[PATCH bpf-next v4 5/9] bpf,x86: introduce emit_st_r0_imm64() for trampoline
From: Menglong Dong <hidden>
Date: 2025-12-17 09:55:27
Also in:
bpf, lkml
Subsystem:
bpf jit for x86 64-bit, bpf [general] (safe dynamic programs and tools), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Introduce the helper emit_st_r0_imm64(), which is used to store a imm64 to the stack with the help of r0. Signed-off-by: Menglong Dong <redacted> --- arch/x86/net/bpf_jit_comp.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b69dc7194e2c..8cbeefb26192 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c@@ -1300,6 +1300,15 @@ 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_st_r0_imm64(u8 **pprog, u64 value, int off) +{ + /* mov rax, value + * mov QWORD PTR [rbp - off], rax + */ + emit_mov_imm64(pprog, BPF_REG_0, value >> 32, (u32) value); + emit_stx(pprog, BPF_DW, BPF_REG_FP, BPF_REG_0, -off); +} + static int emit_atomic_rmw(u8 **pprog, u32 atomic_op, u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size) {
@@ -3341,16 +3350,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im * 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); + emit_st_r0_imm64(&prog, nr_regs, nregs_off); 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); + emit_st_r0_imm64(&prog, (long)func_addr, ip_off); } save_args(m, &prog, regs_off, false, flags);
--
2.52.0