[ARM] support tracing when using newer compilers

Since gcc 4.4 the name and calling convention for function profiling
on ARM changed. With this patch both types are supported.

See http://sourceware.org/ml/libc-ports/2008-04/msg00009.html for some
details.

Lightly-Tested-by: Anand Gadiyar <[e-mail]>
Tested-by: Kevin Hilman <[e-mail]>
Signed-off-by: Uwe Kleine-König <[e-mail]>

arch/arm/include/asm/ftrace.h

···
 
 #ifndef __ASSEMBLY__
 extern void mcount(void);
+extern void __gnu_mcount_nc(void);
 #endif
 
 #endif

arch/arm/kernel/armksyms.c

···
 
 #ifdef CONFIG_FUNCTION_TRACER
 EXPORT_SYMBOL(mcount);
+EXPORT_SYMBOL(__gnu_mcount_nc);
 #endif

arch/arm/kernel/entry-common.S

···
 
 #else
 
+ENTRY(__gnu_mcount_nc)
+	stmdb sp!, {r0-r3, lr}
+	ldr r0, =ftrace_trace_function
+	ldr r2, [r0]
+	adr r0, ftrace_stub
+	cmp r0, r2
+	bne gnu_trace
+	ldmia sp!, {r0-r3, ip, lr}
+	bx ip
+
+gnu_trace:
+	ldr r1, [sp, #20]			@ lr of instrumented routine
+	mov r0, lr
+	sub r0, r0, #MCOUNT_INSN_SIZE
+	mov lr, pc
+	mov pc, r2
+	ldmia sp!, {r0-r3, ip, lr}
+	bx ip
+
 ENTRY(mcount)
 	stmdb sp!, {r0-r3, lr}
 	ldr r0, =ftrace_trace_function