ARC: Unaligned access emulation
ARC700 doesn't natively support unaligned access, but can be emulated -Unaligned Access Exception -Disassembly at the Fault address to find the exact insn (long/short) Also per Arnd's comment, we runtime control it using 2 sysctl knobs: * SYSCTL_ARCH_UNALIGN_ALLOW: Runtime enable/disble * SYSCTL_ARCH_UNALIGN_NO_WARN: Warn on each emulation attempt Originally contributed by Tim Yao <tim.yao@amlogic.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Cc: Tim Yao <tim.yao@amlogic.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Vineet Gupta
parent
bf14e3b979
commit
2e651ea159
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@ -336,6 +336,17 @@ config ARC_CURR_IN_REG
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This reserved Register R25 to point to Current Task in
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kernel mode. This saves memory access for each such access
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config ARC_MISALIGN_ACCESS
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bool "Emulate unaligned memory access (userspace only)"
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default N
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select SYSCTL_ARCH_UNALIGN_NO_WARN
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select SYSCTL_ARCH_UNALIGN_ALLOW
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help
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This enables misaligned 16 & 32 bit memory access from user space.
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Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide
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potential bugs in code
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config ARC_STACK_NONEXEC
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bool "Make stack non-executable"
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default n
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@ -52,7 +52,6 @@ generic-y += topology.h
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generic-y += trace_clock.h
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generic-y += types.h
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generic-y += ucontext.h
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generic-y += unaligned.h
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generic-y += user.h
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generic-y += vga.h
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generic-y += xor.h
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@ -97,6 +97,9 @@ struct callee_regs {
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sp; \
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})
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/* return 1 if PC in delay slot */
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#define delay_mode(regs) ((regs->status32 & STATUS_DE_MASK) == STATUS_DE_MASK)
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#define in_syscall(regs) (regs->event & orig_r8_IS_SCALL)
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#define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT)
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@ -0,0 +1,29 @@
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/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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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 version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _ASM_ARC_UNALIGNED_H
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#define _ASM_ARC_UNALIGNED_H
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/* ARC700 can't handle unaligned Data accesses. */
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#include <asm-generic/unaligned.h>
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#include <asm/ptrace.h>
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#ifdef CONFIG_ARC_MISALIGN_ACCESS
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int misaligned_fixup(unsigned long address, struct pt_regs *regs,
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unsigned long cause, struct callee_regs *cregs);
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#else
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static inline int
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misaligned_fixup(unsigned long address, struct pt_regs *regs,
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unsigned long cause, struct callee_regs *cregs)
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{
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return 0;
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}
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#endif
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#endif /* _ASM_ARC_UNALIGNED_H */
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@ -16,6 +16,7 @@ obj-$(CONFIG_MODULES) += arcksyms.o module.o
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obj-$(CONFIG_SMP) += smp.o
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obj-$(CONFIG_ARC_DW2_UNWIND) += unwind.o
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obj-$(CONFIG_KPROBES) += kprobes.o
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obj-$(CONFIG_ARC_MISALIGN_ACCESS) += unaligned.o
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obj-$(CONFIG_ARC_FPU_SAVE_RESTORE) += fpu.o
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CFLAGS_fpu.o += -mdpfp
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@ -15,7 +15,7 @@
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#include <asm/disasm.h>
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#include <asm/uaccess.h>
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#if defined(CONFIG_KGDB) || defined(CONFIG_MISALIGN_ACCESS) || \
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#if defined(CONFIG_KGDB) || defined(CONFIG_ARC_MISALIGN_ACCESS) || \
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defined(CONFIG_KPROBES)
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/* disasm_instr: Analyses instruction at addr, stores
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@ -7,6 +7,9 @@
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg: May 2011
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* -Userspace unaligned access emulation
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*
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* vineetg: Feb 2011 (ptrace low level code fixes)
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* -traced syscall return code (r0) was not saved into pt_regs for restoring
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* into user reg-file when traded task rets to user space.
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@ -387,7 +390,17 @@ ARC_ENTRY EV_TLBProtV
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mov r1, r4 ; faulting address
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mov r2, sp ; pt_regs
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#ifdef CONFIG_ARC_MISALIGN_ACCESS
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SAVE_CALLEE_SAVED_USER
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mov r3, sp ; callee_regs
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#endif
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bl do_misaligned_access
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#ifdef CONFIG_ARC_MISALIGN_ACCESS
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DISCARD_CALLEE_SAVED_USER
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#endif
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b ret_from_exception
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ARC_EXIT EV_TLBProtV
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@ -7,6 +7,9 @@
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg: May 2011
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* -user-space unaligned access emulation
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*
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* Rahul Trivedi: Codito Technologies 2004
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*/
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@ -16,6 +19,7 @@
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#include <asm/ptrace.h>
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#include <asm/setup.h>
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#include <asm/kprobes.h>
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#include <asm/unaligned.h>
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void __init trap_init(void)
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{
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@ -79,7 +83,29 @@ DO_ERROR_INFO(SIGILL, "Illegal Insn (or Seq)", insterror_is_error, ILL_ILLOPC)
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DO_ERROR_INFO(SIGBUS, "Invalid Mem Access", do_memory_error, BUS_ADRERR)
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DO_ERROR_INFO(SIGTRAP, "Breakpoint Set", trap_is_brkpt, TRAP_BRKPT)
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#ifdef CONFIG_ARC_MISALIGN_ACCESS
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/*
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* Entry Point for Misaligned Data access Exception, for emulating in software
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*/
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int do_misaligned_access(unsigned long cause, unsigned long address,
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struct pt_regs *regs, struct callee_regs *cregs)
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{
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if (misaligned_fixup(address, regs, cause, cregs) != 0) {
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siginfo_t info;
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info.si_signo = SIGBUS;
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info.si_errno = 0;
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info.si_code = BUS_ADRALN;
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info.si_addr = (void __user *)address;
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return handle_exception(cause, "Misaligned Access", regs,
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&info);
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}
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return 0;
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}
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#else
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DO_ERROR_INFO(SIGSEGV, "Misaligned Access", do_misaligned_access, SEGV_ACCERR)
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#endif
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/*
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* Entry point for miscll errors such as Nested Exceptions
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@ -0,0 +1,245 @@
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/*
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* Copyright (C) 2011-2012 Synopsys (www.synopsys.com)
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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 version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg : May 2011
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* -Adapted (from .26 to .35)
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* -original contribution by Tim.yao@amlogic.com
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*
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*/
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/uaccess.h>
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#include <asm/disasm.h>
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#define __get8_unaligned_check(val, addr, err) \
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__asm__( \
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"1: ldb.ab %1, [%2, 1]\n" \
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"2:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"3: mov %0, 1\n" \
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" b 2b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 3b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (val), "=r" (addr) \
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: "0" (err), "2" (addr))
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#define get16_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v, a = addr; \
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__get8_unaligned_check(v, a, err); \
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val = v ; \
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__get8_unaligned_check(v, a, err); \
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val |= v << 8; \
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if (err) \
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goto fault; \
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} while (0)
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#define get32_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v, a = addr; \
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__get8_unaligned_check(v, a, err); \
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val = v << 0; \
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__get8_unaligned_check(v, a, err); \
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val |= v << 8; \
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__get8_unaligned_check(v, a, err); \
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val |= v << 16; \
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__get8_unaligned_check(v, a, err); \
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val |= v << 24; \
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if (err) \
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goto fault; \
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} while (0)
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#define put16_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v = val, a = addr;\
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\
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__asm__( \
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"1: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"2: stb %1, [%2]\n" \
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"3:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"4: mov %0, 1\n" \
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" b 3b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 4b\n" \
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" .long 2b, 4b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (v), "=&r" (a) \
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: "0" (err), "1" (v), "2" (a)); \
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\
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if (err) \
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goto fault; \
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} while (0)
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#define put32_unaligned_check(val, addr) \
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do { \
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unsigned int err = 0, v = val, a = addr;\
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__asm__( \
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\
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"1: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"2: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"3: stb.ab %1, [%2, 1]\n" \
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" lsr %1, %1, 8\n" \
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"4: stb %1, [%2]\n" \
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"5:\n" \
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" .section .fixup,\"ax\"\n" \
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" .align 4\n" \
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"6: mov %0, 1\n" \
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" b 5b\n" \
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" .previous\n" \
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" .section __ex_table,\"a\"\n" \
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" .align 4\n" \
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" .long 1b, 6b\n" \
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" .long 2b, 6b\n" \
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" .long 3b, 6b\n" \
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" .long 4b, 6b\n" \
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" .previous\n" \
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: "=r" (err), "=&r" (v), "=&r" (a) \
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: "0" (err), "1" (v), "2" (a)); \
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\
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if (err) \
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goto fault; \
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} while (0)
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/* sysctl hooks */
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int unaligned_enabled __read_mostly = 1; /* Enabled by default */
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int no_unaligned_warning __read_mostly = 1; /* Only 1 warning by default */
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static void fixup_load(struct disasm_state *state, struct pt_regs *regs,
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struct callee_regs *cregs)
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{
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int val;
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/* register write back */
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if ((state->aa == 1) || (state->aa == 2)) {
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set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs);
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if (state->aa == 2)
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state->src2 = 0;
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}
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if (state->zz == 0) {
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get32_unaligned_check(val, state->src1 + state->src2);
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} else {
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get16_unaligned_check(val, state->src1 + state->src2);
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if (state->x)
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val = (val << 16) >> 16;
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}
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if (state->pref == 0)
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set_reg(state->dest, val, regs, cregs);
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return;
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fault: state->fault = 1;
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}
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static void fixup_store(struct disasm_state *state, struct pt_regs *regs,
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struct callee_regs *cregs)
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{
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/* register write back */
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if ((state->aa == 1) || (state->aa == 2)) {
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set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs);
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if (state->aa == 3)
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state->src3 = 0;
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} else if (state->aa == 3) {
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if (state->zz == 2) {
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set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
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regs, cregs);
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} else if (!state->zz) {
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set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
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regs, cregs);
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} else {
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goto fault;
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}
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}
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/* write fix-up */
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if (!state->zz)
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put32_unaligned_check(state->src1, state->src2 + state->src3);
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else
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put16_unaligned_check(state->src1, state->src2 + state->src3);
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return;
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fault: state->fault = 1;
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}
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/*
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* Handle an unaligned access
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* Returns 0 if successfully handled, 1 if some error happened
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*/
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int misaligned_fixup(unsigned long address, struct pt_regs *regs,
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unsigned long cause, struct callee_regs *cregs)
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{
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struct disasm_state state;
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char buf[TASK_COMM_LEN];
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/* handle user mode only and only if enabled by sysadmin */
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if (!user_mode(regs) || !unaligned_enabled)
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return 1;
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if (no_unaligned_warning) {
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pr_warn_once("%s(%d) made unaligned access which was emulated"
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" by kernel assist\n. This can degrade application"
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" performance significantly\n. To enable further"
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" logging of such instances, please \n"
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" echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
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get_task_comm(buf, current), task_pid_nr(current));
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} else {
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/* Add rate limiting if it gets down to it */
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pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
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get_task_comm(buf, current), task_pid_nr(current),
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address, regs->ret);
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}
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disasm_instr(regs->ret, &state, 1, regs, cregs);
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if (state.fault)
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goto fault;
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/* ldb/stb should not have unaligned exception */
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if ((state.zz == 1) || (state.di))
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goto fault;
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if (!state.write)
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fixup_load(&state, regs, cregs);
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else
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fixup_store(&state, regs, cregs);
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if (state.fault)
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goto fault;
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if (delay_mode(regs)) {
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regs->ret = regs->bta;
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regs->status32 &= ~STATUS_DE_MASK;
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} else {
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regs->ret += state.instr_len;
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}
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return 0;
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fault:
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pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
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state.words[0], address);
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return 1;
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}
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