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linux/arch/mips/kernel/branch.c

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/*
* 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, 97, 2000, 2001 by Ralf Baechle
* Copyright (C) 2001 MIPS Technologies, Inc.
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/module.h>
#include <asm/branch.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/fpu.h>
#include <asm/fpu_emulator.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
/*
* Calculate and return exception PC in case of branch delay slot
* for microMIPS and MIPS16e. It does not clear the ISA mode bit.
*/
int __isa_exception_epc(struct pt_regs *regs)
{
unsigned short inst;
long epc = regs->cp0_epc;
/* Calculate exception PC in branch delay slot. */
if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
/* This should never happen because delay slot was checked. */
force_sig(SIGSEGV, current);
return epc;
}
if (cpu_has_mips16) {
if (((union mips16e_instruction)inst).ri.opcode
== MIPS16e_jal_op)
epc += 4;
else
epc += 2;
} else if (mm_insn_16bit(inst))
epc += 2;
else
epc += 4;
return epc;
}
/*
* Compute return address and emulate branch in microMIPS mode after an
* exception only. It does not handle compact branches/jumps and cannot
* be used in interrupt context. (Compact branches/jumps do not cause
* exceptions.)
*/
int __microMIPS_compute_return_epc(struct pt_regs *regs)
{
u16 __user *pc16;
u16 halfword;
unsigned int word;
unsigned long contpc;
struct mm_decoded_insn mminsn = { 0 };
mminsn.micro_mips_mode = 1;
/* This load never faults. */
pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
__get_user(halfword, pc16);
pc16++;
contpc = regs->cp0_epc + 2;
word = ((unsigned int)halfword << 16);
mminsn.pc_inc = 2;
if (!mm_insn_16bit(halfword)) {
__get_user(halfword, pc16);
pc16++;
contpc = regs->cp0_epc + 4;
mminsn.pc_inc = 4;
word |= halfword;
}
mminsn.insn = word;
if (get_user(halfword, pc16))
goto sigsegv;
mminsn.next_pc_inc = 2;
word = ((unsigned int)halfword << 16);
if (!mm_insn_16bit(halfword)) {
pc16++;
if (get_user(halfword, pc16))
goto sigsegv;
mminsn.next_pc_inc = 4;
word |= halfword;
}
mminsn.next_insn = word;
mm_isBranchInstr(regs, mminsn, &contpc);
regs->cp0_epc = contpc;
return 0;
sigsegv:
force_sig(SIGSEGV, current);
return -EFAULT;
}
/*
* Compute return address and emulate branch in MIPS16e mode after an
* exception only. It does not handle compact branches/jumps and cannot
* be used in interrupt context. (Compact branches/jumps do not cause
* exceptions.)
*/
int __MIPS16e_compute_return_epc(struct pt_regs *regs)
{
u16 __user *addr;
union mips16e_instruction inst;
u16 inst2;
u32 fullinst;
long epc;
epc = regs->cp0_epc;
/* Read the instruction. */
addr = (u16 __user *)msk_isa16_mode(epc);
if (__get_user(inst.full, addr)) {
force_sig(SIGSEGV, current);
return -EFAULT;
}
switch (inst.ri.opcode) {
case MIPS16e_extend_op:
regs->cp0_epc += 4;
return 0;
/*
* JAL and JALX in MIPS16e mode
*/
case MIPS16e_jal_op:
addr += 1;
if (__get_user(inst2, addr)) {
force_sig(SIGSEGV, current);
return -EFAULT;
}
fullinst = ((unsigned)inst.full << 16) | inst2;
regs->regs[31] = epc + 6;
epc += 4;
epc >>= 28;
epc <<= 28;
/*
* JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
*
* ......TARGET[15:0].................TARGET[20:16]...........
* ......TARGET[25:21]
*/
epc |=
((fullinst & 0xffff) << 2) | ((fullinst & 0x3e00000) >> 3) |
((fullinst & 0x1f0000) << 7);
if (!inst.jal.x)
set_isa16_mode(epc); /* Set ISA mode bit. */
regs->cp0_epc = epc;
return 0;
/*
* J(AL)R(C)
*/
case MIPS16e_rr_op:
if (inst.rr.func == MIPS16e_jr_func) {
if (inst.rr.ra)
regs->cp0_epc = regs->regs[31];
else
regs->cp0_epc =
regs->regs[reg16to32[inst.rr.rx]];
if (inst.rr.l) {
if (inst.rr.nd)
regs->regs[31] = epc + 2;
else
regs->regs[31] = epc + 4;
}
return 0;
}
break;
}
/*
* All other cases have no branch delay slot and are 16-bits.
* Branches do not cause an exception.
*/
regs->cp0_epc += 2;
return 0;
}
/**
* __compute_return_epc_for_insn - Computes the return address and do emulate
* branch simulation, if required.
*
* @regs: Pointer to pt_regs
* @insn: branch instruction to decode
* @returns: -EFAULT on error and forces SIGBUS, and on success
* returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
* evaluating the branch.
*/
int __compute_return_epc_for_insn(struct pt_regs *regs,
union mips_instruction insn)
{
unsigned int bit, fcr31, dspcontrol;
long epc = regs->cp0_epc;
int ret = 0;
switch (insn.i_format.opcode) {
/*
* jr and jalr are in r_format format.
*/
case spec_op:
switch (insn.r_format.func) {
case jalr_op:
regs->regs[insn.r_format.rd] = epc + 8;
/* Fall through */
case jr_op:
regs->cp0_epc = regs->regs[insn.r_format.rs];
break;
}
break;
/*
* This group contains:
* bltz_op, bgez_op, bltzl_op, bgezl_op,
* bltzal_op, bgezal_op, bltzall_op, bgezall_op.
*/
case bcond_op:
switch (insn.i_format.rt) {
case bltz_op:
case bltzl_op:
if ((long)regs->regs[insn.i_format.rs] < 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bltzl_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bgez_op:
case bgezl_op:
if ((long)regs->regs[insn.i_format.rs] >= 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bgezl_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bltzal_op:
case bltzall_op:
regs->regs[31] = epc + 8;
if ((long)regs->regs[insn.i_format.rs] < 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bltzall_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bgezal_op:
case bgezall_op:
regs->regs[31] = epc + 8;
if ((long)regs->regs[insn.i_format.rs] >= 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bgezall_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bposge32_op:
if (!cpu_has_dsp)
goto sigill;
dspcontrol = rddsp(0x01);
if (dspcontrol >= 32) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
} else
epc += 8;
regs->cp0_epc = epc;
break;
}
break;
/*
* These are unconditional and in j_format.
*/
case jal_op:
regs->regs[31] = regs->cp0_epc + 8;
case j_op:
epc += 4;
epc >>= 28;
epc <<= 28;
epc |= (insn.j_format.target << 2);
regs->cp0_epc = epc;
if (insn.i_format.opcode == jalx_op)
set_isa16_mode(regs->cp0_epc);
break;
/*
* These are conditional and in i_format.
*/
case beq_op:
case beql_op:
if (regs->regs[insn.i_format.rs] ==
regs->regs[insn.i_format.rt]) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == beql_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bne_op:
case bnel_op:
if (regs->regs[insn.i_format.rs] !=
regs->regs[insn.i_format.rt]) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bnel_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case blez_op: /* not really i_format */
case blezl_op:
/* rt field assumed to be zero */
if ((long)regs->regs[insn.i_format.rs] <= 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bnel_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case bgtz_op:
case bgtzl_op:
/* rt field assumed to be zero */
if ((long)regs->regs[insn.i_format.rs] > 0) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == bnel_op)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
/*
* And now the FPA/cp1 branch instructions.
*/
case cop1_op:
preempt_disable();
if (is_fpu_owner())
asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
else
fcr31 = current->thread.fpu.fcr31;
preempt_enable();
bit = (insn.i_format.rt >> 2);
bit += (bit != 0);
bit += 23;
switch (insn.i_format.rt & 3) {
case 0: /* bc1f */
case 2: /* bc1fl */
if (~fcr31 & (1 << bit)) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == 2)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
case 1: /* bc1t */
case 3: /* bc1tl */
if (fcr31 & (1 << bit)) {
epc = epc + 4 + (insn.i_format.simmediate << 2);
if (insn.i_format.rt == 3)
ret = BRANCH_LIKELY_TAKEN;
} else
epc += 8;
regs->cp0_epc = epc;
break;
}
break;
#ifdef CONFIG_CPU_CAVIUM_OCTEON
case lwc2_op: /* This is bbit0 on Octeon */
if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
== 0)
epc = epc + 4 + (insn.i_format.simmediate << 2);
else
epc += 8;
regs->cp0_epc = epc;
break;
case ldc2_op: /* This is bbit032 on Octeon */
if ((regs->regs[insn.i_format.rs] &
(1ull<<(insn.i_format.rt+32))) == 0)
epc = epc + 4 + (insn.i_format.simmediate << 2);
else
epc += 8;
regs->cp0_epc = epc;
break;
case swc2_op: /* This is bbit1 on Octeon */
if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
epc = epc + 4 + (insn.i_format.simmediate << 2);
else
epc += 8;
regs->cp0_epc = epc;
break;
case sdc2_op: /* This is bbit132 on Octeon */
if (regs->regs[insn.i_format.rs] &
(1ull<<(insn.i_format.rt+32)))
epc = epc + 4 + (insn.i_format.simmediate << 2);
else
epc += 8;
regs->cp0_epc = epc;
break;
#endif
}
return ret;
sigill:
printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
force_sig(SIGBUS, current);
return -EFAULT;
}
EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);
int __compute_return_epc(struct pt_regs *regs)
{
unsigned int __user *addr;
long epc;
union mips_instruction insn;
epc = regs->cp0_epc;
if (epc & 3)
goto unaligned;
/*
* Read the instruction
*/
addr = (unsigned int __user *) epc;
if (__get_user(insn.word, addr)) {
force_sig(SIGSEGV, current);
return -EFAULT;
}
return __compute_return_epc_for_insn(regs, insn);
unaligned:
printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
force_sig(SIGBUS, current);
return -EFAULT;
}
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