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#include <asm/branch.h>
#include <asm/cacheflush.h>
#include <asm/fpu_emulator.h>
#include <asm/inst.h>
#include <asm/mipsregs.h>
#include <asm/uaccess.h>
#include "ieee754.h"
/*
* Emulate the arbritrary instruction ir at xcp->cp0_epc. Required when
* we have to emulate the instruction in a COP1 branch delay slot. Do
* not change cp0_epc due to the instruction
*
* According to the spec:
* 1) it shouldn't be a branch :-)
* 2) it can be a COP instruction :-(
* 3) if we are tring to run a protected memory space we must take
* special care on memory access instructions :-(
*/
/*
* "Trampoline" return routine to catch exception following
* execution of delay-slot instruction execution.
*/
struct emuframe {
mips_instruction emul;
mips_instruction badinst;
mips_instruction cookie;
unsigned long epc;
};
/*
* Set up an emulation frame for instruction IR, from a delay slot of
* a branch jumping to CPC. Return 0 if successful, -1 if no emulation
* required, otherwise a signal number causing a frame setup failure.
*/
int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
{
struct emuframe __user *fr;
int err;
/* NOP is easy */
if ((get_isa16_mode(regs->cp0_epc) && ((ir >> 16) == MM_NOP16)) ||
(ir == 0))
return -1;
pr_debug("dsemul %lx %lx\n", regs->cp0_epc, cpc);
/*
* The strategy is to push the instruction onto the user stack
* and put a trap after it which we can catch and jump to
* the required address any alternative apart from full
* instruction emulation!!.
*
* Algorithmics used a system call instruction, and
* borrowed that vector. MIPS/Linux version is a bit
* more heavyweight in the interests of portability and
* multiprocessor support. For Linux we generate a
* an unaligned access and force an address error exception.
*
* For embedded systems (stand-alone) we prefer to use a
* non-existing CP1 instruction. This prevents us from emulating
* branches, but gives us a cleaner interface to the exception
* handler (single entry point).
*/
/* Ensure that the two instructions are in the same cache line */
fr = (struct emuframe __user *)
((regs->regs[29] - sizeof(struct emuframe)) & ~0x7);
/* Verify that the stack pointer is not competely insane */
if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe))))
return SIGBUS;
if (get_isa16_mode(regs->cp0_epc)) {
err = __put_user(ir >> 16, (u16 __user *)(&fr->emul));
err |= __put_user(ir & 0xffff, (u16 __user *)((long)(&fr->emul) + 2));
err |= __put_user(BREAK_MATH >> 16, (u16 __user *)(&fr->badinst));
err |= __put_user(BREAK_MATH & 0xffff, (u16 __user *)((long)(&fr->badinst) + 2));
} else {
err = __put_user(ir, &fr->emul);
err |= __put_user((mips_instruction)BREAK_MATH, &fr->badinst);
}
err |= __put_user((mips_instruction)BD_COOKIE, &fr->cookie);
err |= __put_user(cpc, &fr->epc);
if (unlikely(err)) {
MIPS_FPU_EMU_INC_STATS(errors);
return SIGBUS;
}
regs->cp0_epc = ((unsigned long) &fr->emul) |
get_isa16_mode(regs->cp0_epc);
flush_cache_sigtramp((unsigned long)&fr->emul);
return 0;
}
int do_dsemulret(struct pt_regs *xcp)
{
struct emuframe __user *fr;
unsigned long epc;
u32 insn, cookie;
int err = 0;
u16 instr[2];
fr = (struct emuframe __user *)
(msk_isa16_mode(xcp->cp0_epc) - sizeof(mips_instruction));
/*
* If we can't even access the area, something is very wrong, but we'll
* leave that to the default handling
*/
if (!access_ok(VERIFY_READ, fr, sizeof(struct emuframe)))
return 0;
/*
* Do some sanity checking on the stackframe:
*
* - Is the instruction pointed to by the EPC an BREAK_MATH?
* - Is the following memory word the BD_COOKIE?
*/
if (get_isa16_mode(xcp->cp0_epc)) {
err = __get_user(instr[0], (u16 __user *)(&fr->badinst));
err |= __get_user(instr[1], (u16 __user *)((long)(&fr->badinst) + 2));
insn = (instr[0] << 16) | instr[1];
} else {
err = __get_user(insn, &fr->badinst);
}
err |= __get_user(cookie, &fr->cookie);
if (unlikely(err || (insn != BREAK_MATH) || (cookie != BD_COOKIE))) {
MIPS_FPU_EMU_INC_STATS(errors);
return 0;
}
/*
* At this point, we are satisfied that it's a BD emulation trap. Yes,
* a user might have deliberately put two malformed and useless
* instructions in a row in his program, in which case he's in for a
* nasty surprise - the next instruction will be treated as a
* continuation address! Alas, this seems to be the only way that we
* can handle signals, recursion, and longjmps() in the context of
* emulating the branch delay instruction.
*/
pr_debug("dsemulret\n");
if (__get_user(epc, &fr->epc)) { /* Saved EPC */
/* This is not a good situation to be in */
force_sig(SIGBUS, current);
return 0;
}
/* Set EPC to return to post-branch instruction */
xcp->cp0_epc = epc;
MIPS_FPU_EMU_INC_STATS(ds_emul);
return 1;
}
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