kbuild: Avoid inconsistent kallsyms data

Several reports on inconsistent kallsyms data has been caused by the aliased symbols
__sched_text_start and __down to shift places in the output of nm.
The root cause was that on second pass ld aligned __sched_text_start to a 4 byte boundary
which is the function alignment on i386.
sched.text and spinlock.text is now aligned to an 8 byte boundary to make sure they
are aligned to a function alignemnt on most (all?) archs.

Tested by: Paulo Marques <pmarques@grupopie.com>
Tested by: Alexander Stohr <Alexander.Stohr@gmx.de>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b3bb326..3fa9428 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -6,6 +6,9 @@
 #define VMLINUX_SYMBOL(_sym_) _sym_
 #endif
 
+/* Align . to a 8 byte boundary equals to maximum function alignment. */
+#define ALIGN_FUNCTION()  . = ALIGN(8)
+
 #define RODATA                                                         \
        .rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {           \
                *(.rodata) *(.rodata.*)                                 \
@@ -79,12 +82,18 @@
                VMLINUX_SYMBOL(__security_initcall_end) = .;            \
        }
 
+/* sched.text is aling to function alignment to secure we have same
+ * address even at second ld pass when generating System.map */
 #define SCHED_TEXT                                                     \
+               ALIGN_FUNCTION();                                       \
                VMLINUX_SYMBOL(__sched_text_start) = .;                 \
                *(.sched.text)                                          \
                VMLINUX_SYMBOL(__sched_text_end) = .;
 
+/* spinlock.text is aling to function alignment to secure we have same
+ * address even at second ld pass when generating System.map */
 #define LOCK_TEXT                                                      \
+               ALIGN_FUNCTION();                                       \
                VMLINUX_SYMBOL(__lock_text_start) = .;                  \
                *(.spinlock.text)                                       \
                VMLINUX_SYMBOL(__lock_text_end) = .;