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[PATCH 4.4 23/32] powerpc: Dont try to fix up misaligned load-with-reservation instructions

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Mackerras <paulus@ozlabs.org>

commit 48fe9e9488743eec9b7c1addd3c93f12f2123d54 upstream.

In the past, there was only one load-with-reservation instruction,
lwarx, and if a program attempted a lwarx on a misaligned address, it
would take an alignment interrupt and the kernel handler would emulate
it as though it was lwzx, which was not really correct, but benign since
it is loading the right amount of data, and the lwarx should be paired
with a stwcx. to the same address, which would also cause an alignment
interrupt which would result in a SIGBUS being delivered to the process.

We now have 5 different sizes of load-with-reservation instruction. Of
those, lharx and ldarx cause an immediate SIGBUS by luck since their
entries in aligninfo[] overlap instructions which were not fixed up, but
lqarx overlaps with lhz and will be emulated as such. lbarx can never
generate an alignment interrupt since it only operates on 1 byte.

To straighten this out and fix the lqarx case, this adds code to detect
the l[hwdq]arx instructions and return without fixing them up, resulting
in a SIGBUS being delivered to the process.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/align.c |   27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -808,14 +808,25 @@ int fix_alignment(struct pt_regs *regs)
 	nb = aligninfo[instr].len;
 	flags = aligninfo[instr].flags;
 
-	/* ldbrx/stdbrx overlap lfs/stfs in the DSISR unfortunately */
-	if (IS_XFORM(instruction) && ((instruction >> 1) & 0x3ff) == 532) {
-		nb = 8;
-		flags = LD+SW;
-	} else if (IS_XFORM(instruction) &&
-		   ((instruction >> 1) & 0x3ff) == 660) {
-		nb = 8;
-		flags = ST+SW;
+	/*
+	 * Handle some cases which give overlaps in the DSISR values.
+	 */
+	if (IS_XFORM(instruction)) {
+		switch (get_xop(instruction)) {
+		case 532:	/* ldbrx */
+			nb = 8;
+			flags = LD+SW;
+			break;
+		case 660:	/* stdbrx */
+			nb = 8;
+			flags = ST+SW;
+			break;
+		case 20:	/* lwarx */
+		case 84:	/* ldarx */
+		case 116:	/* lharx */
+		case 276:	/* lqarx */
+			return 0;	/* not emulated ever */
+		}
 	}
 
 	/* Byteswap little endian loads and stores */

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[PATCH 4.4 00/32] 4.4.61-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 05/32] drm/vmwgfx: Remove getparam error message Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 01/32] drm/vmwgfx: Type-check lookups of fence objects Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 06/32] drm/vmwgfx: fix integer overflow in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 28/32] MIPS: ralink: Fix typos in rt3883 pinctrl Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 09/32] arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 16/32] metag/usercopy: Fix alignment error checking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 30/32] MIPS: Lantiq: fix missing xbar kernel panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 32/32] mm/mempolicy.c: fix error handling in set_mempolicy and mbind. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 23/32] powerpc: Dont try to fix up misaligned load-with-reservation instructions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 20/32] metag/usercopy: Fix src fixup in from user rapf loops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 08/32] staging: android: ashmem: lseek failed due to no FMODE_LSEEK. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 29/32] MIPS: End spinlocks with .insn Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6 kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
    Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels "Maciej W. Rozycki" <macro@linux-mips.org> - 2017-04-15 01:50 +0200
      Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 15:20 +0200
  [PATCH 4.4 26/32] s390/uaccess: get_user() should zero on failure (again) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 31/32] MIPS: Flush wrong invalid FTLB entry for huge page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 14/32] ring-buffer: Fix return value check in test_ringbuffer() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 17/32] metag/usercopy: Add early abort to copy_to_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 22/32] powerpc/mm: Add missing global TLB invalidate if cxl is active Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 04/32] drm/ttm, drm/vmwgfx: Relax permission checking when opening surfaces Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 25/32] s390/decompressor: fix initrd corruption caused by bss clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 15/32] metag/usercopy: Drop unused macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 24/32] nios2: reserve boot memory for device tree Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 21/32] metag/usercopy: Add missing fixups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 11/32] iio: bmg160: reset chip when probing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 19/32] metag/usercopy: Set flags before ADDZ Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 13/32] ptrace: fix PTRACE_LISTEN race corrupting task->state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 18/32] metag/usercopy: Zero rest of buffer from copy_from_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 10/32] arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 12/32] Reset TreeId to zero on SMB2 TREE_CONNECT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 02/32] drm/vmwgfx: NULL pointer dereference in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 07/32] sysfs: be careful of error returns from ops->show() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  Re: [PATCH 4.4 00/32] 4.4.61-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-04-10 22:40 +0200

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