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powerpc/kuap: Check KUAP activation in generic functions
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Today, every platform checks that KUAP is not de-activated
before doing the real job.

Move the verification out of platform specific functions.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/894f110397fcd248e125fb855d1e863e4e633a0d.1634627931.git.christophe.leroy@csgroup.eu
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@chleroy @mpe
chleroy authored and mpe committed Dec 9, 2021
1 parent ba454f9 commit c252f38
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Showing 4 changed files with 56 additions and 76 deletions.
34 changes: 5 additions & 29 deletions arch/powerpc/include/asm/book3s/32/kup.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,11 +13,6 @@

extern struct static_key_false disable_kuap_key;

static __always_inline bool kuap_is_disabled(void)
{
return !IS_ENABLED(CONFIG_PPC_KUAP) || static_branch_unlikely(&disable_kuap_key);
}

static __always_inline bool kuep_is_disabled(void)
{
return !IS_ENABLED(CONFIG_PPC_KUEP);
Expand All @@ -30,6 +25,11 @@ static __always_inline bool kuep_is_disabled(void)
#define KUAP_NONE (~0UL)
#define KUAP_ALL (~1UL)

static __always_inline bool kuap_is_disabled(void)
{
return static_branch_unlikely(&disable_kuap_key);
}

static inline void kuap_lock_one(unsigned long addr)
{
mtsr(mfsr(addr) | SR_KS, addr);
Expand Down Expand Up @@ -81,9 +81,6 @@ static inline void __kuap_save_and_lock(struct pt_regs *regs)
{
unsigned long kuap = current->thread.kuap;

if (kuap_is_disabled())
return;

regs->kuap = kuap;
if (unlikely(kuap == KUAP_NONE))
return;
Expand All @@ -98,9 +95,6 @@ static inline void kuap_user_restore(struct pt_regs *regs)

static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long kuap)
{
if (kuap_is_disabled())
return;

if (unlikely(kuap != KUAP_NONE)) {
current->thread.kuap = KUAP_NONE;
kuap_lock(kuap, false);
Expand All @@ -118,9 +112,6 @@ static inline unsigned long __kuap_get_and_assert_locked(void)
{
unsigned long kuap = current->thread.kuap;

if (kuap_is_disabled())
return KUAP_NONE;

WARN_ON_ONCE(IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && kuap != KUAP_NONE);

return kuap;
Expand All @@ -134,9 +125,6 @@ static inline void __kuap_assert_locked(void)
static __always_inline void __allow_user_access(void __user *to, const void __user *from,
u32 size, unsigned long dir)
{
if (kuap_is_disabled())
return;

BUILD_BUG_ON(!__builtin_constant_p(dir));

if (!(dir & KUAP_WRITE))
Expand All @@ -150,9 +138,6 @@ static __always_inline void __prevent_user_access(unsigned long dir)
{
u32 kuap = current->thread.kuap;

if (kuap_is_disabled())
return;

BUILD_BUG_ON(!__builtin_constant_p(dir));

if (!(dir & KUAP_WRITE))
Expand All @@ -166,9 +151,6 @@ static inline unsigned long __prevent_user_access_return(void)
{
unsigned long flags = current->thread.kuap;

if (kuap_is_disabled())
return KUAP_NONE;

if (flags != KUAP_NONE) {
current->thread.kuap = KUAP_NONE;
kuap_lock(flags, true);
Expand All @@ -179,9 +161,6 @@ static inline unsigned long __prevent_user_access_return(void)

static inline void __restore_user_access(unsigned long flags)
{
if (kuap_is_disabled())
return;

if (flags != KUAP_NONE) {
current->thread.kuap = flags;
kuap_unlock(flags, true);
Expand All @@ -193,9 +172,6 @@ __bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
unsigned long kuap = regs->kuap;

if (kuap_is_disabled())
return false;

if (!is_write || kuap == KUAP_ALL)
return false;
if (kuap == KUAP_NONE)
Expand Down
41 changes: 20 additions & 21 deletions arch/powerpc/include/asm/book3s/64/kup.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -229,6 +229,11 @@ static inline u64 current_thread_iamr(void)

#ifdef CONFIG_PPC_KUAP

static __always_inline bool kuap_is_disabled(void)
{
return !mmu_has_feature(MMU_FTR_BOOK3S_KUAP);
}

static inline void kuap_user_restore(struct pt_regs *regs)
{
bool restore_amr = false, restore_iamr = false;
Expand Down Expand Up @@ -270,36 +275,32 @@ static inline void kuap_user_restore(struct pt_regs *regs)

static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long amr)
{
if (mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) {
if (unlikely(regs->amr != amr)) {
isync();
mtspr(SPRN_AMR, regs->amr);
/*
* No isync required here because we are about to rfi
* back to previous context before any user accesses
* would be made, which is a CSI.
*/
}
}
if (likely(regs->amr == amr))
return;

isync();
mtspr(SPRN_AMR, regs->amr);
/*
* No isync required here because we are about to rfi
* back to previous context before any user accesses
* would be made, which is a CSI.
*
* No need to restore IAMR when returning to kernel space.
*/
}

static inline unsigned long __kuap_get_and_assert_locked(void)
{
if (mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) {
unsigned long amr = mfspr(SPRN_AMR);
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG)) /* kuap_check_amr() */
WARN_ON_ONCE(amr != AMR_KUAP_BLOCKED);
return amr;
}
return 0;
unsigned long amr = mfspr(SPRN_AMR);

if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG)) /* kuap_check_amr() */
WARN_ON_ONCE(amr != AMR_KUAP_BLOCKED);
return amr;
}

static inline void __kuap_assert_locked(void)
{
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && mmu_has_feature(MMU_FTR_BOOK3S_KUAP))
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
WARN_ON_ONCE(mfspr(SPRN_AMR) != AMR_KUAP_BLOCKED);
}

Expand Down Expand Up @@ -340,8 +341,6 @@ static inline void set_kuap(unsigned long value)

static inline bool __bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
if (!mmu_has_feature(MMU_FTR_BOOK3S_KUAP))
return false;
/*
* For radix this will be a storage protection fault (DSISR_PROTFAULT).
* For hash this will be a key fault (DSISR_KEYFAULT)
Expand Down
29 changes: 29 additions & 0 deletions arch/powerpc/include/asm/kup.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,8 @@ void setup_kuap(bool disabled);
#else
static inline void setup_kuap(bool disabled) { }

static __always_inline bool kuap_is_disabled(void) { return true; }

static inline bool
__bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
Expand Down Expand Up @@ -73,50 +75,77 @@ static inline void __restore_user_access(unsigned long flags) { }
static __always_inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
if (kuap_is_disabled())
return false;

return __bad_kuap_fault(regs, address, is_write);
}

static __always_inline void kuap_assert_locked(void)
{
if (kuap_is_disabled())
return;

__kuap_assert_locked();
}

#ifdef CONFIG_PPC32
static __always_inline void kuap_save_and_lock(struct pt_regs *regs)
{
if (kuap_is_disabled())
return;

__kuap_save_and_lock(regs);
}
#endif

static __always_inline void kuap_kernel_restore(struct pt_regs *regs, unsigned long amr)
{
if (kuap_is_disabled())
return;

__kuap_kernel_restore(regs, amr);
}

static __always_inline unsigned long kuap_get_and_assert_locked(void)
{
if (kuap_is_disabled())
return 0;

return __kuap_get_and_assert_locked();
}

#ifndef CONFIG_PPC_BOOK3S_64
static __always_inline void allow_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
{
if (kuap_is_disabled())
return;

__allow_user_access(to, from, size, dir);
}

static __always_inline void prevent_user_access(unsigned long dir)
{
if (kuap_is_disabled())
return;

__prevent_user_access(dir);
}

static __always_inline unsigned long prevent_user_access_return(void)
{
if (kuap_is_disabled())
return 0;

return __prevent_user_access_return();
}

static __always_inline void restore_user_access(unsigned long flags)
{
if (kuap_is_disabled())
return;

__restore_user_access(flags);
}
#endif /* CONFIG_PPC_BOOK3S_64 */
Expand Down
28 changes: 2 additions & 26 deletions arch/powerpc/include/asm/nohash/32/kup-8xx.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,9 +22,6 @@ static __always_inline bool kuap_is_disabled(void)

static inline void __kuap_save_and_lock(struct pt_regs *regs)
{
if (kuap_is_disabled())
return;

regs->kuap = mfspr(SPRN_MD_AP);
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
Expand All @@ -35,19 +32,13 @@ static inline void kuap_user_restore(struct pt_regs *regs)

static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long kuap)
{
if (kuap_is_disabled())
return;

mtspr(SPRN_MD_AP, regs->kuap);
}

static inline unsigned long __kuap_get_and_assert_locked(void)
{
unsigned long kuap;

if (kuap_is_disabled())
return MD_APG_INIT;

kuap = mfspr(SPRN_MD_AP);

if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
Expand All @@ -58,34 +49,25 @@ static inline unsigned long __kuap_get_and_assert_locked(void)

static inline void __kuap_assert_locked(void)
{
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && !kuap_is_disabled())
kuap_get_and_assert_locked();
if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
__kuap_get_and_assert_locked();
}

static inline void __allow_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
{
if (kuap_is_disabled())
return;

mtspr(SPRN_MD_AP, MD_APG_INIT);
}

static inline void __prevent_user_access(unsigned long dir)
{
if (kuap_is_disabled())
return;

mtspr(SPRN_MD_AP, MD_APG_KUAP);
}

static inline unsigned long __prevent_user_access_return(void)
{
unsigned long flags;

if (kuap_is_disabled())
return MD_APG_INIT;

flags = mfspr(SPRN_MD_AP);

mtspr(SPRN_MD_AP, MD_APG_KUAP);
Expand All @@ -95,18 +77,12 @@ static inline unsigned long __prevent_user_access_return(void)

static inline void __restore_user_access(unsigned long flags)
{
if (kuap_is_disabled())
return;

mtspr(SPRN_MD_AP, flags);
}

static inline bool
__bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
if (kuap_is_disabled())
return false;

return !((regs->kuap ^ MD_APG_KUAP) & 0xff000000);
}

Expand Down

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