Commit 3d7dfd63 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: Implement user_access_save() and user_access_restore() 



Implement user_access_save() and user_access_restore()

On 8xx and radix:
  - On save, get the value of the associated special register then
    prevent user access.
  - On restore, set back the saved value to the associated special
    register.

On book3s/32:
  - On save, get the value stored in current->thread.kuap and prevent
    user access.
  - On restore, regenerate address range from the stored value and
    reopen read/write access for that range.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/54f2f74938006b33c55a416674807b42ef222068.1579866752.git.christophe.leroy@c-s.fr
parent 5cd62333

arch/powerpc/include/asm/book3s/32/kup.h

+23 −0
Original line number Diff line number Diff line
@@ -153,6 +153,29 @@ static __always_inline void prevent_user_access(void __user *to, const void __us 
	kuap_update_sr(mfsrin(addr) | SR_KS, addr, end);	/* set Ks */

}



static inline unsigned long prevent_user_access_return(void)

{

	unsigned long flags = current->thread.kuap;

	unsigned long addr = flags & 0xf0000000;

	unsigned long end = flags << 28;

	void __user *to = (__force void __user *)addr;



	if (flags)

		prevent_user_access(to, to, end - addr, KUAP_READ_WRITE);



	return flags;

}



static inline void restore_user_access(unsigned long flags)

{

	unsigned long addr = flags & 0xf0000000;

	unsigned long end = flags << 28;

	void __user *to = (__force void __user *)addr;



	if (flags)

		allow_user_access(to, to, end - addr, KUAP_READ_WRITE);

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

{

arch/powerpc/include/asm/book3s/64/kup-radix.h

+22 −0
Original line number Diff line number Diff line
@@ -63,6 +63,14 @@ 
 * because that would require an expensive read/modify write of the AMR.

 */



static inline unsigned long get_kuap(void)

{

	if (!early_mmu_has_feature(MMU_FTR_RADIX_KUAP))

		return 0;



	return mfspr(SPRN_AMR);

}



static inline void set_kuap(unsigned long value)

{

	if (!early_mmu_has_feature(MMU_FTR_RADIX_KUAP))
@@ -98,6 +106,20 @@ static inline void prevent_user_access(void __user *to, const void __user *from, 
	set_kuap(AMR_KUAP_BLOCKED);

}



static inline unsigned long prevent_user_access_return(void)

{

	unsigned long flags = get_kuap();



	set_kuap(AMR_KUAP_BLOCKED);



	return flags;

}



static inline void restore_user_access(unsigned long flags)

{

	set_kuap(flags);

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

{

arch/powerpc/include/asm/kup.h

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,8 @@ static inline void allow_user_access(void __user *to, const void __user *from, 
				     unsigned long size, unsigned long dir) { }

static inline void prevent_user_access(void __user *to, const void __user *from,

				       unsigned long size, unsigned long dir) { }

static inline unsigned long prevent_user_access_return(void) { return 0UL; }

static inline void restore_user_access(unsigned long flags) { }

static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

{

arch/powerpc/include/asm/nohash/32/kup-8xx.h

+14 −0
Original line number Diff line number Diff line
@@ -46,6 +46,20 @@ static inline void prevent_user_access(void __user *to, const void __user *from, 
	mtspr(SPRN_MD_AP, MD_APG_KUAP);

}



static inline unsigned long prevent_user_access_return(void)

{

	unsigned long flags = mfspr(SPRN_MD_AP);



	mtspr(SPRN_MD_AP, MD_APG_KUAP);



	return flags;

}



static inline void restore_user_access(unsigned long flags)

{

	mtspr(SPRN_MD_AP, flags);

}



static inline bool

bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)

{

arch/powerpc/include/asm/uaccess.h

+2 −3
Original line number Diff line number Diff line
@@ -465,9 +465,8 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t 
}

#define user_access_begin	user_access_begin

#define user_access_end		prevent_current_access_user



static inline unsigned long user_access_save(void) { return 0UL; }

static inline void user_access_restore(unsigned long flags) { }

#define user_access_save	prevent_user_access_return

#define user_access_restore	restore_user_access



#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)

#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)

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