arm64: mm: add code to safely replace TTBR1_EL1

[cascardo/linux.git] / arch / arm64 / mm / proc.S

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index c164d2c..0c19534 100644 (file)
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -140,6 +140,34 @@ ENTRY(cpu_do_switch_mm)
        ret
 ENDPROC(cpu_do_switch_mm)
 
+       .pushsection ".idmap.text", "ax"
+/*
+ * void idmap_cpu_replace_ttbr1(phys_addr_t new_pgd)
+ *
+ * This is the low-level counterpart to cpu_replace_ttbr1, and should not be
+ * called by anything else. It can only be executed from a TTBR0 mapping.
+ */
+ENTRY(idmap_cpu_replace_ttbr1)
+       mrs     x2, daif
+       msr     daifset, #0xf
+
+       adrp    x1, empty_zero_page
+       msr     ttbr1_el1, x1
+       isb
+
+       tlbi    vmalle1
+       dsb     nsh
+       isb
+
+       msr     ttbr1_el1, x0
+       isb
+
+       msr     daif, x2
+
+       ret
+ENDPROC(idmap_cpu_replace_ttbr1)
+       .popsection
+
 /*
  *     __cpu_setup
  *