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Date: Wed, 2 Jul 2014 16:35:23 -0700 From: Chema Gonzalez <chema@...gle.com> To: Alexei Starovoitov <ast@...mgrid.com> Cc: "David S. Miller" <davem@...emloft.net>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Daniel Borkmann <dborkman@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Arnaldo Carvalho de Melo <acme@...radead.org>, Jiri Olsa <jolsa@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Linux API <linux-api@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH RFC net-next 08/14] bpf: add eBPF verifier On Wed, Jul 2, 2014 at 4:04 PM, Alexei Starovoitov <ast@...mgrid.com> wrote: >>> + reg = regs + BPF_REG_1; /* 1st arg to a function */ >>> + reg->ptr = PTR_TO_CTX; >> Wait, doesn't this depend on doing "BPF_MOV64_REG(BPF_REG_CTX, >> BPF_REG_ARG1)" (the bpf-to-ebpf prologue), which is only enforced on >> filters converted from bpf? In fact, shouldn't this set >> regs[BPF_REG_CTX] instead of regs[BPF_REG_1] ? > > nope. it's REG_1. > as you said r6=r1 is only emitted by converted classic filters. > Verifier will see this 'r6=r1' assignment and will copy the r1 type into r6. You're right. I read BPF_MOV64_REG() AT&T-syntax-style. BTW, check_stack_write() in kernel/bpf/verifier.c has a couple of assignments of a slot->ptr to 0 (instead of INVALID_PTR). I assume this is unintended. -Chema -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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