Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 5 Jan 2023 11:47:27 +0800 | Subject | Re: [PATCH bpf-next] bpf, x86: Simplify the parsing logic of structure parameters | From | Pu Lehui <> |
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On 2023/1/5 2:24, Yonghong Song wrote: > > > On 1/2/23 5:31 PM, Pu Lehui wrote: >> From: Pu Lehui <pulehui@huawei.com> >> >> 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@huawei.com> > > Thanks for refactoring. Using nr_regs instead of nr_args indeed > making things easier to understand. Ack with a few nits below. > > Acked-by: Yonghong Song <yhs@fb.com> > >> --- >> arch/x86/net/bpf_jit_comp.c | 99 +++++++++++++++++-------------------- >> 1 file changed, 46 insertions(+), 53 deletions(-) >> >> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c >> index e3e2b57e4e13..e7b72299f5a4 100644 >> --- a/arch/x86/net/bpf_jit_comp.c >> +++ b/arch/x86/net/bpf_jit_comp.c >> @@ -1839,62 +1839,57 @@ 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 is_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++) { >> + arg_size = m->arg_size[j]; >> + if (arg_size > 8) { >> arg_size = 8; >> - } else { >> - nr_regs = 1; >> - arg_size = m->arg_size[i]; >> + is_struct ^= 1; >> } >> - 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 = is_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 is_struct = false; > > Maybe > bool next_same_struct = false > to better characterize what it means? >
agree, will do as suggested bellow.
>> /* 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++) { > > Let us put a comment here so the later users can understand the logic > behind 'is_struct ^= 1'. > > /* 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]; >> + is_struct ^= 1; > > next_same_struct = !next_same_struct; > > The same for above save_regs(). > >> } >> - 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 = is_struct ? j : j + 1; >> } >> } > [...]
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