Hi Russell,
Russell King - ARM Linux <li...@arm.linux.org.uk> writes:
> On Wed, Mar 20, 2013 at 05:01:58PM -0700, Kevin Hilman wrote:
>> Add ARM support for the context tracking subsystem by instrumenting
>> exception entry/exit points.
>>
>> Special thanks to Mats Liljegren for testing, collaboration and adding
>> support for exceptions/faults that were missing in early test versions.
[...]
>> @@ -405,7 +406,9 @@ asmlinkage void __exception do_undefinstr(struct pt_regs
>> *regs)
>> unsigned int instr;
>> siginfo_t info;
>> void __user *pc;
>> + enum ctx_state prev_state;
>>
>> + prev_state = exception_enter();
>> pc = (void __user *)instruction_pointer(regs);
>>
>> if (processor_mode(regs) == SVC_MODE) {
>> @@ -433,8 +436,10 @@ asmlinkage void __exception do_undefinstr(struct
>> pt_regs *regs)
>> goto die_sig;
>> }
>>
>> - if (call_undef_hook(regs, instr) == 0)
>> + if (call_undef_hook(regs, instr) == 0) {
>> + exception_exit(prev_state);
>> return;
>> + }
>>
>> die_sig:
>> #ifdef CONFIG_DEBUG_USER
>> @@ -451,12 +456,17 @@ die_sig:
>> info.si_addr = pc;
>>
>> arm_notify_die("Oops - undefined instruction", regs, &info, 0, 6);
>> + exception_exit(prev_state);
>
> So, FP emulation and VFP support happens via a separate path. Does this
> also need to be instrumented?
Looking a little closer at how FP/VFP support are handled along with the
rest of the exceptions, I wondered if it might be simpler to do
something like the patch below. It instruments the assembly directly
using the existing usr_entry macro, and the ret_to_user path.
Doing that would replace instrumenting the various handlers
(do_DataAbort/do_PrefetchAbort), and would handle the FP emulation VFP
support as well.
If this looks OK, I can probably rework the syscall support as well.
This approach covers the slow syscall return path already. Instead of
forcing the slowpath on all syscalls, I would just need to instrument
the syscall entry and fast syscall return.
Kevin
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 0f82098..050472c 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -396,6 +396,9 @@ ENDPROC(__pabt_svc)
#ifdef CONFIG_IRQSOFF_TRACER
bl trace_hardirqs_off
#endif
+#ifdef CONFIG_CONTEXT_TRACKING
+ bl user_exit
+#endif
.endm
.macro kuser_cmpxchg_check
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 3248cde..3bef99b 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -74,6 +74,9 @@ no_work_pending:
#if defined(CONFIG_IRQSOFF_TRACER)
asm_trace_hardirqs_on
#endif
+#if defined(CONFIG_CONTEXT_TRACKING)
+ bl user_enter
+#endif
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr
--
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