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powerpc: store and restore the pkey state across context switches

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Store and restore the AMR, IAMR and UAMOR register state of the task
before scheduling out and after scheduling in, respectively.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ram Pai
2018-01-18 17:50:31 -08:00
committed by Michael Ellerman
parent dcf872956d
commit 06bb53b338
5 changed files with 70 additions and 1 deletions
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52
arch/powerpc/mm/pkeys.c
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@@ -12,6 +12,8 @@ DEFINE_STATIC_KEY_TRUE(pkey_disabled);
bool pkey_execute_disable_supported;
int pkeys_total; /* Total pkeys as per device tree */
u32 initial_allocation_mask; /* Bits set for reserved keys */
u64 pkey_amr_uamor_mask; /* Bits in AMR/UMOR not to be touched */
u64 pkey_iamr_mask; /* Bits in AMR not to be touched */
#define AMR_BITS_PER_PKEY 2
#define AMR_RD_BIT 0x1UL
@@ -70,8 +72,16 @@ int pkey_initialize(void)
* programming note.
*/
initial_allocation_mask = ~0x0;
for (i = 2; i < (pkeys_total - os_reserved); i++)
/* register mask is in BE format */
pkey_amr_uamor_mask = ~0x0ul;
pkey_iamr_mask = ~0x0ul;
for (i = 2; i < (pkeys_total - os_reserved); i++) {
initial_allocation_mask &= ~(0x1 << i);
pkey_amr_uamor_mask &= ~(0x3ul << pkeyshift(i));
pkey_iamr_mask &= ~(0x1ul << pkeyshift(i));
}
return 0;
}
@@ -206,3 +216,43 @@ int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
init_amr(pkey, new_amr_bits);
return 0;
}
void thread_pkey_regs_save(struct thread_struct *thread)
{
if (static_branch_likely(&pkey_disabled))
return;
/*
* TODO: Skip saving registers if @thread hasn't used any keys yet.
*/
thread->amr = read_amr();
thread->iamr = read_iamr();
thread->uamor = read_uamor();
}
void thread_pkey_regs_restore(struct thread_struct *new_thread,
struct thread_struct *old_thread)
{
if (static_branch_likely(&pkey_disabled))
return;
/*
* TODO: Just set UAMOR to zero if @new_thread hasn't used any keys yet.
*/
if (old_thread->amr != new_thread->amr)
write_amr(new_thread->amr);
if (old_thread->iamr != new_thread->iamr)
write_iamr(new_thread->iamr);
if (old_thread->uamor != new_thread->uamor)
write_uamor(new_thread->uamor);
}
void thread_pkey_regs_init(struct thread_struct *thread)
{
if (static_branch_likely(&pkey_disabled))
return;
write_amr(read_amr() & pkey_amr_uamor_mask);
write_iamr(read_iamr() & pkey_iamr_mask);
write_uamor(read_uamor() & pkey_amr_uamor_mask);
}