[PATCH v2 bpf-next 03/13] bpf: x86: Factor out function to emit NEG

[Brendan Jackman]

There's currently only one usage of this but implementation of
atomic_sub add another.

Signed-off-by: Brendan Jackman <jackm...@google.com>
---
 arch/x86/net/bpf_jit_comp.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index a839c1a54276..49dea0c1a130 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -783,6 +783,22 @@ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, 
u32 src_reg, int off)
        *pprog = prog;
 }
 
+
+static void emit_neg(u8 **pprog, u32 reg, bool is64)
+{
+       u8 *prog = *pprog;
+       int cnt = 0;
+
+       /* Emit REX byte if necessary */
+       if (is64)
+               EMIT1(add_1mod(0x48, reg));
+       else if (is_ereg(reg))
+               EMIT1(add_1mod(0x40, reg));
+
+       EMIT2(0xF7, add_1reg(0xD8, reg)); /* x86 NEG */
+       *pprog = prog;
+}
+
 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)
@@ -884,11 +900,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, 
u8 *image,
                        /* neg dst */
                case BPF_ALU | BPF_NEG:
                case BPF_ALU64 | BPF_NEG:
-                       if (BPF_CLASS(insn->code) == BPF_ALU64)
-                               EMIT1(add_1mod(0x48, dst_reg));
-                       else if (is_ereg(dst_reg))
-                               EMIT1(add_1mod(0x40, dst_reg));
-                       EMIT2(0xF7, add_1reg(0xD8, dst_reg));
+                       emit_neg(&prog, dst_reg,
+                                BPF_CLASS(insn->code) == BPF_ALU64);
                        break;
 
                case BPF_ALU | BPF_ADD | BPF_K:
-- 
2.29.2.454.gaff20da3a2-goog