[PATCH v4 07/36] arm64/gcs: Provide copy_to_user_gcs()

Mark Brown
2023-08-07T22:02:25Z

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 */

--
2.30.2