| Message ID | 1386922149-4561-1-git-send-email-jonas.jensen@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Dec 13, 2013 at 09:09:09AM +0100, Jonas Jensen wrote: > CPU_FA526 lacks thumb state support and doesn't get along with some > of the options enabled by ARCH_MULTI_V4T. > > More specifically it doesn't get along with CPU_ARM920T: > > CPU_ABRT_EV4T > CPU_CACHE_V4WT > CPU_COPY_V4WB > CPU_TLB_V4WBI Having these selected doesn't change how the kernel is compiled or how the kernel uses the code which these provide. These mainly control which files are built. They also control indirectly how the code is called - but the ultimate decision is made by the CPU which is detected and the block in __fa526_proc_info. So, having these symbols enabled (provided the right ones for FA526 are also enabled) makes no difference. So I don't buy your explanation.
On 13 December 2013 10:56, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > So, having these symbols enabled (provided the right ones for FA526 are > also enabled) makes no difference. So I don't buy your explanation. The explanation is indeed false, CPU_FA526 and CPU_ARM920T get along just fine. That's not where the problem is. Panic goes away after removing CONFIG_ARM_THUMB=y. I assume this is what should happen on processors without thumb? Thanks, Jonas
On Fri, Dec 13, 2013 at 11:51:09AM +0100, Jonas Jensen wrote: > On 13 December 2013 10:56, Russell King - ARM Linux > <linux@arm.linux.org.uk> wrote: > > So, having these symbols enabled (provided the right ones for FA526 are > > also enabled) makes no difference. So I don't buy your explanation. > > The explanation is indeed false, CPU_FA526 and CPU_ARM920T get along just fine. > That's not where the problem is. > > Panic goes away after removing CONFIG_ARM_THUMB=y. > > I assume this is what should happen on processors without thumb? I see what's causing this: the kuser helpers are using "bx lr" to return which will be undefined on non-Thumb CPUs. We generally cope fine with non-Thumb CPUs, conditionalising where necessary on HWCAP_THUMB or the T bit in the PSR being set. However, it looks like the kuser helpers got missed. As a check, please look at arch/arm/kernel/entry-armv.S, find the line with: .macro usr_ret, reg and ensure that the mov pc, \reg case always gets used. Please report back. Thanks.
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index b64a8ef..4f88ff3 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -863,6 +863,11 @@ menu "Multiple platform selection" comment "CPU Core family selection" +config ARCH_MULTI_V4 + bool "ARMv4 based platforms (FA526, StrongARM)" + depends on !ARCH_MULTI_V6_V7 + select ARCH_MULTI_V4_V5 + config ARCH_MULTI_V4T bool "ARMv4T based platforms (ARM720T, ARM920T, ...)" depends on !ARCH_MULTI_V6_V7
CPU_FA526 lacks thumb state support and doesn't get along with some of the options enabled by ARCH_MULTI_V4T. More specifically it doesn't get along with CPU_ARM920T: CPU_ABRT_EV4T CPU_CACHE_V4WT CPU_COPY_V4WB CPU_TLB_V4WBI One or a combination of the above cause trouble for userspace, the following happens when kernel tries to exec init: [ 11.790000] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004 [ 11.790000] [ 11.790000] CPU: 0 PID: 1 Comm: init Not tainted 3.13.0-rc3-next-20131212+ #1332 [ 11.790000] [<c000d620>] (unwind_backtrace) from [<c000ba54>] (show_stack+0x18/0x1c) [ 11.790000] [<c000ba54>] (show_stack) from [<c027f498>] (dump_stack+0x20/0x28) [ 11.790000] [<c027f498>] (dump_stack) from [<c027ce80>] (panic+0x98/0x1ec) [ 11.790000] [<c027ce80>] (panic) from [<c0016d4c>] (do_exit+0x80c/0x8e8) [ 11.790000] [<c0016d4c>] (do_exit) from [<c0016ea4>] (do_group_exit+0x44/0xb8) [ 11.790000] [<c0016ea4>] (do_group_exit) from [<c0022dbc>] (get_signal_to_deliver+0x2fc/0x5a4) [ 11.790000] [<c0022dbc>] (get_signal_to_deliver) from [<c027ca38>] (do_signal+0xac/0x3e0) [ 11.790000] [<c027ca38>] (do_signal) from [<c000b460>] (do_work_pending+0xcc/0xe8) [ 11.790000] [<c000b460>] (do_work_pending) from [<c0009374>] (work_pending+0xc/0x20) Reinsert ARCH_MULTI_V4 so it can be used on platforms with CPU_FA526. Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com> --- Notes: I don't know how to handle this so I'm making it standalone for your feedback (it was broken out from MOXA ART SoC series). This is important for MOXA ART (and other FA526 platforms), please have a look. Applies to next-20131213 arch/arm/Kconfig | 5 +++++ 1 file changed, 5 insertions(+)