[PATCH 0/2] Fix ftracetest issues

[Naresh Kamboju]

On 27 November 2017 at 22:55, Naresh Kamboju <naresh.kamboju at linaro.org> wrote:
> Hi Alex Shi,
>
> On 26 November 2017 at 20:46, Alex Shi <alex.shi at linaro.org> wrote:
>> CC Naresh,
>>
>> Could you like to test the patch for our bug 3297?
>>
>> BTW,
>> The 2nd has 2 build error on stm32_defconfig:
>>
>> arch/arm/kernel/traps.o: In function `dump_backtrace_entry':
>> /mmkernels/kernel/arch/arm/kernel/traps.c:77: undefined reference to
>> `__entry_text_start'
>> /mmkernels/kernel/arch/arm/kernel/traps.c:77: undefined reference to
>> `__entry_text_end'
>>
>
> Case 1: Build PASS on linux-4.14.y
> -----------
> Tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> Branch: linux-4.14.y
> Commit id: f9f0b03dedc1 (HEAD -> linux-4.14.y, tag: v4.14.2,
> origin/linux-4.14.y) Linux 4.14.2
>
> Patches 1 and 2 applies smooth and build PASS with defconfig.
> Ftrace test did not hang on beagleboard x15.

Tested-by: Naresh Kamboju <naresh.kamboju at linaro.org>

- Naresh

>
>
>
> Case 2: Build failed on linux-4.9.y and linux-4.4.y
> -----------
> Tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> Branch: linux-4.9.y
> Commit id: 133e6ccf46f1 (HEAD -> linux-4.9.y, tag: v4.9.65,
> origin/linux-4.9.y) Linux 4.9.65
>
> Tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> Branch: linux-4.4.y
> Commit id: 29ffb9c1fb4a (HEAD, tag: v4.4.102, origin/linux-4.4.y) Linux 4.4.102
>
> Patch-1 : Patch applied smooth.
> Patch-2: Patch failed to apply. Manually changed this file
> "arch/arm/include/asm/traps.h"
>
> Build failed on linux-4.9.y and linux-4.4.y with defconfig.
>
> Build Error
> ---------------
> arch/arm/kernel/traps.c: In function ‘dump_backtrace_entry’:
> arch/arm/kernel/traps.c:73:2: error: implicit declaration of function
> ‘in_entry_text’ [-Werror=implicit-function-declaration]
> cc1: some warnings being treated as errors
> make[1]: *** [arch/arm/kernel/traps.o] Error 1
> make: *** [arch/arm/kernel] Error 2
>
> - Naresh
>
>> On 11/25/2017 07:33 PM, Russell King - ARM Linux wrote:
>>> ftracetest provokes the kernel to try and return to userspace addresses
>>> in kernel mode.  These two patches prevent that.
>>>
>>> The first patch, which I intend merging with Linus tonight, ensures that
>>> we catch the condition before we hit userspace, meaning that there is no
>>> possibility of executing user code while in kernel mode.
>>>
>>> The second patch fixes the ftracetest issue itself by ensuring that it
>>> is not possible to set a kprobe on any of the "special" assembler code.
>>> Such code includes:
>>> - the kernel primary/secondary CPU startup code
>>> - exception entry code
>>> - idmap code
>>>
>>> This is because the conditions under which this code is executed does
>>> not meet the kprobes requirements, which is basically that the
>>> "function" is C-like - it does something and then returns to the parent,
>>> and has a stack.  This is just not universally true of the above code.
>>>
>>> This patch is larger than one may desire as we re-organise the sections
>>> that some code ends up in, the way the unwinder works, and how we print
>>> stack frames.
>>>
>>>  arch/arm/include/asm/assembler.h | 18 ++++++++++++++++++
>>>  arch/arm/include/asm/exception.h |  3 +--
>>>  arch/arm/include/asm/sections.h  | 21 +++++++++++++++++++++
>>>  arch/arm/include/asm/traps.h     | 12 ------------
>>>  arch/arm/kernel/entry-armv.S     |  6 +-----
>>>  arch/arm/kernel/entry-common.S   |  1 +
>>>  arch/arm/kernel/entry-header.S   |  6 ++++++
>>>  arch/arm/kernel/stacktrace.c     | 14 ++------------
>>>  arch/arm/kernel/traps.c          |  4 ++--
>>>  arch/arm/kernel/vmlinux.lds.S    |  6 +++---
>>>  arch/arm/mm/fault.c              |  5 ++---
>>>  arch/arm/probes/kprobes/core.c   | 14 +++++++++++---
>>>  12 files changed, 68 insertions(+), 42 deletions(-)
>>>