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ARM: 8800/1: use choice for kernel unwinders

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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>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Stefan Agner 2018-09-30 23:02:33 +01:00 committed by Russell King
parent 3f53950190
commit f9b58e8c7d
2 changed files with 31 additions and 19 deletions
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44
arch/arm/Kconfig.debug
View File

@ -45,30 +45,42 @@ 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
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 DEBUG_USER
bool "Verbose user fault messages"

6
lib/Kconfig.debug
View File

@ -1179,7 +1179,7 @@ config LOCKDEP
bool
depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
select STACKTRACE
select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86
select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
select KALLSYMS
select KALLSYMS_ALL
@ -1590,7 +1590,7 @@ 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 && !X86
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
help
Provide stacktrace filter for fault-injection capabilities
@ -1599,7 +1599,7 @@ 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 && !X86
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
select KALLSYMS
select KALLSYMS_ALL
select STACKTRACE