diff options
| author | Alexei Starovoitov <ast@fb.com> | 2017-05-30 13:31:34 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-05-31 19:29:48 -0400 |
| commit | 177366bf7ceb35860281a6ebe824e42bf96fd95d (patch) | |
| tree | d8cb564978e0f74b91e0a297e98976c2b3af79ba /arch/x86/net/bpf_jit.S | |
| parent | b870aa901f4be1d32c13faf9e8f40bf2a8562e19 (diff) | |
| download | linux-177366bf7ceb35860281a6ebe824e42bf96fd95d.tar.bz2 | |
bpf: change x86 JITed program stack layout
in order to JIT programs with different stack sizes we need to
make epilogue and exception path to be stack size independent,
hence move auxiliary stack space from the bottom of the stack
to the top of the stack.
Nice side effect is that JITed function prologue becomes shorter
due to imm8 offset encoding vs imm32.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/x86/net/bpf_jit.S')
| -rw-r--r-- | arch/x86/net/bpf_jit.S | 20 |
1 files changed, 9 insertions, 11 deletions
diff --git a/arch/x86/net/bpf_jit.S b/arch/x86/net/bpf_jit.S index f2a7faf4706e..b33093f84528 100644 --- a/arch/x86/net/bpf_jit.S +++ b/arch/x86/net/bpf_jit.S @@ -19,9 +19,6 @@ */ #define SKBDATA %r10 #define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */ -#define MAX_BPF_STACK (512 /* from filter.h */ + \ - 32 /* space for rbx,r13,r14,r15 */ + \ - 8 /* space for skb_copy_bits */) #define FUNC(name) \ .globl name; \ @@ -66,7 +63,7 @@ FUNC(sk_load_byte_positive_offset) /* rsi contains offset and can be scratched */ #define bpf_slow_path_common(LEN) \ - lea -MAX_BPF_STACK + 32(%rbp), %rdx;\ + lea 32(%rbp), %rdx;\ FRAME_BEGIN; \ mov %rbx, %rdi; /* arg1 == skb */ \ push %r9; \ @@ -83,14 +80,14 @@ FUNC(sk_load_byte_positive_offset) bpf_slow_path_word: bpf_slow_path_common(4) js bpf_error - mov - MAX_BPF_STACK + 32(%rbp),%eax + mov 32(%rbp),%eax bswap %eax ret bpf_slow_path_half: bpf_slow_path_common(2) js bpf_error - mov - MAX_BPF_STACK + 32(%rbp),%ax + mov 32(%rbp),%ax rol $8,%ax movzwl %ax,%eax ret @@ -98,7 +95,7 @@ bpf_slow_path_half: bpf_slow_path_byte: bpf_slow_path_common(1) js bpf_error - movzbl - MAX_BPF_STACK + 32(%rbp),%eax + movzbl 32(%rbp),%eax ret #define sk_negative_common(SIZE) \ @@ -148,9 +145,10 @@ FUNC(sk_load_byte_negative_offset) bpf_error: # force a return 0 from jit handler xor %eax,%eax - mov - MAX_BPF_STACK(%rbp),%rbx - mov - MAX_BPF_STACK + 8(%rbp),%r13 - mov - MAX_BPF_STACK + 16(%rbp),%r14 - mov - MAX_BPF_STACK + 24(%rbp),%r15 + mov (%rbp),%rbx + mov 8(%rbp),%r13 + mov 16(%rbp),%r14 + mov 24(%rbp),%r15 + add $40, %rbp leaveq ret |