Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorDaniel Borkmann <daniel@iogearbox.net>2019-04-26 21:48:21 +0200
committerAlexei Starovoitov <ast@kernel.org>2019-04-26 18:53:15 -0700
commit8968c67a82ab7501bc3b9439c3624a49b42fe54c (patch)
treeb377d4184b0c45b275e6548e163961ece6443539
parent0c0cad2c2824ac38106ad0649263eca30954beb6 (diff)
bpf, arm64: remove prefetch insn in xadd mapping
Prefetch-with-intent-to-write is currently part of the XADD mapping in the AArch64 JIT and follows the kernel's implementation of atomic_add. This may interfere with other threads executing the LDXR/STXR loop, leading to potential starvation and fairness issues. Drop the optional prefetch instruction. Fixes: 85f68fe89832 ("bpf, arm64: implement jiting of BPF_XADD") Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
-rw-r--r--arch/arm64/net/bpf_jit.h6
-rw-r--r--arch/arm64/net/bpf_jit_comp.c1
2 files changed, 0 insertions, 7 deletions
diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h
index 783de51a6c4e..6c881659ee8a 100644
--- a/arch/arm64/net/bpf_jit.h
+++ b/arch/arm64/net/bpf_jit.h
@@ -100,12 +100,6 @@
#define A64_STXR(sf, Rt, Rn, Rs) \
A64_LSX(sf, Rt, Rn, Rs, STORE_EX)
-/* Prefetch */
-#define A64_PRFM(Rn, type, target, policy) \
- aarch64_insn_gen_prefetch(Rn, AARCH64_INSN_PRFM_TYPE_##type, \
- AARCH64_INSN_PRFM_TARGET_##target, \
- AARCH64_INSN_PRFM_POLICY_##policy)
-
/* Add/subtract (immediate) */
#define A64_ADDSUB_IMM(sf, Rd, Rn, imm12, type) \
aarch64_insn_gen_add_sub_imm(Rd, Rn, imm12, \
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index aaddc0217e73..a1420626fca2 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -762,7 +762,6 @@ emit_cond_jmp:
case BPF_STX | BPF_XADD | BPF_DW:
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
- emit(A64_PRFM(tmp, PST, L1, STRM), ctx);
emit(A64_LDXR(isdw, tmp2, tmp), ctx);
emit(A64_ADD(isdw, tmp2, tmp2, src), ctx);
emit(A64_STXR(isdw, tmp2, tmp, tmp3), ctx);