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Re: [PATCH] cleanup vmalloc_fault for 64bit kernel

To: Wu Fei <at.wufei@gmail.com>
Subject: Re: [PATCH] cleanup vmalloc_fault for 64bit kernel
From: David Daney <ddaney@caviumnetworks.com>
Date: Wed, 09 Sep 2009 08:35:26 -0700
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
In-reply-to: <20090831132811.GA6924@desktop>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20090831132811.GA6924@desktop>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.21 (X11/20090320)
Wu Fei wrote:
64bit kernel won't arrive vmalloc_fault, it's not necessary or possible
to copy the page table from init_mm.pgd. swapper_pg_dir, module_pg_dir
and the process's pgd represent the different virtual address area, and
the tlb exception handler accesses the suitable one directly.

Signed-off-by: Wu Fei <at.wufei@gmail.com>
---
 arch/mips/mm/fault.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index f956ecb..e769789 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -58,11 +58,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned 
long write,
         * only copy the information from the master page table,
         * nothing more.
         */
+#ifdef CONFIG_32BIT
        if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
                goto vmalloc_fault;
-#ifdef MODULE_START
-       if (unlikely(address >= MODULE_START && address < MODULE_END))
-               goto vmalloc_fault;
 #endif

That is not correct. You can still arrive at do_page_fault() from faults in the vmalloc range. We need to go directly to the panic code as I did in my patch: Message-Id: <1251931654-21268-1-git-send-email-ddaney@caviumnetworks.com>

AKA: [PATCH] MIPS: Don't corrupt page tables on vmalloc fault.



        /*
@@ -203,6 +201,7 @@ do_sigbus:
        force_sig_info(SIGBUS, &info, tsk);
return;
+#ifdef CONFIG_32BIT
 vmalloc_fault:
        {
                /*
@@ -241,4 +240,5 @@ vmalloc_fault:
                        goto no_context;
                return;
        }
+#endif
 }


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