bpf, x86: save/restore regs with BPF_DW size

As we already reserve 8 byte in the stack for each reg, it is ok to
store/restore the regs in BPF_DW size. This will make the code in
save_regs()/restore_regs() simpler.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230713040738.1789742-2-imagedong@tencent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 438adb6..fcbd3b7 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1860,57 +1860,34 @@ emit_jmp:
 static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_regs,
                      int stack_size)
 {
-       int i, j, arg_size;
-       bool next_same_struct = false;
+       int i;
 
        /* 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_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;
-                       next_same_struct = !next_same_struct;
-               }
-
-               emit_stx(prog, bytes_to_bpf_size(arg_size),
-                        BPF_REG_FP,
+       for (i = 0; i < min(nr_regs, 6); i++)
+               emit_stx(prog, BPF_DW, 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_regs,
                         int stack_size)
 {
-       int i, j, arg_size;
-       bool next_same_struct = false;
+       int i;
 
        /* 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_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;
-                       next_same_struct = !next_same_struct;
-               }
-
-               emit_ldx(prog, bytes_to_bpf_size(arg_size),
+       for (i = 0; i < min(nr_regs, 6); i++)
+               emit_ldx(prog, BPF_DW,
                         i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
                         BPF_REG_FP,
                         -(stack_size - i * 8));
-
-               j = next_same_struct ? j : j + 1;
-       }
 }
 
 static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,