Modify the build_prologue function to ensure the return address
register ra is saved to t0 before entering trampoline operations.
This change ensures accurate return address handling when a BPF
program calls another BPF program, preventing errors in the
BPF-to-BPF call chain.

Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
---
 arch/loongarch/net/bpf_jit.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 76cd24646bec..c560d1e14b9d 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -139,6 +139,7 @@ static void build_prologue(struct jit_ctx *ctx)
 	stack_adjust = round_up(stack_adjust, 16);
 	stack_adjust += bpf_stack_adjust;
 
+	move_reg(ctx, LOONGARCH_GPR_T0, LOONGARCH_GPR_RA);
 	/* Reserve space for the move_imm + jirl instruction */
 	for (i = 0; i < LOONGARCH_LONG_JUMP_NINSNS; i++)
 		emit_insn(ctx, nop);
-- 
2.25.1