Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 4 Jan 2023 10:24:07 -0800 | Subject | Re: [PATCH bpf-next] bpf, x86: Simplify the parsing logic of structure parameters | From | Yonghong Song <> |
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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?
> > /* 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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