diff options
| author | Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> | 2013-03-25 13:08:40 -0500 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2013-05-09 17:55:18 +0200 |
| commit | fb6883e5809c08e43de23581759af4570ca91b0f (patch) | |
| tree | 2bf479748d969f85c79cb8880a1573b2ca7c61ee /arch/mips/kernel/branch.c | |
| parent | 2a0b24f56c2492b932f1aed617ae80fb23500d21 (diff) | |
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>
Diffstat (limited to 'arch/mips/kernel/branch.c')
| -rw-r--r-- | arch/mips/kernel/branch.c | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c index 83ffe950f710..a03836b5b683 100644 --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -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; /* |