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authorBrendan Jackman <jackmanb@google.com>2021-01-14 18:17:46 +0000
committerAlexei Starovoitov <ast@kernel.org>2021-01-14 18:34:29 -0800
commit5ca419f2864a2c60940dcf4bbaeb69546200e36f (patch)
treeedd181e67503cb404dfa55cfaae6d757db3e22b6 /arch/x86/net
parentc5bcb5eb4db632280b4123135d583a7bc8caea3e (diff)
downloadlinux-5ca419f2864a2c60940dcf4bbaeb69546200e36f.tar.bz2
bpf: Add BPF_FETCH field / create atomic_fetch_add instruction
The BPF_FETCH field can be set in bpf_insn.imm, for BPF_ATOMIC instructions, in order to have the previous value of the atomically-modified memory location loaded into the src register after an atomic op is carried out. Suggested-by: Yonghong Song <yhs@fb.com> Signed-off-by: Brendan Jackman <jackmanb@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20210114181751.768687-7-jackmanb@google.com
Diffstat (limited to 'arch/x86/net')
-rw-r--r--arch/x86/net/bpf_jit_comp.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b1829a534da1..eea7d8b0bb12 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -811,6 +811,10 @@ static int emit_atomic(u8 **pprog, u8 atomic_op,
/* lock *(u32/u64*)(dst_reg + off) <op>= src_reg */
EMIT1(simple_alu_opcodes[atomic_op]);
break;
+ case BPF_ADD | BPF_FETCH:
+ /* src_reg = atomic_fetch_add(dst_reg + off, src_reg); */
+ EMIT2(0x0F, 0xC1);
+ break;
default:
pr_err("bpf_jit: unknown atomic opcode %02x\n", atomic_op);
return -EFAULT;