From: Alexei Starovoitov <ast@kernel.org>
To: <davem@davemloft.net>
Cc: <daniel@iogearbox.net>, <x86@kernel.org>,
<netdev@vger.kernel.org>, <bpf@vger.kernel.org>,
<kernel-team@fb.com>
Subject: [PATCH v4 bpf-next 13/20] bpf: Reserve space for BPF trampoline in BPF programs
Date: Thu, 14 Nov 2019 10:57:13 -0800 [thread overview]
Message-ID: <20191114185720.1641606-14-ast@kernel.org> (raw)
In-Reply-To: <20191114185720.1641606-1-ast@kernel.org>
BPF trampoline can be made to work with existing 5 bytes of BPF program
prologue, but let's add 5 bytes of NOPs to the beginning of every JITed BPF
program to make BPF trampoline job easier. They can be removed in the future.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
arch/x86/net/bpf_jit_comp.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index be2b43a894f6..c06096df9118 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -206,7 +206,7 @@ struct jit_context {
/* number of bytes emit_call() needs to generate call instruction */
#define X86_CALL_SIZE 5
-#define PROLOGUE_SIZE 20
+#define PROLOGUE_SIZE 25
/*
* Emit x86-64 prologue code for BPF program and check its size.
@@ -215,8 +215,13 @@ struct jit_context {
static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
{
u8 *prog = *pprog;
- int cnt = 0;
+ int cnt = X86_CALL_SIZE;
+ /* BPF trampoline can be made to work without these nops,
+ * but let's waste 5 bytes for now and optimize later
+ */
+ memcpy(prog, ideal_nops[NOP_ATOMIC5], cnt);
+ prog += cnt;
EMIT1(0x55); /* push rbp */
EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
/* sub rsp, rounded_stack_depth */
--
2.23.0
next prev parent reply other threads:[~2019-11-14 18:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 18:57 [PATCH v4 bpf-next 00/20] Introduce BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 01/20] x86/alternatives: Teach text_poke_bp() to emulate instructions Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 02/20] bpf: refactor x86 JIT into helpers Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 03/20] bpf: Add bpf_arch_text_poke() helper Alexei Starovoitov
2019-11-15 22:18 ` Andrii Nakryiko
2019-11-14 18:57 ` [PATCH v4 bpf-next 04/20] bpf: Introduce BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 05/20] libbpf: Introduce btf__find_by_name_kind() Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 06/20] libbpf: Add support to attach to fentry/fexit tracing progs Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 07/20] selftest/bpf: Simple test for fentry/fexit Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 08/20] bpf: Add kernel test functions for fentry testing Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 09/20] selftests/bpf: Add test for BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 10/20] selftests/bpf: Add fexit tests " Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 11/20] selftests/bpf: Add combined fentry/fexit test Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 12/20] selftests/bpf: Add stress test for maximum number of progs Alexei Starovoitov
2019-11-14 18:57 ` Alexei Starovoitov [this message]
2019-11-14 18:57 ` [PATCH v4 bpf-next 14/20] bpf: Fix race in btf_resolve_helper_id() Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 15/20] bpf: Annotate context types Alexei Starovoitov
2019-11-14 22:55 ` Song Liu
2019-11-14 23:01 ` Alexei Starovoitov
2019-11-14 23:19 ` Song Liu
2019-11-14 23:23 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 16/20] bpf: Compare BTF types of functions arguments with actual types Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 17/20] bpf: Support attaching tracing BPF program to other BPF programs Alexei Starovoitov
2019-11-14 23:30 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 18/20] libbpf: Add support for attaching BPF programs " Alexei Starovoitov
2019-11-14 23:39 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 19/20] selftests/bpf: Extend test_pkt_access test Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 20/20] selftests/bpf: Add a test for attaching BPF prog to another BPF prog and subprog Alexei Starovoitov
2019-11-16 0:01 ` [PATCH v4 bpf-next 00/20] Introduce BPF trampoline Daniel Borkmann
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