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bpf: implement insn_is_cast_user() helper for JITs

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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: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20240324183226.29674-1-puranjay12@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2024-03-24 18:32:26 +00:00 committed by Alexei Starovoitov
parent a8497506cd
commit 770546ae9f
2 changed files with 11 additions and 2 deletions
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3
arch/x86/net/bpf_jit_comp.c
View File

@ -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);

10
include/linux/filter.h
View File

@ -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)