[PATCH v1 3/3] LoongArch: BPF: support 12 function arguments for trampoline
From: Tiezhu Yang
Date: Tue Feb 24 2026 - 02:40:11 EST
Currently, LoongArch bpf trampoline supports up to 8 function arguments.
According to the statistics from commit 473e3150e30a ("bpf, x86: allow
function arguments up to 12 for TRACING"), there are over 200 functions
accept 9 to 12 arguments, so add 12 arguments support for trampoline.
With this patch, the following related testcases passed:
sudo ./test_progs -a tracing_struct/struct_many_args
sudo ./test_progs -a fentry_test/fentry_many_args
sudo ./test_progs -a fexit_test/fexit_many_args
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
arch/loongarch/net/bpf_jit.c | 79 +++++++++++++++++++++++++-----------
1 file changed, 55 insertions(+), 24 deletions(-)
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index fef002bd3ffb..6037f2495cf6 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1460,26 +1460,48 @@ int bpf_arch_text_invalidate(void *dst, size_t len)
return ret;
}
-static void store_args(struct jit_ctx *ctx, int nregs, int args_off)
+static void store_args(struct jit_ctx *ctx, int nr_arg_slots, int args_off)
{
int i;
- for (i = 0; i < nregs; i++) {
- emit_insn(ctx, std, LOONGARCH_GPR_A0 + i, LOONGARCH_GPR_FP, -args_off);
+ for (i = 0; i < nr_arg_slots; i++) {
+ if (i < LOONGARCH_MAX_REG_ARGS) {
+ emit_insn(ctx, std, LOONGARCH_GPR_A0 + i, LOONGARCH_GPR_FP, -args_off);
+ } else {
+ /* skip slots for T0 and FP of traced function */
+ emit_insn(ctx, ldd, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP,
+ 16 + (i - LOONGARCH_MAX_REG_ARGS) * 8);
+ emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -args_off);
+ }
args_off -= 8;
}
}
-static void restore_args(struct jit_ctx *ctx, int nregs, int args_off)
+static void restore_args(struct jit_ctx *ctx, int nr_reg_args, int args_off)
{
int i;
- for (i = 0; i < nregs; i++) {
+ for (i = 0; i < nr_reg_args; i++) {
emit_insn(ctx, ldd, LOONGARCH_GPR_A0 + i, LOONGARCH_GPR_FP, -args_off);
args_off -= 8;
}
}
+static void restore_stk_args(struct jit_ctx *ctx, int nr_stk_args,
+ int args_off, int stk_arg_off)
+{
+ int i;
+
+ for (i = 0; i < nr_stk_args; i++) {
+ emit_insn(ctx, ldd, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP,
+ -(args_off - LOONGARCH_MAX_REG_ARGS * 8));
+ emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP,
+ -stk_arg_off);
+ args_off -= 8;
+ stk_arg_off -= 8;
+ }
+}
+
static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
int args_off, int retval_off, int run_ctx_off, bool save_ret)
{
@@ -1590,7 +1612,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
void *func_addr, u32 flags)
{
int i, ret, save_ret;
- int stack_size, nregs = m->nr_args;
+ int stack_size, nr_arg_slots = 0, stk_arg_off;
int retval_off, args_off, nregs_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off;
bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT;
void *orig_call = func_addr;
@@ -1624,25 +1646,27 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
* FP - sreg_off [ callee saved reg ]
*
* FP - tcc_ptr_off [ tail_call_cnt_ptr ]
+ *
+ * [ stack_argN ]
+ * [ ... ]
+ * FP - stk_arg_off [ stack_arg1 ] BPF_TRAMP_F_CALL_ORIG
*/
+ if (m->nr_args > MAX_BPF_FUNC_ARGS)
+ return -ENOTSUPP;
+
/* Extra registers for struct arguments */
for (i = 0; i < m->nr_args; i++) {
- if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) {
- /*
- * The struct argument size is at most 16 bytes,
- * enforced by the verifier. The struct argument
- * may be passed in a pair of registers if its
- * size is more than 8 bytes and no more than 16
- * bytes.
- */
- nregs += round_up(m->arg_size[i], 8) / 8 - 1;
- }
+ /*
+ * The struct argument size is at most 16 bytes,
+ * enforced by the verifier. The struct argument
+ * may be passed in a pair of registers if its
+ * size is more than 8 bytes and no more than 16
+ * bytes.
+ */
+ nr_arg_slots += round_up(m->arg_size[i], 8) / 8;
}
- if (nregs > LOONGARCH_MAX_REG_ARGS)
- return -ENOTSUPP;
-
if (flags & (BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_SHARE_IPMODIFY))
return -ENOTSUPP;
@@ -1656,7 +1680,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
retval_off = stack_size;
/* Room of trampoline frame to store args */
- stack_size += nregs * 8;
+ stack_size += nr_arg_slots * 8;
args_off = stack_size;
/* Room of trampoline frame to store args number */
@@ -1682,8 +1706,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
tcc_ptr_off = stack_size;
}
+ if ((flags & BPF_TRAMP_F_CALL_ORIG) && (nr_arg_slots - LOONGARCH_MAX_REG_ARGS > 0))
+ stack_size += (nr_arg_slots - LOONGARCH_MAX_REG_ARGS) * 8;
+
stack_size = round_up(stack_size, 16);
+ /* Room for args on stack must be at the top of stack */
+ stk_arg_off = stack_size;
+
if (is_struct_ops) {
/*
* For the trampoline called directly, just handle
@@ -1725,10 +1755,10 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
}
/* store arg regs count */
- move_imm(ctx, LOONGARCH_GPR_T1, nregs, false);
+ move_imm(ctx, LOONGARCH_GPR_T1, nr_arg_slots, false);
emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -nregs_off);
- store_args(ctx, nregs, args_off);
+ store_args(ctx, nr_arg_slots, args_off);
/* To traced function */
/* Ftrace jump skips 2 NOP instructions */
@@ -1770,7 +1800,8 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
- restore_args(ctx, nregs, args_off);
+ restore_args(ctx, min_t(int, nr_arg_slots, LOONGARCH_MAX_REG_ARGS), args_off);
+ restore_stk_args(ctx, nr_arg_slots - LOONGARCH_MAX_REG_ARGS, args_off, stk_arg_off);
if (flags & BPF_TRAMP_F_TAIL_CALL_CTX)
emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_FP, -tcc_ptr_off);
@@ -1806,7 +1837,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
}
if (flags & BPF_TRAMP_F_RESTORE_REGS)
- restore_args(ctx, nregs, args_off);
+ restore_args(ctx, min_t(int, nr_arg_slots, LOONGARCH_MAX_REG_ARGS), args_off);
if (save_ret) {
emit_insn(ctx, ldd, regmap[BPF_REG_0], LOONGARCH_GPR_FP, -(retval_off - 8));
--
2.42.0