From: Michael Schmitz <schmitzmic@gmail.com>
To: Finn Thain <fthain@linux-m68k.org>
Cc: geert@linux-m68k.org, linux-m68k@lists.linux-m68k.org
Subject: Re: [PATCH RFC v2 1/2] m68k: Handle __generic_copy_to_user faults more carefully
Date: Fri, 26 Apr 2024 13:22:54 +1200 [thread overview]
Message-ID: <1b49c8a1-c753-428d-b526-06b6eb3e551c@gmail.com> (raw)
In-Reply-To: <b9d281db-c06e-0eb3-0f49-b95f576a9891@linux-m68k.org>
Hi Finn,
yes, that would explain that.
Using a start address of badpage-4 and path '/tmp' or '/temp' in order
to use either the movesw or movesb branches of the code (and force a
fault on the first byte in the movesw case), I see no more Oops. Still
have to test forcing the fault on the second byte of a movesw (making it
a misaligned access again).
Cheers,
Michael
On 26/04/24 13:00, Finn Thain wrote:
> On Fri, 26 Apr 2024, Michael Schmitz wrote:
>
>> Not sure you noticed this - the 040 passed __clear_user without fault.
>> We managed to test this one without meaning to. Exception handling in
>> there appears to work OK (for the cases we're testing).
>>
>> No idea why you have the __clear_user call occur within
>> __generic_copy_to_user - it does not appear in my disassembly.
>>
> I'm afraid I neglected to mention that I added the patch below in order to
> exercise that code path.
>
> diff --git a/arch/m68k/lib/uaccess.c b/arch/m68k/lib/uaccess.c
> index ef761fc10981..1c9a24a0b554 100644
> --- a/arch/m68k/lib/uaccess.c
> +++ b/arch/m68k/lib/uaccess.c
> @@ -58,6 +58,8 @@ unsigned long __generic_copy_to_user(void __user *to, const void *from,
> {
> unsigned long tmp, res;
>
> + __clear_user(to, n);
> +
> asm volatile ("\n"
> " tst.l %0\n"
> " jeq 5f\n"
next prev parent reply other threads:[~2024-04-26 1:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 2:29 [PATCH RFC v2 0/2] m68k uaccess fault handling fixes Michael Schmitz
2024-04-22 2:29 ` [PATCH RFC v2 1/2] m68k: Handle __generic_copy_to_user faults more carefully Michael Schmitz
2024-04-25 4:16 ` Finn Thain
2024-04-25 5:32 ` Michael Schmitz
2024-04-25 6:32 ` Finn Thain
2024-04-25 7:52 ` Michael Schmitz
2024-04-25 5:45 ` Michael Schmitz
2024-04-25 6:47 ` Finn Thain
2024-04-25 7:43 ` Michael Schmitz
2024-04-25 8:20 ` Michael Schmitz
2024-04-25 19:15 ` Michael Schmitz
2024-04-26 1:00 ` Finn Thain
2024-04-26 1:22 ` Michael Schmitz [this message]
2024-04-26 7:10 ` Michael Schmitz
2024-04-26 7:57 ` Finn Thain
2024-04-26 8:31 ` Michael Schmitz
2024-04-26 7:58 ` Finn Thain
2024-04-27 1:44 ` Finn Thain
2024-04-27 4:41 ` Michael Schmitz
2024-04-22 2:29 ` [PATCH RFC v2 2/2] m68k: improve __constant_copy_to_user_asm() fault handling Michael Schmitz
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