Commit 02a6dfa8 authored by Menglong Dong's avatar Menglong Dong Committed by Alexei Starovoitov
Browse files

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: default avatarMenglong Dong <imagedong@tencent.com>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230713040738.1789742-2-imagedong@tencent.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 0a5550b1

arch/x86/net/bpf_jit_comp.c

+6 −29
Original line number Diff line number Diff line
@@ -1860,57 +1860,34 @@ st: if (is_imm8(insn->off)) 
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,