x86: prepare kprobes code for x86 unification

This patch cleanup kprobes code on x86 for unification.
This patch is based on Arjan's previous work.

- Remove spurious whitespace changes
- Add harmless includes
- Make the 32/64 files more identical
 - Generalize structure fields' and local variable name.
 - Wrap accessing to stack address by macros.
 - Modify bitmap making macro.
 - Merge fixup code into is_riprel() and change its name to fix_riprel().
 - Set MAX_INSN_SIZE to 16 on both arch.
 - Use u32 for bitmaps on both architectures.
 - Clarify some comments.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 212 insertions, 197 deletions

diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index bc93b1dd9a01..2d7763749b1b 100644
--- a/arch/x86/kernel/kprobes_64.c
+++ b/arch/x86/kernel/kprobes_64.c
@@ -40,16 +40,97 @@
 #include <linux/module.h>
 #include <linux/kdebug.h>
 
+#include <asm/cacheflush.h>
+#include <asm/desc.h>
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 #include <asm/alternative.h>
 
 void jprobe_return_end(void);
-static void __kprobes arch_copy_kprobe(struct kprobe *p);
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
+#define stack_addr(regs) ((unsigned long *)regs->sp)
+
+#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
+        (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
+          (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
+          (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
+          (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
+         << (row % 32))
+        /*
+         * Undefined/reserved opcodes, conditional jump, Opcode Extension
+         * Groups, and some special opcodes can not boost.
+         */
+static const u32 twobyte_is_boostable[256 / 32] = {
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+        /*      ----------------------------------------------          */
+        W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
+        W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
+        W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
+        W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
+        W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
+        W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
+        W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
+        W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
+        W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
+        W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
+        W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
+        W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
+        W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
+        W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
+        W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
+        W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0)   /* f0 */
+        /*      -----------------------------------------------         */
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+};
+static const u32 onebyte_has_modrm[256 / 32] = {
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+        /*      -----------------------------------------------         */
+        W(0x00, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 00 */
+        W(0x10, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) , /* 10 */
+        W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 20 */
+        W(0x30, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) , /* 30 */
+        W(0x40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 40 */
+        W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
+        W(0x60, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0) | /* 60 */
+        W(0x70, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 70 */
+        W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
+        W(0x90, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 90 */
+        W(0xa0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* a0 */
+        W(0xb0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* b0 */
+        W(0xc0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0) | /* c0 */
+        W(0xd0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
+        W(0xe0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* e0 */
+        W(0xf0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1)   /* f0 */
+        /*      -----------------------------------------------         */
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+};
+static const u32 twobyte_has_modrm[256 / 32] = {
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+        /*      -----------------------------------------------         */
+        W(0x00, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1) | /* 0f */
+        W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0) , /* 1f */
+        W(0x20, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 2f */
+        W(0x30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 3f */
+        W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 4f */
+        W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 5f */
+        W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 6f */
+        W(0x70, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1) , /* 7f */
+        W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 8f */
+        W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 9f */
+        W(0xa0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) | /* af */
+        W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1) , /* bf */
+        W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0) | /* cf */
+        W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* df */
+        W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* ef */
+        W(0xf0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0)   /* ff */
+        /*      -----------------------------------------------         */
+        /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f          */
+};
+#undef W
+
 struct kretprobe_blackpoint kretprobe_blacklist[] = {
         {"__switch_to", }, /* This function switches only current task, but
                               doesn't switch kernel stack.*/
@@ -70,44 +151,11 @@ static __always_inline void set_jmp_op(void *from, void *to)
 }
 
 /*
- * returns non-zero if opcode is boostable
+ * returns non-zero if opcode is boostable.
  * RIP relative instructions are adjusted at copying time
  */
 static __always_inline int can_boost(kprobe_opcode_t *opcodes)
 {
-#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
-        (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
-          (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
-          (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
-          (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
-         << (row % 64))
-        /*
-         * Undefined/reserved opcodes, conditional jump, Opcode Extension
-         * Groups, and some special opcodes can not boost.
-         */
-        static const unsigned long twobyte_is_boostable[256 / 64] = {
-                /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f        */
-                /*      ----------------------------------------------        */
-                W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0)|/* 00 */
-                W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)|/* 10 */
-                W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)|/* 20 */
-                W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),/* 30 */
-                W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1)|/* 40 */
-                W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)|/* 50 */
-                W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1)|/* 60 */
-                W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1),/* 70 */
-                W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)|/* 80 */
-                W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1)|/* 90 */
-                W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1)|/* a0 */
-                W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1),/* b0 */
-                W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1)|/* c0 */
-                W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1)|/* d0 */
-                W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1)|/* e0 */
-                W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
-                /*      -----------------------------------------------       */
-                /*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f        */
-        };
-#undef W
         kprobe_opcode_t opcode;
         kprobe_opcode_t *orig_opcodes = opcodes;
 
@@ -120,7 +168,8 @@ retry:
         if (opcode == 0x0f) {
                 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
                         return 0;
-                return test_bit(*opcodes, twobyte_is_boostable);
+                return test_bit(*opcodes,
+                                (unsigned long *)twobyte_is_boostable);
         }
 
         switch (opcode & 0xf0) {
@@ -169,80 +218,25 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
                 return 1;
         }
 
-        if (*insn  >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
-                return 1;
-        return 0;
-}
-
-int __kprobes arch_prepare_kprobe(struct kprobe *p)
-{
-        /* insn: must be on special executable page on x86_64. */
-        p->ainsn.insn = get_insn_slot();
-        if (!p->ainsn.insn) {
-                return -ENOMEM;
-        }
-        arch_copy_kprobe(p);
+        /*
+         * on 64 bit x86, 0x40-0x4f are prefixes so we need to look
+         * at the next byte instead.. but of course not recurse infinitely
+         */
+        if (*insn  >= 0x40 && *insn <= 0x4f)
+                return is_IF_modifier(++insn);
         return 0;
 }
 
 /*
- * Determine if the instruction uses the %rip-relative addressing mode.
+ * Adjust the displacement if the instruction uses the %rip-relative
+ * addressing mode.
  * If it does, Return the address of the 32-bit displacement word.
  * If not, return null.
  */
-static s32 __kprobes *is_riprel(u8 *insn)
+static void __kprobes fix_riprel(struct kprobe *p)
 {
-#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)                \
-        (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
-          (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
-          (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
-          (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
-         << (row % 64))
-        static const u64 onebyte_has_modrm[256 / 64] = {
-                /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
-                /*      -------------------------------         */
-                W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
-                W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
-                W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
-                W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
-                W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
-                W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
-                W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
-                W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
-                W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
-                W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
-                W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
-                W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
-                W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
-                W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
-                W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
-                W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1)  /* f0 */
-                /*      -------------------------------         */
-                /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
-        };
-        static const u64 twobyte_has_modrm[256 / 64] = {
-                /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
-                /*      -------------------------------         */
-                W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
-                W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
-                W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
-                W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
-                W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
-                W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
-                W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
-                W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
-                W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
-                W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
-                W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
-                W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
-                W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
-                W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
-                W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
-                W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0)  /* ff */
-                /*      -------------------------------         */
-                /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
-        };
-#undef  W
+        u8 *insn = p->ainsn.insn;
+        s64 disp;
         int need_modrm;
 
         /* Skip legacy instruction prefixes.  */
@@ -271,54 +265,60 @@ static s32 __kprobes *is_riprel(u8 *insn)
 
         if (*insn == 0x0f) {    /* Two-byte opcode.  */
                 ++insn;
-                need_modrm = test_bit(*insn, twobyte_has_modrm);
-        } else {                /* One-byte opcode.  */
-                need_modrm = test_bit(*insn, onebyte_has_modrm);
-        }
+                need_modrm = test_bit(*insn,
+                                      (unsigned long *)twobyte_has_modrm);
+        } else                  /* One-byte opcode.  */
+                need_modrm = test_bit(*insn,
+                                      (unsigned long *)onebyte_has_modrm);
 
         if (need_modrm) {
                 u8 modrm = *++insn;
                 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
                         /* Displacement follows ModRM byte.  */
-                        return (s32 *) ++insn;
+                        ++insn;
+                        /*
+                         * The copied instruction uses the %rip-relative
+                         * addressing mode.  Adjust the displacement for the
+                         * difference between the original location of this
+                         * instruction and the location of the copy that will
+                         * actually be run.  The tricky bit here is making sure
+                         * that the sign extension happens correctly in this
+                         * calculation, since we need a signed 32-bit result to
+                         * be sign-extended to 64 bits when it's added to the
+                         * %rip value and yield the same 64-bit result that the
+                         * sign-extension of the original signed 32-bit
+                         * displacement would have given.
+                         */
+                        disp = (u8 *) p->addr + *((s32 *) insn) -
+                               (u8 *) p->ainsn.insn;
+                        BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
+                        *(s32 *)insn = (s32) disp;
                 }
         }
-
-        /* No %rip-relative addressing mode here.  */
-        return NULL;
 }
 
 static void __kprobes arch_copy_kprobe(struct kprobe *p)
 {
-        s32 *ripdisp;
-        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
-        ripdisp = is_riprel(p->ainsn.insn);
-        if (ripdisp) {
-                /*
-                 * The copied instruction uses the %rip-relative
-                 * addressing mode.  Adjust the displacement for the
-                 * difference between the original location of this
-                 * instruction and the location of the copy that will
-                 * actually be run.  The tricky bit here is making sure
-                 * that the sign extension happens correctly in this
-                 * calculation, since we need a signed 32-bit result to
-                 * be sign-extended to 64 bits when it's added to the
-                 * %rip value and yield the same 64-bit result that the
-                 * sign-extension of the original signed 32-bit
-                 * displacement would have given.
-                 */
-                s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
-                BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
-                *ripdisp = disp;
-        }
-        if (can_boost(p->addr)) {
+        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+        fix_riprel(p);
+        if (can_boost(p->addr))
                 p->ainsn.boostable = 0;
-        } else {
+        else
                 p->ainsn.boostable = -1;
-        }
+
         p->opcode = *p->addr;
 }
 
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+        /* insn: must be on special executable page on x86. */
+        p->ainsn.insn = get_insn_slot();
+        if (!p->ainsn.insn)
+                return -ENOMEM;
+        arch_copy_kprobe(p);
+        return 0;
+}
+
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
         text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
@@ -340,26 +340,26 @@ 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.old_rflags = kcb->kprobe_old_rflags;
-        kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
+        kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
+        kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
 }
 
 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_old_rflags = kcb->prev_kprobe.old_rflags;
-        kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
+        kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
+        kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
 }
 
 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_saved_rflags = kcb->kprobe_old_rflags
+        kcb->kprobe_saved_flags = kcb->kprobe_old_flags
                 = (regs->flags & (TF_MASK | IF_MASK));
         if (is_IF_modifier(p->ainsn.insn))
-                kcb->kprobe_saved_rflags &= ~IF_MASK;
+                kcb->kprobe_saved_flags &= ~IF_MASK;
 }
 
 static __always_inline void clear_btf(void)
@@ -390,20 +390,27 @@ static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
                                       struct pt_regs *regs)
 {
-        unsigned long *sara = (unsigned long *)regs->sp;
+        unsigned long *sara = stack_addr(regs);
 
         ri->ret_addr = (kprobe_opcode_t *) *sara;
+
         /* Replace the return addr with trampoline addr */
         *sara = (unsigned long) &kretprobe_trampoline;
 }
 
-int __kprobes kprobe_handler(struct pt_regs *regs)
+/*
+ * Interrupts are disabled on entry as trap3 is an interrupt gate and they
+ * remain disabled thorough out this function.
+ */
+static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
         struct kprobe *p;
         int ret = 0;
-        kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
+        kprobe_opcode_t *addr;
         struct kprobe_ctlblk *kcb;
 
+        addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
+
         /*
          * We don't want to be preempted for the entire
          * duration of kprobe processing
@@ -418,7 +425,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
                                 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
                                 regs->flags &= ~TF_MASK;
-                                regs->flags |= kcb->kprobe_saved_rflags;
+                                regs->flags |= kcb->kprobe_saved_flags;
                                 goto no_kprobe;
                         } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
                                 /* TODO: Provide re-entrancy from
@@ -429,22 +436,20 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
                                 arch_disarm_kprobe(p);
                                 regs->ip = (unsigned long)p->addr;
                                 reset_current_kprobe();
-                                ret = 1;
-                        } else {
-                                /* We have reentered the kprobe_handler(), since
-                                 * another probe was hit while within the
-                                 * handler. We here save the original kprobe
-                                 * variables and just single step on 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);
-                                prepare_singlestep(p, regs);
-                                kcb->kprobe_status = KPROBE_REENTER;
                                 return 1;
                         }
+                        /* 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);
+                        prepare_singlestep(p, regs);
+                        kcb->kprobe_status = KPROBE_REENTER;
+                        return 1;
                 } else {
                         if (*addr != BREAKPOINT_INSTRUCTION) {
                         /* The breakpoint instruction was removed by
@@ -578,23 +583,23 @@ fastcall void * __kprobes trampoline_handler(struct pt_regs *regs)
         INIT_HLIST_HEAD(&empty_rp);
         spin_lock_irqsave(&kretprobe_lock, flags);
         head = kretprobe_inst_table_head(current);
-        /* fixup rt_regs */
+        /* fixup registers */
         regs->cs = __KERNEL_CS;
         regs->ip = trampoline_address;
-        regs->orig_ax = 0xffffffffffffffff;
+        regs->orig_ax = ~0UL;
 
         /*
          * 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 then one return
+         * task either because multiple functions in the call path have
+         * return probes installed on them, and/or more then one
          * return probe was registered for a target function.
          *
          * We can handle this because:
-         *     - instances are always inserted at the head of the list
+         *     - instances are always pushed into 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
+         *       function, the (chronologically) first instance's ret_addr
+         *       will be 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)
@@ -661,9 +666,9 @@ fastcall void * __kprobes trampoline_handler(struct pt_regs *regs)
 static void __kprobes resume_execution(struct kprobe *p,
                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 {
-        unsigned long *tos = (unsigned long *)regs->sp;
-        unsigned long copy_rip = (unsigned long)p->ainsn.insn;
-        unsigned long orig_rip = (unsigned long)p->addr;
+        unsigned long *tos = stack_addr(regs);
+        unsigned long copy_ip = (unsigned long)p->ainsn.insn;
+        unsigned long orig_ip = (unsigned long)p->addr;
         kprobe_opcode_t *insn = p->ainsn.insn;
 
         /*skip the REX prefix*/
@@ -674,7 +679,7 @@ static void __kprobes resume_execution(struct kprobe *p,
         switch (*insn) {
         case 0x9c:      /* pushfl */
                 *tos &= ~(TF_MASK | IF_MASK);
-                *tos |= kcb->kprobe_old_rflags;
+                *tos |= kcb->kprobe_old_flags;
                 break;
         case 0xc2:      /* iret/ret/lret */
         case 0xc3:
@@ -686,18 +691,23 @@ static void __kprobes resume_execution(struct kprobe *p,
                 p->ainsn.boostable = 1;
                 goto no_change;
         case 0xe8:      /* call relative - Fix return addr */
-                *tos = orig_rip + (*tos - copy_rip);
+                *tos = orig_ip + (*tos - copy_ip);
                 break;
         case 0xff:
                 if ((insn[1] & 0x30) == 0x10) {
-                        /* call absolute, indirect */
-                        /* Fix return addr; ip is correct. */
-                        /* not boostable */
-                        *tos = orig_rip + (*tos - copy_rip);
+                        /*
+                         * call absolute, indirect
+                         * Fix return addr; ip is correct.
+                         * But this is not boostable
+                         */
+                        *tos = orig_ip + (*tos - copy_ip);
                         goto no_change;
-                } else if (((insn[1] & 0x31) == 0x20) ||        /* jmp near, absolute indirect */
-                           ((insn[1] & 0x31) == 0x21)) {        /* jmp far, absolute indirect */
-                        /* ip is correct. And this is boostable */
+                } else if (((insn[1] & 0x31) == 0x20) ||
+                           ((insn[1] & 0x31) == 0x21)) {
+                        /*
+                         * jmp near and far, absolute indirect
+                         * ip is correct. And this is boostable
+                         */
                         p->ainsn.boostable = 1;
                         goto no_change;
                 }
@@ -706,21 +716,21 @@ static void __kprobes resume_execution(struct kprobe *p,
         }
 
         if (p->ainsn.boostable == 0) {
-                if ((regs->ip > copy_rip) &&
-                    (regs->ip - copy_rip) + 5 < MAX_INSN_SIZE) {
+                if ((regs->ip > copy_ip) &&
+                    (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
                         /*
                          * These instructions can be executed directly if it
                          * jumps back to correct address.
                          */
                         set_jmp_op((void *)regs->ip,
-                                   (void *)orig_rip + (regs->ip - copy_rip));
+                                   (void *)orig_ip + (regs->ip - copy_ip));
                         p->ainsn.boostable = 1;
                 } else {
                         p->ainsn.boostable = -1;
                 }
         }
 
-        regs->ip = orig_rip + (regs->ip - copy_rip);
+        regs->ip += orig_ip - copy_ip;
 
 no_change:
         restore_btf();
@@ -728,7 +738,11 @@ no_change:
         return;
 }
 
-int __kprobes post_kprobe_handler(struct pt_regs *regs)
+/*
+ * Interrupts are disabled on entry as trap1 is an interrupt gate and they
+ * remain disabled thoroughout this function.
+ */
+static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 {
         struct kprobe *cur = kprobe_running();
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
@@ -742,10 +756,10 @@ int __kprobes post_kprobe_handler(struct pt_regs *regs)
         }
 
         resume_execution(cur, regs, kcb);
-        regs->flags |= kcb->kprobe_saved_rflags;
+        regs->flags |= kcb->kprobe_saved_flags;
         trace_hardirqs_fixup_flags(regs->flags);
 
-        /* Restore the original saved kprobes variables and continue. */
+        /* Restore back the original saved kprobes variables and continue. */
         if (kcb->kprobe_status == KPROBE_REENTER) {
                 restore_previous_kprobe(kcb);
                 goto out;
@@ -782,7 +796,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
                  * normal page fault.
                  */
                 regs->ip = (unsigned long)cur->addr;
-                regs->flags |= kcb->kprobe_old_rflags;
+                regs->flags |= kcb->kprobe_old_flags;
                 if (kcb->kprobe_status == KPROBE_REENTER)
                         restore_previous_kprobe(kcb);
                 else
@@ -793,7 +807,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
         case KPROBE_HIT_SSDONE:
                 /*
                  * We increment the nmissed count for accounting,
-                 * we can also use npre/npostfault count for accouting
+                 * we can also use npre/npostfault count for accounting
                  * these specific fault cases.
                  */
                 kprobes_inc_nmissed_count(cur);
@@ -819,7 +833,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
                 }
 
                 /*
-                 * fixup() could not handle it,
+                 * fixup routine could not handle it,
                  * Let do_page_fault() fix it.
                  */
                 break;
@@ -838,7 +852,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         struct die_args *args = (struct die_args *)data;
         int ret = NOTIFY_DONE;
 
-        if (args->regs && user_mode(args->regs))
+        if (args->regs && user_mode_vm(args->regs))
                 return ret;
 
         switch (val) {
@@ -871,8 +885,9 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
         kcb->jprobe_saved_regs = *regs;
-        kcb->jprobe_saved_rsp = (long *) regs->sp;
-        addr = (unsigned long)(kcb->jprobe_saved_rsp);
+        kcb->jprobe_saved_sp = stack_addr(regs);
+        addr = (unsigned long)(kcb->jprobe_saved_sp);
+
         /*
          * As Linus pointed out, gcc assumes that the callee
          * owns the argument space and could overwrite it, e.g.
@@ -897,21 +912,20 @@ void __kprobes jprobe_return(void)
                       "       .globl jprobe_return_end  \n"
                       "       jprobe_return_end:        \n"
                       "       nop                       \n"::"b"
-                      (kcb->jprobe_saved_rsp):"memory");
+                      (kcb->jprobe_saved_sp):"memory");
 }
 
 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 {
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
         u8 *addr = (u8 *) (regs->ip - 1);
-        unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
         struct jprobe *jp = container_of(p, struct jprobe, kp);
 
         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
-                if ((unsigned long *)regs->sp != kcb->jprobe_saved_rsp) {
+                if (stack_addr(regs) != kcb->jprobe_saved_sp) {
                         struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
                         printk("current sp %p does not match saved sp %p\n",
-                               (long *)regs->sp, kcb->jprobe_saved_rsp);
+                               stack_addr(regs), kcb->jprobe_saved_sp);
                         printk("Saved registers for jprobe %p\n", jp);
                         show_registers(saved_regs);
                         printk("Current registers\n");
@@ -919,8 +933,9 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
                         BUG();
                 }
                 *regs = kcb->jprobe_saved_regs;
-                memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
-                       MIN_STACK_SIZE(stack_addr));
+                memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp),
+                       kcb->jprobes_stack,
+                       MIN_STACK_SIZE(kcb->jprobe_saved_sp));
                 preempt_enable_no_resched();
                 return 1;
         }