From: Alexei Starovoitov <ast@fb.com>
Date: Tue, 30 May 2017 13:31:35 -0700
Subject: bpf: take advantage of stack_depth tracking in x64 JIT
Patch-mainline: v4.13-rc1
Git-commit: 2960ae48c4636778761610dd49187691c3774465
References: bsc#1083647

Take advantage of stack_depth tracking in x64 JIT.
Round up allocated stack by 8 bytes to make sure it stays aligned
for functions called from JITed bpf program.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Gary Lin <glin@suse.com>
---
 arch/x86/net/bpf_jit_comp.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -206,7 +206,7 @@ struct jit_context {
 /* emit x64 prologue code for BPF program and check it's size.
  * bpf_tail_call helper will skip it while jumping into another program
  */
-static void emit_prologue(u8 **pprog)
+static void emit_prologue(u8 **pprog, u32 stack_depth)
 {
 	u8 *prog = *pprog;
 	int cnt = 0;
@@ -214,8 +214,9 @@ static void emit_prologue(u8 **pprog)
 	EMIT1(0x55); /* push rbp */
 	EMIT3(0x48, 0x89, 0xE5); /* mov rbp,rsp */
 
-	/* sub rsp, MAX_BPF_STACK + AUX_STACK_SPACE */
-	EMIT3_off32(0x48, 0x81, 0xEC, MAX_BPF_STACK + AUX_STACK_SPACE);
+	/* sub rsp, rounded_stack_depth + AUX_STACK_SPACE */
+	EMIT3_off32(0x48, 0x81, 0xEC,
+		    round_up(stack_depth, 8) + AUX_STACK_SPACE);
 
 	/* sub rbp, AUX_STACK_SPACE */
 	EMIT4(0x48, 0x83, 0xED, AUX_STACK_SPACE);
@@ -363,7 +364,7 @@ static int do_jit(struct bpf_prog *bpf_p
 	int proglen = 0;
 	u8 *prog = temp;
 
-	emit_prologue(&prog);
+	emit_prologue(&prog, bpf_prog->aux->stack_depth);
 
 	if (seen_ld_abs)
 		emit_load_skb_data_hlen(&prog);