diff options
| author | Brendan Jackman <jackmanb@google.com> | 2021-01-14 18:17:44 +0000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-01-14 18:34:29 -0800 |
| commit | 91c960b0056672e74627776655c926388350fa30 (patch) | |
| tree | b15d68c17ead28b128791f8e710d9efa2a711267 /arch/x86/net | |
| parent | e5f02caccfae94f5baf6ec6dbb57ce8a7e9a40e7 (diff) | |
| download | linux-91c960b0056672e74627776655c926388350fa30.tar.bz2 | |
bpf: Rename BPF_XADD and prepare to encode other atomics in .imm
A subsequent patch will add additional atomic operations. These new
operations will use the same opcode field as the existing XADD, with
the immediate discriminating different operations.
In preparation, rename the instruction mode BPF_ATOMIC and start
calling the zero immediate BPF_ADD.
This is possible (doesn't break existing valid BPF progs) because the
immediate field is currently reserved MBZ and BPF_ADD is zero.
All uses are removed from the tree but the BPF_XADD definition is
kept around to avoid breaking builds for people including kernel
headers.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-5-jackmanb@google.com
Diffstat (limited to 'arch/x86/net')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 46 | ||||
| -rw-r--r-- | arch/x86/net/bpf_jit_comp32.c | 6 |
2 files changed, 36 insertions, 16 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 93f32e0ba0ef..b1829a534da1 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -795,6 +795,33 @@ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off) *pprog = prog; } +static int emit_atomic(u8 **pprog, u8 atomic_op, + u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size) +{ + u8 *prog = *pprog; + int cnt = 0; + + EMIT1(0xF0); /* lock prefix */ + + maybe_emit_mod(&prog, dst_reg, src_reg, bpf_size == BPF_DW); + + /* emit opcode */ + switch (atomic_op) { + case BPF_ADD: + /* lock *(u32/u64*)(dst_reg + off) <op>= src_reg */ + EMIT1(simple_alu_opcodes[atomic_op]); + break; + default: + pr_err("bpf_jit: unknown atomic opcode %02x\n", atomic_op); + return -EFAULT; + } + + emit_insn_suffix(&prog, dst_reg, src_reg, off); + + *pprog = prog; + return 0; +} + static bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs, int trapnr, unsigned long error_code, unsigned long fault_addr) @@ -839,6 +866,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, int i, cnt = 0, excnt = 0; int proglen = 0; u8 *prog = temp; + int err; detect_reg_usage(insn, insn_cnt, callee_regs_used, &tail_call_seen); @@ -1250,18 +1278,12 @@ st: if (is_imm8(insn->off)) } break; - /* STX XADD: lock *(u32*)(dst_reg + off) += src_reg */ - case BPF_STX | BPF_XADD | BPF_W: - /* Emit 'lock add dword ptr [rax + off], eax' */ - if (is_ereg(dst_reg) || is_ereg(src_reg)) - EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01); - else - EMIT2(0xF0, 0x01); - goto xadd; - case BPF_STX | BPF_XADD | BPF_DW: - EMIT3(0xF0, add_2mod(0x48, dst_reg, src_reg), 0x01); -xadd: - emit_modrm_dstoff(&prog, dst_reg, src_reg, insn->off); + case BPF_STX | BPF_ATOMIC | BPF_W: + case BPF_STX | BPF_ATOMIC | BPF_DW: + err = emit_atomic(&prog, insn->imm, dst_reg, src_reg, + insn->off, BPF_SIZE(insn->code)); + if (err) + return err; break; /* call */ diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 96fde03aa987..d17b67c69f89 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -2243,10 +2243,8 @@ emit_jmp: return -EFAULT; } break; - /* STX XADD: lock *(u32 *)(dst + off) += src */ - case BPF_STX | BPF_XADD | BPF_W: - /* STX XADD: lock *(u64 *)(dst + off) += src */ - case BPF_STX | BPF_XADD | BPF_DW: + case BPF_STX | BPF_ATOMIC | BPF_W: + case BPF_STX | BPF_ATOMIC | BPF_DW: goto notyet; case BPF_JMP | BPF_EXIT: if (seen_exit) { |