ARM: 8225/1: Add unwinding support for memory copy functions

The memory copy functions(memcpy, __copy_from_user, __copy_to_user)
never had unwinding annotations added. Currently, when accessing
invalid pointer by these functions occurs the backtrace shown will
stop at these functions or some completely unrelated function.
Add unwinding annotations in hopes of getting a more useful backtrace
in following cases:
1. die on accessing invalid pointer by these functions
2. kprobe trapped at any instruction within these functions
3. interrupted at any instruction within these functions

Signed-off-by: Lin Yongting <linyongting@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 45 insertions, 0 deletions

diff --git a/arch/arm/lib/copy_from_user.S b/arch/arm/lib/copy_from_user.S
index 66a477a3e3cc..7a235b9952be 100644
--- a/arch/arm/lib/copy_from_user.S
+++ b/arch/arm/lib/copy_from_user.S
@@ -12,6 +12,7 @@
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
+#include <asm/unwind.h>
 
 /*
  * Prototype:
@@ -77,6 +78,10 @@
         stmdb   sp!, {r0, r2, r3, \reg1, \reg2}
         .endm
 
+        .macro usave reg1 reg2
+        UNWIND( .save {r0, r2, r3, \reg1, \reg2}        )
+        .endm
+
         .macro exit reg1 reg2
         add     sp, sp, #8
         ldmfd   sp!, {r0, \reg1, \reg2}
diff --git a/arch/arm/lib/copy_template.S b/arch/arm/lib/copy_template.S
index 3bc8eb811a73..652e4d98cd47 100644
--- a/arch/arm/lib/copy_template.S
+++ b/arch/arm/lib/copy_template.S
@@ -53,6 +53,12 @@
  *      data as needed by the implementation including this code. Called
  *      upon code entry.
  *
+ * usave reg1 reg2
+ *
+ *      Unwind annotation macro is corresponding for 'enter' macro.
+ *      It tell unwinder that preserved some provided registers on the stack
+ *      and additional data by a prior 'enter' macro.
+ *
  * exit reg1 reg2
  *
  *      Restore registers with the values previously saved with the
@@ -67,7 +73,12 @@
  */
 
 
+        UNWIND( .fnstart                        )
                 enter   r4, lr
+        UNWIND( .fnend                          )
+
+        UNWIND( .fnstart                        )
+                usave   r4, lr                    @ in first stmdb block
 
                 subs    r2, r2, #4
                 blt     8f
@@ -79,6 +90,11 @@
 
 1:              subs    r2, r2, #(28)
                 stmfd   sp!, {r5 - r8}
+        UNWIND( .fnend                          )
+
+        UNWIND( .fnstart                        )
+                usave   r4, lr
+        UNWIND( .save   {r5 - r8}               ) @ in second stmfd block
                 blt     5f
 
         CALGN(  ands    ip, r0, #31             )
@@ -144,7 +160,10 @@
         CALGN(  bcs     2b                      )
 
 7:              ldmfd   sp!, {r5 - r8}
+        UNWIND( .fnend                          ) @ end of second stmfd block
 
+        UNWIND( .fnstart                        )
+                usave   r4, lr                    @ still in first stmdb block
 8:              movs    r2, r2, lsl #31
                 ldr1b   r1, r3, ne, abort=21f
                 ldr1b   r1, r4, cs, abort=21f
@@ -173,10 +192,13 @@
                 ldr1w   r1, lr, abort=21f
                 beq     17f
                 bgt     18f
+        UNWIND( .fnend                          )
 
 
                 .macro  forward_copy_shift pull push
 
+        UNWIND( .fnstart                        )
+                usave   r4, lr                    @ still in first stmdb block
                 subs    r2, r2, #28
                 blt     14f
 
@@ -187,7 +209,11 @@
         CALGN(  bcc     15f                     )
 
 11:             stmfd   sp!, {r5 - r9}
+        UNWIND( .fnend                          )
 
+        UNWIND( .fnstart                        )
+                usave   r4, lr
+        UNWIND( .save   {r5 - r9}               ) @ in new second stmfd block
         PLD(    pld     [r1, #0]                )
         PLD(    subs    r2, r2, #96             )
         PLD(    pld     [r1, #28]               )
@@ -221,7 +247,10 @@
         PLD(    bge     13b                     )
 
                 ldmfd   sp!, {r5 - r9}
+        UNWIND( .fnend                          ) @ end of the second stmfd block
 
+        UNWIND( .fnstart                        )
+                usave   r4, lr                    @ still in first stmdb block
 14:             ands    ip, r2, #28
                 beq     16f
 
@@ -236,6 +265,7 @@
 
 16:             sub     r1, r1, #(\push / 8)
                 b       8b
+        UNWIND( .fnend                          )
 
                 .endm
 
diff --git a/arch/arm/lib/copy_to_user.S b/arch/arm/lib/copy_to_user.S
index d066df686e17..a9d3db16ecb5 100644
--- a/arch/arm/lib/copy_to_user.S
+++ b/arch/arm/lib/copy_to_user.S
@@ -12,6 +12,7 @@
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
+#include <asm/unwind.h>
 
 /*
  * Prototype:
@@ -80,6 +81,10 @@
         stmdb   sp!, {r0, r2, r3, \reg1, \reg2}
         .endm
 
+        .macro usave reg1 reg2
+        UNWIND( .save {r0, r2, r3, \reg1, \reg2}        )
+        .endm
+
         .macro exit reg1 reg2
         add     sp, sp, #8
         ldmfd   sp!, {r0, \reg1, \reg2}
diff --git a/arch/arm/lib/memcpy.S b/arch/arm/lib/memcpy.S
index a9b9e2287a09..7797e81e40e0 100644
--- a/arch/arm/lib/memcpy.S
+++ b/arch/arm/lib/memcpy.S
@@ -12,6 +12,7 @@
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
+#include <asm/unwind.h>
 
 #define LDR1W_SHIFT     0
 #define STR1W_SHIFT     0
@@ -48,6 +49,10 @@
         stmdb sp!, {r0, \reg1, \reg2}
         .endm
 
+        .macro usave reg1 reg2
+        UNWIND( .save   {r0, \reg1, \reg2}      )
+        .endm
+
         .macro exit reg1 reg2
         ldmfd sp!, {r0, \reg1, \reg2}
         .endm