Re: [ipipe 4.14][PATCH] x86: ipipe: Fix trap hooking for userspace routes

[Jan Kiszka <jan.kiszka@siemens.com>]

On 26.10.18 13:50, Henning Schild wrote:
> Hey,
> 
> looks like this one is for the #PF from the sigdebug smokey test. With
> this patch applied i do not see the crash anymore, but the test gets
> stuck.
> Did it work for you, or did i get the context wrong?

Yes, this solved the issue for me, and I was able to finish the test. But that 
might be related to configuration variations (I think I sent my configuration 
earlier to the list).

Jan

> 
> Henning
> 
> Am Wed, 10 Oct 2018 13:05:28 +0200
> schrieb Jan Kiszka <jan.kiszka@siemens.com>:
> 
>> Also hook into the trap path when the exception was taken over
>> userspace code.
>>
>> Fixes: e6b81a0ce7fb (x86: ipipe: route traps to co-kernel)
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>
>> Makes sense? I'm not feeling 100% safe yet /wrt paranoid and the
>> userspace path. Should we handle this identically to the kernel path
>> or not?
>>
>> Eventually this should be merged into the original patch, at least on
>> next major rebase.
>>
>>   arch/x86/entry/entry_64.S | 80
>> +++++++++++++++++++++++++++-------------------- 1 file changed, 46
>> insertions(+), 34 deletions(-)
>>
>> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
>> index f6fe849d66ed..42e31d1fddc6 100644
>> --- a/arch/x86/entry/entry_64.S
>> +++ b/arch/x86/entry/entry_64.S
>> @@ -904,6 +904,46 @@ ENTRY(switch_to_thread_stack)
>>   	ret
>>   END(switch_to_thread_stack)
>>   
>> +.macro ipipe_idtentry_prologue paranoid=0 trapnr=-1
>> skip_label=-invalid- +#ifdef CONFIG_IPIPE
>> +	movq	EFLAGS(%rsp), %r14		/* regs->flags
>> */
>> +	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>> +	movl	$\trapnr, %esi			/* trap
>> number */
>> +	subq	$8, %rsp
>> +	movq	%rsp, %rdx			/* &flags */
>> +	call	__ipipe_trap_prologue
>> +	popq	%r13
>> +	mov	%rax, %r12			/* save
>> propagation status */
>> +	.if \paranoid == 0			/* paranoid may
>> not skip handler */
>> +	testl	%eax, %eax
>> +	jg	\skip_label			/* skip regular
>> handler if > 0 */
>> +	.endif
>> +#endif
>> +.endm
>> +
>> +.macro ipipe_idtentry_epilogue paranoid=0 skip_label=-invalid-
>> +#ifdef CONFIG_IPIPE
>> +	testl	%r12d, %r12d
>> +	jnz	1000f
>> +	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>> +	movq	%r13, %rsi			/* &flags from
>> prologue */
>> +	movq	%r14, %rdx			/* original
>> regs->flags before fixup */
>> +	call	__ipipe_trap_epilogue
>> +1000:
>> +	.if \paranoid == 0			/* paranoid
>> implies normal epilogue */
>> +	testl	%r12d, %r12d
>> +	jz	1001f
>> +\skip_label:
>> +	UNWIND_HINT_REGS
>> +	DISABLE_INTERRUPTS(CLBR_ANY)
>> +	testl	%ebx, %ebx	/* %ebx: return to kernel
>> mode */
>> +	jnz	retint_kernel_early
>> +	jmp	retint_user_early
>> +	.endif
>> +1001:
>> +#endif
>> +.endm
>> +
>>   .macro idtentry sym do_sym has_error_code:req paranoid=0
>> shift_ist=-1 trapnr=-1 ENTRY(\sym)
>>   	UNWIND_HINT_IRET_REGS offset=\has_error_code*8
>> @@ -940,20 +980,7 @@ ENTRY(\sym)
>>   	.endif
>>   	.endif
>>   
>> -#ifdef CONFIG_IPIPE
>> -	movq	EFLAGS(%rsp), %r14		/* regs->flags
>> */
>> -	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>> -	movl	$\trapnr, %esi			/* trap
>> number */
>> -	subq	$8, %rsp
>> -	movq	%rsp, %rdx			/* &flags */
>> -	call	__ipipe_trap_prologue
>> -	popq	%r13
>> -	mov	%rax, %r12			/* save
>> propagation status */
>> -	.if \paranoid == 0			/* paranoid may
>> not skip handler */
>> -	testl	%eax, %eax
>> -	jg	98f				/* skip regular
>> handler if > 0 */
>> -	.endif
>> -#endif
>> +	ipipe_idtentry_prologue paranoid=\paranoid trapnr=\trapnr
>> skip_label=kernel_skip_\@
>>   	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>> @@ -970,26 +997,7 @@ ENTRY(\sym)
>>   
>>   	call	\do_sym
>>   
>> -#ifdef CONFIG_IPIPE
>> -	testl	%r12d, %r12d
>> -	jnz	97f
>> -	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>> -	movq	%r13, %rsi			/* &flags from
>> prologue */
>> -	movq	%r14, %rdx			/* original
>> regs->flags before fixup */
>> -	call	__ipipe_trap_epilogue
>> -97:
>> -	.if \paranoid == 0			/* paranoid
>> implies normal epilogue */
>> -	testl	%r12d, %r12d
>> -	jz	99f
>> -98:
>> -	UNWIND_HINT_REGS
>> -	DISABLE_INTERRUPTS(CLBR_ANY)
>> -	testl	%ebx, %ebx	/* %ebx: return to kernel
>> mode */
>> -	jnz	retint_kernel_early
>> -	jmp	retint_user_early
>> -	.endif
>> -99:
>> -#endif
>> +	ipipe_idtentry_epilogue paranoid=\paranoid
>> skip_label=kernel_skip_\@
>>   	.if \shift_ist != -1
>>   	addq	$EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
>> @@ -1011,6 +1019,8 @@ ENTRY(\sym)
>>   .Lfrom_usermode_switch_stack_\@:
>>   	call	error_entry
>>   
>> +	ipipe_idtentry_prologue paranoid=\paranoid trapnr=\trapnr
>> skip_label=user_skip_\@ +
>>   	movq	%rsp, %rdi			/* pt_regs
>> pointer */
>>   	.if \has_error_code
>> @@ -1022,6 +1032,8 @@ ENTRY(\sym)
>>   
>>   	call	\do_sym
>>   
>> +	ipipe_idtentry_epilogue paranoid=\paranoid
>> skip_label=user_skip_\@ +
>>   	jmp	error_exit
>>   	.endif
>>   END(\sym)
> 

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