);
+ /* stg %tmp_reg,stack_off(%r15) */
+ EMIT6_DISP_LH(0xe3000000, 0x0024, tmp_reg, REG_0, REG_15, stack_off);
+}
+
static int invoke_bpf_prog(struct bpf_tramp_jit *tjit,
const struct btf_func_model *m,
struct bpf_tramp_link *tlink, bool save_ret)
@@ -2520,10 +2527,7 @@ static int invoke_bpf_prog(struct bpf_tramp_jit *tjit,
* run_ctx.cookie = tlink->cookie;
*/

- /* %r0 = tlink->cookie */
- load_imm64(jit, REG_W0, tlink->cookie);
- /* stg %r0,cookie_off(%r15) */
- EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W0, REG_0, REG_15, cookie_off);
+ emit_store_stack_imm64(jit, REG_W0, cookie_off, tlink->cookie);

/*
* if ((start = __bpf_prog_enter(p, &run_ctx)) == 0)
@@ -2743,18 +2747,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
* arg_cnt = m->nr_args;
*/

- if (flags & BPF_TRAMP_F_IP_ARG) {
- /* %r0 = func_addr */
- load_imm64(jit, REG_0, (u64)func_addr);
- /* stg %r0,ip_off(%r15) */
- EMIT6_DISP_LH(0xe3000000, 0x0024, REG_0, REG_0, REG_15,
- tjit->ip_off);
- }
- /* lghi %r0,nr_bpf_args */
- EMIT4_IMM(0xa7090000, REG_0, nr_bpf_args);
- /* stg %r0,arg_cnt_off(%r15) */
- EMIT6_DISP_LH(0xe3000000, 0x0024, REG_0, REG_0, REG_15,
- tjit->arg_cnt_off);
+ if (flags & BPF_TRAMP_F_IP_ARG)
+ emit_store_stack_imm64(jit, REG_0, tjit->ip_off, (u64)func_addr);
+ emit_store_stack_imm64(jit, REG_0, tjit->arg_cnt_off, nr_bpf_args);

if (flags & BPF_TRAMP_F_CALL_ORIG) {
/*
--
2.53.0