linux-kernel - [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack

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Message-ID: <20260203055231.1088479-2-dongml2@chinatelecom.cn>
Date: Tue,  3 Feb 2026 13:52:29 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: ast@...nel.org
Cc: daniel@...earbox.net,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
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	jiang.biao@...ux.dev,
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	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

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

Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
---
 arch/riscv/net/bpf_jit_comp64.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 37888abee70c..e4f45e2e7e2f 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -926,6 +926,14 @@ static void restore_stack_args(int nr_stack_args, int args_off, int stk_arg_off,
 	}
 }
 
+static void emit_store_stack_imm64(u8 reg, int stack_off, u64 imm64,
+				   struct rv_jit_context *ctx)
+{
+	/* Load imm64 into reg and store it at [FP + stack_off]. */
+	emit_imm(reg, (s64)imm64, ctx);
+	emit_sd(RV_REG_FP, stack_off, reg, ctx);
+}
+
 static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_off,
 			   int run_ctx_off, bool save_ret, struct rv_jit_context *ctx)
 {
@@ -933,12 +941,10 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
 	struct bpf_prog *p = l->link.prog;
 	int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
 
-	if (l->cookie) {
-		emit_imm(RV_REG_T1, l->cookie, ctx);
-		emit_sd(RV_REG_FP, -run_ctx_off + cookie_off, RV_REG_T1, ctx);
-	} else {
+	if (l->cookie)
+		emit_store_stack_imm64(RV_REG_T1, -run_ctx_off + cookie_off, l->cookie, ctx);
+	else
 		emit_sd(RV_REG_FP, -run_ctx_off + cookie_off, RV_REG_ZERO, ctx);
-	}
 
 	/* arg1: prog */
 	emit_imm(RV_REG_A0, (const s64)p, ctx);
@@ -1123,13 +1129,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	emit_sd(RV_REG_FP, -sreg_off, RV_REG_S1, ctx);
 
 	/* store ip address of the traced function */
-	if (flags & BPF_TRAMP_F_IP_ARG) {
-		emit_imm(RV_REG_T1, (const s64)func_addr, ctx);
-		emit_sd(RV_REG_FP, -ip_off, RV_REG_T1, ctx);
-	}
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		emit_store_stack_imm64(RV_REG_T1, -ip_off, (u64)func_addr, ctx);
 
-	emit_li(RV_REG_T1, nr_arg_slots, ctx);
-	emit_sd(RV_REG_FP, -nregs_off, RV_REG_T1, ctx);
+	emit_store_stack_imm64(RV_REG_T1, -nregs_off, nr_arg_slots, ctx);
 
 	store_args(nr_arg_slots, args_off, ctx);
 
-- 
2.52.0