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-rw-r--r--debian/patches-rt/0040-ARM-enable-irq-in-translation-section-permission-fau.patch97
1 files changed, 97 insertions, 0 deletions
diff --git a/debian/patches-rt/0040-ARM-enable-irq-in-translation-section-permission-fau.patch b/debian/patches-rt/0040-ARM-enable-irq-in-translation-section-permission-fau.patch
new file mode 100644
index 000000000..ee53f7bd6
--- /dev/null
+++ b/debian/patches-rt/0040-ARM-enable-irq-in-translation-section-permission-fau.patch
@@ -0,0 +1,97 @@
+From 802d6978bf4ebdec28d2ba4e715c2e414d9c7d06 Mon Sep 17 00:00:00 2001
+From: "Yadi.hu" <yadi.hu@windriver.com>
+Date: Wed, 10 Dec 2014 10:32:09 +0800
+Subject: [PATCH 40/62] ARM: enable irq in translation/section permission fault
+ handlers
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz
+
+Probably happens on all ARM, with
+CONFIG_PREEMPT_RT
+CONFIG_DEBUG_ATOMIC_SLEEP
+
+This simple program....
+
+int main() {
+ *((char*)0xc0001000) = 0;
+};
+
+[ 512.742724] BUG: sleeping function called from invalid context at kernel/rtmutex.c:658
+[ 512.743000] in_atomic(): 0, irqs_disabled(): 128, pid: 994, name: a
+[ 512.743217] INFO: lockdep is turned off.
+[ 512.743360] irq event stamp: 0
+[ 512.743482] hardirqs last enabled at (0): [< (null)>] (null)
+[ 512.743714] hardirqs last disabled at (0): [<c0426370>] copy_process+0x3b0/0x11c0
+[ 512.744013] softirqs last enabled at (0): [<c0426370>] copy_process+0x3b0/0x11c0
+[ 512.744303] softirqs last disabled at (0): [< (null)>] (null)
+[ 512.744631] [<c041872c>] (unwind_backtrace+0x0/0x104)
+[ 512.745001] [<c09af0c4>] (dump_stack+0x20/0x24)
+[ 512.745355] [<c0462490>] (__might_sleep+0x1dc/0x1e0)
+[ 512.745717] [<c09b6770>] (rt_spin_lock+0x34/0x6c)
+[ 512.746073] [<c0441bf0>] (do_force_sig_info+0x34/0xf0)
+[ 512.746457] [<c0442668>] (force_sig_info+0x18/0x1c)
+[ 512.746829] [<c041d880>] (__do_user_fault+0x9c/0xd8)
+[ 512.747185] [<c041d938>] (do_bad_area+0x7c/0x94)
+[ 512.747536] [<c041d990>] (do_sect_fault+0x40/0x48)
+[ 512.747898] [<c040841c>] (do_DataAbort+0x40/0xa0)
+[ 512.748181] Exception stack(0xecaa1fb0 to 0xecaa1ff8)
+
+Oxc0000000 belongs to kernel address space, user task can not be
+allowed to access it. For above condition, correct result is that
+test case should receive a “segment fault” and exits but not stacks.
+
+the root cause is commit 02fe2845d6a8 ("avoid enabling interrupts in
+prefetch/data abort handlers"),it deletes irq enable block in Data
+abort assemble code and move them into page/breakpiont/alignment fault
+handlers instead. But author does not enable irq in translation/section
+permission fault handlers. ARM disables irq when it enters exception/
+interrupt mode, if kernel doesn't enable irq, it would be still disabled
+during translation/section permission fault.
+
+We see the above splat because do_force_sig_info is still called with
+IRQs off, and that code eventually does a:
+
+ spin_lock_irqsave(&t->sighand->siglock, flags);
+
+As this is architecture independent code, and we've not seen any other
+need for other arch to have the siglock converted to raw lock, we can
+conclude that we should enable irq for ARM translation/section
+permission exception.
+
+
+Signed-off-by: Yadi.hu <yadi.hu@windriver.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+---
+ arch/arm/mm/fault.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
+index b0db85310331..77877dcb54ed 100644
+--- a/arch/arm/mm/fault.c
++++ b/arch/arm/mm/fault.c
+@@ -400,6 +400,9 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
+ if (addr < TASK_SIZE)
+ return do_page_fault(addr, fsr, regs);
+
++ if (interrupts_enabled(regs))
++ local_irq_enable();
++
+ if (user_mode(regs))
+ goto bad_area;
+
+@@ -470,6 +473,9 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
+ static int
+ do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+ {
++ if (interrupts_enabled(regs))
++ local_irq_enable();
++
+ do_bad_area(addr, fsr, regs);
+ return 0;
+ }
+--
+2.43.0
+