diff options
Diffstat (limited to 'arch/mips/kernel/branch.c')
| -rw-r--r-- | arch/mips/kernel/branch.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c new file mode 100644 index 0000000..01117e9 --- /dev/null +++ b/arch/mips/kernel/branch.c @@ -0,0 +1,199 @@ +/* + * 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 <asm/branch.h> +#include <asm/cpu.h> +#include <asm/cpu-features.h> +#include <asm/inst.h> +#include <asm/ptrace.h> +#include <asm/uaccess.h> + +/* + * Compute the return address and do emulate branch simulation, if required. + */ +int __compute_return_epc(struct pt_regs *regs) +{ + unsigned int *addr, bit, fcr31; + long epc; + union mips_instruction insn; + + epc = regs->cp0_epc; + if (epc & 3) + goto unaligned; + + /* + * Read the instruction + */ + addr = (unsigned int *) epc; + if (__get_user(insn.word, addr)) { + force_sig(SIGSEGV, current); + return -EFAULT; + } + + regs->regs[0] = 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); + 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); + 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); + 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); + 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; + 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); + 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); + 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); + 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); + else + epc += 8; + regs->cp0_epc = epc; + break; + + /* + * And now the FPA/cp1 branch instructions. + */ + case cop1_op: + if (!cpu_has_fpu) + fcr31 = current->thread.fpu.soft.fcr31; + else + asm volatile("cfc1\t%0,$31" : "=r" (fcr31)); + bit = (insn.i_format.rt >> 2); + bit += (bit != 0); + bit += 23; + switch (insn.i_format.rt) { + case 0: /* bc1f */ + case 2: /* bc1fl */ + if (~fcr31 & (1 << bit)) + epc = epc + 4 + (insn.i_format.simmediate << 2); + 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); + else + epc += 8; + regs->cp0_epc = epc; + break; + } + break; + } + + return 0; + +unaligned: + printk("%s: unaligned epc - sending SIGBUS.\n", current->comm); + force_sig(SIGBUS, current); + return -EFAULT; +} |