arm64: kernel: Add support for User Access Override

[cascardo/linux.git] / arch / arm64 / kernel / process.c

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 88d742b..c1ca4ea 100644 (file)
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -46,6 +46,7 @@
 #include <linux/notifier.h>
 #include <trace/events/power.h>
 
+#include <asm/alternative.h>
 #include <asm/compat.h>
 #include <asm/cacheflush.h>
 #include <asm/fpsimd.h>
@@ -280,6 +281,9 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
        } else {
                memset(childregs, 0, sizeof(struct pt_regs));
                childregs->pstate = PSR_MODE_EL1h;
+               if (IS_ENABLED(CONFIG_ARM64_UAO) &&
+                   cpus_have_cap(ARM64_HAS_UAO))
+                       childregs->pstate |= PSR_UAO_BIT;
                p->thread.cpu_context.x19 = stack_start;
                p->thread.cpu_context.x20 = stk_sz;
        }
@@ -308,6 +312,20 @@ static void tls_thread_switch(struct task_struct *next)
        : : "r" (tpidr), "r" (tpidrro));
 }
 
+/* Restore the UAO state depending on next's addr_limit */
+static void uao_thread_switch(struct task_struct *next)
+{
+       unsigned long next_sp = next->thread.cpu_context.sp;
+
+       if (IS_ENABLED(CONFIG_ARM64_UAO) &&
+           get_thread_info(next_sp)->addr_limit == KERNEL_DS)
+               asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO,
+                               CONFIG_ARM64_UAO));
+       else
+               asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
+                               CONFIG_ARM64_UAO));
+}
+
 /*
  * Thread switching.
  */
@@ -320,6 +338,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
        tls_thread_switch(next);
        hw_breakpoint_thread_switch(next);
        contextidr_thread_switch(next);
+       uao_thread_switch(next);
 
        /*
         * Complete any pending TLB or cache maintenance on this CPU in case