summaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorMatt Redfearn <matt.redfearn@imgtec.com>2016-12-19 14:20:58 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-18 07:14:36 +0200
commit93a82f8dbef8ee421fac80a1bd0564124a8ac41c (patch)
tree891c9914fdb26b099d65bb0ac3628ecb0037c44f /arch
parent3363653512853754fcc7592d2c68c4769a4825c9 (diff)
MIPS: Only change $28 to thread_info if coming from user mode
commit 510d86362a27577f5ee23f46cfb354ad49731e61 upstream. The SAVE_SOME macro is used to save the execution context on all exceptions. If an exception occurs while executing user code, the stack is switched to the kernel's stack for the current task, and register $28 is switched to point to the current_thread_info, which is at the bottom of the stack region. If the exception occurs while executing kernel code, the stack is left, and this change ensures that register $28 is not updated. This is the correct behaviour when the kernel can be executing on the separate irq stack, because the thread_info will not be at the base of it. With this change, register $28 is only switched to it's kernel conventional usage of the currrent thread info pointer at the point at which execution enters kernel space. Doing it on every exception was redundant, but OK without an IRQ stack, but will be erroneous once that is introduced. Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com> Acked-by: Jason A. Donenfeld <jason@zx2c4.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: James Hogan <james.hogan@imgtec.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/14742/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Amit Pundir <amit.pundir@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/mips/include/asm/stackframe.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index a71da576883c..5347f130f536 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -216,12 +216,19 @@
LONG_S $25, PT_R25(sp)
LONG_S $28, PT_R28(sp)
LONG_S $31, PT_R31(sp)
+
+ /* Set thread_info if we're coming from user mode */
+ mfc0 k0, CP0_STATUS
+ sll k0, 3 /* extract cu0 bit */
+ bltz k0, 9f
+
ori $28, sp, _THREAD_MASK
xori $28, _THREAD_MASK
#ifdef CONFIG_CPU_CAVIUM_OCTEON
.set mips64
pref 0, 0($28) /* Prefetch the current pointer */
#endif
+9:
.set pop
.endm