[ 39/75] ARM: 7396/1: errata: only handle ARM erratum #326103 on affected cores

Greg KH
2012-05-04T21:12:40Z

From: Will Deacon <will.deacon@arm.com>

commit f0c4b8d653f5ee091fb8d4d02ed7eaad397491bb upstream.

Erratum #326103 ("FSR write bit incorrect on a SWP to read-only memory")
only affects the ARM 1136 core prior to r1p0. The workaround
disassembles the faulting instruction to determine whether it was a read
or write access on all v6 cores.

An issue has been reported on the ARM 11MPCore whereby loading the
faulting instruction may happen in parallel with that page being
unmapped, resulting in a deadlock due to the lack of TLB broadcasting
in hardware:

http://lists.infradead.org/pipermail/linux-arm-kernel/2012-March/091561.html

This patch limits the workaround so that it is only used on affected
cores, which are known to be UP only. Other v6 cores can rely on the
FSR to indicate the access type correctly.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm/Kconfig | 9 +++++++++
arch/arm/mm/abort-ev6.S | 17 +++++++++++------
2 files changed, 20 insertions(+), 6 deletions(-)

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1163,6 +1163,15 @@ if !MMU
source "arch/arm/Kconfig-nommu"
endif

+config ARM_ERRATA_326103
+ bool "ARM errata: FSR write bit incorrect on a SWP to read-only memory"
+ depends on CPU_V6
+ help
+ Executing a SWP instruction to read-only memory does not set bit 11
+ of the FSR on the ARM 1136 prior to r1p0. This causes the kernel to
+ treat the access as a read, preventing a COW from occurring and
+ causing the faulting task to livelock.
+
config ARM_ERRATA_411920
bool "ARM errata: Invalidation of the Instruction Cache operation can fail"
depends on CPU_V6 || CPU_V6K
--- a/arch/arm/mm/abort-ev6.S
+++ b/arch/arm/mm/abort-ev6.S
@@ -26,18 +26,23 @@ ENTRY(v6_early_abort)
mrc p15, 0, r1, c5, c0, 0 @ get FSR
mrc p15, 0, r0, c6, c0, 0 @ get FAR
/*
- * Faulty SWP instruction on 1136 doesn't set bit 11 in DFSR (erratum 326103).
- * The test below covers all the write situations, including Java bytecodes
+ * Faulty SWP instruction on 1136 doesn't set bit 11 in DFSR.
*/
- bic r1, r1, #1 << 11 @ clear bit 11 of FSR
+#ifdef CONFIG_ARM_ERRATA_326103
+ ldr ip, =0x4107b36
+ mrc p15, 0, r3, c0, c0, 0 @ get processor id
+ teq ip, r3, lsr #4 @ r0 ARM1136?
+ bne do_DataAbort
tst r5, #PSR_J_BIT @ Java?
+ tsteq r5, #PSR_T_BIT @ Thumb?
bne do_DataAbort
- do_thumb_abort fsr=r1, pc=r4, psr=r5, tmp=r3
- ldreq r3, [r4] @ read aborted ARM instruction
+ bic r1, r1, #1 << 11 @ clear bit 11 of FSR
+ ldr r3, [r4] @ read aborted ARM instruction
#ifdef CONFIG_CPU_ENDIAN_BE8
- reveq r3, r3
+ rev r3, r3
#endif
do_ldrd_abort tmp=ip, insn=r3
tst r3, #1 << 20 @ L = 0 -> write
orreq r1, r1, #1 << 11 @ yes.
+#endif
b do_DataAbort