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authorDaniel Borkmann <daniel@iogearbox.net>2017-06-07 13:45:37 +0200
committerDavid S. Miller <davem@davemloft.net>2017-06-07 15:27:20 -0400
commit7005cade1bdbb423413f8aafcbf17a1ec614a585 (patch)
tree77db17f9c82e93e483ff877ae2df8ef0fed79bcc /arch/arm64/net/bpf_jit_comp.c
parentnet: mvpp2: do not bypass the mvpp22_port_mii_set function (diff)
downloadlinux-dev-7005cade1bdbb423413f8aafcbf17a1ec614a585.tar.xz
linux-dev-7005cade1bdbb423413f8aafcbf17a1ec614a585.zip
bpf, arm64: use separate register for state in stxr
Will reported that in BPF_XADD we must use a different register in stxr instruction for the status flag due to otherwise CONSTRAINED UNPREDICTABLE behavior per architecture. Reference manual says [1]: If s == t, then one of the following behaviors must occur: * The instruction is UNDEFINED. * The instruction executes as a NOP. * The instruction performs the store to the specified address, but the value stored is UNKNOWN. Thus, use a different temporary register for the status flag to fix it. Disassembly extract from test 226/STX_XADD_DW from test_bpf.ko: [...] 0000003c: c85f7d4b ldxr x11, [x10] 00000040: 8b07016b add x11, x11, x7 00000044: c80c7d4b stxr w12, x11, [x10] 00000048: 35ffffac cbnz w12, 0x0000003c [...] [1] https://static.docs.arm.com/ddi0487/b/DDI0487B_a_armv8_arm.pdf, p.6132 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: Will Deacon <will.deacon@arm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
-rw-r--r--arch/arm64/net/bpf_jit_comp.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 71f930501ade..c870d6f01ac2 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -36,6 +36,7 @@ int bpf_jit_enable __read_mostly;
#define TMP_REG_1 (MAX_BPF_JIT_REG + 0)
#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)
#define TCALL_CNT (MAX_BPF_JIT_REG + 2)
+#define TMP_REG_3 (MAX_BPF_JIT_REG + 3)
/* Map BPF registers to A64 registers */
static const int bpf2a64[] = {
@@ -57,6 +58,7 @@ static const int bpf2a64[] = {
/* temporary registers for internal BPF JIT */
[TMP_REG_1] = A64_R(10),
[TMP_REG_2] = A64_R(11),
+ [TMP_REG_3] = A64_R(12),
/* tail_call_cnt */
[TCALL_CNT] = A64_R(26),
/* temporary register for blinding constants */
@@ -319,6 +321,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
+ const u8 tmp3 = bpf2a64[TMP_REG_3];
const s16 off = insn->off;
const s32 imm = insn->imm;
const int i = insn - ctx->prog->insnsi;
@@ -689,10 +692,10 @@ emit_cond_jmp:
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, tmp2), ctx);
+ emit(A64_STXR(isdw, tmp2, tmp, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
- emit(A64_CBNZ(0, tmp2, jmp_offset), ctx);
+ emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
break;
/* R0 = ntohx(*(size *)(((struct sk_buff *)R6)->data + imm)) */