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From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	rppt@kernel.org, penberg@kernel.org, geert@linux-m68k.org,
	giancarlo.ferrari@nokia.com
Subject: Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated
Date: Mon, 1 Feb 2021 11:34:36 +0000	[thread overview]
Message-ID: <20210201113436.GE1463@shell.armlinux.org.uk> (raw)
In-Reply-To: <1612140296-12546-1-git-send-email-giancarlo.ferrari89@gmail.com>

I wish others who know this code would get involved, and such stuff
wasn't left to me to research and work out whether a patch is correct
or not.

On Mon, Feb 01, 2021 at 12:44:56AM +0000, Giancarlo Ferrari wrote:
> machine_kexec() need to set rw permission in text and rodata sections
> to assign some variables (e.g. kexec_start_address). To do that at
> the end (after flushing pdm in memory, etc.) it needs to invalidate
> TLB [section] entries.
> 
> If during the TLB invalidation an interrupt occours, which might cause
> a context switch, there is the risk to inject invalid TLBs, with ro
> permissions.
> 
> When trying to assign .text labels, this lead to the following:
> 
>  Unable to handle kernel paging request at virtual address 80112f38
>  pgd = fd7ef03e
>  [80112f38] *pgd=0001141e(bad)
>  Internal error: Oops: 80d [#1] PREEMPT SMP ARM
>  ...
> 
> Signed-off-by: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>

I don't know this code very well, but I don't think this patch is
correct. What happens if we have CRASH_DUMP enabled, and we enter this
function with IRQs already disabled? Should we really be re-enabling
IRQs?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
Cc: linux-kernel@vger.kernel.org, penberg@kernel.org,
	geert@linux-m68k.org, linux-arm-kernel@lists.infradead.org,
	akpm@linux-foundation.org, rppt@kernel.org,
	giancarlo.ferrari@nokia.com
Subject: Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated
Date: Mon, 1 Feb 2021 11:34:36 +0000	[thread overview]
Message-ID: <20210201113436.GE1463@shell.armlinux.org.uk> (raw)
In-Reply-To: <1612140296-12546-1-git-send-email-giancarlo.ferrari89@gmail.com>

I wish others who know this code would get involved, and such stuff
wasn't left to me to research and work out whether a patch is correct
or not.

On Mon, Feb 01, 2021 at 12:44:56AM +0000, Giancarlo Ferrari wrote:
> machine_kexec() need to set rw permission in text and rodata sections
> to assign some variables (e.g. kexec_start_address). To do that at
> the end (after flushing pdm in memory, etc.) it needs to invalidate
> TLB [section] entries.
> 
> If during the TLB invalidation an interrupt occours, which might cause
> a context switch, there is the risk to inject invalid TLBs, with ro
> permissions.
> 
> When trying to assign .text labels, this lead to the following:
> 
>  Unable to handle kernel paging request at virtual address 80112f38
>  pgd = fd7ef03e
>  [80112f38] *pgd=0001141e(bad)
>  Internal error: Oops: 80d [#1] PREEMPT SMP ARM
>  ...
> 
> Signed-off-by: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>

I don't know this code very well, but I don't think this patch is
correct. What happens if we have CRASH_DUMP enabled, and we enter this
function with IRQs already disabled? Should we really be re-enabling
IRQs?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-02-01 11:36 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-01  0:44 [PATCH] ARM: kexec: Fix panic after TLB are invalidated Giancarlo Ferrari
2021-02-01  0:44 ` Giancarlo Ferrari
2021-02-01 11:34 ` Russell King - ARM Linux admin [this message]
2021-02-01 11:34   ` Russell King - ARM Linux admin
2021-02-01 12:47 ` Mark Rutland
2021-02-01 12:47   ` Mark Rutland
2021-02-01 13:03   ` Russell King - ARM Linux admin
2021-02-01 13:03     ` Russell King - ARM Linux admin
2021-02-01 13:57     ` Mark Rutland
2021-02-01 13:57       ` Mark Rutland
2021-02-01 16:08       ` Russell King - ARM Linux admin
2021-02-01 16:08         ` Russell King - ARM Linux admin
2021-02-01 16:32         ` Mark Rutland
2021-02-01 16:32           ` Mark Rutland
2021-02-01 16:37           ` Russell King - ARM Linux admin
2021-02-01 16:37             ` Russell King - ARM Linux admin
2021-02-01 20:07         ` Giancarlo Ferrari
2021-02-01 20:07           ` Giancarlo Ferrari
2021-02-01 20:16           ` Russell King - ARM Linux admin
2021-02-01 20:16             ` Russell King - ARM Linux admin
2021-02-01 22:18             ` Giancarlo Ferrari
2021-02-01 22:18               ` Giancarlo Ferrari
2021-02-04 23:48               ` Giancarlo Ferrari
2021-02-04 23:48                 ` Giancarlo Ferrari
2021-02-05  0:18                 ` Russell King - ARM Linux admin
2021-02-05  0:18                   ` Russell King - ARM Linux admin
2021-02-05  0:40                   ` Giancarlo Ferrari
2021-02-05  0:40                     ` Giancarlo Ferrari
2021-02-05  0:45                     ` Giancarlo Ferrari
2021-02-05  0:45                       ` Giancarlo Ferrari
2021-02-05  9:44                     ` Russell King - ARM Linux admin
2021-02-05  9:44                       ` Russell King - ARM Linux admin
2021-02-05 14:36                       ` Giancarlo Ferrari
2021-02-05 14:36                         ` Giancarlo Ferrari
2021-02-01 14:39   ` Giancarlo Ferrari
2021-02-01 14:39     ` Giancarlo Ferrari
2021-02-01 15:30     ` Mark Rutland
2021-02-01 15:30       ` Mark Rutland
2021-02-01 19:09       ` Giancarlo Ferrari
2021-02-01 19:09         ` Giancarlo Ferrari
  -- strict thread matches above, loose matches on Subject: below --
2021-01-12 16:49 Giancarlo Ferrari
2021-01-12 16:49 ` Giancarlo Ferrari
2021-02-01 10:10 ` Giancarlo Ferrari
2021-02-01 10:10   ` Giancarlo Ferrari

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