[PATCH 0/2] Fix ftracetest issues

[Sam Protsenko]

On 28 November 2017 at 16:08, Naresh Kamboju <naresh.kamboju at linaro.org> wrote:
> 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
>

Tested-by: Sam Protsenko <semen.protsenko at linaro.org>

This series fixed ftracetest on X15 board. After manually applying
second patch (on linux-mainline kernel):

    [PATCH 2/2] ARM: probes: avoid adding kprobes to sensitive
kernel-entry/exit code

all tests are passing. Some inputs:
 - log without applying the patch: [1]
 - log with patch applied: [2]
 - corresponding bug report: [3]

Hope that patch will be merged soon.

Thanks.

[1] http://pastebin.ubuntu.com/26189372/
[2] http://pastebin.ubuntu.com/26189667/
[3] https://bugs.linaro.org/show_bug.cgi?id=3304

>>
>>
>>
>> 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(-)
>>>>
>
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