Commit 770546ae authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Alexei Starovoitov
Browse files

bpf: implement insn_is_cast_user() helper for JITs 



Implement a helper function to check if an instruction is
addr_space_cast from as(0) to as(1). Use this helper in the x86 JIT.

Other JITs can use this helper when they add support for this instruction.

Signed-off-by: default avatarPuranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20240324183226.29674-1-puranjay12@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent a8497506

arch/x86/net/bpf_jit_comp.c

+1 −2
Original line number Diff line number Diff line
@@ -1351,8 +1351,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image 
			break;



		case BPF_ALU64 | BPF_MOV | BPF_X:

			if (insn->off == BPF_ADDR_SPACE_CAST &&

			    insn->imm == 1U << 16) {

			if (insn_is_cast_user(insn)) {

				if (dst_reg != src_reg)

					/* 32-bit mov */

					emit_mov_reg(&prog, false, dst_reg, src_reg);

include/linux/filter.h

+10 −0
Original line number Diff line number Diff line
@@ -228,6 +228,16 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) 
	return insn->code == (BPF_ALU | BPF_MOV | BPF_X) && insn->imm == 1;

}



/* addr_space_cast from as(0) to as(1) is for converting bpf arena pointers

 * to pointers in user vma.

 */

static inline bool insn_is_cast_user(const struct bpf_insn *insn)

{

	return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) &&

			      insn->off == BPF_ADDR_SPACE_CAST &&

			      insn->imm == 1U << 16;

}



/* BPF_LD_IMM64 macro encodes single 'load 64-bit immediate' insn */

#define BPF_LD_IMM64(DST, IMM)					\

	BPF_LD_IMM64_RAW(DST, 0, IMM)