[1/4] powerpc: Track KUAP state in the PACA

Necessary for subsequent patches that enable KUAP support for radix.
Could plausibly be useful for other platforms too, if similar to the
radix case, reading the register that manages these accesses is
costly.

Has the unfortunate downside of another layer of abstraction for
platforms that implement the locks and unlocks, but this could be
useful in future for other things too, like counters for benchmarking
or smartly handling lots of small accesses at once.

Signed-off-by: Russell Currey <ruscur@russell.cc>
---
this is all because I can't do PACA things from radix.h and I spent
an hour figuring this out at midnight
---
 arch/powerpc/include/asm/nohash/32/pte-8xx.h |  8 +++----
 arch/powerpc/include/asm/paca.h              |  3 +++
 arch/powerpc/include/asm/uaccess.h           | 23 +++++++++++++++++++-
 arch/powerpc/kernel/asm-offsets.c            |  1 +
 4 files changed, 30 insertions(+), 5 deletions(-)

On 11/22/2018 02:04 PM, Russell Currey wrote:
> Necessary for subsequent patches that enable KUAP support for radix.
> Could plausibly be useful for other platforms too, if similar to the
> radix case, reading the register that manages these accesses is
> costly.
> 
> Has the unfortunate downside of another layer of abstraction for
> platforms that implement the locks and unlocks, but this could be
> useful in future for other things too, like counters for benchmarking
> or smartly handling lots of small accesses at once.
> 
> Signed-off-by: Russell Currey <ruscur@russell.cc>

Build failure.

[root@po14163vm linux-powerpc]# make mpc885_ads_defconfig
#
# configuration written to .config
#
[root@po14163vm linux-powerpc]# make
scripts/kconfig/conf  --syncconfig Kconfig
   UPD     include/config/kernel.release
   UPD     include/generated/utsrelease.h
   CC      kernel/bounds.s
   CC      arch/powerpc/kernel/asm-offsets.s
In file included from ./include/linux/uaccess.h:14:0,
                  from ./include/linux/compat.h:19,
                  from arch/powerpc/kernel/asm-offsets.c:16:
./arch/powerpc/include/asm/uaccess.h: In function ‘unlock_user_rd_access’:
./arch/powerpc/include/asm/uaccess.h:70:2: error: implicit declaration 
of function ‘get_paca’ [-Werror=implicit-function-declaration]
   get_paca()->user_access_allowed = 1;
   ^
./arch/powerpc/include/asm/uaccess.h:70:12: error: invalid type argument 
of ‘->’ (have ‘int’)
   get_paca()->user_access_allowed = 1;
             ^
./arch/powerpc/include/asm/uaccess.h: In function ‘lock_user_rd_access’:
./arch/powerpc/include/asm/uaccess.h:75:12: error: invalid type argument 
of ‘->’ (have ‘int’)
   get_paca()->user_access_allowed = 0;
             ^
./arch/powerpc/include/asm/uaccess.h: In function ‘unlock_user_wr_access’:
./arch/powerpc/include/asm/uaccess.h:80:12: error: invalid type argument 
of ‘->’ (have ‘int’)
   get_paca()->user_access_allowed = 1;
             ^
./arch/powerpc/include/asm/uaccess.h: In function ‘lock_user_wr_access’:
./arch/powerpc/include/asm/uaccess.h:85:12: error: invalid type argument 
of ‘->’ (have ‘int’)
   get_paca()->user_access_allowed = 0;
             ^
cc1: some warnings being treated as errors
make[1]: *** [arch/powerpc/kernel/asm-offsets.s] Error 1
make: *** [prepare0] Error 2

Christophe

> ---
> this is all because I can't do PACA things from radix.h and I spent
> an hour figuring this out at midnight
> ---
>   arch/powerpc/include/asm/nohash/32/pte-8xx.h |  8 +++----
>   arch/powerpc/include/asm/paca.h              |  3 +++
>   arch/powerpc/include/asm/uaccess.h           | 23 +++++++++++++++++++-
>   arch/powerpc/kernel/asm-offsets.c            |  1 +
>   4 files changed, 30 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> index f1ec7cf949d5..7bc0955a56e9 100644
> --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
> @@ -137,22 +137,22 @@ static inline pte_t pte_mkhuge(pte_t pte)
>   #define pte_mkhuge pte_mkhuge
>   
>   #ifdef CONFIG_PPC_KUAP
> -static inline void lock_user_wr_access(void)
> +static inline void __lock_user_wr_access(void)
>   {
>   	mtspr(SPRN_MD_AP, MD_APG_KUAP);
>   }
>   
> -static inline void unlock_user_wr_access(void)
> +static inline void __unlock_user_wr_access(void)
>   {
>   	mtspr(SPRN_MD_AP, MD_APG_INIT);
>   }
>   
> -static inline void lock_user_rd_access(void)
> +static inline void __lock_user_rd_access(void)
>   {
>   	mtspr(SPRN_MD_AP, MD_APG_KUAP);
>   }
>   
> -static inline void unlock_user_rd_access(void)
> +static inline void __unlock_user_rd_access(void)
>   {
>   	mtspr(SPRN_MD_AP, MD_APG_INIT);
>   }
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index e843bc5d1a0f..56236f6d8c89 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -169,6 +169,9 @@ struct paca_struct {
>   	u64 saved_r1;			/* r1 save for RTAS calls or PM or EE=0 */
>   	u64 saved_msr;			/* MSR saved here by enter_rtas */
>   	u16 trap_save;			/* Used when bad stack is encountered */
> +#ifdef CONFIG_PPC_KUAP
> +	u8 user_access_allowed;		/* can the kernel access user memory? */
> +#endif
>   	u8 irq_soft_mask;		/* mask for irq soft masking */
>   	u8 irq_happened;		/* irq happened while soft-disabled */
>   	u8 io_sync;			/* writel() needs spin_unlock sync */
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 2f3625cbfcee..76dae1095f7e 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -63,7 +63,28 @@ static inline int __access_ok(unsigned long addr, unsigned long size,
>   
>   #endif
>   
> -#ifndef CONFIG_PPC_KUAP
> +#ifdef CONFIG_PPC_KUAP
> +static inline void unlock_user_rd_access(void)
> +{
> +	__unlock_user_rd_access();
> +	get_paca()->user_access_allowed = 1;
> +}
> +static inline void lock_user_rd_access(void)
> +{
> +	__lock_user_rd_access();
> +	get_paca()->user_access_allowed = 0;
> +}
> +static inline void unlock_user_wr_access(void)
> +{
> +	__unlock_user_wr_access();
> +	get_paca()->user_access_allowed = 1;
> +}
> +static inline void lock_user_wr_access(void)
> +{
> +	__lock_user_wr_access();
> +	get_paca()->user_access_allowed = 0;
> +}
> +#else
>   static inline void unlock_user_rd_access(void) { }
>   static inline void lock_user_rd_access(void) { }
>   static inline void unlock_user_wr_access(void) { }
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index da2f5d011ddb..899e9835b45f 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -260,6 +260,7 @@ int main(void)
>   	OFFSET(ACCOUNT_STARTTIME_USER, paca_struct, accounting.starttime_user);
>   	OFFSET(ACCOUNT_USER_TIME, paca_struct, accounting.utime);
>   	OFFSET(ACCOUNT_SYSTEM_TIME, paca_struct, accounting.stime);
> +	OFFSET(PACA_USER_ACCESS_ALLOWED, paca_struct, user_access_allowed);
>   	OFFSET(PACA_TRAP_SAVE, paca_struct, trap_save);
>   	OFFSET(PACA_NAPSTATELOST, paca_struct, nap_state_lost);
>   	OFFSET(PACA_SPRG_VDSO, paca_struct, sprg_vdso);
>