From: Ingo Molnar <mingo@elte.hu>
To: Masami Hiramatsu <mhiramat@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
systemtap-ml <systemtap@sources.redhat.com>
Subject: Re: [BUGFIX][PATCH -tip] x86: fix text_poke to handle highmem pages
Date: Wed, 08 Apr 2009 12:33:00 -0000 [thread overview]
Message-ID: <20090408123133.GE18581@elte.hu> (raw)
In-Reply-To: <49DA37CB.4020901@redhat.com>
* Masami Hiramatsu <mhiramat@redhat.com> wrote:
> @@ -514,27 +515,39 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
> {
> unsigned long flags;
> char *vaddr;
> - struct page *pages[2];
> + struct page *page;
> int i;
> + unsigned long endp = ((unsigned long)addr + len) & PAGE_MASK;
>
> - if (!core_kernel_text((unsigned long)addr)) {
> - pages[0] = vmalloc_to_page(addr);
> - pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
> - } else {
> - pages[0] = virt_to_page(addr);
> - WARN_ON(!PageReserved(pages[0]));
> - pages[1] = virt_to_page(addr + PAGE_SIZE);
> + /*
> + * If the written range covers 2 pages, we'll split it, because
> + * vmalloc pages are not always continuous -- e.g. 1st page is
> + * lowmem and 2nd page is highmem.
> + */
> + if (((unsigned long)addr & PAGE_MASK) != endp) {
> + text_poke(addr, opcode, endp - (unsigned long)addr);
> + addr = (void *)endp;
> + opcode = (char *)opcode + (endp - (unsigned long)addr);
> + len -= endp - (unsigned long)addr;
> }
> - BUG_ON(!pages[0]);
> +
> + if (!core_kernel_text((unsigned long)addr))
> + page = vmalloc_to_page(addr);
> + else
> + page = virt_to_page(addr);
hm, the bug is upstream now. And your fix turns a
supposed-to-be-simpler kmap based patching thing back into something
fragile looking again. We might be better off with a revert - or we
do a real clean patch.
Firstly, that core_kernel_text() distinction above looks
artificially open-coded - dont we have a proper, generic
"look-up-the-page" variant in the MM somewhere?
> + BUG_ON(!page);
> local_irq_save(flags);
> - set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
> - if (pages[1])
> - set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
> - vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
> + if (PageHighMem(page))
> + vaddr = kmap_atomic(page, KM_TEXT_POKE);
> + else {
> + set_fixmap(FIX_TEXT_POKE, page_to_phys(page));
> + vaddr = (char *)fix_to_virt(FIX_TEXT_POKE);
> + }
that too looks artificially complex. Why cannot we kmap lowmem pages
too? If the API isnt available on !HIGHMEM kernels .. then the
solution is to make it available, not to branch our way around it.
> memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
> - clear_fixmap(FIX_TEXT_POKE0);
> - if (pages[1])
> - clear_fixmap(FIX_TEXT_POKE1);
> + if (PageHighMem(page))
> + kunmap_atomic(vaddr, KM_TEXT_POKE);
> + else
> + clear_fixmap(FIX_TEXT_POKE);
ditto.
Thanks,
Ingo
next prev parent reply other threads:[~2009-04-08 12:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-04 14:34 [BUG][-tip] kprobes on module functions hits kernel BUG in text_poke on x86-32 Masami Hiramatsu
2009-04-04 15:42 ` Mathieu Desnoyers
2009-04-04 18:28 ` Masami Hiramatsu
2009-04-04 19:03 ` Masami Hiramatsu
2009-04-05 3:45 ` Masami Hiramatsu
2009-04-05 3:49 ` Masami Hiramatsu
2009-04-06 17:10 ` [BUGFIX][PATCH -tip] x86: fix text_poke to handle highmem pages Masami Hiramatsu
2009-04-06 17:32 ` Mathieu Desnoyers
2009-04-06 17:43 ` Masami Hiramatsu
2009-04-06 17:58 ` Mathieu Desnoyers
2009-04-06 20:22 ` Masami Hiramatsu
2009-04-08 12:33 ` Ingo Molnar [this message]
2009-04-08 14:57 ` Masami Hiramatsu
2009-04-08 15:00 ` Ingo Molnar
2009-04-09 17:55 ` [BUGFIX][PATCH] x86: fix set_fixmap to use phys_addr_t Masami Hiramatsu
2009-04-09 18:46 ` Mathieu Desnoyers
2009-04-09 21:51 ` Masami Hiramatsu
2009-04-10 14:09 ` [tip:x86/urgent] " Masami Hiramatsu
2009-04-10 15:20 ` Masami Hiramatsu
2009-04-10 16:11 ` Mathieu Desnoyers
2009-04-10 17:48 ` Masami Hiramatsu
2009-04-10 18:32 ` Masami Hiramatsu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090408123133.GE18581@elte.hu \
--to=mingo@elte.hu \
--cc=akpm@linux-foundation.org \
--cc=ananth@in.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@polymtl.ca \
--cc=mhiramat@redhat.com \
--cc=systemtap@sources.redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).