Re: [PATCH v5 10/26] powerpc/book3s64/pkeys: Convert pkey_total to max_pkey
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-07-06 07:04:15
"Aneesh Kumar K.V" [off-list ref] writes:
quoted hunk ↗ jump to hunk
max_pkey now represents max key value that userspace can allocate. Signed-off-by: Aneesh Kumar K.V <redacted> --- arch/powerpc/include/asm/pkeys.h | 7 +++++-- arch/powerpc/mm/book3s64/pkeys.c | 14 +++++++------- 2 files changed, 12 insertions(+), 9 deletions(-)diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h index 75d2a2c19c04..652bad7334f3 100644 --- a/arch/powerpc/include/asm/pkeys.h +++ b/arch/powerpc/include/asm/pkeys.h@@ -12,7 +12,7 @@ #include <asm/firmware.h> DECLARE_STATIC_KEY_FALSE(pkey_disabled); -extern int pkeys_total; /* total pkeys as per device tree */ +extern int max_pkey; extern u32 initial_allocation_mask; /* bits set for the initially allocated keys */ extern u32 reserved_allocation_mask; /* bits set for reserved keys */@@ -44,7 +44,10 @@ static inline int vma_pkey(struct vm_area_struct *vma) return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT; } -#define arch_max_pkey() pkeys_total +static inline int arch_max_pkey(void) +{ + return max_pkey; +}
If pkeys_total = 32 then max_pkey = 31. So we can't just substitute one for the other. ie. arch_max_pkey() must have been wrong, or it is wrong now.
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c index 87d882a9aaf2..a4d7287082a8 100644 --- a/arch/powerpc/mm/book3s64/pkeys.c +++ b/arch/powerpc/mm/book3s64/pkeys.c@@ -14,7 +14,7 @@ DEFINE_STATIC_KEY_FALSE(pkey_disabled); DEFINE_STATIC_KEY_FALSE(execute_pkey_disabled); -int pkeys_total; /* Total pkeys as per device tree */ +int max_pkey; /* Maximum key value supported */ u32 initial_allocation_mask; /* Bits set for the initially allocated keys */ /* * Keys marked in the reservation list cannot be allocated by userspace@@ -84,7 +84,7 @@ static int scan_pkey_feature(void) static int pkey_initialize(void) { - int os_reserved, i; + int pkeys_total, i; /* * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral@@ -122,12 +122,12 @@ static int pkey_initialize(void) * The OS can manage only 8 pkeys due to its inability to represent them * in the Linux 4K PTE. Mark all other keys reserved. */ - os_reserved = pkeys_total - 8; + max_pkey = min(8, pkeys_total);
Shouldn't it be 7 ?
#else
- os_reserved = 0;
+ max_pkey = pkeys_total;
#endif
- if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) {
+ if (unlikely(max_pkey <= execute_only_key)) {Isn't that an off-by-one now? This is one-off boot time code, there's no need to clutter it with unlikely.
quoted hunk ↗ jump to hunk
/* * Insufficient number of keys to support * execute only key. Mark it unavailable.@@ -174,10 +174,10 @@ static int pkey_initialize(void) default_uamor &= ~(0x3ul << pkeyshift(1)); /* - * Prevent the usage of OS reserved the keys. Update UAMOR + * Prevent the usage of OS reserved keys. Update UAMOR * for those keys. */ - for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) { + for (i = max_pkey; i < pkeys_total; i++) {
Another off-by-one? Shouldn't we start from max_pkey + 1 ?
reserved_allocation_mask |= (0x1 << i); default_uamor &= ~(0x3ul << pkeyshift(i)); }
cheers