This is a note to let you know that I've just added the patch titled
x86: bpf_jit: small optimization in emit_bpf_tail_call()
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-bpf_jit-small-optimization-in-emit_bpf_tail_call.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Mon Jan 29 13:22:08 CET 2018
From: Daniel Borkmann daniel@iogearbox.net Date: Mon, 29 Jan 2018 02:48:54 +0100 Subject: x86: bpf_jit: small optimization in emit_bpf_tail_call() To: gregkh@linuxfoundation.org Cc: ast@kernel.org, stable@vger.kernel.org, Eric Dumazet edumazet@google.com, Daniel Borkmann daniel@iogearbox.net, "David S . Miller" davem@davemloft.net Message-ID: 0f909080f2ef055783fc7b394e8111e0df3c4971.1517190206.git.daniel@iogearbox.net
From: Eric Dumazet edumazet@google.com
[ upstream commit 84ccac6e7854ebbfb56d2fc6d5bef9be49bb304c ]
Saves 4 bytes replacing following instructions :
lea rax, [rsi + rdx * 8 + offsetof(...)] mov rax, qword ptr [rax] cmp rax, 0
by :
mov rax, [rsi + rdx * 8 + offsetof(...)] test rax, rax
Signed-off-by: Eric Dumazet edumazet@google.com Cc: Alexei Starovoitov ast@kernel.org Cc: Daniel Borkmann daniel@iogearbox.net Acked-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Alexei Starovoitov ast@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/net/bpf_jit_comp.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -281,7 +281,7 @@ static void emit_bpf_tail_call(u8 **ppro EMIT4(0x48, 0x8B, 0x46, /* mov rax, qword ptr [rsi + 16] */ offsetof(struct bpf_array, map.max_entries)); EMIT3(0x48, 0x39, 0xD0); /* cmp rax, rdx */ -#define OFFSET1 47 /* number of bytes to jump */ +#define OFFSET1 43 /* number of bytes to jump */ EMIT2(X86_JBE, OFFSET1); /* jbe out */ label1 = cnt;
@@ -290,21 +290,20 @@ static void emit_bpf_tail_call(u8 **ppro */ EMIT2_off32(0x8B, 0x85, -STACKSIZE + 36); /* mov eax, dword ptr [rbp - 516] */ EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */ -#define OFFSET2 36 +#define OFFSET2 32 EMIT2(X86_JA, OFFSET2); /* ja out */ label2 = cnt; EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */ EMIT2_off32(0x89, 0x85, -STACKSIZE + 36); /* mov dword ptr [rbp - 516], eax */
/* prog = array->ptrs[index]; */ - EMIT4_off32(0x48, 0x8D, 0x84, 0xD6, /* lea rax, [rsi + rdx * 8 + offsetof(...)] */ + EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */ offsetof(struct bpf_array, ptrs)); - EMIT3(0x48, 0x8B, 0x00); /* mov rax, qword ptr [rax] */
/* if (prog == NULL) * goto out; */ - EMIT4(0x48, 0x83, 0xF8, 0x00); /* cmp rax, 0 */ + EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */ #define OFFSET3 10 EMIT2(X86_JE, OFFSET3); /* je out */ label3 = cnt;
Patches currently in stable-queue which might be from daniel@iogearbox.net are
queue-4.9/bpf-avoid-false-sharing-of-map-refcount-with-max_entries.patch queue-4.9/x86-bpf_jit-small-optimization-in-emit_bpf_tail_call.patch queue-4.9/bpf-reject-stores-into-ctx-via-st-and-xadd.patch queue-4.9/bpf-fix-32-bit-divide-by-zero.patch queue-4.9/bpf-fix-bpf_tail_call-x64-jit.patch queue-4.9/bpf-arsh-is-not-supported-in-32-bit-alu-thus-reject-it.patch queue-4.9/bpf-fix-divides-by-zero.patch queue-4.9/bpf-introduce-bpf_jit_always_on-config.patch