From: Stefan Agner stefan@agner.ch
commit f9b58e8c7d031b0daa5c9a9ee27f5a4028ba53ac upstream.
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 Reviewed-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: Anders Roxell anders.roxell@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/Kconfig.debug | 44 ++++++++++++++++++++++++++++---------------- lib/Kconfig.debug | 6 +++--- 2 files changed, 31 insertions(+), 19 deletions(-)
--- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -15,30 +15,42 @@ config ARM_PTDUMP kernel. If in doubt, say "N"
-# 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 - 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 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 ARM_UNWIND - bool "Enable stack unwinding support (EXPERIMENTAL)" +config UNWINDER_FRAME_POINTER + bool "Frame pointer unwinder" + depends on !THUMB2_KERNEL && !CC_IS_CLANG + select ARCH_WANT_FRAME_POINTERS + select FRAME_POINTER + help + This option enables the frame pointer unwinder for unwinding + kernel stack traces. + +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 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1091,7 +1091,7 @@ config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select STACKTRACE - select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE + select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !SCORE select KALLSYMS select KALLSYMS_ALL
@@ -1670,7 +1670,7 @@ config FAULT_INJECTION_STACKTRACE_FILTER depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT depends on !X86_64 select STACKTRACE - select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE + select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !SCORE help Provide stacktrace filter for fault-injection capabilities
@@ -1679,7 +1679,7 @@ config LATENCYTOP depends on DEBUG_KERNEL depends on STACKTRACE_SUPPORT depends on PROC_FS - select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC + select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC select KALLSYMS select KALLSYMS_ALL select STACKTRACE