Hi Russell,
Russell King - ARM Linux linux@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);- }
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