From: Pu Lehui <pulehui@xxxxxxxxxx> Extra_nregs of structure parameters and nr_args can be added directly at the beginning, and using a flip flag to identifiy structure parameters. Meantime, renaming some variables to make them more sense. Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> --- v2: - renaming flip flag and add comment for better understanding. - add ACK by Yonghong. v1: https://lore.kernel.org/bpf/20230103013158.1945869-1-pulehui@xxxxxxxxxxxxxxx arch/x86/net/bpf_jit_comp.c | 101 +++++++++++++++++------------------- 1 file changed, 48 insertions(+), 53 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index e3e2b57e4e13..ecdfc7bc45d2 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1839,62 +1839,59 @@ st: if (is_imm8(insn->off)) return proglen; } -static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args, +static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_regs, int stack_size) { - int i, j, arg_size, nr_regs; + int i, j, arg_size; + bool next_same_struct = false; + /* Store function arguments to stack. * For a function that accepts two pointers the sequence will be: * mov QWORD PTR [rbp-0x10],rdi * mov QWORD PTR [rbp-0x8],rsi */ - for (i = 0, j = 0; i < min(nr_args, 6); i++) { - if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) { - nr_regs = (m->arg_size[i] + 7) / 8; + for (i = 0, j = 0; i < min(nr_regs, 6); i++) { + /* The arg_size is at most 16 bytes, enforced by the verifier. */ + arg_size = m->arg_size[j]; + if (arg_size > 8) { arg_size = 8; - } else { - nr_regs = 1; - arg_size = m->arg_size[i]; + next_same_struct = !next_same_struct; } - while (nr_regs) { - emit_stx(prog, bytes_to_bpf_size(arg_size), - BPF_REG_FP, - j == 5 ? X86_REG_R9 : BPF_REG_1 + j, - -(stack_size - j * 8)); - nr_regs--; - j++; - } + emit_stx(prog, bytes_to_bpf_size(arg_size), + BPF_REG_FP, + i == 5 ? X86_REG_R9 : BPF_REG_1 + i, + -(stack_size - i * 8)); + + j = next_same_struct ? j : j + 1; } } -static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args, +static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_regs, int stack_size) { - int i, j, arg_size, nr_regs; + int i, j, arg_size; + bool next_same_struct = false; /* Restore function arguments from stack. * For a function that accepts two pointers the sequence will be: * EMIT4(0x48, 0x8B, 0x7D, 0xF0); mov rdi,QWORD PTR [rbp-0x10] * EMIT4(0x48, 0x8B, 0x75, 0xF8); mov rsi,QWORD PTR [rbp-0x8] */ - for (i = 0, j = 0; i < min(nr_args, 6); i++) { - if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) { - nr_regs = (m->arg_size[i] + 7) / 8; + for (i = 0, j = 0; i < min(nr_regs, 6); i++) { + /* The arg_size is at most 16 bytes, enforced by the verifier. */ + arg_size = m->arg_size[j]; + if (arg_size > 8) { arg_size = 8; - } else { - nr_regs = 1; - arg_size = m->arg_size[i]; + next_same_struct = !next_same_struct; } - while (nr_regs) { - emit_ldx(prog, bytes_to_bpf_size(arg_size), - j == 5 ? X86_REG_R9 : BPF_REG_1 + j, - BPF_REG_FP, - -(stack_size - j * 8)); - nr_regs--; - j++; - } + emit_ldx(prog, bytes_to_bpf_size(arg_size), + i == 5 ? X86_REG_R9 : BPF_REG_1 + i, + BPF_REG_FP, + -(stack_size - i * 8)); + + j = next_same_struct ? j : j + 1; } } @@ -2120,8 +2117,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i struct bpf_tramp_links *tlinks, void *func_addr) { - int ret, i, nr_args = m->nr_args, extra_nregs = 0; - int regs_off, ip_off, args_off, stack_size = nr_args * 8, run_ctx_off; + int i, ret, nr_regs = m->nr_args, stack_size = 0; + int regs_off, nregs_off, ip_off, run_ctx_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]; @@ -2130,17 +2127,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i u8 *prog; bool save_ret; - /* x86-64 supports up to 6 arguments. 7+ can be added in the future */ - if (nr_args > 6) - return -ENOTSUPP; - - for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) { + /* extra registers for struct arguments */ + for (i = 0; i < m->nr_args; i++) if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) - extra_nregs += (m->arg_size[i] + 7) / 8 - 1; - } - if (nr_args + extra_nregs > 6) + nr_regs += (m->arg_size[i] + 7) / 8 - 1; + + /* x86-64 supports up to 6 arguments. 7+ can be added in the future */ + if (nr_regs > 6) return -ENOTSUPP; - stack_size += extra_nregs * 8; /* Generated trampoline stack layout: * @@ -2154,7 +2148,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i * [ ... ] * RBP - regs_off [ reg_arg1 ] program's ctx pointer * - * RBP - args_off [ arg regs count ] always + * RBP - nregs_off [ regs count ] always * * RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag * @@ -2166,11 +2160,12 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i if (save_ret) stack_size += 8; + stack_size += nr_regs * 8; regs_off = stack_size; - /* args count */ + /* regs count */ stack_size += 8; - args_off = stack_size; + nregs_off = stack_size; if (flags & BPF_TRAMP_F_IP_ARG) stack_size += 8; /* room for IP address argument */ @@ -2198,11 +2193,11 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i EMIT1(0x53); /* push rbx */ /* Store number of argument registers of the traced function: - * mov rax, nr_args + extra_nregs - * mov QWORD PTR [rbp - args_off], rax + * mov rax, nr_regs + * mov QWORD PTR [rbp - nregs_off], rax */ - emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args + extra_nregs); - emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -args_off); + emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_regs); + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -nregs_off); if (flags & BPF_TRAMP_F_IP_ARG) { /* Store IP address of the traced function: @@ -2213,7 +2208,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ip_off); } - save_regs(m, &prog, nr_args, regs_off); + save_regs(m, &prog, nr_regs, regs_off); if (flags & BPF_TRAMP_F_CALL_ORIG) { /* arg1: mov rdi, im */ @@ -2243,7 +2238,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i } if (flags & BPF_TRAMP_F_CALL_ORIG) { - restore_regs(m, &prog, nr_args, regs_off); + restore_regs(m, &prog, nr_regs, regs_off); if (flags & BPF_TRAMP_F_ORIG_STACK) { emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); @@ -2284,7 +2279,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i } if (flags & BPF_TRAMP_F_RESTORE_REGS) - restore_regs(m, &prog, nr_args, regs_off); + restore_regs(m, &prog, nr_regs, regs_off); /* This needs to be done regardless. If there were fmod_ret programs, * the return value is only updated on the stack and still needs to be -- 2.25.1
