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Message-Id: <20240323154652.54572-3-puranjay12@gmail.com>
Date: Sat, 23 Mar 2024 15:46:52 +0000
From: Puranjay Mohan <puranjay12@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Björn Töpel <bjorn@...nel.org>,
Luke Nelson <luke.r.nels@...il.com>,
Xi Wang <xi.wang@...il.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
bpf@...r.kernel.org,
linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org
Cc: puranjay12@...il.com
Subject: [PATCH bpf-next 2/2] bpf,riscv: Implement bpf_addr_space_cast instruction
LLVM generates bpf_addr_space_cast instruction while translating
pointers between native (zero) address space and
__attribute__((address_space(N))). The addr_space=0 is reserved as
bpf_arena address space.
rY = addr_space_cast(rX, 0, 1) is processed by the verifier and
converted to normal 32-bit move: wX = wY
rY = addr_space_cast(rX, 1, 0) has to be converted by JIT:
Here I explain using symbolic language what the JIT is supposed to do:
We have:
src = [src_upper32][src_lower32] // 64 bit src kernel pointer
uvm = [uvm_upper32][uvm_lower32] // 64 bit user_vm_start
The JIT has to make the dst reg like following
dst = [uvm_upper32][src_lower32] // if src_lower32 != 0
dst = [00000000000][00000000000] // if src_lower32 == 0
Signed-off-by: Puranjay Mohan <puranjay12@...il.com>
---
arch/riscv/net/bpf_jit.h | 1 +
arch/riscv/net/bpf_jit_comp64.c | 15 +++++++++++++++
arch/riscv/net/bpf_jit_core.c | 1 +
3 files changed, 17 insertions(+)
diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
index 8a47da08dd9c..5fc374ed98ea 100644
--- a/arch/riscv/net/bpf_jit.h
+++ b/arch/riscv/net/bpf_jit.h
@@ -82,6 +82,7 @@ struct rv_jit_context {
unsigned long flags;
int stack_size;
u64 arena_vm_start;
+ u64 user_vm_start;
};
/* Convert from ninsns to bytes. */
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index f51b832eafb6..3c389e75cb96 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1083,6 +1083,16 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
/* dst = src */
case BPF_ALU | BPF_MOV | BPF_X:
case BPF_ALU64 | BPF_MOV | BPF_X:
+ if (BPF_CLASS(insn->code) == BPF_ALU64 && insn->off == BPF_ADDR_SPACE_CAST &&
+ insn->imm == 1U << 16) {
+ emit_mv(RV_REG_T1, rs, ctx);
+ emit_zextw(RV_REG_T1, RV_REG_T1, ctx);
+ emit_imm(rd, (ctx->user_vm_start >> 32) << 32, ctx);
+ emit(rv_beq(RV_REG_T1, RV_REG_ZERO, 4), ctx);
+ emit_or(RV_REG_T1, rd, RV_REG_T1, ctx);
+ emit_mv(rd, RV_REG_T1, ctx);
+ break;
+ }
if (imm == 1) {
/* Special mov32 for zext */
emit_zextw(rd, rd, ctx);
@@ -2010,3 +2020,8 @@ bool bpf_jit_supports_ptr_xchg(void)
{
return true;
}
+
+bool bpf_jit_supports_arena(void)
+{
+ return true;
+}
diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index 9b6696b1290a..aaef1d0c7c46 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -82,6 +82,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
}
ctx->arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena);
+ ctx->user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena);
ctx->prog = prog;
ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
if (!ctx->offset) {
--
2.40.1
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