ARM: 6314/1: ftrace: allow build without frame pointers on ARM

With a new enough GCC, ARM function tracing can be supported without the
need for frame pointers.  This is essential for Thumb-2 support, since
frame pointers aren't available then.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 91344af..4dbce53 100644 (file)
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -27,6 +27,11 @@ config ARM_UNWIND
          the performance is not affected. Currently, this feature
          only works with EABI compilers. If unsure say Y.
 
          the performance is not affected. Currently, this feature
          only works with EABI compilers. If unsure say Y.
 

+config OLD_MCOUNT
+       bool
+       depends on FUNCTION_TRACER && FRAME_POINTER
+       default y
+

 config DEBUG_USER
        bool "Verbose user fault messages"
        help
 config DEBUG_USER
        bool "Verbose user fault messages"
        help

diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 8214bfe..e5e1e53 100644 (file)
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -165,6 +165,8 @@ EXPORT_SYMBOL(_find_next_bit_be);
 #endif
 
 #ifdef CONFIG_FUNCTION_TRACER
 #endif
 
 #ifdef CONFIG_FUNCTION_TRACER

+#ifdef CONFIG_OLD_MCOUNT

 EXPORT_SYMBOL(mcount);
 EXPORT_SYMBOL(mcount);

+#endif

 EXPORT_SYMBOL(__gnu_mcount_nc);
 #endif
 EXPORT_SYMBOL(__gnu_mcount_nc);
 #endif

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index f05a35a..6805a72 100644 (file)
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -128,6 +128,13 @@ ENDPROC(ret_from_fork)
  * allows it to be clobbered in subroutines and doesn't use it to hold
  * parameters.)
  */
  * allows it to be clobbered in subroutines and doesn't use it to hold
  * parameters.)
  */

+
+#ifndef CONFIG_OLD_MCOUNT
+#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
+#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
+#endif
+#endif
+

 #ifdef CONFIG_DYNAMIC_FTRACE
 ENTRY(mcount)
        stmdb   sp!, {r0-r3, lr}
 #ifdef CONFIG_DYNAMIC_FTRACE
 ENTRY(mcount)
        stmdb   sp!, {r0-r3, lr}


@@ -173,6 +180,12 @@ gnu_trace:
        ldmia   sp!, {r0-r3, ip, lr}
        mov     pc, ip
 
        ldmia   sp!, {r0-r3, ip, lr}
        mov     pc, ip
 

+#ifdef CONFIG_OLD_MCOUNT
+/*
+ * This is under an ifdef in order to force link-time errors for people trying
+ * to build with !FRAME_POINTER with a GCC which doesn't use the new-style
+ * mcount.
+ */

 ENTRY(mcount)
        stmdb   sp!, {r0-r3, lr}
        ldr     r0, =ftrace_trace_function
 ENTRY(mcount)
        stmdb   sp!, {r0-r3, lr}
        ldr     r0, =ftrace_trace_function


@@ -191,6 +204,7 @@ trace:
        mov     pc, r2
        ldr     lr, [fp, #-4]                   @ restore lr
        ldmia   sp!, {r0-r3, pc}
        mov     pc, r2
        ldr     lr, [fp, #-4]                   @ restore lr
        ldmia   sp!, {r0-r3, pc}

+#endif

 
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 
 #endif /* CONFIG_DYNAMIC_FTRACE */
 

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 538501c..6329d06 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -121,7 +121,7 @@ if FTRACE
 config FUNCTION_TRACER
        bool "Kernel Function Tracer"
        depends on HAVE_FUNCTION_TRACER
 config FUNCTION_TRACER
        bool "Kernel Function Tracer"
        depends on HAVE_FUNCTION_TRACER

-       select FRAME_POINTER
+       select FRAME_POINTER if (!ARM_UNWIND)

        select KALLSYMS
        select GENERIC_TRACER
        select CONTEXT_SWITCH_TRACER
        select KALLSYMS
        select GENERIC_TRACER
        select CONTEXT_SWITCH_TRACER