From: Timur Tabi <timur@kernel.org>
To: Kees Cook <keescook@chromium.org>, Matthew Wilcox <willy@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
Petr Mladek <pmladek@suse.com>,
roman.fietze@magna.com, Steven Rostedt <rostedt@goodmis.org>,
John Ogness <john.ogness@linutronix.de>,
linux-mm@kvack.org, Akinobu Mita <akinobu.mita@gmail.com>
Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps
Date: Tue, 19 Jan 2021 13:55:29 -0600 [thread overview]
Message-ID: <29122c86-bfea-2f25-d111-00641cc660ba@kernel.org> (raw)
In-Reply-To: <202101191135.A78A570@keescook>
On 1/19/21 1:45 PM, Kees Cook wrote:
> How about this so the base address is hashed once, with the offset added
> to it for each line instead of each line having a "new" hash that makes
> no sense:
>
> diff --git a/lib/hexdump.c b/lib/hexdump.c
> index 9301578f98e8..20264828752d 100644
> --- a/lib/hexdump.c
> +++ b/lib/hexdump.c
> @@ -242,12 +242,17 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
> const void *buf, size_t len, bool ascii)
> {
> const u8 *ptr = buf;
> + const u8 *addr;
> int i, linelen, remaining = len;
> unsigned char linebuf[32 * 3 + 2 + 32 + 1];
>
> if (rowsize != 16 && rowsize != 32)
> rowsize = 16;
>
> + if (prefix_type == DUMP_PREFIX_ADDRESS &&
> + ptr_to_hashval(ptr, &addr))
> + addr = 0;
> +
> for (i = 0; i < len; i += rowsize) {
> linelen = min(remaining, rowsize);
> remaining -= rowsize;
> @@ -258,7 +263,7 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
> switch (prefix_type) {
> case DUMP_PREFIX_ADDRESS:
> printk("%s%s%p: %s\n",
> - level, prefix_str, ptr + i, linebuf);
> + level, prefix_str, addr + i, linebuf);
Well, this is better than nothing, but not by much. Again, as long as
%px exists for printk(), I just cannot understand any resistance to
allowing it in print_hex_dump().
Frankly, I think this patch and my patch should both be added. During
debugging, it's very difficult if not impossible to work with hashed
addresses. I use print_hex_dump() with an unhashed address all the
time, either by applying my patch to my own kernel or just replacing the
%p with %px.
next prev parent reply other threads:[~2021-01-19 19:57 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-16 22:09 [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Timur Tabi
2021-01-16 22:09 ` [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses Timur Tabi
2021-01-18 10:03 ` Andy Shevchenko
2021-01-18 10:03 ` Andy Shevchenko
2021-01-18 15:57 ` Timur Tabi
2021-01-18 17:14 ` Andy Shevchenko
2021-01-18 17:53 ` Timur Tabi
2021-01-16 22:09 ` [PATCH 2/2] mm/page_poison: use unhashed address in hexdump for check_poison_mem() Timur Tabi
2021-01-18 18:26 ` [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Matthew Wilcox
2021-01-18 19:03 ` Timur Tabi
2021-01-19 0:53 ` Sergey Senozhatsky
2021-01-19 1:47 ` Matthew Wilcox
2021-01-19 10:38 ` Sergey Senozhatsky
2021-01-19 19:45 ` Kees Cook
2021-01-26 16:47 ` Vlastimil Babka
2021-01-26 16:59 ` Timur Tabi
2021-01-26 17:14 ` Steven Rostedt
2021-01-26 17:14 ` Vlastimil Babka
2021-01-26 17:30 ` Timur Tabi
2021-01-26 17:39 ` Steven Rostedt
2021-01-26 17:40 ` Steven Rostedt
2021-01-26 19:23 ` John Ogness
2021-01-27 2:11 ` Sergey Senozhatsky
2021-01-27 3:22 ` Timur Tabi
2021-01-27 10:11 ` Petr Mladek
2021-01-27 10:38 ` Vlastimil Babka
2021-01-19 19:45 ` Kees Cook
2021-01-19 19:55 ` Timur Tabi [this message]
2021-01-19 20:10 ` Steven Rostedt
2021-01-19 20:49 ` Timur Tabi
2021-01-19 21:15 ` Steven Rostedt
2021-01-19 21:25 ` Timur Tabi
2021-01-20 9:19 ` Petr Mladek
2021-01-20 12:17 ` Matthew Wilcox
2021-01-20 19:39 ` Linus Torvalds
2021-01-20 19:39 ` Linus Torvalds
2021-01-19 20:18 ` Randy Dunlap
2021-01-20 20:28 ` Kees Cook
2021-01-19 2:30 ` Timur Tabi
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