arm64/gcs: Provide put_user_gcs()

In order for EL1 to write to an EL0 GCS it must use the GCSSTTR instruction
rather than a normal STTR. Provide a put_user_gcs() which does this.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-10-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 0db494b24dd0efc62da22d3e9ee37a74bb97f318..5b91803201ef885a7ab8ebf329c29496d1c56d8e 100644 (file)
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -522,6 +522,24 @@ static inline int gcssttr(unsigned long __user *addr, unsigned long val)
        return err;
 }
 
+static inline void put_user_gcs(unsigned long val, unsigned long __user *addr,
+                               int *err)
+{
+       int ret;
+
+       if (!access_ok((char __user *)addr, sizeof(u64))) {
+               *err = -EFAULT;
+               return;
+       }
+
+       uaccess_ttbr0_enable();
+       ret = gcssttr(addr, val);
+       if (ret != 0)
+               *err = ret;
+       uaccess_ttbr0_disable();
+}
+
+
 #endif /* CONFIG_ARM64_GCS */
 
 #endif /* __ASM_UACCESS_H */