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Commit 2960ae48 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: take advantage of stack_depth tracking in x64 JIT 



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: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 177366bf

arch/x86/net/bpf_jit_comp.c

+5 −4
Original line number Diff line number Diff line
@@ -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_prog, int *addrs, u8 *image, 
	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);