Messages in this thread Patch in this message |  | | From | Stefan Agner <> | Subject | [PATCH] ARM: use choice for kernel unwinders | Date | Wed, 22 Aug 2018 00:24:16 +0200 |
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While in theory multiple unwinders could be compiled in, it does not make sense in practise. Use a choice to make the unwinder selection mutually exclusive and mandatory.
Already before this commit it has not been possible to deselect FRAME_POINTER. Remove the obsolete comment.
Furthermore, to produce a meaningful backtrace with FRAME_POINTER enabled the kernel needs a specific function prologue: mov ip, sp stmfd sp!, {fp, ip, lr, pc} sub fp, ip, #4
To get to the required prologue gcc uses apcs and no-sched-prolog. This compiler options are not available on clang, and clang is not able to generate the required prologue. Make the FRAME_POINTER config symbol depending on !clang.
Suggested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Stefan Agner <stefan@agner.ch> --- arch/arm/Kconfig.debug | 43 ++++++++++++++++++++++++++---------------- 1 file changed, 27 insertions(+), 16 deletions(-)
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 693f84392f1b..ba09e744384a 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -48,30 +48,41 @@ config DEBUG_WX If in doubt, say "Y". -# RMK wants arm kernels compiled with frame pointers or stack unwinding. -# If you know what you are doing and are willing to live without stack -# traces, you can get a slightly smaller kernel by setting this option to -# n, but then RMK will have to kill you ;). -config FRAME_POINTER - bool - depends on !THUMB2_KERNEL - default y if !ARM_UNWIND || FUNCTION_GRAPH_TRACER +choice + prompt "Choose kernel unwinder" + default UNWINDER_ARM if AEABI && !FUNCTION_GRAPH_TRACER + default UNWINDER_FRAME_POINTER if !AEABI || FUNCTION_GRAPH_TRACER + help + This determines which method will be used for unwinding kernel stack + traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack, + livepatch, lockdep, and more. + +config UNWINDER_FRAME_POINTER + bool "Frame pointer unwinder" + depends on !THUMB2_KERNEL && !CC_IS_CLANG + select FRAME_POINTER help - If you say N here, the resulting kernel will be slightly smaller and - faster. However, if neither FRAME_POINTER nor ARM_UNWIND are enabled, - when a problem occurs with the kernel, the information that is - reported is severely limited. + This option enables the frame pointer unwinder for unwinding + kernel stack traces. -config ARM_UNWIND - bool "Enable stack unwinding support (EXPERIMENTAL)" +config UNWINDER_ARM + bool "ARM EABI stack unwinder" depends on AEABI - default y + select ARM_UNWIND help This option enables stack unwinding support in the kernel using the information automatically generated by the compiler. The resulting kernel image is slightly bigger but the performance is not affected. Currently, this feature - only works with EABI compilers. If unsure say Y. + only works with EABI compilers. + +endchoice + +config ARM_UNWIND + bool + +config FRAME_POINTER + bool config OLD_MCOUNT bool -- 2.18.0
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