diff options
Diffstat (limited to 'arch/s390/kernel/kprobes.c')
| -rw-r--r-- | arch/s390/kernel/kprobes.c | 525 |
1 files changed, 525 insertions, 0 deletions
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c new file mode 100644 index 000000000..d4b863ed0 --- /dev/null +++ b/arch/s390/kernel/kprobes.c @@ -0,0 +1,525 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Kernel Probes (KProbes) + * + * Copyright IBM Corp. 2002, 2006 + * + * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com> + */ + +#define pr_fmt(fmt) "kprobes: " fmt + +#include <linux/moduleloader.h> +#include <linux/kprobes.h> +#include <linux/ptrace.h> +#include <linux/preempt.h> +#include <linux/stop_machine.h> +#include <linux/kdebug.h> +#include <linux/uaccess.h> +#include <linux/extable.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/hardirq.h> +#include <linux/ftrace.h> +#include <asm/set_memory.h> +#include <asm/sections.h> +#include <asm/dis.h> +#include "kprobes.h" +#include "entry.h" + +DEFINE_PER_CPU(struct kprobe *, current_kprobe); +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); + +struct kretprobe_blackpoint kretprobe_blacklist[] = { }; + +static int insn_page_in_use; + +void *alloc_insn_page(void) +{ + void *page; + + page = module_alloc(PAGE_SIZE); + if (!page) + return NULL; + set_memory_rox((unsigned long)page, 1); + return page; +} + +static void *alloc_s390_insn_page(void) +{ + if (xchg(&insn_page_in_use, 1) == 1) + return NULL; + return &kprobes_insn_page; +} + +static void free_s390_insn_page(void *page) +{ + xchg(&insn_page_in_use, 0); +} + +struct kprobe_insn_cache kprobe_s390_insn_slots = { + .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex), + .alloc = alloc_s390_insn_page, + .free = free_s390_insn_page, + .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages), + .insn_size = MAX_INSN_SIZE, +}; + +static void copy_instruction(struct kprobe *p) +{ + kprobe_opcode_t insn[MAX_INSN_SIZE]; + s64 disp, new_disp; + u64 addr, new_addr; + unsigned int len; + + len = insn_length(*p->addr >> 8); + memcpy(&insn, p->addr, len); + p->opcode = insn[0]; + if (probe_is_insn_relative_long(&insn[0])) { + /* + * For pc-relative instructions in RIL-b or RIL-c format patch + * the RI2 displacement field. We have already made sure that + * the insn slot for the patched instruction is within the same + * 2GB area as the original instruction (either kernel image or + * module area). Therefore the new displacement will always fit. + */ + disp = *(s32 *)&insn[1]; + addr = (u64)(unsigned long)p->addr; + new_addr = (u64)(unsigned long)p->ainsn.insn; + new_disp = ((addr + (disp * 2)) - new_addr) / 2; + *(s32 *)&insn[1] = new_disp; + } + s390_kernel_write(p->ainsn.insn, &insn, len); +} +NOKPROBE_SYMBOL(copy_instruction); + +static int s390_get_insn_slot(struct kprobe *p) +{ + /* + * Get an insn slot that is within the same 2GB area like the original + * instruction. That way instructions with a 32bit signed displacement + * field can be patched and executed within the insn slot. + */ + p->ainsn.insn = NULL; + if (is_kernel((unsigned long)p->addr)) + p->ainsn.insn = get_s390_insn_slot(); + else if (is_module_addr(p->addr)) + p->ainsn.insn = get_insn_slot(); + return p->ainsn.insn ? 0 : -ENOMEM; +} +NOKPROBE_SYMBOL(s390_get_insn_slot); + +static void s390_free_insn_slot(struct kprobe *p) +{ + if (!p->ainsn.insn) + return; + if (is_kernel((unsigned long)p->addr)) + free_s390_insn_slot(p->ainsn.insn, 0); + else + free_insn_slot(p->ainsn.insn, 0); + p->ainsn.insn = NULL; +} +NOKPROBE_SYMBOL(s390_free_insn_slot); + +/* Check if paddr is at an instruction boundary */ +static bool can_probe(unsigned long paddr) +{ + unsigned long addr, offset = 0; + kprobe_opcode_t insn; + struct kprobe *kp; + + if (paddr & 0x01) + return false; + + if (!kallsyms_lookup_size_offset(paddr, NULL, &offset)) + return false; + + /* Decode instructions */ + addr = paddr - offset; + while (addr < paddr) { + if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn))) + return false; + + if (insn >> 8 == 0) { + if (insn != BREAKPOINT_INSTRUCTION) { + /* + * Note that QEMU inserts opcode 0x0000 to implement + * software breakpoints for guests. Since the size of + * the original instruction is unknown, stop following + * instructions and prevent setting a kprobe. + */ + return false; + } + /* + * Check if the instruction has been modified by another + * kprobe, in which case the original instruction is + * decoded. + */ + kp = get_kprobe((void *)addr); + if (!kp) { + /* not a kprobe */ + return false; + } + insn = kp->opcode; + } + addr += insn_length(insn >> 8); + } + return addr == paddr; +} + +int arch_prepare_kprobe(struct kprobe *p) +{ + if (!can_probe((unsigned long)p->addr)) + return -EINVAL; + /* Make sure the probe isn't going on a difficult instruction */ + if (probe_is_prohibited_opcode(p->addr)) + return -EINVAL; + if (s390_get_insn_slot(p)) + return -ENOMEM; + copy_instruction(p); + return 0; +} +NOKPROBE_SYMBOL(arch_prepare_kprobe); + +struct swap_insn_args { + struct kprobe *p; + unsigned int arm_kprobe : 1; +}; + +static int swap_instruction(void *data) +{ + struct swap_insn_args *args = data; + struct kprobe *p = args->p; + u16 opc; + + opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode; + s390_kernel_write(p->addr, &opc, sizeof(opc)); + return 0; +} +NOKPROBE_SYMBOL(swap_instruction); + +void arch_arm_kprobe(struct kprobe *p) +{ + struct swap_insn_args args = {.p = p, .arm_kprobe = 1}; + + stop_machine_cpuslocked(swap_instruction, &args, NULL); +} +NOKPROBE_SYMBOL(arch_arm_kprobe); + +void arch_disarm_kprobe(struct kprobe *p) +{ + struct swap_insn_args args = {.p = p, .arm_kprobe = 0}; + + stop_machine_cpuslocked(swap_instruction, &args, NULL); +} +NOKPROBE_SYMBOL(arch_disarm_kprobe); + +void arch_remove_kprobe(struct kprobe *p) +{ + s390_free_insn_slot(p); +} +NOKPROBE_SYMBOL(arch_remove_kprobe); + +static void enable_singlestep(struct kprobe_ctlblk *kcb, + struct pt_regs *regs, + unsigned long ip) +{ + struct per_regs per_kprobe; + + /* Set up the PER control registers %cr9-%cr11 */ + per_kprobe.control = PER_EVENT_IFETCH; + per_kprobe.start = ip; + per_kprobe.end = ip; + + /* Save control regs and psw mask */ + __ctl_store(kcb->kprobe_saved_ctl, 9, 11); + kcb->kprobe_saved_imask = regs->psw.mask & + (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT); + + /* Set PER control regs, turns on single step for the given address */ + __ctl_load(per_kprobe, 9, 11); + regs->psw.mask |= PSW_MASK_PER; + regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT); + regs->psw.addr = ip; +} +NOKPROBE_SYMBOL(enable_singlestep); + +static void disable_singlestep(struct kprobe_ctlblk *kcb, + struct pt_regs *regs, + unsigned long ip) +{ + /* Restore control regs and psw mask, set new psw address */ + __ctl_load(kcb->kprobe_saved_ctl, 9, 11); + regs->psw.mask &= ~PSW_MASK_PER; + regs->psw.mask |= kcb->kprobe_saved_imask; + regs->psw.addr = ip; +} +NOKPROBE_SYMBOL(disable_singlestep); + +/* + * Activate a kprobe by storing its pointer to current_kprobe. The + * previous kprobe is stored in kcb->prev_kprobe. A stack of up to + * two kprobes can be active, see KPROBE_REENTER. + */ +static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p) +{ + kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe); + kcb->prev_kprobe.status = kcb->kprobe_status; + __this_cpu_write(current_kprobe, p); +} +NOKPROBE_SYMBOL(push_kprobe); + +/* + * Deactivate a kprobe by backing up to the previous state. If the + * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL, + * for any other state prev_kprobe.kp will be NULL. + */ +static void pop_kprobe(struct kprobe_ctlblk *kcb) +{ + __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); + kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->prev_kprobe.kp = NULL; +} +NOKPROBE_SYMBOL(pop_kprobe); + +static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p) +{ + switch (kcb->kprobe_status) { + case KPROBE_HIT_SSDONE: + case KPROBE_HIT_ACTIVE: + kprobes_inc_nmissed_count(p); + break; + case KPROBE_HIT_SS: + case KPROBE_REENTER: + default: + /* + * A kprobe on the code path to single step an instruction + * is a BUG. The code path resides in the .kprobes.text + * section and is executed with interrupts disabled. + */ + pr_err("Failed to recover from reentered kprobes.\n"); + dump_kprobe(p); + BUG(); + } +} +NOKPROBE_SYMBOL(kprobe_reenter_check); + +static int kprobe_handler(struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb; + struct kprobe *p; + + /* + * We want to disable preemption for the entire duration of kprobe + * processing. That includes the calls to the pre/post handlers + * and single stepping the kprobe instruction. + */ + preempt_disable(); + kcb = get_kprobe_ctlblk(); + p = get_kprobe((void *)(regs->psw.addr - 2)); + + if (p) { + if (kprobe_running()) { + /* + * We have hit a kprobe while another is still + * active. This can happen in the pre and post + * handler. Single step the instruction of the + * new probe but do not call any handler function + * of this secondary kprobe. + * push_kprobe and pop_kprobe saves and restores + * the currently active kprobe. + */ + kprobe_reenter_check(kcb, p); + push_kprobe(kcb, p); + kcb->kprobe_status = KPROBE_REENTER; + } else { + /* + * If we have no pre-handler or it returned 0, we + * continue with single stepping. If we have a + * pre-handler and it returned non-zero, it prepped + * for changing execution path, so get out doing + * nothing more here. + */ + push_kprobe(kcb, p); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + if (p->pre_handler && p->pre_handler(p, regs)) { + pop_kprobe(kcb); + preempt_enable_no_resched(); + return 1; + } + kcb->kprobe_status = KPROBE_HIT_SS; + } + enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn); + return 1; + } /* else: + * No kprobe at this address and no active kprobe. The trap has + * not been caused by a kprobe breakpoint. The race of breakpoint + * vs. kprobe remove does not exist because on s390 as we use + * stop_machine to arm/disarm the breakpoints. + */ + preempt_enable_no_resched(); + return 0; +} +NOKPROBE_SYMBOL(kprobe_handler); + +/* + * 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. + */ +static void resume_execution(struct kprobe *p, struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + unsigned long ip = regs->psw.addr; + int fixup = probe_get_fixup_type(p->ainsn.insn); + + if (fixup & FIXUP_PSW_NORMAL) + ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn; + + if (fixup & FIXUP_BRANCH_NOT_TAKEN) { + int ilen = insn_length(p->ainsn.insn[0] >> 8); + if (ip - (unsigned long) p->ainsn.insn == ilen) + ip = (unsigned long) p->addr + ilen; + } + + if (fixup & FIXUP_RETURN_REGISTER) { + int reg = (p->ainsn.insn[0] & 0xf0) >> 4; + regs->gprs[reg] += (unsigned long) p->addr - + (unsigned long) p->ainsn.insn; + } + + disable_singlestep(kcb, regs, ip); +} +NOKPROBE_SYMBOL(resume_execution); + +static int post_kprobe_handler(struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + struct kprobe *p = kprobe_running(); + + if (!p) + return 0; + + resume_execution(p, regs); + if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + p->post_handler(p, regs, 0); + } + pop_kprobe(kcb); + preempt_enable_no_resched(); + + /* + * if somebody else is singlestepping across a probe point, psw mask + * will have PER set, in which case, continue the remaining processing + * of do_single_step, as if this is not a probe hit. + */ + if (regs->psw.mask & PSW_MASK_PER) + return 0; + + return 1; +} +NOKPROBE_SYMBOL(post_kprobe_handler); + +static int kprobe_trap_handler(struct pt_regs *regs, int trapnr) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + struct kprobe *p = kprobe_running(); + + 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 nip points back to the probe address + * and allow the page fault handler to continue as a + * normal page fault. + */ + disable_singlestep(kcb, regs, (unsigned long) p->addr); + pop_kprobe(kcb); + preempt_enable_no_resched(); + break; + case KPROBE_HIT_ACTIVE: + case KPROBE_HIT_SSDONE: + /* + * In case the user-specified fault handler returned + * zero, try to fix up. + */ + if (fixup_exception(regs)) + return 1; + /* + * fixup_exception() could not handle it, + * Let do_page_fault() fix it. + */ + break; + default: + break; + } + return 0; +} +NOKPROBE_SYMBOL(kprobe_trap_handler); + +int kprobe_fault_handler(struct pt_regs *regs, int trapnr) +{ + int ret; + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_disable(); + ret = kprobe_trap_handler(regs, trapnr); + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); + return ret; +} +NOKPROBE_SYMBOL(kprobe_fault_handler); + +/* + * Wrapper routine to for handling exceptions. + */ +int kprobe_exceptions_notify(struct notifier_block *self, + unsigned long val, void *data) +{ + struct die_args *args = (struct die_args *) data; + struct pt_regs *regs = args->regs; + int ret = NOTIFY_DONE; + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_disable(); + + switch (val) { + case DIE_BPT: + if (kprobe_handler(regs)) + ret = NOTIFY_STOP; + break; + case DIE_SSTEP: + if (post_kprobe_handler(regs)) + ret = NOTIFY_STOP; + break; + case DIE_TRAP: + if (!preemptible() && kprobe_running() && + kprobe_trap_handler(regs, args->trapnr)) + ret = NOTIFY_STOP; + break; + default: + break; + } + + if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) + local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); + + return ret; +} +NOKPROBE_SYMBOL(kprobe_exceptions_notify); + +int __init arch_init_kprobes(void) +{ + return 0; +} + +int arch_trampoline_kprobe(struct kprobe *p) +{ + return 0; +} +NOKPROBE_SYMBOL(arch_trampoline_kprobe); |