For now, the offset of the return value in trampoline is fixed 8-bytes. In this commit, we introduce the variable "ret_off" to represent the offset of the return value. For now, the "ret_off" is just 8. And in the following patch, we will make it something else to use the room after it.
Signed-off-by: Menglong Dong <[email protected]> --- arch/x86/net/bpf_jit_comp.c | 41 +++++++++++++++++++++---------------- 1 file changed, 23 insertions(+), 18 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 389c3a96e2b8..7a604ee9713f 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -2940,7 +2940,7 @@ static void restore_regs(const struct btf_func_model *m, u8 **prog, static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, struct bpf_tramp_link *l, int stack_size, - int run_ctx_off, bool save_ret, + int run_ctx_off, bool save_ret, int ret_off, void *image, void *rw_image) { u8 *prog = *pprog; @@ -3005,7 +3005,7 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, * value of BPF_PROG_TYPE_STRUCT_OPS prog. */ if (save_ret) - emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8); + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ret_off); /* replace 2 nops with JE insn, since jmp target is known */ jmp_insn[0] = X86_JE; @@ -3055,7 +3055,7 @@ static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond) static int invoke_bpf(const struct btf_func_model *m, u8 **pprog, struct bpf_tramp_links *tl, int stack_size, - int run_ctx_off, bool save_ret, + int run_ctx_off, bool save_ret, int ret_off, void *image, void *rw_image) { int i; @@ -3063,7 +3063,8 @@ static int invoke_bpf(const struct btf_func_model *m, u8 **pprog, for (i = 0; i < tl->nr_links; i++) { if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size, - run_ctx_off, save_ret, image, rw_image)) + run_ctx_off, save_ret, ret_off, image, + rw_image)) return -EINVAL; } *pprog = prog; @@ -3072,7 +3073,7 @@ static int invoke_bpf(const struct btf_func_model *m, u8 **pprog, static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog, struct bpf_tramp_links *tl, int stack_size, - int run_ctx_off, u8 **branches, + int run_ctx_off, int ret_off, u8 **branches, void *image, void *rw_image) { u8 *prog = *pprog; @@ -3082,18 +3083,18 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog, * Set this to 0 to avoid confusing the program. */ emit_mov_imm32(&prog, false, BPF_REG_0, 0); - emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8); + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ret_off); for (i = 0; i < tl->nr_links; i++) { if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size, run_ctx_off, true, - image, rw_image)) + ret_off, image, rw_image)) return -EINVAL; - /* mod_ret prog stored return value into [rbp - 8]. Emit: - * if (*(u64 *)(rbp - 8) != 0) + /* mod_ret prog stored return value into [rbp - ret_off]. Emit: + * if (*(u64 *)(rbp - ret_off) != 0) * goto do_fexit; */ - /* cmp QWORD PTR [rbp - 0x8], 0x0 */ - EMIT4(0x48, 0x83, 0x7d, 0xf8); EMIT1(0x00); + /* cmp QWORD PTR [rbp - ret_off], 0x0 */ + EMIT4(0x48, 0x83, 0x7d, -ret_off); EMIT1(0x00); /* Save the location of the branch and Generate 6 nops * (4 bytes for an offset and 2 bytes for the jump) These nops @@ -3179,7 +3180,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im void *func_addr) { int i, ret, nr_regs = m->nr_args, stack_size = 0; - int regs_off, nregs_off, ip_off, run_ctx_off, arg_stack_off, rbx_off; + int ret_off, regs_off, nregs_off, ip_off, run_ctx_off, arg_stack_off, + rbx_off; struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY]; struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT]; struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN]; @@ -3213,7 +3215,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im * RBP + 8 [ return address ] * RBP + 0 [ RBP ] * - * RBP - 8 [ return value ] BPF_TRAMP_F_CALL_ORIG or + * RBP - ret_off [ return value ] BPF_TRAMP_F_CALL_ORIG or * BPF_TRAMP_F_RET_FENTRY_RET flags * * [ reg_argN ] always @@ -3239,6 +3241,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); if (save_ret) stack_size += 8; + ret_off = stack_size; stack_size += nr_regs * 8; regs_off = stack_size; @@ -3341,7 +3344,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im if (fentry->nr_links) { if (invoke_bpf(m, &prog, fentry, regs_off, run_ctx_off, - flags & BPF_TRAMP_F_RET_FENTRY_RET, image, rw_image)) + flags & BPF_TRAMP_F_RET_FENTRY_RET, ret_off, + image, rw_image)) return -EINVAL; } @@ -3352,7 +3356,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im return -ENOMEM; if (invoke_bpf_mod_ret(m, &prog, fmod_ret, regs_off, - run_ctx_off, branches, image, rw_image)) { + run_ctx_off, ret_off, branches, + image, rw_image)) { ret = -EINVAL; goto cleanup; } @@ -3380,7 +3385,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im } } /* remember return value in a stack for bpf prog to access */ - emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8); + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ret_off); im->ip_after_call = image + (prog - (u8 *)rw_image); emit_nops(&prog, X86_PATCH_SIZE); } @@ -3403,7 +3408,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im if (fexit->nr_links) { if (invoke_bpf(m, &prog, fexit, regs_off, run_ctx_off, - false, image, rw_image)) { + false, ret_off, image, rw_image)) { ret = -EINVAL; goto cleanup; } @@ -3433,7 +3438,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im /* restore return value of orig_call or fentry prog back into RAX */ if (save_ret) - emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8); + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -ret_off); emit_ldx(&prog, BPF_DW, BPF_REG_6, BPF_REG_FP, -rbx_off); EMIT1(0xC9); /* leave */ -- 2.51.1
