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arm64: uaccess: remove redundant PAN toggling

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Some code (e.g. futex) needs to make privileged accesses to userspace
memory, and uses uaccess_{enable,disable}_privileged() in order to
permit this. All other uaccess primitives use LDTR/STTR, and never need
to toggle PAN.

Remove the redundant PAN toggling.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-12-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2020-12-02 13:15:57 +00:00 committed by Catalin Marinas
parent b5a5a01d8e
commit 7cf283c7bd
3 changed files with 19 additions and 58 deletions
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1
arch/arm64/include/asm/cpucaps.h
View File

@ -17,7 +17,6 @@
#define ARM64_WORKAROUND_834220 7
#define ARM64_HAS_NO_HW_PREFETCH 8
#define ARM64_HAS_UAO 9
#define ARM64_ALT_PAN_NOT_UAO 10
#define ARM64_HAS_VIRT_HOST_EXTN 11
#define ARM64_WORKAROUND_CAVIUM_27456 12
#define ARM64_HAS_32BIT_EL0 13

59
arch/arm64/include/asm/uaccess.h
View File

@ -159,41 +159,20 @@ static inline void __uaccess_enable_hw_pan(void)
CONFIG_ARM64_PAN));
}
#define __uaccess_disable(alt) \
do { \
if (!uaccess_ttbr0_disable()) \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \
CONFIG_ARM64_PAN)); \
} while (0)
#define __uaccess_enable(alt) \
do { \
if (!uaccess_ttbr0_enable()) \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \
CONFIG_ARM64_PAN)); \
} while (0)
static inline void uaccess_disable_privileged(void)
{
__uaccess_disable(ARM64_HAS_PAN);
if (uaccess_ttbr0_disable())
return;
__uaccess_enable_hw_pan();
}
static inline void uaccess_enable_privileged(void)
{
__uaccess_enable(ARM64_HAS_PAN);
}
if (uaccess_ttbr0_enable())
return;
/*
* These functions are no-ops when UAO is present.
*/
static inline void uaccess_disable_not_uao(void)
{
__uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
}
static inline void uaccess_enable_not_uao(void)
{
__uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
__uaccess_disable_hw_pan();
}
/*
@ -265,9 +244,9 @@ do { \
#define __raw_get_user(x, ptr, err) \
do { \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
uaccess_ttbr0_enable(); \
__raw_get_mem("ldtr", x, ptr, err); \
uaccess_disable_not_uao(); \
uaccess_ttbr0_disable(); \
} while (0)
#define __get_user_error(x, ptr, err) \
@ -338,9 +317,9 @@ do { \
#define __raw_put_user(x, ptr, err) \
do { \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
uaccess_ttbr0_enable(); \
__raw_put_mem("sttr", x, ptr, err); \
uaccess_disable_not_uao(); \
uaccess_ttbr0_disable(); \
} while (0)
#define __put_user_error(x, ptr, err) \
@ -378,10 +357,10 @@ extern unsigned long __must_check __arch_copy_from_user(void *to, const void __u
#define raw_copy_from_user(to, from, n) \
({ \
unsigned long __acfu_ret; \
uaccess_enable_not_uao(); \
uaccess_ttbr0_enable(); \
__acfu_ret = __arch_copy_from_user((to), \
__uaccess_mask_ptr(from), (n)); \
uaccess_disable_not_uao(); \
uaccess_ttbr0_disable(); \
__acfu_ret; \
})
@ -389,10 +368,10 @@ extern unsigned long __must_check __arch_copy_to_user(void __user *to, const voi
#define raw_copy_to_user(to, from, n) \
({ \
unsigned long __actu_ret; \
uaccess_enable_not_uao(); \
uaccess_ttbr0_enable(); \
__actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \
(from), (n)); \
uaccess_disable_not_uao(); \
uaccess_ttbr0_disable(); \
__actu_ret; \
})
@ -400,10 +379,10 @@ extern unsigned long __must_check __arch_copy_in_user(void __user *to, const voi
#define raw_copy_in_user(to, from, n) \
({ \
unsigned long __aciu_ret; \
uaccess_enable_not_uao(); \
uaccess_ttbr0_enable(); \
__aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to), \
__uaccess_mask_ptr(from), (n)); \
uaccess_disable_not_uao(); \
uaccess_ttbr0_disable(); \
__aciu_ret; \
})
@ -414,9 +393,9 @@ extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned lo
static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
{
if (access_ok(to, n)) {
uaccess_enable_not_uao();
uaccess_ttbr0_enable();
n = __arch_clear_user(__uaccess_mask_ptr(to), n);
uaccess_disable_not_uao();
uaccess_ttbr0_disable();
}
return n;
}

17
arch/arm64/kernel/cpufeature.c
View File

@ -153,10 +153,6 @@ EXPORT_SYMBOL(cpu_hwcap_keys);
.width = 0, \
}
/* meta feature for alternatives */
static bool __maybe_unused
cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused);
static void cpu_enable_cnp(struct arm64_cpu_capabilities const *cap);
static bool __system_matches_cap(unsigned int n);
@ -1779,13 +1775,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 1,
},
#endif /* CONFIG_ARM64_UAO */
#ifdef CONFIG_ARM64_PAN
{
.capability = ARM64_ALT_PAN_NOT_UAO,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
.matches = cpufeature_pan_not_uao,
},
#endif /* CONFIG_ARM64_PAN */
#ifdef CONFIG_ARM64_VHE
{
.desc = "Virtualization Host Extensions",
@ -2736,12 +2725,6 @@ void __init setup_cpu_features(void)
ARCH_DMA_MINALIGN);
}
static bool __maybe_unused
cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
{
return (__system_matches_cap(ARM64_HAS_PAN) && !__system_matches_cap(ARM64_HAS_UAO));
}
static void __maybe_unused cpu_enable_cnp(struct arm64_cpu_capabilities const *cap)
{
cpu_replace_ttbr1(lm_alias(swapper_pg_dir));