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Subject[RFC Patch v1 44/55] ARC: kprobes support
Date
From: Vineet Gupta <vgupta@synopsys.com>

Origin port done by Rajeshwar Ranga <rajeshwar.ranga@gmail.com>

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/Kconfig | 2 +
arch/arc/include/asm/kprobes.h | 62 +++++
arch/arc/kernel/Makefile | 1 +
arch/arc/kernel/disasm.c | 5 +-
arch/arc/kernel/kprobes.c | 525 ++++++++++++++++++++++++++++++++++++++++
arch/arc/kernel/traps.c | 13 +
6 files changed, 605 insertions(+), 3 deletions(-)
create mode 100644 arch/arc/include/asm/kprobes.h
create mode 100644 arch/arc/kernel/kprobes.c

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 26609d6..3ef21be 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -22,6 +22,8 @@ config ARC
select GENERIC_SMP_IDLE_THREAD
select HAVE_ARCH_TRACEHOOK
select HAVE_GENERIC_HARDIRQS
+ select HAVE_KPROBES
+ select HAVE_KRETPROBES
select HAVE_MOD_ARCH_SPECIFIC if ARC_DW2_UNWIND
select HAVE_OPROFILE
select HOTPLUG if !INITRAMFS_SOURCE=""
diff --git a/arch/arc/include/asm/kprobes.h b/arch/arc/include/asm/kprobes.h
new file mode 100644
index 0000000..4d9c211
--- /dev/null
+++ b/arch/arc/include/asm/kprobes.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _ARC_KPROBES_H
+#define _ARC_KPROBES_H
+
+#ifdef CONFIG_KPROBES
+
+typedef u16 kprobe_opcode_t;
+
+#define UNIMP_S_INSTRUCTION 0x79e0
+#define TRAP_S_2_INSTRUCTION 0x785e
+
+#define MAX_INSN_SIZE 8
+#define MAX_STACK_SIZE 64
+
+struct arch_specific_insn {
+ int is_short;
+ kprobe_opcode_t *t1_addr, *t2_addr;
+ kprobe_opcode_t t1_opcode, t2_opcode;
+};
+
+#define flush_insn_slot(p) do { } while (0)
+
+#define kretprobe_blacklist_size 0
+
+struct kprobe;
+
+void arch_remove_kprobe(struct kprobe *p);
+
+int kprobe_exceptions_notify(struct notifier_block *self,
+ unsigned long val, void *data);
+
+struct prev_kprobe {
+ struct kprobe *kp;
+ unsigned long status;
+};
+
+struct kprobe_ctlblk {
+ unsigned int kprobe_status;
+ struct pt_regs jprobe_saved_regs;
+ char jprobes_stack[MAX_STACK_SIZE];
+ struct prev_kprobe prev_kprobe;
+};
+
+int kprobe_fault_handler(struct pt_regs *regs, unsigned long cause);
+void kretprobe_trampoline(void);
+void trap_is_kprobe(unsigned long cause, unsigned long address,
+ struct pt_regs *regs);
+#else
+static void trap_is_kprobe(unsigned long cause, unsigned long address,
+ struct pt_regs *regs)
+{
+}
+#endif
+
+#endif
diff --git a/arch/arc/kernel/Makefile b/arch/arc/kernel/Makefile
index 1fc0461..442d024 100644
--- a/arch/arc/kernel/Makefile
+++ b/arch/arc/kernel/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_MODULES) += arcksyms.o module.o
obj-$(CONFIG_ARC_DBG_EVENT_TIMELINE) += event-log.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_ARC_DW2_UNWIND) += unwind.o
+obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_ARC_FPU_SAVE_RESTORE) += fpu.o
CFLAGS_fpu.o += -mdpfp

diff --git a/arch/arc/kernel/disasm.c b/arch/arc/kernel/disasm.c
index 254d11a..51bad8f 100644
--- a/arch/arc/kernel/disasm.c
+++ b/arch/arc/kernel/disasm.c
@@ -497,9 +497,8 @@ void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
* @pc +2/4/6 (ARCompact ISA allows free intermixing of 16/32 bit insns).
*
* If @pc is a branch
- * -@tgt_if_br is set to branch target.
- * -If branch has delay slot, @next_pc updated with actual next PC.
- *
+ * -@tgt_if_br is set to branch target.
+ * -If branch has delay slot, @next_pc updated with actual next PC.
*/
int __kprobes disasm_next_pc(unsigned long pc, struct pt_regs *regs,
struct callee_regs *cregs,
diff --git a/arch/arc/kernel/kprobes.c b/arch/arc/kernel/kprobes.c
new file mode 100644
index 0000000..47e42f2
--- /dev/null
+++ b/arch/arc/kernel/kprobes.c
@@ -0,0 +1,525 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/kprobes.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/current.h>
+#include <asm/disasm.h>
+
+#define MIN_STACK_SIZE(addr) min((unsigned long)MAX_STACK_SIZE, \
+ (unsigned long)current_thread_info() + THREAD_SIZE - (addr))
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+ /* Attempt to probe at unaligned address */
+ if ((unsigned long)p->addr & 0x01)
+ return -EINVAL;
+
+ /* Address should not be in exception handling code */
+
+ p->ainsn.is_short = is_short_instr((unsigned long)p->addr);
+ p->opcode = *p->addr;
+
+ return 0;
+}
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+ *p->addr = UNIMP_S_INSTRUCTION;
+
+ flush_icache_range((unsigned long)p->addr,
+ (unsigned long)p->addr + sizeof(kprobe_opcode_t));
+}
+
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+ *p->addr = p->opcode;
+
+ flush_icache_range((unsigned long)p->addr,
+ (unsigned long)p->addr + sizeof(kprobe_opcode_t));
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+ arch_disarm_kprobe(p);
+
+ /* Can we remove the kprobe in the middle of kprobe handling? */
+ if (p->ainsn.t1_addr) {
+ *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
+
+ flush_icache_range((unsigned long)p->ainsn.t1_addr,
+ (unsigned long)p->ainsn.t1_addr +
+ sizeof(kprobe_opcode_t));
+
+ p->ainsn.t1_addr = NULL;
+ }
+
+ if (p->ainsn.t2_addr) {
+ *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
+
+ flush_icache_range((unsigned long)p->ainsn.t2_addr,
+ (unsigned long)p->ainsn.t2_addr +
+ sizeof(kprobe_opcode_t));
+
+ p->ainsn.t2_addr = NULL;
+ }
+}
+
+static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+ kcb->prev_kprobe.kp = kprobe_running();
+ kcb->prev_kprobe.status = kcb->kprobe_status;
+}
+
+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;
+}
+
+static inline void __kprobes set_current_kprobe(struct kprobe *p)
+{
+ __get_cpu_var(current_kprobe) = p;
+}
+
+static void __kprobes resume_execution(struct kprobe *p, unsigned long addr,
+ struct pt_regs *regs)
+{
+ /* Remove the trap instructions inserted for single step and
+ * restore the original instructions
+ */
+ if (p->ainsn.t1_addr) {
+ *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
+
+ flush_icache_range((unsigned long)p->ainsn.t1_addr,
+ (unsigned long)p->ainsn.t1_addr +
+ sizeof(kprobe_opcode_t));
+
+ p->ainsn.t1_addr = NULL;
+ }
+
+ if (p->ainsn.t2_addr) {
+ *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
+
+ flush_icache_range((unsigned long)p->ainsn.t2_addr,
+ (unsigned long)p->ainsn.t2_addr +
+ sizeof(kprobe_opcode_t));
+
+ p->ainsn.t2_addr = NULL;
+ }
+
+ return;
+}
+
+static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+ unsigned long next_pc;
+ unsigned long tgt_if_br = 0;
+ int is_branch;
+ unsigned long bta;
+
+ /* Copy the opcode back to the kprobe location and execute the
+ * instruction. Because of this we will not be able to get into the
+ * same kprobe until this kprobe is done
+ */
+ *(p->addr) = p->opcode;
+
+ flush_icache_range((unsigned long)p->addr,
+ (unsigned long)p->addr + sizeof(kprobe_opcode_t));
+
+ /* Now we insert the trap at the next location after this instruction to
+ * single step. If it is a branch we insert the trap at possible branch
+ * targets
+ */
+
+ bta = regs->bta;
+
+ if (regs->status32 & 0x40) {
+ /* We are in a delay slot with the branch taken */
+
+ next_pc = bta & ~0x01;
+
+ if (!p->ainsn.is_short) {
+ if (bta & 0x01)
+ regs->blink += 2;
+ else {
+ /* Branch not taken */
+ next_pc += 2;
+
+ /* next pc is taken from bta after executing the
+ * delay slot instruction
+ */
+ regs->bta += 2;
+ }
+ }
+
+ is_branch = 0;
+ } else
+ is_branch =
+ disasm_next_pc((unsigned long)p->addr, regs,
+ (struct callee_regs *) current->thread.callee_reg,
+ &next_pc, &tgt_if_br);
+
+ p->ainsn.t1_addr = (kprobe_opcode_t *) next_pc;
+ p->ainsn.t1_opcode = *(p->ainsn.t1_addr);
+ *(p->ainsn.t1_addr) = TRAP_S_2_INSTRUCTION;
+
+ flush_icache_range((unsigned long)p->ainsn.t1_addr,
+ (unsigned long)p->ainsn.t1_addr +
+ sizeof(kprobe_opcode_t));
+
+ if (is_branch) {
+ p->ainsn.t2_addr = (kprobe_opcode_t *) tgt_if_br;
+ p->ainsn.t2_opcode = *(p->ainsn.t2_addr);
+ *(p->ainsn.t2_addr) = TRAP_S_2_INSTRUCTION;
+
+ flush_icache_range((unsigned long)p->ainsn.t2_addr,
+ (unsigned long)p->ainsn.t2_addr +
+ sizeof(kprobe_opcode_t));
+ }
+}
+
+int __kprobes arc_kprobe_handler(unsigned long addr, struct pt_regs *regs)
+{
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+
+ preempt_disable();
+
+ kcb = get_kprobe_ctlblk();
+ p = get_kprobe((unsigned long *)addr);
+
+ if (p) {
+ /*
+ * We have reentered the kprobe_handler, since another kprobe
+ * was hit while within the handler, we save the original
+ * kprobes and single step on the instruction of the new probe
+ * without calling any user handlers to avoid recursive
+ * kprobes.
+ */
+ if (kprobe_running()) {
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p);
+ kprobes_inc_nmissed_count(p);
+ setup_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_REENTER;
+ return 1;
+ }
+
+ set_current_kprobe(p);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+ /* If we have no pre-handler or it returned 0, we continue with
+ * normal processing. If we have a pre-handler and it returned
+ * non-zero - which is expected from setjmp_pre_handler for
+ * jprobe, we return without single stepping and leave that to
+ * the break-handler which is invoked by a kprobe from
+ * jprobe_return
+ */
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
+ setup_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ }
+
+ return 1;
+ } else if (kprobe_running()) {
+ p = __get_cpu_var(current_kprobe);
+ if (p->break_handler && p->break_handler(p, regs)) {
+ setup_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ return 1;
+ }
+ }
+
+ /* no_kprobe: */
+ preempt_enable_no_resched();
+ return 0;
+}
+
+static int __kprobes arc_post_kprobe_handler(unsigned long addr,
+ struct pt_regs *regs)
+{
+ struct kprobe *cur = kprobe_running();
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ if (!cur)
+ return 0;
+
+ resume_execution(cur, addr, regs);
+
+ /* Rearm the kprobe */
+ arch_arm_kprobe(cur);
+
+ /*
+ * When we return from trap instruction we go to the next instruction
+ * We restored the actual instruction in resume_exectuiont and we to
+ * return to the same address and execute it
+ */
+ regs->ret = addr;
+
+ if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ cur->post_handler(cur, regs, 0);
+ }
+
+ if (kcb->kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe(kcb);
+ goto out;
+ }
+
+ reset_current_kprobe();
+
+out:
+ preempt_enable_no_resched();
+ return 1;
+}
+
+/*
+ * Fault can be for the instruction being single stepped or for the
+ * pre/post handlers in the module.
+ * This is applicable for applications like user probes, where we have the
+ * probe in user space and the handlers in the kernel
+ */
+
+int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr)
+{
+ struct kprobe *cur = kprobe_running();
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_SS:
+ case KPROBE_REENTER:
+ /*
+ * We are here because the instruction being single stepped
+ * caused the fault. We reset the current kprobe and allow the
+ * exception handler as if it is regular exception. In our
+ * case it doesn't matter because the system will be halted
+ */
+ resume_execution(cur, (unsigned long)cur->addr, regs);
+
+ 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 are here because the instructions in the pre/post handler
+ * caused the fault.
+ */
+
+ /* 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.
+ */
+ if (fixup_exception(regs))
+ return 1;
+
+ /*
+ * fixup_exception() could not handle it,
+ * Let do_page_fault() fix it.
+ */
+ break;
+
+ default:
+ break;
+ }
+ return 0;
+}
+
+int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ unsigned long addr = args->err;
+ int ret = NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_IERR:
+ if (arc_kprobe_handler(addr, args->regs))
+ return NOTIFY_STOP;
+ break;
+
+ case DIE_TRAP:
+ if (arc_post_kprobe_handler(addr, args->regs))
+ return NOTIFY_STOP;
+ break;
+
+ default:
+ break;
+ }
+
+ return ret;
+}
+
+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();
+ unsigned long sp_addr = regs->sp;
+
+ kcb->jprobe_saved_regs = *regs;
+ memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
+ regs->ret = (unsigned long)(jp->entry);
+
+ return 1;
+}
+
+void __kprobes jprobe_return(void)
+{
+ __asm__ __volatile__("unimp_s");
+ return;
+}
+
+int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ unsigned long sp_addr;
+
+ *regs = kcb->jprobe_saved_regs;
+ sp_addr = regs->sp;
+ memcpy((void *)sp_addr, kcb->jprobes_stack, MIN_STACK_SIZE(sp_addr));
+ preempt_enable_no_resched();
+
+ return 1;
+}
+
+static void __used kretprobe_trampoline_holder(void)
+{
+ __asm__ __volatile__(".global kretprobe_trampoline\n"
+ "kretprobe_trampoline:\n" "nop\n");
+}
+
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+{
+
+ ri->ret_addr = (kprobe_opcode_t *) regs->blink;
+
+ /* Replace the return addr with trampoline addr */
+ regs->blink = (unsigned long)&kretprobe_trampoline;
+}
+
+static int __kprobes trampoline_probe_handler(struct kprobe *p,
+ struct pt_regs *regs)
+{
+ struct kretprobe_instance *ri = NULL;
+ struct hlist_head *head, empty_rp;
+ struct hlist_node *node, *tmp;
+ unsigned long flags, orig_ret_address = 0;
+ unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
+
+ INIT_HLIST_HEAD(&empty_rp);
+ kretprobe_hash_lock(current, &head, &flags);
+
+ /*
+ * It is possible to have multiple instances associated with a given
+ * task either because an multiple functions in the call path
+ * have a return probe installed on them, and/or more than one return
+ * return probe was registered for a target function.
+ *
+ * We can handle this because:
+ * - instances are always inserted at the head of the list
+ * - when multiple return probes are registered for the same
+ * function, the first instance's ret_addr will point to the
+ * real return address, and all the rest will point to
+ * kretprobe_trampoline
+ */
+ hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ if (ri->rp && ri->rp->handler)
+ ri->rp->handler(ri, regs);
+
+ orig_ret_address = (unsigned long)ri->ret_addr;
+ recycle_rp_inst(ri, &empty_rp);
+
+ if (orig_ret_address != trampoline_address) {
+ /*
+ * This is the real return address. Any other
+ * instances associated with this task are for
+ * other calls deeper on the call stack
+ */
+ break;
+ }
+ }
+
+ kretprobe_assert(ri, orig_ret_address, trampoline_address);
+ regs->ret = orig_ret_address;
+
+ reset_current_kprobe();
+ kretprobe_hash_unlock(current, &flags);
+ preempt_enable_no_resched();
+
+ hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+ hlist_del(&ri->hlist);
+ kfree(ri);
+ }
+
+ /* By returning a non zero value, we are telling the kprobe handler
+ * that we don't want the post_handler to run
+ */
+ return 1;
+}
+
+static struct kprobe trampoline_p = {
+ .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+ .pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+ /* Registering the trampoline code for the kret probe */
+ return register_kprobe(&trampoline_p);
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+ if (p->addr == (kprobe_opcode_t *) &kretprobe_trampoline)
+ return 1;
+
+ return 0;
+}
+
+void trap_is_kprobe(unsigned long cause, unsigned long address,
+ struct pt_regs *regs)
+{
+ notify_die(DIE_TRAP, "kprobe_trap", regs, address, cause, SIGTRAP);
+}
diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c
index fd2457c..c6396b4 100644
--- a/arch/arc/kernel/traps.c
+++ b/arch/arc/kernel/traps.c
@@ -15,6 +15,7 @@
#include <linux/uaccess.h>
#include <asm/ptrace.h>
#include <asm/setup.h>
+#include <asm/kprobes.h>

void __init trap_init(void)
{
@@ -90,6 +91,7 @@ void do_machine_check_fault(unsigned long cause, unsigned long address,
die("Machine Check Exception", regs, address, cause);
}

+
/*
* Entry point for traps induced by ARCompact TRAP_S <n> insn
* This is same family as TRAP0/SWI insn (use the same vector).
@@ -109,6 +111,10 @@ void do_non_swi_trap(unsigned long cause, unsigned long address,
trap_is_brkpt(cause, address, regs);
break;

+ case 2:
+ trap_is_kprobe(param, address, regs);
+ break;
+
default:
break;
}
@@ -116,10 +122,17 @@ void do_non_swi_trap(unsigned long cause, unsigned long address,

/*
* Entry point for Instruction Error Exception
+ * -For a corner case, ARC kprobes implementation resorts to using
+ * this exception, hence the check
*/
void do_insterror_or_kprobe(unsigned long cause,
unsigned long address,
struct pt_regs *regs)
{
+ /* Check if this exception is caused by kprobes */
+ if (notify_die(DIE_IERR, "kprobe_ierr", regs, address,
+ cause, SIGILL) == NOTIFY_STOP)
+ return;
+
insterror_is_error(cause, address, regs);
}
--
1.7.4.1


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