2024-03-24 18:32:45

by Puranjay Mohan

Subject: [PATCH bpf-next] 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: Puranjay Mohan <[email protected]>
---
arch/x86/net/bpf_jit_comp.c | 3 +--
include/linux/filter.h | 10 ++++++++++
2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 9b3136187938..98349d11fae2 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1350,8 +1350,7 @@ 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);
diff --git a/include/linux/filter.h b/include/linux/filter.h
index cf12bfa2a78c..42dbceb04ca6 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -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)
--
2.40.1

2024-03-25 17:35:47

by patchwork-bot+netdevbpf

Subject: Re: [PATCH bpf-next] bpf: implement insn_is_cast_user() helper for JITs

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <[email protected]>:

On Sun, 24 Mar 2024 18:32:26 +0000 you wrote:
> 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 <[email protected]>
>
> [...]

Here is the summary with links:
- [bpf-next] bpf: implement insn_is_cast_user() helper for JITs
https://git.kernel.org/bpf/bpf-next/c/770546ae9f4c

You are awesome, thank you!
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