From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
live-patching@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>, Jiri Slaby <jslaby@suse.cz>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC PATCH 10/10] x86/unwind: add undwarf unwinder
Date: Thu, 1 Jun 2017 13:05:39 +0200 [thread overview]
Message-ID: <20170601110539.helelmmngwaba7fa@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <89552d4047e5aed843f7b6a54277f9af62da6a82.1496293620.git.jpoimboe@redhat.com>
On Thu, Jun 01, 2017 at 12:44:16AM -0500, Josh Poimboeuf wrote:
> +static struct undwarf *__undwarf_lookup(struct undwarf *undwarf,
> + unsigned int num, unsigned long ip)
> +{
> + struct undwarf *first = undwarf;
> + struct undwarf *last = undwarf + num - 1;
> + struct undwarf *mid;
> + unsigned long u_ip;
> +
> + while (first <= last) {
> + mid = first + ((last - first) / 2);
> + u_ip = undwarf_ip(mid);
> +
> + if (ip >= u_ip) {
> + if (ip < u_ip + mid->len)
> + return mid;
> + first = mid + 1;
> + } else
> + last = mid - 1;
> + }
> +
> + return NULL;
> +}
That's a bog standard binary search thing, don't we have a helper for
that someplace?
> +static struct undwarf *undwarf_lookup(unsigned long ip)
> +{
> + struct undwarf *undwarf;
> + struct module *mod;
> +
> + /* Look in vmlinux undwarf section: */
> + undwarf = __undwarf_lookup(__undwarf_start, __undwarf_end - __undwarf_start, ip);
> + if (undwarf)
> + return undwarf;
> +
> + /* Look in module undwarf sections: */
> + preempt_disable();
> + mod = __module_address(ip);
> + if (!mod || !mod->arch.undwarf)
> + goto module_out;
> + undwarf = __undwarf_lookup(mod->arch.undwarf, mod->arch.num_undwarves, ip);
> +
> +module_out:
> + preempt_enable();
> + return undwarf;
> +}
A few points here:
- that first lookup is entirely pointless if !core_kernel_text(ip)
- that preempt_{dis,en}able() muck is 'pointless', for while it shuts
up the warnings from __modules_address(), nothing preserves the
struct undwarf you get a pointer to after the preempt_enable().
- what about 'interesting' things like, ftrace_trampoline, kprobe insn
slots and bpf text?
> +static bool stack_access_ok(struct unwind_state *state, unsigned long addr,
> + size_t len)
> +{
> + struct stack_info *info = &state->stack_info;
> +
> + /*
> + * If the next bp isn't on the current stack, switch to the next one.
> + *
> + * We may have to traverse multiple stacks to deal with the possibility
> + * that info->next_sp could point to an empty stack and the next bp
> + * could be on a subsequent stack.
> + */
> + while (!on_stack(info, (void *)addr, len)) {
> + if (get_stack_info(info->next_sp, state->task, info,
> + &state->stack_mask))
> + return false;
}
> +
> + return true;
> +}
next prev parent reply other threads:[~2017-06-01 11:05 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 5:44 [RFC PATCH 00/10] x86: undwarf unwinder Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 01/10] objtool: move checking code to check.c Josh Poimboeuf
2017-06-14 7:22 ` Jiri Slaby
2017-06-01 5:44 ` [RFC PATCH 02/10] objtool, x86: add several functions and files to the objtool whitelist Josh Poimboeuf
2017-06-14 7:24 ` Jiri Slaby
2017-06-14 13:03 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 03/10] objtool: stack validation 2.0 Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 04/10] objtool: add undwarf debuginfo generation Josh Poimboeuf
2017-06-14 8:42 ` Jiri Slaby
2017-06-14 13:27 ` Josh Poimboeuf
2017-06-22 7:47 ` Jiri Slaby
2017-06-22 12:49 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 05/10] objtool, x86: add facility for asm code to provide CFI hints Josh Poimboeuf
2017-06-01 13:57 ` Andy Lutomirski
2017-06-01 14:16 ` Josh Poimboeuf
2017-06-01 14:40 ` Andy Lutomirski
2017-06-01 15:02 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 06/10] x86/entry: add CFI hint undwarf annotations Josh Poimboeuf
2017-06-01 14:03 ` Andy Lutomirski
2017-06-01 14:23 ` Josh Poimboeuf
2017-06-01 14:28 ` Josh Poimboeuf
2017-06-01 14:39 ` Andy Lutomirski
2017-06-01 15:01 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 07/10] x86/asm: add CFI hint annotations to sync_core() Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 08/10] extable: rename 'sortextable' script to 'sorttable' Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 09/10] extable: add undwarf table sorting ability to sorttable script Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 10/10] x86/unwind: add undwarf unwinder Josh Poimboeuf
2017-06-01 11:05 ` Peter Zijlstra [this message]
2017-06-01 12:26 ` Josh Poimboeuf
2017-06-01 12:47 ` Jiri Slaby
2017-06-01 13:02 ` Josh Poimboeuf
2017-06-01 13:42 ` Peter Zijlstra
2017-06-01 13:10 ` Peter Zijlstra
2017-06-01 12:13 ` Peter Zijlstra
2017-06-01 12:36 ` Josh Poimboeuf
2017-06-01 13:12 ` Peter Zijlstra
2017-06-01 15:03 ` Josh Poimboeuf
2017-06-14 11:45 ` Jiri Slaby
2017-06-14 13:44 ` Josh Poimboeuf
2017-06-01 6:08 ` [RFC PATCH 00/10] x86: " Ingo Molnar
2017-06-01 11:58 ` Josh Poimboeuf
2017-06-01 12:17 ` Peter Zijlstra
2017-06-01 12:33 ` Jiri Slaby
2017-06-01 12:52 ` Josh Poimboeuf
2017-06-01 12:57 ` Jiri Slaby
2017-06-01 12:47 ` Josh Poimboeuf
2017-06-01 13:25 ` Peter Zijlstra
2017-06-06 14:14 ` Sergey Senozhatsky
2017-06-01 13:50 ` Andy Lutomirski
2017-06-01 13:50 ` Ingo Molnar
2017-06-01 13:58 ` Jiri Slaby
2017-06-02 8:30 ` Jiri Slaby
2017-06-01 14:05 ` Josh Poimboeuf
2017-06-01 14:08 ` Jiri Slaby
2017-06-02 10:40 ` Mel Gorman
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