diff options
| author | Alexei Starovoitov <[email protected]> | 2019-11-14 10:57:13 -0800 |
|---|---|---|
| committer | Daniel Borkmann <[email protected]> | 2019-11-15 23:44:06 +0100 |
| commit | 9fd4a39dc7fe734d26eb89ea97e8c91331c6378c (patch) | |
| tree | 5783728bdca357b04e48d656d84eb07b1624a4a8 | |
| parent | e76d776e9ca1fe266b3a7f8091eee5d1e635a545 (diff) | |
bpf: Reserve space for BPF trampoline in BPF programs
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 <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Acked-by: Song Liu <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 9 |
1 files 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 */ |