In order for EL1 to write to an EL0 GCS it must use the GCSSTTR instruction rather than a normal STTR. Provide a copy_to_user_gcs() which does this. Since it is not possible to store anything other than a 64 bit value the interface is presented in terms of 64 bit values, using unsigned long rather than u64 due to sparse.
Signed-off-by: Mark Brown broonie@kernel.org --- arch/arm64/include/asm/uaccess.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 22e10e79f56a..24aa804e95a7 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -445,6 +445,26 @@ static inline int gcssttr(unsigned long __user *addr, unsigned long val) return err; }
+static inline int copy_to_user_gcs(unsigned long __user *addr, + unsigned long *val, + int count) +{ + int ret = -EFAULT; + int i; + + if (access_ok((char __user *)addr, count * sizeof(u64))) { + uaccess_ttbr0_enable(); + for (i = 0; i < count; i++) { + ret = gcssttr(addr++, *val++); + if (ret != 0) + break; + } + uaccess_ttbr0_disable(); + } + + return ret; +} + #endif /* CONFIG_ARM64_GCS */
#endif /* __ASM_UACCESS_H */