From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk
Cc: Ard Biesheuvel <ardb@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Guenter Roeck <linux@roeck-us.net>,
Peter Zijlstra <peterz@infradead.org>,
Linus Walleij <linus.walleij@linaro.org>,
Arnd Bergmann <arnd@arndb.de>,
stable@vger.kernel.org
Subject: [PATCH v4 04/12] ARM: entry: Fix iWMMXT TIF flag handling
Date: Mon, 20 Mar 2023 14:18:37 +0100 [thread overview]
Message-ID: <20230320131845.3138015-5-ardb@kernel.org> (raw)
In-Reply-To: <20230320131845.3138015-1-ardb@kernel.org>
The conditional MOVS instruction that appears to have been added to test
for the TIF_USING_IWMMXT thread_info flag only sets the N and Z
condition flags and register R7, none of which are referenced in the
subsequent code. This means that the instruction does nothing, which
means that we might misidentify faulting FPE instructions as iWMMXT
instructions on kernels that were built to support both.
This seems to have been part of the original submission of the code, and
so this has never worked as intended, and nobody ever noticed, and so we
might decide to just leave this as-is. However, with the ongoing move
towards multiplatform kernels, the issue becomes more likely to
manifest, and so it is better to fix it.
So check whether we are dealing with an undef exception regarding
coprocessor index #0 or #1, and if so, load the thread_info flag and
only dispatch it as a iWMMXT trap if the flag is set.
Cc: <stable@vger.kernel.org> # v2.6.9+
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm/kernel/entry-armv.S | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index c39303e5c23470e6..c5d2f07994fb0d87 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -606,10 +606,11 @@ call_fpe:
strb r7, [r6, #TI_USED_CP] @ set appropriate used_cp[]
#ifdef CONFIG_IWMMXT
@ Test if we need to give access to iWMMXt coprocessors
- ldr r5, [r10, #TI_FLAGS]
- rsbs r7, r8, #(1 << 8) @ CP 0 or 1 only
- movscs r7, r5, lsr #(TIF_USING_IWMMXT + 1)
- bcs iwmmxt_task_enable
+ tst r8, #0xe << 8 @ CP 0 or 1?
+ ldreq r5, [r10, #TI_FLAGS] @ if so, load thread_info flags
+ andeq r5, r5, #1 << TIF_USING_IWMMXT @ isolate TIF_USING_IWMMXT flag
+ teqeq r5, #1 << TIF_USING_IWMMXT @ check whether it is set
+ beq iwmmxt_task_enable @ branch if set
#endif
ARM( add pc, pc, r8, lsr #6 )
THUMB( lsr r8, r8, #6 )
--
2.39.2
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-03-20 13:20 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 13:18 [PATCH v4 00/12] ARM: vfp: Switch to C API to en/disable softirqs Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 01/12] ARM: vfp: Pass thread_info pointer to vfp_support_entry Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 02/12] ARM: vfp: Pass successful return address via register R3 Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 03/12] ARM: vfp: Fix broken softirq handling with instrumentation enabled Ard Biesheuvel
2023-04-09 14:29 ` Linux regression tracking (Thorsten Leemhuis)
2023-04-10 20:15 ` Guenter Roeck
2023-03-20 13:18 ` Ard Biesheuvel [this message]
2023-03-21 14:32 ` [PATCH v4 04/12] ARM: entry: Fix iWMMXT TIF flag handling Linus Walleij
2023-03-21 19:19 ` Nicolas Pitre
2023-03-21 19:32 ` Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 05/12] ARM: vfp: Record VFP bounces as perf emulation faults Ard Biesheuvel
2023-03-21 14:33 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 06/12] ARM: vfp: Remove workaround for Feroceon CPUs Ard Biesheuvel
2023-03-21 14:44 ` Linus Walleij
2023-03-21 15:42 ` Ard Biesheuvel
2023-03-21 20:40 ` Linus Walleij
2023-03-22 7:26 ` Arnd Bergmann
2023-03-21 20:00 ` Nicolas Pitre
2023-03-20 13:18 ` [PATCH v4 07/12] ARM: vfp: Reimplement VFP exception entry in C code Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 08/12] ARM: kernel: Get rid of thread_info::used_cp[] array Ard Biesheuvel
2023-03-21 14:58 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 09/12] ARM: vfp: Use undef hook for handling VFP exceptions Ard Biesheuvel
2023-03-21 14:59 ` Linus Walleij
2023-03-21 15:41 ` Ard Biesheuvel
2023-03-20 13:18 ` [PATCH v4 10/12] ARM: entry: Disregard Thumb undef exception in coproc dispatch Ard Biesheuvel
2023-03-21 15:05 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 11/12] ARM: iwmmxt: Use undef hook to enable coprocessor for task Ard Biesheuvel
2023-03-21 15:06 ` Linus Walleij
2023-03-20 13:18 ` [PATCH v4 12/12] ARM: entry: Make asm coproc dispatch code NWFPE only Ard Biesheuvel
2023-03-21 15:11 ` Linus Walleij
2023-03-23 2:44 ` [PATCH v4 00/12] ARM: vfp: Switch to C API to en/disable softirqs Guenter Roeck
2023-03-23 8:33 ` Ard Biesheuvel
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=20230320131845.3138015-5-ardb@kernel.org \
--to=ardb@kernel.org \
--cc=arnd@arndb.de \
--cc=frederic@kernel.org \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux@armlinux.org.uk \
--cc=linux@roeck-us.net \
--cc=peterz@infradead.org \
--cc=stable@vger.kernel.org \
/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 NNTP newsgroup(s).