[PATCH bpf-next v10 06/12] bpf,x86: introduce emit_store_stack_imm64() for trampoline
From: Menglong Dong <hidden>
Date: 2026-01-15 11:23:59
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_store_stack_imm64(), which is used to store a imm64 to the stack with the help of a register. Signed-off-by: Menglong Dong <redacted> --- v10: - add the "reg" to the function arguments of emit_store_stack_imm64() - use the positive offset in emit_store_stack_imm64() - remove some unnecessary comment, as we already have proper comment in emit_store_stack_imm64() v9: - rename emit_st_r0_imm64() to emit_store_stack_imm64() --- arch/x86/net/bpf_jit_comp.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index e3b1c4b1d550..2f31331955b5 100644
--- 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);
--
2.52.0