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 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
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-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Feb 1 09:05:44 CET 2018
From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Date: Tue, 30 Jan 2018 03:37:39 +0100
Subject: x86: bpf_jit: small optimization in emit_bpf_tail_call()
To: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: ast@xxxxxxxxxx, daniel@xxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx, Eric Dumazet <edumazet@xxxxxxxxxx>, "David S . Miller" <davem@xxxxxxxxxxxxx>
Message-ID: <e0ee628ad21177055e3bad4cea8995f7d66b11c0.1517279268.git.daniel@xxxxxxxxxxxxx>
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -269,7 +269,7 @@ 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;
@@ -278,21 +278,20 @@ 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@xxxxxxxxxxxxx are
queue-4.4/bpf-fix-branch-pruning-logic.patch
queue-4.4/bpf-avoid-false-sharing-of-map-refcount-with-max_entries.patch
queue-4.4/x86-bpf_jit-small-optimization-in-emit_bpf_tail_call.patch
queue-4.4/bpf-reject-stores-into-ctx-via-st-and-xadd.patch
queue-4.4/bpf-fix-32-bit-divide-by-zero.patch
queue-4.4/bpf-fix-bpf_tail_call-x64-jit.patch
queue-4.4/bpf-arsh-is-not-supported-in-32-bit-alu-thus-reject-it.patch
queue-4.4/bpf-fix-divides-by-zero.patch
queue-4.4/bpf-introduce-bpf_jit_always_on-config.patch