diff options
Diffstat (limited to 'arch/powerpc/lib/sstep.c')
| -rw-r--r-- | arch/powerpc/lib/sstep.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c new file mode 100644 index 00000000000..e79123d1485 --- /dev/null +++ b/arch/powerpc/lib/sstep.c @@ -0,0 +1,141 @@ +/* + * Single-step support. + * + * Copyright (C) 2004 Paul Mackerras <paulus@au.ibm.com>, IBM + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ +#include <linux/kernel.h> +#include <linux/ptrace.h> +#include <asm/sstep.h> +#include <asm/processor.h> + +extern char system_call_common[]; + +/* Bits in SRR1 that are copied from MSR */ +#define MSR_MASK 0xffffffff87c0ffff + +/* + * Determine whether a conditional branch instruction would branch. + */ +static int branch_taken(unsigned int instr, struct pt_regs *regs) +{ + unsigned int bo = (instr >> 21) & 0x1f; + unsigned int bi; + + if ((bo & 4) == 0) { + /* decrement counter */ + --regs->ctr; + if (((bo >> 1) & 1) ^ (regs->ctr == 0)) + return 0; + } + if ((bo & 0x10) == 0) { + /* check bit from CR */ + bi = (instr >> 16) & 0x1f; + if (((regs->ccr >> (31 - bi)) & 1) != ((bo >> 3) & 1)) + return 0; + } + return 1; +} + +/* + * Emulate instructions that cause a transfer of control. + * Returns 1 if the step was emulated, 0 if not, + * or -1 if the instruction is one that should not be stepped, + * such as an rfid, or a mtmsrd that would clear MSR_RI. + */ +int emulate_step(struct pt_regs *regs, unsigned int instr) +{ + unsigned int opcode, rd; + unsigned long int imm; + + opcode = instr >> 26; + switch (opcode) { + case 16: /* bc */ + imm = (signed short)(instr & 0xfffc); + if ((instr & 2) == 0) + imm += regs->nip; + regs->nip += 4; + if ((regs->msr & MSR_SF) == 0) + regs->nip &= 0xffffffffUL; + if (instr & 1) + regs->link = regs->nip; + if (branch_taken(instr, regs)) + regs->nip = imm; + return 1; + case 17: /* sc */ + /* + * N.B. this uses knowledge about how the syscall + * entry code works. If that is changed, this will + * need to be changed also. + */ + regs->gpr[9] = regs->gpr[13]; + regs->gpr[11] = regs->nip + 4; + regs->gpr[12] = regs->msr & MSR_MASK; + regs->gpr[13] = (unsigned long) get_paca(); + regs->nip = (unsigned long) &system_call_common; + regs->msr = MSR_KERNEL; + return 1; + case 18: /* b */ + imm = instr & 0x03fffffc; + if (imm & 0x02000000) + imm -= 0x04000000; + if ((instr & 2) == 0) + imm += regs->nip; + if (instr & 1) { + regs->link = regs->nip + 4; + if ((regs->msr & MSR_SF) == 0) + regs->link &= 0xffffffffUL; + } + if ((regs->msr & MSR_SF) == 0) + imm &= 0xffffffffUL; + regs->nip = imm; + return 1; + case 19: + switch (instr & 0x7fe) { + case 0x20: /* bclr */ + case 0x420: /* bcctr */ + imm = (instr & 0x400)? regs->ctr: regs->link; + regs->nip += 4; + if ((regs->msr & MSR_SF) == 0) { + regs->nip &= 0xffffffffUL; + imm &= 0xffffffffUL; + } + if (instr & 1) + regs->link = regs->nip; + if (branch_taken(instr, regs)) + regs->nip = imm; + return 1; + case 0x24: /* rfid, scary */ + return -1; + } + case 31: + rd = (instr >> 21) & 0x1f; + switch (instr & 0x7fe) { + case 0xa6: /* mfmsr */ + regs->gpr[rd] = regs->msr & MSR_MASK; + regs->nip += 4; + if ((regs->msr & MSR_SF) == 0) + regs->nip &= 0xffffffffUL; + return 1; + case 0x164: /* mtmsrd */ + /* only MSR_EE and MSR_RI get changed if bit 15 set */ + /* mtmsrd doesn't change MSR_HV and MSR_ME */ + imm = (instr & 0x10000)? 0x8002: 0xefffffffffffefffUL; + imm = (regs->msr & MSR_MASK & ~imm) + | (regs->gpr[rd] & imm); + if ((imm & MSR_RI) == 0) + /* can't step mtmsrd that would clear MSR_RI */ + return -1; + regs->msr = imm; + regs->nip += 4; + if ((imm & MSR_SF) == 0) + regs->nip &= 0xffffffffUL; + return 1; + } + } + return 0; +} |