/* arch/sparc64/kernel/kprobes.c * * Copyright (C) 2004 David S. Miller <davem@davemloft.net> */ #include <linux/kernel.h> #include <linux/kprobes.h> #include <linux/module.h> #include <asm/kdebug.h> #include <asm/signal.h> #include <asm/cacheflush.h> #include <asm/uaccess.h> /* We do not have hardware single-stepping on sparc64. * So we implement software single-stepping with breakpoint * traps. The top-level scheme is similar to that used * in the x86 kprobes implementation. * * In the kprobe->ainsn.insn[] array we store the original * instruction at index zero and a break instruction at * index one. * * When we hit a kprobe we: * - Run the pre-handler * - Remember "regs->tnpc" and interrupt level stored in * "regs->tstate" so we can restore them later * - Disable PIL interrupts * - Set regs->tpc to point to kprobe->ainsn.insn[0] * - Set regs->tnpc to point to kprobe->ainsn.insn[1] * - Mark that we are actively in a kprobe * * At this point we wait for the second breakpoint at * kprobe->ainsn.insn[1] to hit. When it does we: * - Run the post-handler * - Set regs->tpc to "remembered" regs->tnpc stored above, * restore the PIL interrupt level in "regs->tstate" as well * - Make any adjustments necessary to regs->tnpc in order * to handle relative branches correctly. See below. * - Mark that we are no longer actively in a kprobe. */ DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); int __kprobes arch_prepare_kprobe(struct kprobe *p) { p->ainsn.insn[0] = *p->addr; p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2; p->opcode = *p->addr; return 0; } void __kprobes arch_arm_kprobe(struct kprobe *p) { *p->addr = BREAKPOINT_INSTRUCTION; flushi(p->addr); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { *p->addr = p->opcode; flushi(p->addr); } static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc; kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil; } static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; kcb->kprobe_status = kcb->prev_kprobe.status; kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc; kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil; } static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = p; kcb->kprobe_orig_tnpc = regs->tnpc; kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL); } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { regs->tstate |= TSTATE_PIL; /*single step inline, if it a breakpoint instruction*/ if (p->opcode == BREAKPOINT_INSTRUCTION) { regs->tpc = (unsigned long) p->addr; regs->tnpc = kcb->kprobe_orig_tnpc; } else { regs->tpc = (unsigned long) &p->ainsn.insn[0]; regs->tnpc = (unsigned long) &p->ainsn.insn[1]; } } static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; void *addr = (void *) regs->tpc; int ret = 0; struct kprobe_ctlblk *kcb; /* * We don't want to be preempted for the entire * duration of kprobe processing */ preempt_disable(); kcb = get_kprobe_ctlblk(); if (kprobe_running()) { p = get_kprobe(addr); if (p) { if (kcb->kprobe_status == KPROBE_HIT_SS) { regs->tstate = ((regs->tstate & ~TSTATE_PIL) | kcb->kprobe_orig_tstate_pil); goto no_kprobe; } /* We have reentered the kprobe_handler(), since * another probe was hit while within the handler. * We here save the original kprobes variables and * just single step on the instruction of the new probe * without calling any user handlers. */ save_previous_kprobe(kcb); set_current_kprobe(p, regs, kcb); kprobes_inc_nmissed_count(p); kcb->kprobe_status = KPROBE_REENTER; prepare_singlestep(p, regs, kcb); return 1; } else { if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { /* The breakpoint instruction was removed by * another cpu right after we hit, no further * handling of this interrupt is appropriate */ ret = 1; goto no_kprobe; } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) goto ss_probe; } goto no_kprobe; } p = get_kprobe(addr); if (!p) { if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { /* * The breakpoint instruction was removed right * after we hit it. Another cpu has removed * either a probepoint or a debugger breakpoint * at this address. In either case, no further * handling of this interrupt is appropriate. */ ret = 1; } /* Not one of ours: let kernel handle it */ goto no_kprobe; } set_current_kprobe(p, regs, kcb); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (p->pre_handler && p->pre_handler(p, regs)) return 1; ss_probe: prepare_singlestep(p, regs, kcb); kcb->kprobe_status = KPROBE_HIT_SS; return 1; no_kprobe: preempt_enable_no_resched(); return ret; } /* If INSN is a relative control transfer instruction, * return the corrected branch destination value. * * The original INSN location was REAL_PC, it actually * executed at PC and produced destination address NPC. */ static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc, unsigned long pc, unsigned long npc) { /* Branch not taken, no mods necessary. */ if (npc == pc + 0x4UL) return real_pc + 0x4UL; /* The three cases are call, branch w/prediction, * and traditional branch. */ if ((insn & 0xc0000000) == 0x40000000 || (insn & 0xc1c00000) == 0x00400000 || (insn & 0xc1c00000) == 0x00800000) { /* The instruction did all the work for us * already, just apply the offset to the correct * instruction location. */ return (real_pc + (npc - pc)); } return real_pc + 0x4UL; } /* If INSN is an instruction which writes it's PC location * into a destination register, fix that up. */ static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn, unsigned long real_pc) { unsigned long *slot = NULL; /* Simplest cast is call, which always uses %o7 */ if ((insn & 0xc0000000) == 0x40000000) { slot = ®s->u_regs[UREG_I7]; } /* Jmpl encodes the register inside of the opcode */ if ((insn & 0xc1f80000) == 0x81c00000) { unsigned long rd = ((insn >> 25) & 0x1f); if (rd <= 15) { slot = ®s->u_regs[rd]; } else { /* Hard case, it goes onto the stack. */ flushw_all(); rd -= 16; slot = (unsigned long *) (regs->u_regs[UREG_FP] + STACK_BIAS); slot += rd; } } if (slot != NULL) *slot = real_pc; } /* * Called after single-stepping. p->addr is the address of the * instruction whose first byte has been replaced by the breakpoint * instruction. To avoid the SMP problems that can occur when we * temporarily put back the original opcode to single-step, we * single-stepped a copy of the instruction. The address of this * copy is p->ainsn.insn. * * This function prepares to return from the post-single-step * breakpoint trap. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { u32 insn = p->ainsn.insn[0]; regs->tpc = kcb->kprobe_orig_tnpc; regs->tnpc = relbranch_fixup(insn, (unsigned long) p->addr, (unsigned long) &p->ainsn.insn[0], regs->tnpc); retpc_fixup(regs, insn, (unsigned long) p->addr); regs->tstate = ((regs->tstate & ~TSTATE_PIL) | kcb->kprobe_orig_tstate_pil); } static int __kprobes post_kprobe_handler(struct pt_regs *regs) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); if (!cur) return 0; if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { kcb->kprobe_status = KPROBE_HIT_SSDONE; cur->post_handler(cur, regs, 0); } resume_execution(cur, regs, kcb); /*Restore back the original saved kprobes variables and continue. */ if (kcb->kprobe_status == KPROBE_REENTER) { restore_previous_kprobe(kcb); goto out; } reset_current_kprobe(); out: preempt_enable_no_resched(); return 1; } static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); const struct exception_table_entry *entry; switch(kcb->kprobe_status) { case KPROBE_HIT_SS: case KPROBE_REENTER: /* * We are here because the instruction being single * stepped caused a page fault. We reset the current * kprobe and the tpc points back to the probe address * and allow the page fault handler to continue as a * normal page fault. */ regs->tpc = (unsigned long)cur->addr; regs->tnpc = kcb->kprobe_orig_tnpc; regs->tstate = ((regs->tstate & ~TSTATE_PIL) | kcb->kprobe_orig_tstate_pil); if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); else reset_current_kprobe(); preempt_enable_no_resched(); break; case KPROBE_HIT_ACTIVE: case KPROBE_HIT_SSDONE: /* * We increment the nmissed count for accounting, * we can also use npre/npostfault count for accouting * these specific fault cases. */ kprobes_inc_nmissed_count(cur); /* * We come here because instructions in the pre/post * handler caused the page_fault, this could happen * if handler tries to access user space by * copy_from_user(), get_user() etc. Let the * user-specified handler try to fix it first. */ if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) return 1; /* * In case the user-specified fault handler returned * zero, try to fix up. */ entry = search_exception_tables(regs->tpc); if (entry) { regs->tpc = entry->fixup; regs->tnpc = regs->tpc + 4; return 1; } /* * fixup_exception() could not handle it, * Let do_page_fault() fix it. */ break; default: break; } return 0; } /* * Wrapper routine to for handling exceptions. */ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data) { struct die_args *args = (struct die_args *)data; int ret = NOTIFY_DONE; if (args->regs && user_mode(args->regs)) return ret; switch (val) { case DIE_DEBUG: if (kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_DEBUG_2: if (post_kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_GPF: case DIE_PAGE_FAULT: /* kprobe_running() needs smp_processor_id() */ preempt_disable(); if (kprobe_running() && kprobe_fault_handler(args->regs, args->trapnr)) ret = NOTIFY_STOP; preempt_enable(); break; default: break; } return ret; } asmlinkage void __kprobes kprobe_trap(unsigned long trap_level, struct pt_regs *regs) { BUG_ON(trap_level != 0x170 && trap_level != 0x171); if (user_mode(regs)) { local_irq_enable(); bad_trap(regs, trap_level); return; } /* trap_level == 0x170 --> ta 0x70 * trap_level == 0x171 --> ta 0x71 */ if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2, (trap_level == 0x170) ? "debug" : "debug_2", regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP) bad_trap(regs, trap_level); } /* Jprobes support. */ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct jprobe *jp = container_of(p, struct jprobe, kp); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); kcb->jprobe_saved_regs_location = regs; memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs)); /* Save a whole stack frame, this gets arguments * pushed onto the stack after using up all the * arg registers. */ memcpy(&(kcb->jprobe_saved_stack), (char *) (regs->u_regs[UREG_FP] + STACK_BIAS), sizeof(kcb->jprobe_saved_stack)); regs->tpc = (unsigned long) jp->entry; regs->tnpc = ((unsigned long) jp->entry) + 0x4UL; regs->tstate |= TSTATE_PIL; return 1; } void __kprobes jprobe_return(void) { __asm__ __volatile__( ".globl jprobe_return_trap_instruction\n" "jprobe_return_trap_instruction:\n\t" "ta 0x70"); } extern void jprobe_return_trap_instruction(void); extern void __show_regs(struct pt_regs * regs); int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { u32 *addr = (u32 *) regs->tpc; struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); if (addr == (u32 *) jprobe_return_trap_instruction) { if (kcb->jprobe_saved_regs_location != regs) { printk("JPROBE: Current regs (%p) does not match " "saved regs (%p).\n", regs, kcb->jprobe_saved_regs_location); printk("JPROBE: Saved registers\n"); __show_regs(kcb->jprobe_saved_regs_location); printk("JPROBE: Current registers\n"); __show_regs(regs); BUG(); } /* Restore old register state. Do pt_regs * first so that UREG_FP is the original one for * the stack frame restore. */ memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs)); memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS), &(kcb->jprobe_saved_stack), sizeof(kcb->jprobe_saved_stack)); preempt_enable_no_resched(); return 1; } return 0; } /* architecture specific initialization */ int arch_init_kprobes(void) { return 0; }