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-rw-r--r--arch/s390/kernel/kprobes.c525
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 0000000000..d4b863ed0a
--- /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);