MIPS: kprobe: Add support.

This patch is based on previous work by Sony and Himanshu Chauhan.

I have done some cleanup and implemented JProbes and KRETPROBES.  The
KRETPROBES part is pretty much copied verbatim from powerpc.  A possible
future enhance might be to factor out the common code.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: Himanshu Chauhan <hschauhan@nulltrace.org>
To: linux-mips@linux-mips.org
To: ananth@in.ibm.com,
To: anil.s.keshavamurthy@intel.com
To: davem@davemloft.net
To: masami.hiramatsu.pt@hitachi.com
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1525/
Patchwork: https://patchwork.linux-mips.org/patch/1530/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -10,6 +10,8 @@ config MIPS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_KPROBES
+	select HAVE_KRETPROBES
 	select RTC_LIB if !MACH_LOONGSON
 
 mainmenu "Linux/MIPS Kernel Configuration"

arch/mips/Makefile

@@ -259,6 +259,9 @@ endif
 vmlinux.32: vmlinux
 	$(OBJCOPY) -O $(32bit-bfd) $(OBJCOPYFLAGS) $< $@
 
+
+#obj-$(CONFIG_KPROBES)		+= kprobes.o
+
 #
 # The 64-bit ELF tools are pretty broken so at this time we generate 64-bit
 # ELF files from 32-bit files by conversion.

arch/mips/include/asm/break.h

@@ -30,6 +30,8 @@
 #define BRK_BUG		512	/* Used by BUG() */
 #define BRK_KDB		513	/* Used in KDB_ENTER() */
 #define BRK_MEMU	514	/* Used by FPU emulator */
+#define BRK_KPROBE_BP	515	/* Kprobe break */
+#define BRK_KPROBE_SSTEPBP 516	/* Kprobe single step software implementation */
 #define BRK_MULOVF	1023	/* Multiply overflow */
 
 #endif /* __ASM_BREAK_H */

arch/mips/include/asm/kdebug.h

@@ -8,6 +8,9 @@ enum die_val {
 	DIE_FP,
 	DIE_TRAP,
 	DIE_RI,
+	DIE_PAGE_FAULT,
+	DIE_BREAK,
+	DIE_SSTEPBP
 };
 
 #endif /* _ASM_MIPS_KDEBUG_H */

arch/mips/include/asm/kprobes.h

+/*
+ *  Kernel Probes (KProbes)
+ *  include/asm-mips/kprobes.h
+ *
+ *  Copyright 2006 Sony Corp.
+ *  Copyright 2010 Cavium Networks
+ *
+ *  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; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef _ASM_KPROBES_H
+#define _ASM_KPROBES_H
+
+#include <linux/ptrace.h>
+#include <linux/types.h>
+
+#include <asm/cacheflush.h>
+#include <asm/kdebug.h>
+#include <asm/inst.h>
+
+#define  __ARCH_WANT_KPROBES_INSN_SLOT
+
+struct kprobe;
+struct pt_regs;
+
+typedef union mips_instruction kprobe_opcode_t;
+
+#define MAX_INSN_SIZE 2
+
+#define flush_insn_slot(p)						\
+do {									\
+	flush_icache_range((unsigned long)p->addr,			\
+			   (unsigned long)p->addr +			\
+			   (MAX_INSN_SIZE * sizeof(kprobe_opcode_t)));	\
+} while (0)
+
+
+#define kretprobe_blacklist_size 0
+
+void arch_remove_kprobe(struct kprobe *p);
+
+/* Architecture specific copy of original instruction*/
+struct arch_specific_insn {
+	/* copy of the original instruction */
+	kprobe_opcode_t *insn;
+};
+
+struct prev_kprobe {
+	struct kprobe *kp;
+	unsigned long status;
+	unsigned long old_SR;
+	unsigned long saved_SR;
+	unsigned long saved_epc;
+};
+
+#define MAX_JPROBES_STACK_SIZE 128
+#define MAX_JPROBES_STACK_ADDR \
+	(((unsigned long)current_thread_info()) + THREAD_SIZE - 32 - sizeof(struct pt_regs))
+
+#define MIN_JPROBES_STACK_SIZE(ADDR)					\
+	((((ADDR) + MAX_JPROBES_STACK_SIZE) > MAX_JPROBES_STACK_ADDR)	\
+		? MAX_JPROBES_STACK_ADDR - (ADDR)			\
+		: MAX_JPROBES_STACK_SIZE)
+
+
+/* per-cpu kprobe control block */
+struct kprobe_ctlblk {
+	unsigned long kprobe_status;
+	unsigned long kprobe_old_SR;
+	unsigned long kprobe_saved_SR;
+	unsigned long kprobe_saved_epc;
+	unsigned long jprobe_saved_sp;
+	struct pt_regs jprobe_saved_regs;
+	u8 jprobes_stack[MAX_JPROBES_STACK_SIZE];
+	struct prev_kprobe prev_kprobe;
+};
+
+extern int kprobe_exceptions_notify(struct notifier_block *self,
+				    unsigned long val, void *data);
+
+#endif				/* _ASM_KPROBES_H */

arch/mips/kernel/Makefile

@@ -76,6 +76,7 @@ obj-$(CONFIG_IRQ_TXX9)		+= irq_txx9.o
 obj-$(CONFIG_IRQ_GT641XX)	+= irq-gt641xx.o
 obj-$(CONFIG_IRQ_GIC)		+= irq-gic.o
 
+obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_32BIT)		+= scall32-o32.o
 obj-$(CONFIG_64BIT)		+= scall64-64.o
 obj-$(CONFIG_MIPS32_COMPAT)	+= linux32.o ptrace32.o signal32.o

arch/mips/kernel/traps.c

@@ -25,6 +25,7 @@
 #include <linux/ptrace.h>
 #include <linux/kgdb.h>
 #include <linux/kdebug.h>
+#include <linux/kprobes.h>
 #include <linux/notifier.h>
 #include <linux/kdb.h>
 
@@ -334,7 +335,7 @@ void show_regs(struct pt_regs *regs)
 	__show_regs((struct pt_regs *)regs);
 }
 
-void show_registers(const struct pt_regs *regs)
+void show_registers(struct pt_regs *regs)
 {
 	const int field = 2 * sizeof(unsigned long);
 
@@ -783,6 +784,25 @@ asmlinkage void do_bp(struct pt_regs *regs)
 	if (bcode >= (1 << 10))
 		bcode >>= 10;
 
+	/*
+	 * notify the kprobe handlers, if instruction is likely to
+	 * pertain to them.
+	 */
+	switch (bcode) {
+	case BRK_KPROBE_BP:
+		if (notify_die(DIE_BREAK, "debug", regs, bcode, 0, 0) == NOTIFY_STOP)
+			return;
+		else
+			break;
+	case BRK_KPROBE_SSTEPBP:
+		if (notify_die(DIE_SSTEPBP, "single_step", regs, bcode, 0, 0) == NOTIFY_STOP)
+			return;
+		else
+			break;
+	default:
+		break;
+	}
+
 	do_trap_or_bp(regs, bcode, "Break");
 	return;
 

arch/mips/mm/fault.c

@@ -17,6 +17,7 @@
 #include <linux/mm.h>
 #include <linux/smp.h>
 #include <linux/module.h>
+#include <linux/kprobes.h>
 
 #include <asm/branch.h>
 #include <asm/mmu_context.h>
@@ -24,13 +25,14 @@
 #include <asm/uaccess.h>
 #include <asm/ptrace.h>
 #include <asm/highmem.h>		/* For VMALLOC_END */
+#include <linux/kdebug.h>
 
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
  */
-asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
+asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, unsigned long write,
 			      unsigned long address)
 {
 	struct vm_area_struct * vma = NULL;
@@ -46,6 +48,17 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
 	       field, regs->cp0_epc);
 #endif
 
+#ifdef CONFIG_KPROBES
+	/*
+	 * This is to notify the fault handler of the kprobes.  The
+	 * exception code is redundant as it is also carried in REGS,
+	 * but we pass it anyhow.
+	 */
+	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
+		       (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
+		return;
+#endif
+
 	info.si_code = SEGV_MAPERR;
 
 	/*