ARM: fix function graph tracer and unwinder dependencies

commit 503621628b32782a07b2318e4112bd4372aa3401 upstream.

Naresh Kamboju recently reported that the function-graph tracer crashes
on ARM. The function-graph tracer assumes that the kernel is built with
frame pointers.

We explicitly disabled the function-graph tracer when building Thumb2,
since the Thumb2 ABI doesn't have frame pointers.

We recently changed the way the unwinder method was selected, which
seems to have made it more likely that we can end up with the function-
graph tracer enabled but without the kernel built with frame pointers.

Fix up the function graph tracer dependencies so the option is not
available when we have no possibility of having frame pointers, and
adjust the dependencies on the unwinder option to hide the non-frame
pointer unwinder options if the function-graph tracer is enabled.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Danilo Cezar Zanella <danilo.zanella@iag.usp.br>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0f1dbd3238a5ecf6bfa36361cf138868e3395100..0429d1d20393e29d68a4e55ce3207590d389fd09 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -53,7 +53,7 @@ config ARM
        select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
        select HAVE_EXIT_THREAD
        select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)
-       select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL)
+       select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL && !CC_IS_CLANG)
        select HAVE_FUNCTION_TRACER if (!XIP_KERNEL)
        select HAVE_FUTEX_CMPXCHG if FUTEX
        select HAVE_GCC_PLUGINS

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 8df8cdd093e98f9d32ba90d98a05f1fc7a16096c..8558b47df7a06feae017297342c5b1f59277228d 100644 (file)
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -17,8 +17,8 @@ config ARM_PTDUMP
 
 choice
        prompt "Choose kernel unwinder"
-       default UNWINDER_ARM if AEABI && !FUNCTION_GRAPH_TRACER
-       default UNWINDER_FRAME_POINTER if !AEABI || FUNCTION_GRAPH_TRACER
+       default UNWINDER_ARM if AEABI
+       default UNWINDER_FRAME_POINTER if !AEABI
        help
          This determines which method will be used for unwinding kernel stack
          traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
@@ -35,7 +35,7 @@ config UNWINDER_FRAME_POINTER
 
 config UNWINDER_ARM
        bool "ARM EABI stack unwinder"
-       depends on AEABI
+       depends on AEABI && !FUNCTION_GRAPH_TRACER
        select ARM_UNWIND
        help
          This option enables stack unwinding support in the kernel