From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Song Liu <songliubraving@fb.com>, Kairui Song <kasong@redhat.com>
Subject: Re: [PATCH 7/9] x86/unwind/orc: Fall back to using frame pointers for generated code
Date: Fri, 14 Jun 2019 08:34:48 -0500 [thread overview]
Message-ID: <20190614133004.gopjz64vbqmbbzqn@treble> (raw)
In-Reply-To: <20190614060006.na6nfl6shawsyj3i@ast-mbp.dhcp.thefacebook.com>
On Thu, Jun 13, 2019 at 11:00:09PM -0700, Alexei Starovoitov wrote:
> > + if (src_reg == BPF_REG_FP) {
> > + /*
> > + * If the value was copied from RBP (real frame pointer),
> > + * adjust it to the BPF program's frame pointer value.
> > + *
> > + * add dst, -40
> > + */
> > + EMIT4(add_1mod(0x48, dst_reg), 0x83, add_1reg(0xC0, dst_reg),
> > + 0xD8);
> > + }
> > +
>
> That won't work. Any register can point to a stack.
Right, but if the stack pointer comes from BPF_REG_FP then won't the
above correct it? Then if the pointer gets passed around to other
registers it will have the correct value. Or did I miss your point?
> The register can point to a stack of a different JITed function as well.
Do you mean tail calls? Or something else? For tail calls the stack is
shared and the stack layout is the same.
--
Josh
next prev parent reply other threads:[~2019-06-14 13:34 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 13:20 [PATCH 0/9] x86/bpf: unwinder fixes Josh Poimboeuf
2019-06-13 13:20 ` [PATCH 1/9] perf/x86: Always store regs->ip in perf_callchain_kernel() Josh Poimboeuf
2019-06-13 13:20 ` [PATCH 2/9] objtool: Fix ORC unwinding in non-JIT BPF generated code Josh Poimboeuf
2019-06-13 20:57 ` Alexei Starovoitov
2019-06-14 1:20 ` Josh Poimboeuf
2019-06-14 1:37 ` Alexei Starovoitov
2019-06-14 1:51 ` Josh Poimboeuf
2019-06-14 7:08 ` Peter Zijlstra
2019-06-14 7:35 ` Alexei Starovoitov
2019-06-14 8:11 ` Peter Zijlstra
2019-06-14 15:13 ` Alexei Starovoitov
2019-06-14 16:11 ` Josh Poimboeuf
2019-06-13 13:21 ` [PATCH 3/9] x86/bpf: Move epilogue generation to a dedicated function Josh Poimboeuf
2019-06-13 18:57 ` Song Liu
2019-06-13 19:12 ` Josh Poimboeuf
2019-06-13 13:21 ` [PATCH 4/9] x86/bpf: Simplify prologue generation Josh Poimboeuf
2019-06-13 13:21 ` [PATCH 5/9] x86/bpf: Support SIB byte generation Josh Poimboeuf
2019-06-13 13:21 ` [PATCH 6/9] x86/bpf: Fix JIT frame pointer usage Josh Poimboeuf
2019-06-13 21:58 ` Alexei Starovoitov
2019-06-14 1:22 ` Josh Poimboeuf
2019-06-14 1:39 ` Alexei Starovoitov
2019-06-14 1:52 ` Josh Poimboeuf
2019-06-14 10:50 ` David Laight
2019-06-14 13:44 ` Josh Poimboeuf
2019-06-14 13:58 ` David Laight
2019-06-14 17:07 ` Josh Poimboeuf
2019-06-17 15:07 ` David Laight
2019-06-13 13:21 ` [PATCH 7/9] x86/unwind/orc: Fall back to using frame pointers for generated code Josh Poimboeuf
2019-06-13 22:00 ` Alexei Starovoitov
2019-06-14 1:30 ` Josh Poimboeuf
2019-06-14 1:42 ` Alexei Starovoitov
2019-06-14 1:58 ` Josh Poimboeuf
2019-06-14 2:28 ` Josh Poimboeuf
2019-06-14 4:50 ` Josh Poimboeuf
2019-06-14 6:00 ` Alexei Starovoitov
2019-06-14 7:41 ` Peter Zijlstra
2019-06-14 13:31 ` Josh Poimboeuf
2019-06-14 15:29 ` Alexei Starovoitov
2019-06-14 13:34 ` Josh Poimboeuf [this message]
2019-06-14 15:31 ` Alexei Starovoitov
2019-06-14 15:56 ` Josh Poimboeuf
2019-06-13 13:21 ` [PATCH 8/9] x86/bpf: Convert asm comments to AT&T syntax Josh Poimboeuf
2019-06-13 18:52 ` Song Liu
2019-06-13 19:11 ` Josh Poimboeuf
2019-06-14 7:42 ` Peter Zijlstra
2019-06-14 15:13 ` Song Liu
2019-06-13 13:21 ` [PATCH 9/9] x86/bpf: Convert MOV function/macro argument ordering " Josh Poimboeuf
2019-06-13 19:00 ` [PATCH 0/9] x86/bpf: unwinder fixes Song Liu
2019-06-13 20:41 ` Peter Zijlstra
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