From f696b8f471ec987e987e38206b8eb23c39ee5a86 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Tue, 30 May 2017 13:31:28 -0700 Subject: [PATCH] bpf: split bpf core interpreter split __bpf_prog_run() interpreter into stack allocation and execution parts. The code section shrinks which helps interpreter performance in some cases. text data bss dec hex filename 26350 10328 624 37302 91b6 kernel/bpf/core.o.before 25777 10328 624 36729 8f79 kernel/bpf/core.o.after Very short programs got slower (due to extra function call): Before: test_bpf: #89 ALU64_ADD_K: 1 + 2 = 3 jited:0 7 PASS test_bpf: #90 ALU64_ADD_K: 3 + 0 = 3 jited:0 8 PASS test_bpf: #91 ALU64_ADD_K: 1 + 2147483646 = 2147483647 jited:0 7 PASS test_bpf: #92 ALU64_ADD_K: 4294967294 + 2 = 4294967296 jited:0 11 PASS test_bpf: #93 ALU64_ADD_K: 2147483646 + -2147483647 = -1 jited:0 7 PASS After: test_bpf: #89 ALU64_ADD_K: 1 + 2 = 3 jited:0 11 PASS test_bpf: #90 ALU64_ADD_K: 3 + 0 = 3 jited:0 11 PASS test_bpf: #91 ALU64_ADD_K: 1 + 2147483646 = 2147483647 jited:0 11 PASS test_bpf: #92 ALU64_ADD_K: 4294967294 + 2 = 4294967296 jited:0 14 PASS test_bpf: #93 ALU64_ADD_K: 2147483646 + -2147483647 = -1 jited:0 10 PASS Longer programs got faster: Before: test_bpf: #266 BPF_MAXINSNS: Ctx heavy transformations jited:0 20286 20513 PASS test_bpf: #267 BPF_MAXINSNS: Call heavy transformations jited:0 31853 31768 PASS test_bpf: #268 BPF_MAXINSNS: Jump heavy test jited:0 9815 PASS test_bpf: #269 BPF_MAXINSNS: Very long jump backwards jited:0 6 PASS test_bpf: #270 BPF_MAXINSNS: Edge hopping nuthouse jited:0 13959 PASS test_bpf: #271 BPF_MAXINSNS: Jump, gap, jump, ... jited:0 210 PASS test_bpf: #272 BPF_MAXINSNS: ld_abs+get_processor_id jited:0 21724 PASS test_bpf: #273 BPF_MAXINSNS: ld_abs+vlan_push/pop jited:0 19118 PASS After: test_bpf: #266 BPF_MAXINSNS: Ctx heavy transformations jited:0 19008 18827 PASS test_bpf: #267 BPF_MAXINSNS: Call heavy transformations jited:0 29238 28450 PASS test_bpf: #268 BPF_MAXINSNS: Jump heavy test jited:0 9485 PASS test_bpf: #269 BPF_MAXINSNS: Very long jump backwards jited:0 12 PASS test_bpf: #270 BPF_MAXINSNS: Edge hopping nuthouse jited:0 13257 PASS test_bpf: #271 BPF_MAXINSNS: Jump, gap, jump, ... jited:0 213 PASS test_bpf: #272 BPF_MAXINSNS: ld_abs+get_processor_id jited:0 19389 PASS test_bpf: #273 BPF_MAXINSNS: ld_abs+vlan_push/pop jited:0 19583 PASS For real world production programs the difference is noise. This patch is first step towards reducing interpreter stack consumption. Signed-off-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- kernel/bpf/core.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 3392894..abd410d 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -763,10 +763,10 @@ EXPORT_SYMBOL_GPL(__bpf_call_base); * * Decode and execute eBPF instructions. */ -static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn) +static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, + u64 *stack) { - u64 stack[MAX_BPF_STACK / sizeof(u64)]; - u64 regs[MAX_BPF_REG], tmp; + u64 tmp; static const void *jumptable[256] = { [0 ... 255] = &&default_label, /* Now overwrite non-defaults ... */ @@ -874,9 +874,6 @@ static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn) #define CONT ({ insn++; goto select_insn; }) #define CONT_JMP ({ insn++; goto select_insn; }) - FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; - ARG1 = (u64) (unsigned long) ctx; - select_insn: goto *jumptable[insn->code]; @@ -1219,7 +1216,17 @@ load_byte: WARN_RATELIMIT(1, "unknown opcode %02x\n", insn->code); return 0; } -STACK_FRAME_NON_STANDARD(__bpf_prog_run); /* jump table */ +STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */ + +static unsigned int __bpf_prog_run(void *ctx, const struct bpf_insn *insn) +{ + u64 stack[MAX_BPF_STACK / sizeof(u64)]; + u64 regs[MAX_BPF_REG]; + + FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; + ARG1 = (u64) (unsigned long) ctx; + return ___bpf_prog_run(regs, insn, stack); +} bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp) -- 2.7.4