From 769e0de6475e5512f88bfb4dbf6d6323fd23514f Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Sat, 29 Nov 2014 14:46:13 -0800 Subject: [PATCH] bpf: x86: fix epilogue generation for eBPF programs classic BPF has a restriction that last insn is always BPF_RET. eBPF doesn't have BPF_RET instruction and this restriction. It has BPF_EXIT insn which can appear anywhere in the program one or more times and it doesn't have to be last insn. Fix eBPF JIT to emit epilogue when first BPF_EXIT is seen and all other BPF_EXIT instructions will be emitted as jump. Since jump offset to epilogue is computed as: jmp_offset = ctx->cleanup_addr - addrs[i] we need to change type of cleanup_addr to signed to compute the offset as: (long long) ((int)20 - (int)30) instead of: (long long) ((unsigned int)20 - (int)30) Fixes: 622582786c9e ("net: filter: x86: internal BPF JIT") Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller --- arch/x86/net/bpf_jit_comp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 3f627345d51c..7e90244c84e3 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -178,7 +178,7 @@ static void jit_fill_hole(void *area, unsigned int size) } struct jit_context { - unsigned int cleanup_addr; /* epilogue code offset */ + int cleanup_addr; /* epilogue code offset */ bool seen_ld_abs; }; @@ -192,6 +192,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, struct bpf_insn *insn = bpf_prog->insnsi; int insn_cnt = bpf_prog->len; bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0); + bool seen_exit = false; u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY]; int i; int proglen = 0; @@ -854,10 +855,11 @@ common_load: goto common_load; case BPF_JMP | BPF_EXIT: - if (i != insn_cnt - 1) { + if (seen_exit) { jmp_offset = ctx->cleanup_addr - addrs[i]; goto emit_jmp; } + seen_exit = true; /* update cleanup_addr */ ctx->cleanup_addr = proglen; /* mov rbx, qword ptr [rbp-X] */ -- 2.20.1