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MIPS: microMIPS: Support handling of delay slots. 

Add logic needed to properly calculate exceptions for delay slots
when in microMIPS mode.

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
This commit is contained in:
Leonid Yegoshin 2013-03-25 13:08:40 -05:00 committed by Ralf Baechle
parent 2a0b24f56c
commit fb6883e580
2 changed files with 102 additions and 5 deletions
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22
arch/mips/include/asm/branch.h
View File

@ -11,6 +11,13 @@
#include <asm/ptrace.h>
#include <asm/inst.h>
extern int __isa_exception_epc(struct pt_regs *regs);
extern int __compute_return_epc(struct pt_regs *regs);
extern int __compute_return_epc_for_insn(struct pt_regs *regs,
union mips_instruction insn);
extern int __microMIPS_compute_return_epc(struct pt_regs *regs);
static inline int delay_slot(struct pt_regs *regs)
{
return regs->cp0_cause & CAUSEF_BD;
@ -18,20 +25,25 @@ static inline int delay_slot(struct pt_regs *regs)
static inline unsigned long exception_epc(struct pt_regs *regs)
{
if (!delay_slot(regs))
if (likely(!delay_slot(regs)))
return regs->cp0_epc;
if (get_isa16_mode(regs->cp0_epc))
return __isa_exception_epc(regs);
return regs->cp0_epc + 4;
}
#define BRANCH_LIKELY_TAKEN 0x0001
extern int __compute_return_epc(struct pt_regs *regs);
extern int __compute_return_epc_for_insn(struct pt_regs *regs,
union mips_instruction insn);
static inline int compute_return_epc(struct pt_regs *regs)
{
if (get_isa16_mode(regs->cp0_epc)) {
if (cpu_has_mmips)
return __microMIPS_compute_return_epc(regs);
return regs->cp0_epc;
}
if (!delay_slot(regs)) {
regs->cp0_epc += 4;
return 0;

85
arch/mips/kernel/branch.c
View File

@ -14,10 +14,93 @@
#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. It does not clear the ISA mode bit.
*/
int __isa_exception_epc(struct pt_regs *regs)
{
long epc = regs->cp0_epc;
unsigned short inst;
/* 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 (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_epc_for_insn - Computes the return address and do emulate
* branch simulation, if required.
@ -129,6 +212,8 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
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;
/*