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parisc: Clean up fixup routines for get_user()/put_user()
Al Viro noticed that userspace accesses via get_user()/put_user() can be simplified a lot with regard to usage of the exception handling. This patch implements a fixup routine for get_user() and put_user() in such that the exception handler will automatically load -EFAULT into the register %r8 (the error value) in case on a fault on userspace. Additionally the fixup routine will zero the target register on fault in case of a get_user() call. The target register is extracted out of the faulting assembly instruction. This patch brings a few benefits over the old implementation: 1. Exception handling gets much cleaner, easier and smaller in size. 2. Helper functions like fixup_get_user_skip_1 (all of fixup.S) can be dropped. 3. No need to hardcode %r9 as target register for get_user() any longer. This helps the compiler register allocator and thus creates less assembler statements. 4. No dependency on the exception_data contents any longer. 5. Nested faults will be handled cleanly. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Cc: <stable@vger.kernel.org> # v4.9+ Signed-off-by: Helge Deller <deller@gmx.de>
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Helge Deller
parent
554bfeceb8
commit
d19f5e41b3
@ -64,6 +64,15 @@ struct exception_table_entry {
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".word (" #fault_addr " - .), (" #except_addr " - .)\n\t" \
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".previous\n"
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/*
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* ASM_EXCEPTIONTABLE_ENTRY_EFAULT() creates a special exception table entry
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* (with lowest bit set) for which the fault handler in fixup_exception() will
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* load -EFAULT into %r8 for a read or write fault, and zeroes the target
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* register in case of a read fault in get_user().
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*/
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#define ASM_EXCEPTIONTABLE_ENTRY_EFAULT( fault_addr, except_addr )\
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ASM_EXCEPTIONTABLE_ENTRY( fault_addr, except_addr + 1)
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/*
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* The page fault handler stores, in a per-cpu area, the following information
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* if a fixup routine is available.
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@ -91,7 +100,7 @@ struct exception_data {
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#define __get_user(x, ptr) \
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({ \
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register long __gu_err __asm__ ("r8") = 0; \
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register long __gu_val __asm__ ("r9") = 0; \
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register long __gu_val; \
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\
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load_sr2(); \
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switch (sizeof(*(ptr))) { \
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@ -107,22 +116,23 @@ struct exception_data {
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})
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#define __get_user_asm(ldx, ptr) \
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__asm__("\n1:\t" ldx "\t0(%%sr2,%2),%0\n\t" \
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ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_get_user_skip_1)\
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__asm__("1: " ldx " 0(%%sr2,%2),%0\n" \
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"9:\n" \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \
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: "=r"(__gu_val), "=r"(__gu_err) \
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: "r"(ptr), "1"(__gu_err) \
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: "r1");
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: "r"(ptr), "1"(__gu_err));
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#if !defined(CONFIG_64BIT)
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#define __get_user_asm64(ptr) \
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__asm__("\n1:\tldw 0(%%sr2,%2),%0" \
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"\n2:\tldw 4(%%sr2,%2),%R0\n\t" \
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ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_get_user_skip_2)\
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ASM_EXCEPTIONTABLE_ENTRY(2b, fixup_get_user_skip_1)\
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__asm__(" copy %%r0,%R0\n" \
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"1: ldw 0(%%sr2,%2),%0\n" \
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"2: ldw 4(%%sr2,%2),%R0\n" \
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"9:\n" \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(2b, 9b) \
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: "=r"(__gu_val), "=r"(__gu_err) \
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: "r"(ptr), "1"(__gu_err) \
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: "r1");
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: "r"(ptr), "1"(__gu_err));
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#endif /* !defined(CONFIG_64BIT) */
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@ -148,32 +158,31 @@ struct exception_data {
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* The "__put_user/kernel_asm()" macros tell gcc they read from memory
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* instead of writing. This is because they do not write to any memory
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* gcc knows about, so there are no aliasing issues. These macros must
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* also be aware that "fixup_put_user_skip_[12]" are executed in the
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* context of the fault, and any registers used there must be listed
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* as clobbers. In this case only "r1" is used by the current routines.
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* r8/r9 are already listed as err/val.
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* also be aware that fixups are executed in the context of the fault,
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* and any registers used there must be listed as clobbers.
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* r8 is already listed as err.
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*/
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#define __put_user_asm(stx, x, ptr) \
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__asm__ __volatile__ ( \
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"\n1:\t" stx "\t%2,0(%%sr2,%1)\n\t" \
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ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_put_user_skip_1)\
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"1: " stx " %2,0(%%sr2,%1)\n" \
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"9:\n" \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \
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: "=r"(__pu_err) \
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: "r"(ptr), "r"(x), "0"(__pu_err) \
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: "r1")
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: "r"(ptr), "r"(x), "0"(__pu_err))
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#if !defined(CONFIG_64BIT)
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#define __put_user_asm64(__val, ptr) do { \
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__asm__ __volatile__ ( \
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"\n1:\tstw %2,0(%%sr2,%1)" \
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"\n2:\tstw %R2,4(%%sr2,%1)\n\t" \
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ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_put_user_skip_2)\
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ASM_EXCEPTIONTABLE_ENTRY(2b, fixup_put_user_skip_1)\
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"1: stw %2,0(%%sr2,%1)\n" \
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"2: stw %R2,4(%%sr2,%1)\n" \
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"9:\n" \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \
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ASM_EXCEPTIONTABLE_ENTRY_EFAULT(2b, 9b) \
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: "=r"(__pu_err) \
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: "r"(ptr), "r"(__val), "0"(__pu_err) \
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: "r1"); \
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: "r"(ptr), "r"(__val), "0"(__pu_err)); \
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} while (0)
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#endif /* !defined(CONFIG_64BIT) */
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@ -47,16 +47,6 @@ EXPORT_SYMBOL(__cmpxchg_u64);
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EXPORT_SYMBOL(lclear_user);
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EXPORT_SYMBOL(lstrnlen_user);
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/* Global fixups - defined as int to avoid creation of function pointers */
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extern int fixup_get_user_skip_1;
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extern int fixup_get_user_skip_2;
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extern int fixup_put_user_skip_1;
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extern int fixup_put_user_skip_2;
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EXPORT_SYMBOL(fixup_get_user_skip_1);
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EXPORT_SYMBOL(fixup_get_user_skip_2);
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EXPORT_SYMBOL(fixup_put_user_skip_1);
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EXPORT_SYMBOL(fixup_put_user_skip_2);
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#ifndef CONFIG_64BIT
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/* Needed so insmod can set dp value */
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extern int $global$;
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@ -2,7 +2,7 @@
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# Makefile for parisc-specific library files
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#
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lib-y := lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o \
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lib-y := lusercopy.o bitops.o checksum.o io.o memset.o memcpy.o \
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ucmpdi2.o delay.o
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obj-y := iomap.o
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@ -1,98 +0,0 @@
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/*
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* Linux/PA-RISC Project (http://www.parisc-linux.org/)
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*
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* Copyright (C) 2004 Randolph Chung <tausq@debian.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* Fixup routines for kernel exception handling.
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*/
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#include <asm/asm-offsets.h>
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#include <asm/assembly.h>
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#include <asm/errno.h>
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#include <linux/linkage.h>
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#ifdef CONFIG_SMP
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.macro get_fault_ip t1 t2
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loadgp
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addil LT%__per_cpu_offset,%r27
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LDREG RT%__per_cpu_offset(%r1),\t1
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/* t2 = smp_processor_id() */
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mfctl 30,\t2
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ldw TI_CPU(\t2),\t2
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#ifdef CONFIG_64BIT
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extrd,u \t2,63,32,\t2
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#endif
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/* t2 = &__per_cpu_offset[smp_processor_id()]; */
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LDREGX \t2(\t1),\t2
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addil LT%exception_data,%r27
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LDREG RT%exception_data(%r1),\t1
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/* t1 = this_cpu_ptr(&exception_data) */
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add,l \t1,\t2,\t1
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/* %r27 = t1->fault_gp - restore gp */
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LDREG EXCDATA_GP(\t1), %r27
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/* t1 = t1->fault_ip */
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LDREG EXCDATA_IP(\t1), \t1
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.endm
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#else
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.macro get_fault_ip t1 t2
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loadgp
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/* t1 = this_cpu_ptr(&exception_data) */
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addil LT%exception_data,%r27
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LDREG RT%exception_data(%r1),\t2
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/* %r27 = t2->fault_gp - restore gp */
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LDREG EXCDATA_GP(\t2), %r27
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/* t1 = t2->fault_ip */
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LDREG EXCDATA_IP(\t2), \t1
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.endm
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#endif
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.level LEVEL
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.text
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.section .fixup, "ax"
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/* get_user() fixups, store -EFAULT in r8, and 0 in r9 */
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ENTRY_CFI(fixup_get_user_skip_1)
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get_fault_ip %r1,%r8
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ldo 4(%r1), %r1
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ldi -EFAULT, %r8
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bv %r0(%r1)
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copy %r0, %r9
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ENDPROC_CFI(fixup_get_user_skip_1)
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ENTRY_CFI(fixup_get_user_skip_2)
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get_fault_ip %r1,%r8
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ldo 8(%r1), %r1
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ldi -EFAULT, %r8
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bv %r0(%r1)
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copy %r0, %r9
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ENDPROC_CFI(fixup_get_user_skip_2)
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/* put_user() fixups, store -EFAULT in r8 */
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ENTRY_CFI(fixup_put_user_skip_1)
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get_fault_ip %r1,%r8
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ldo 4(%r1), %r1
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bv %r0(%r1)
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ldi -EFAULT, %r8
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ENDPROC_CFI(fixup_put_user_skip_1)
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ENTRY_CFI(fixup_put_user_skip_2)
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get_fault_ip %r1,%r8
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ldo 8(%r1), %r1
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bv %r0(%r1)
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ldi -EFAULT, %r8
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ENDPROC_CFI(fixup_put_user_skip_2)
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@ -150,6 +150,23 @@ int fixup_exception(struct pt_regs *regs)
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d->fault_space = regs->isr;
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d->fault_addr = regs->ior;
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/*
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* Fix up get_user() and put_user().
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* ASM_EXCEPTIONTABLE_ENTRY_EFAULT() sets the least-significant
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* bit in the relative address of the fixup routine to indicate
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* that %r8 should be loaded with -EFAULT to report a userspace
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* access error.
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*/
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if (fix->fixup & 1) {
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regs->gr[8] = -EFAULT;
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/* zero target register for get_user() */
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if (parisc_acctyp(0, regs->iir) == VM_READ) {
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int treg = regs->iir & 0x1f;
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regs->gr[treg] = 0;
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}
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}
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regs->iaoq[0] = (unsigned long)&fix->fixup + fix->fixup;
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regs->iaoq[0] &= ~3;
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/*
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