bpf,x86: introduce emit_store_stack_imm64() for trampoline

Introduce the helper emit_store_stack_imm64(), which is used to store a
imm64 to the stack with the help of a register.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20260124062008.8657-7-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index e3b1c4b1d550419a6b9aab8c11acbe433b3e3a5a..2f31331955b5642aae71b3fdebe262f98b64d812 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1300,6 +1300,16 @@ static void emit_st_r12(u8 **pprog, u32 size, u32 dst_reg, int off, int imm)
        emit_st_index(pprog, size, dst_reg, X86_REG_R12, off, imm);
 }
 
+static void emit_store_stack_imm64(u8 **pprog, int reg, int stack_off, u64 imm64)
+{
+       /*
+        * mov reg, imm64
+        * mov QWORD PTR [rbp + stack_off], reg
+        */
+       emit_mov_imm64(pprog, reg, imm64 >> 32, (u32) imm64);
+       emit_stx(pprog, BPF_DW, BPF_REG_FP, reg, stack_off);
+}
+
 static int emit_atomic_rmw(u8 **pprog, u32 atomic_op,
                           u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size)
 {
@@ -3348,20 +3358,12 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
        /* mov QWORD PTR [rbp - rbx_off], rbx */
        emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_6, -rbx_off);
 
-       /* Store number of argument registers of the traced function:
-        *   mov rax, nr_regs
-        *   mov QWORD PTR [rbp - nregs_off], rax
-        */
-       emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_regs);
-       emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -nregs_off);
+       /* Store number of argument registers of the traced function */
+       emit_store_stack_imm64(&prog, BPF_REG_0, -nregs_off, nr_regs);
 
        if (flags & BPF_TRAMP_F_IP_ARG) {
-               /* Store IP address of the traced function:
-                * movabsq rax, func_addr
-                * mov QWORD PTR [rbp - ip_off], rax
-                */
-               emit_mov_imm64(&prog, BPF_REG_0, (long) func_addr >> 32, (u32) (long) func_addr);
-               emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ip_off);
+               /* Store IP address of the traced function */
+               emit_store_stack_imm64(&prog, BPF_REG_0, -ip_off, (long)func_addr);
        }
 
        save_args(m, &prog, regs_off, false, flags);