[PATCH v4 02/10] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user()

[Christophe Leroy]

Le 28/01/2021 à 11:38, David Laight a écrit :
> From: Christopher M. Riedl
>> Sent: 28 January 2021 04:04
>>
>> Reuse the "safe" implementation from signal.c except for calling
>> unsafe_copy_from_user() to copy into a local buffer.
>>
>> Signed-off-by: Christopher M. Riedl <cmr at codefail.de>
>> ---
>>   arch/powerpc/kernel/signal.h | 33 +++++++++++++++++++++++++++++++++
>>   1 file changed, 33 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
>> index 2559a681536e..c18402d625f1 100644
>> --- a/arch/powerpc/kernel/signal.h
>> +++ b/arch/powerpc/kernel/signal.h
>> @@ -53,6 +53,33 @@ unsigned long copy_ckfpr_from_user(struct task_struct *task, void __user *from);
>>   				&buf[i], label);\
>>   } while (0)
>>
>> +#define unsafe_copy_fpr_from_user(task, from, label)	do {		\
>> +	struct task_struct *__t = task;					\
>> +	u64 __user *__f = (u64 __user *)from;				\
>> +	u64 buf[ELF_NFPREG];						\
> 
> How big is that buffer?

#define ELF_NFPREG	33

So that's 264 bytes.

That's a bit big but still reasonable I think.

Christophe

> Isn't is likely to be reasonably large compared to a reasonable
> kernel stack frame.
> Especially since this isn't even a leaf function.
> 
>> +	int i;								\
>> +									\
>> +	unsafe_copy_from_user(buf, __f, ELF_NFPREG * sizeof(double),	\
> 
> That really ought to be sizeof(buf).
> 
> 	David
> 
> 
>> +				label);					\
>> +	for (i = 0; i < ELF_NFPREG - 1; i++)				\
>> +		__t->thread.TS_FPR(i) = buf[i];				\
>> +	__t->thread.fp_state.fpscr = buf[i];				\
>> +} while (0)
>> +
>> +#define unsafe_copy_vsx_from_user(task, from, label)	do {		\
>> +	struct task_struct *__t = task;					\
>> +	u64 __user *__f = (u64 __user *)from;				\
>> +	u64 buf[ELF_NVSRHALFREG];					\
>> +	int i;								\
>> +									\
>> +	unsafe_copy_from_user(buf, __f,					\
>> +				ELF_NVSRHALFREG * sizeof(double),	\
>> +				label);					\
>> +	for (i = 0; i < ELF_NVSRHALFREG ; i++)				\
>> +		__t->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = buf[i];	\
>> +} while (0)
>> +
>> +
>>   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>>   #define unsafe_copy_ckfpr_to_user(to, task, label)	do {		\
>>   	struct task_struct *__t = task;					\
>> @@ -80,6 +107,10 @@ unsigned long copy_ckfpr_from_user(struct task_struct *task, void __user *from);
>>   	unsafe_copy_to_user(to, (task)->thread.fp_state.fpr,	\
>>   			    ELF_NFPREG * sizeof(double), label)
>>
>> +#define unsafe_copy_fpr_from_user(task, from, label)			\
>> +	unsafe_copy_from_user((task)->thread.fp_state.fpr, from,	\
>> +			    ELF_NFPREG * sizeof(double), label)
>> +
>>   static inline unsigned long
>>   copy_fpr_to_user(void __user *to, struct task_struct *task)
>>   {
>> @@ -115,6 +146,8 @@ copy_ckfpr_from_user(struct task_struct *task, void __user *from)
>>   #else
>>   #define unsafe_copy_fpr_to_user(to, task, label) do { } while (0)
>>
>> +#define unsafe_copy_fpr_from_user(task, from, label) do { } while (0)
>> +
>>   static inline unsigned long
>>   copy_fpr_to_user(void __user *to, struct task_struct *task)
>>   {
>> --
>> 2.26.1
> 
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