recordmcount: arm: Implement make_nop

In similar spirit to x86 and arm64 support, add a make_nop_arm()
to replace calls to mcount with a nop in sections that aren't
traced.

Link: http://lkml.kernel.org/r/20161018234200.5804-1-sboyd@codeaurora.org

Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 5423a58d1b06..aeb34223167c 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -213,6 +213,59 @@ static int make_nop_x86(void *map, size_t const offset)
         return 0;
 }
 
+static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
+static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
+static unsigned char *ideal_nop4_arm;
+
+static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
+static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
+static unsigned char *bl_mcount_arm;
+
+static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
+static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
+static unsigned char *push_arm;
+
+static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
+static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
+static unsigned char *ideal_nop2_thumb;
+
+static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
+static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
+static unsigned char *push_bl_mcount_thumb;
+
+static int make_nop_arm(void *map, size_t const offset)
+{
+        char *ptr;
+        int cnt = 1;
+        int nop_size;
+        size_t off = offset;
+
+        ptr = map + offset;
+        if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
+                if (memcmp(ptr - 4, push_arm, 4) == 0) {
+                        off -= 4;
+                        cnt = 2;
+                }
+                ideal_nop = ideal_nop4_arm;
+                nop_size = 4;
+        } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
+                cnt = 3;
+                nop_size = 2;
+                off -= 2;
+                ideal_nop = ideal_nop2_thumb;
+        } else
+                return -1;
+
+        /* Convert to nop */
+        ulseek(fd_map, off, SEEK_SET);
+
+        do {
+                uwrite(fd_map, ideal_nop, nop_size);
+        } while (--cnt > 0);
+
+        return 0;
+}
+
 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
 static int make_nop_arm64(void *map, size_t const offset)
 {
@@ -430,6 +483,11 @@ do_file(char const *const fname)
                         w2 = w2rev;
                         w8 = w8rev;
                 }
+                ideal_nop4_arm = ideal_nop4_arm_le;
+                bl_mcount_arm = bl_mcount_arm_le;
+                push_arm = push_arm_le;
+                ideal_nop2_thumb = ideal_nop2_thumb_le;
+                push_bl_mcount_thumb = push_bl_mcount_thumb_le;
                 break;
         case ELFDATA2MSB:
                 if (*(unsigned char const *)&endian != 0) {
@@ -438,6 +496,11 @@ do_file(char const *const fname)
                         w2 = w2rev;
                         w8 = w8rev;
                 }
+                ideal_nop4_arm = ideal_nop4_arm_be;
+                bl_mcount_arm = bl_mcount_arm_be;
+                push_arm = push_arm_be;
+                ideal_nop2_thumb = ideal_nop2_thumb_be;
+                push_bl_mcount_thumb = push_bl_mcount_thumb_be;
                 break;
         }  /* end switch */
         if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
@@ -463,6 +526,8 @@ do_file(char const *const fname)
                 break;
         case EM_ARM:     reltype = R_ARM_ABS32;
                          altmcount = "__gnu_mcount_nc";
+                         make_nop = make_nop_arm;
+                         rel_type_nop = R_ARM_NONE;
                          break;
         case EM_AARCH64:
                         reltype = R_AARCH64_ABS64;