#include <linux/compiler.h>
#include <linux/mm.h>
#include <linux/signal.h>
#include <linux/smp.h>
#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/byteorder.h>
#include <asm/cpu.h>
#include <asm/inst.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/branch.h>
#include <asm/mipsregs.h>
#include <asm/system.h>
#include <asm/cacheflush.h>
#include <asm/fpu_emulator.h>
#include "ieee754.h"
#include "dsemul.h"
/* Strap kernel emulator for full MIPS IV emulation */
#ifdef __mips
#undef __mips
#endif
#define __mips 4
/*
* 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 shouldnt 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;
};
int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
{
extern asmlinkage void handle_dsemulret(void);
mips_instruction *dsemul_insns;
struct emuframe *fr;
int err;
if (ir == 0) { /* a nop is easy */
regs->cp0_epc = cpc;
regs->cp0_cause &= ~CAUSEF_BD;
return 0;
}
#ifdef DSEMUL_TRACE
printk("dsemul %lx %lx\n", regs->cp0_epc, cpc);
#endif
/*
* 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 */
dsemul_insns = (mips_instruction *) ((regs->regs[29] - sizeof(struct emuframe)) & ~0x7);
fr = (struct emuframe *) dsemul_insns;
/* Verify that the stack pointer is not competely insane */
if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe))))
return SIGBUS;
err = __put_user(ir, &fr->emul);
err |= __put_user((mips_instruction)BADINST, &fr->badinst);
err |= __put_user((mips_instruction)BD_COOKIE, &fr->cookie);
err |= __put_user(cpc, &fr->epc);
if (unlikely(err)) {
fpuemustats.errors++;
return SIGBUS;
}
regs->cp0_epc = (unsigned long) &fr->emul;
flush_cache_sigtramp((unsigned long)&fr->badinst);
return SIGILL; /* force out of emulation loop */
}
int do_dsemulret(struct pt_regs *xcp)
{
struct emuframe *fr;
unsigned long epc;
u32 insn, cookie;
int err = 0;
fr = (struct emuframe *) (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 BADINST?
* - Is the following memory word the BD_COOKIE?
*/
err = __get_user(insn, &fr->badinst);
err |= __get_user(cookie, &fr->cookie);
if (unlikely(err || (insn != BADINST) || (cookie != BD_COOKIE))) {
fpuemustats.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.
*/
#ifdef DSEMUL_TRACE
printk("dsemulret\n");
#endif
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;
return 1;
}
