551 lines
13 KiB
C
551 lines
13 KiB
C
/*
|
|
* Handle unaligned accesses by emulation.
|
|
*
|
|
* This file is subject to the terms and conditions of the GNU General Public
|
|
* License. See the file "COPYING" in the main directory of this archive
|
|
* for more details.
|
|
*
|
|
* Copyright (C) 1996, 1998, 1999, 2002 by Ralf Baechle
|
|
* Copyright (C) 1999 Silicon Graphics, Inc.
|
|
*
|
|
* This file contains exception handler for address error exception with the
|
|
* special capability to execute faulting instructions in software. The
|
|
* handler does not try to handle the case when the program counter points
|
|
* to an address not aligned to a word boundary.
|
|
*
|
|
* Putting data to unaligned addresses is a bad practice even on Intel where
|
|
* only the performance is affected. Much worse is that such code is non-
|
|
* portable. Due to several programs that die on MIPS due to alignment
|
|
* problems I decided to implement this handler anyway though I originally
|
|
* didn't intend to do this at all for user code.
|
|
*
|
|
* For now I enable fixing of address errors by default to make life easier.
|
|
* I however intend to disable this somewhen in the future when the alignment
|
|
* problems with user programs have been fixed. For programmers this is the
|
|
* right way to go.
|
|
*
|
|
* Fixing address errors is a per process option. The option is inherited
|
|
* across fork(2) and execve(2) calls. If you really want to use the
|
|
* option in your user programs - I discourage the use of the software
|
|
* emulation strongly - use the following code in your userland stuff:
|
|
*
|
|
* #include <sys/sysmips.h>
|
|
*
|
|
* ...
|
|
* sysmips(MIPS_FIXADE, x);
|
|
* ...
|
|
*
|
|
* The argument x is 0 for disabling software emulation, enabled otherwise.
|
|
*
|
|
* Below a little program to play around with this feature.
|
|
*
|
|
* #include <stdio.h>
|
|
* #include <sys/sysmips.h>
|
|
*
|
|
* struct foo {
|
|
* unsigned char bar[8];
|
|
* };
|
|
*
|
|
* main(int argc, char *argv[])
|
|
* {
|
|
* struct foo x = {0, 1, 2, 3, 4, 5, 6, 7};
|
|
* unsigned int *p = (unsigned int *) (x.bar + 3);
|
|
* int i;
|
|
*
|
|
* if (argc > 1)
|
|
* sysmips(MIPS_FIXADE, atoi(argv[1]));
|
|
*
|
|
* printf("*p = %08lx\n", *p);
|
|
*
|
|
* *p = 0xdeadface;
|
|
*
|
|
* for(i = 0; i <= 7; i++)
|
|
* printf("%02x ", x.bar[i]);
|
|
* printf("\n");
|
|
* }
|
|
*
|
|
* Coprocessor loads are not supported; I think this case is unimportant
|
|
* in the practice.
|
|
*
|
|
* TODO: Handle ndc (attempted store to doubleword in uncached memory)
|
|
* exception for the R6000.
|
|
* A store crossing a page boundary might be executed only partially.
|
|
* Undo the partial store in this case.
|
|
*/
|
|
#include <linux/config.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/module.h>
|
|
#include <linux/signal.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/smp_lock.h>
|
|
|
|
#include <asm/asm.h>
|
|
#include <asm/branch.h>
|
|
#include <asm/byteorder.h>
|
|
#include <asm/inst.h>
|
|
#include <asm/uaccess.h>
|
|
#include <asm/system.h>
|
|
|
|
#define STR(x) __STR(x)
|
|
#define __STR(x) #x
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
unsigned long unaligned_instructions;
|
|
#endif
|
|
|
|
static inline int emulate_load_store_insn(struct pt_regs *regs,
|
|
void *addr, unsigned long pc,
|
|
unsigned long **regptr, unsigned long *newvalue)
|
|
{
|
|
union mips_instruction insn;
|
|
unsigned long value;
|
|
unsigned int res;
|
|
|
|
regs->regs[0] = 0;
|
|
*regptr=NULL;
|
|
|
|
/*
|
|
* This load never faults.
|
|
*/
|
|
__get_user(insn.word, (unsigned int *)pc);
|
|
|
|
switch (insn.i_format.opcode) {
|
|
/*
|
|
* These are instructions that a compiler doesn't generate. We
|
|
* can assume therefore that the code is MIPS-aware and
|
|
* really buggy. Emulating these instructions would break the
|
|
* semantics anyway.
|
|
*/
|
|
case ll_op:
|
|
case lld_op:
|
|
case sc_op:
|
|
case scd_op:
|
|
|
|
/*
|
|
* For these instructions the only way to create an address
|
|
* error is an attempted access to kernel/supervisor address
|
|
* space.
|
|
*/
|
|
case ldl_op:
|
|
case ldr_op:
|
|
case lwl_op:
|
|
case lwr_op:
|
|
case sdl_op:
|
|
case sdr_op:
|
|
case swl_op:
|
|
case swr_op:
|
|
case lb_op:
|
|
case lbu_op:
|
|
case sb_op:
|
|
goto sigbus;
|
|
|
|
/*
|
|
* The remaining opcodes are the ones that are really of interest.
|
|
*/
|
|
case lh_op:
|
|
if (!access_ok(VERIFY_READ, addr, 2))
|
|
goto sigbus;
|
|
|
|
__asm__ __volatile__ (".set\tnoat\n"
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tlb\t%0, 0(%2)\n"
|
|
"2:\tlbu\t$1, 1(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tlb\t%0, 1(%2)\n"
|
|
"2:\tlbu\t$1, 0(%2)\n\t"
|
|
#endif
|
|
"sll\t%0, 0x8\n\t"
|
|
"or\t%0, $1\n\t"
|
|
"li\t%1, 0\n"
|
|
"3:\t.set\tat\n\t"
|
|
".section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%1, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=&r" (value), "=r" (res)
|
|
: "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
*newvalue = value;
|
|
*regptr = ®s->regs[insn.i_format.rt];
|
|
break;
|
|
|
|
case lw_op:
|
|
if (!access_ok(VERIFY_READ, addr, 4))
|
|
goto sigbus;
|
|
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tlwl\t%0, (%2)\n"
|
|
"2:\tlwr\t%0, 3(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tlwl\t%0, 3(%2)\n"
|
|
"2:\tlwr\t%0, (%2)\n\t"
|
|
#endif
|
|
"li\t%1, 0\n"
|
|
"3:\t.section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%1, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=&r" (value), "=r" (res)
|
|
: "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
*newvalue = value;
|
|
*regptr = ®s->regs[insn.i_format.rt];
|
|
break;
|
|
|
|
case lhu_op:
|
|
if (!access_ok(VERIFY_READ, addr, 2))
|
|
goto sigbus;
|
|
|
|
__asm__ __volatile__ (
|
|
".set\tnoat\n"
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tlbu\t%0, 0(%2)\n"
|
|
"2:\tlbu\t$1, 1(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tlbu\t%0, 1(%2)\n"
|
|
"2:\tlbu\t$1, 0(%2)\n\t"
|
|
#endif
|
|
"sll\t%0, 0x8\n\t"
|
|
"or\t%0, $1\n\t"
|
|
"li\t%1, 0\n"
|
|
"3:\t.set\tat\n\t"
|
|
".section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%1, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=&r" (value), "=r" (res)
|
|
: "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
*newvalue = value;
|
|
*regptr = ®s->regs[insn.i_format.rt];
|
|
break;
|
|
|
|
case lwu_op:
|
|
#ifdef CONFIG_64BIT
|
|
/*
|
|
* A 32-bit kernel might be running on a 64-bit processor. But
|
|
* if we're on a 32-bit processor and an i-cache incoherency
|
|
* or race makes us see a 64-bit instruction here the sdl/sdr
|
|
* would blow up, so for now we don't handle unaligned 64-bit
|
|
* instructions on 32-bit kernels.
|
|
*/
|
|
if (!access_ok(VERIFY_READ, addr, 4))
|
|
goto sigbus;
|
|
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tlwl\t%0, (%2)\n"
|
|
"2:\tlwr\t%0, 3(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tlwl\t%0, 3(%2)\n"
|
|
"2:\tlwr\t%0, (%2)\n\t"
|
|
#endif
|
|
"dsll\t%0, %0, 32\n\t"
|
|
"dsrl\t%0, %0, 32\n\t"
|
|
"li\t%1, 0\n"
|
|
"3:\t.section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%1, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=&r" (value), "=r" (res)
|
|
: "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
*newvalue = value;
|
|
*regptr = ®s->regs[insn.i_format.rt];
|
|
break;
|
|
#endif /* CONFIG_64BIT */
|
|
|
|
/* Cannot handle 64-bit instructions in 32-bit kernel */
|
|
goto sigill;
|
|
|
|
case ld_op:
|
|
#ifdef CONFIG_64BIT
|
|
/*
|
|
* A 32-bit kernel might be running on a 64-bit processor. But
|
|
* if we're on a 32-bit processor and an i-cache incoherency
|
|
* or race makes us see a 64-bit instruction here the sdl/sdr
|
|
* would blow up, so for now we don't handle unaligned 64-bit
|
|
* instructions on 32-bit kernels.
|
|
*/
|
|
if (!access_ok(VERIFY_READ, addr, 8))
|
|
goto sigbus;
|
|
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tldl\t%0, (%2)\n"
|
|
"2:\tldr\t%0, 7(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tldl\t%0, 7(%2)\n"
|
|
"2:\tldr\t%0, (%2)\n\t"
|
|
#endif
|
|
"li\t%1, 0\n"
|
|
"3:\t.section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%1, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=&r" (value), "=r" (res)
|
|
: "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
*newvalue = value;
|
|
*regptr = ®s->regs[insn.i_format.rt];
|
|
break;
|
|
#endif /* CONFIG_64BIT */
|
|
|
|
/* Cannot handle 64-bit instructions in 32-bit kernel */
|
|
goto sigill;
|
|
|
|
case sh_op:
|
|
if (!access_ok(VERIFY_WRITE, addr, 2))
|
|
goto sigbus;
|
|
|
|
value = regs->regs[insn.i_format.rt];
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
".set\tnoat\n"
|
|
"1:\tsb\t%1, 1(%2)\n\t"
|
|
"srl\t$1, %1, 0x8\n"
|
|
"2:\tsb\t$1, 0(%2)\n\t"
|
|
".set\tat\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
".set\tnoat\n"
|
|
"1:\tsb\t%1, 0(%2)\n\t"
|
|
"srl\t$1,%1, 0x8\n"
|
|
"2:\tsb\t$1, 1(%2)\n\t"
|
|
".set\tat\n\t"
|
|
#endif
|
|
"li\t%0, 0\n"
|
|
"3:\n\t"
|
|
".section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%0, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=r" (res)
|
|
: "r" (value), "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
break;
|
|
|
|
case sw_op:
|
|
if (!access_ok(VERIFY_WRITE, addr, 4))
|
|
goto sigbus;
|
|
|
|
value = regs->regs[insn.i_format.rt];
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tswl\t%1,(%2)\n"
|
|
"2:\tswr\t%1, 3(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tswl\t%1, 3(%2)\n"
|
|
"2:\tswr\t%1, (%2)\n\t"
|
|
#endif
|
|
"li\t%0, 0\n"
|
|
"3:\n\t"
|
|
".section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%0, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=r" (res)
|
|
: "r" (value), "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
break;
|
|
|
|
case sd_op:
|
|
#ifdef CONFIG_64BIT
|
|
/*
|
|
* A 32-bit kernel might be running on a 64-bit processor. But
|
|
* if we're on a 32-bit processor and an i-cache incoherency
|
|
* or race makes us see a 64-bit instruction here the sdl/sdr
|
|
* would blow up, so for now we don't handle unaligned 64-bit
|
|
* instructions on 32-bit kernels.
|
|
*/
|
|
if (!access_ok(VERIFY_WRITE, addr, 8))
|
|
goto sigbus;
|
|
|
|
value = regs->regs[insn.i_format.rt];
|
|
__asm__ __volatile__ (
|
|
#ifdef __BIG_ENDIAN
|
|
"1:\tsdl\t%1,(%2)\n"
|
|
"2:\tsdr\t%1, 7(%2)\n\t"
|
|
#endif
|
|
#ifdef __LITTLE_ENDIAN
|
|
"1:\tsdl\t%1, 7(%2)\n"
|
|
"2:\tsdr\t%1, (%2)\n\t"
|
|
#endif
|
|
"li\t%0, 0\n"
|
|
"3:\n\t"
|
|
".section\t.fixup,\"ax\"\n\t"
|
|
"4:\tli\t%0, %3\n\t"
|
|
"j\t3b\n\t"
|
|
".previous\n\t"
|
|
".section\t__ex_table,\"a\"\n\t"
|
|
STR(PTR)"\t1b, 4b\n\t"
|
|
STR(PTR)"\t2b, 4b\n\t"
|
|
".previous"
|
|
: "=r" (res)
|
|
: "r" (value), "r" (addr), "i" (-EFAULT));
|
|
if (res)
|
|
goto fault;
|
|
break;
|
|
#endif /* CONFIG_64BIT */
|
|
|
|
/* Cannot handle 64-bit instructions in 32-bit kernel */
|
|
goto sigill;
|
|
|
|
case lwc1_op:
|
|
case ldc1_op:
|
|
case swc1_op:
|
|
case sdc1_op:
|
|
/*
|
|
* I herewith declare: this does not happen. So send SIGBUS.
|
|
*/
|
|
goto sigbus;
|
|
|
|
case lwc2_op:
|
|
case ldc2_op:
|
|
case swc2_op:
|
|
case sdc2_op:
|
|
/*
|
|
* These are the coprocessor 2 load/stores. The current
|
|
* implementations don't use cp2 and cp2 should always be
|
|
* disabled in c0_status. So send SIGILL.
|
|
* (No longer true: The Sony Praystation uses cp2 for
|
|
* 3D matrix operations. Dunno if that thingy has a MMU ...)
|
|
*/
|
|
default:
|
|
/*
|
|
* Pheeee... We encountered an yet unknown instruction or
|
|
* cache coherence problem. Die sucker, die ...
|
|
*/
|
|
goto sigill;
|
|
}
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
unaligned_instructions++;
|
|
#endif
|
|
|
|
return 0;
|
|
|
|
fault:
|
|
/* Did we have an exception handler installed? */
|
|
if (fixup_exception(regs))
|
|
return 1;
|
|
|
|
die_if_kernel ("Unhandled kernel unaligned access", regs);
|
|
send_sig(SIGSEGV, current, 1);
|
|
|
|
return 0;
|
|
|
|
sigbus:
|
|
die_if_kernel("Unhandled kernel unaligned access", regs);
|
|
send_sig(SIGBUS, current, 1);
|
|
|
|
return 0;
|
|
|
|
sigill:
|
|
die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs);
|
|
send_sig(SIGILL, current, 1);
|
|
|
|
return 0;
|
|
}
|
|
|
|
asmlinkage void do_ade(struct pt_regs *regs)
|
|
{
|
|
unsigned long *regptr, newval;
|
|
extern int do_dsemulret(struct pt_regs *);
|
|
mm_segment_t seg;
|
|
unsigned long pc;
|
|
|
|
/*
|
|
* Address errors may be deliberately induced by the FPU emulator to
|
|
* retake control of the CPU after executing the instruction in the
|
|
* delay slot of an emulated branch.
|
|
*/
|
|
/* Terminate if exception was recognized as a delay slot return */
|
|
if (do_dsemulret(regs))
|
|
return;
|
|
|
|
/* Otherwise handle as normal */
|
|
|
|
/*
|
|
* Did we catch a fault trying to load an instruction?
|
|
* Or are we running in MIPS16 mode?
|
|
*/
|
|
if ((regs->cp0_badvaddr == regs->cp0_epc) || (regs->cp0_epc & 0x1))
|
|
goto sigbus;
|
|
|
|
pc = exception_epc(regs);
|
|
if ((current->thread.mflags & MF_FIXADE) == 0)
|
|
goto sigbus;
|
|
|
|
/*
|
|
* Do branch emulation only if we didn't forward the exception.
|
|
* This is all so but ugly ...
|
|
*/
|
|
seg = get_fs();
|
|
if (!user_mode(regs))
|
|
set_fs(KERNEL_DS);
|
|
if (!emulate_load_store_insn(regs, (void *)regs->cp0_badvaddr, pc,
|
|
®ptr, &newval)) {
|
|
compute_return_epc(regs);
|
|
/*
|
|
* Now that branch is evaluated, update the dest
|
|
* register if necessary
|
|
*/
|
|
if (regptr)
|
|
*regptr = newval;
|
|
}
|
|
set_fs(seg);
|
|
|
|
return;
|
|
|
|
sigbus:
|
|
die_if_kernel("Kernel unaligned instruction access", regs);
|
|
force_sig(SIGBUS, current);
|
|
|
|
/*
|
|
* XXX On return from the signal handler we should advance the epc
|
|
*/
|
|
}
|