ARM: idmap: populate identity map pgd at init time using .init.text

When disabling and re-enabling the MMU, it is necessary to take out an
identity mapping for the code that manipulates the SCTLR in order to
avoid it disappearing from under our feet. This is useful when soft
rebooting and returning from CPU suspend.

This patch allocates a set of page tables during boot and populates them
with an identity mapping for the .idmap.text section. This means that
users of the identity map do not need to manage their own pgd and can
instead annotate their functions with __idmap or, in the case of assembly
code, place them in the correct section.

Acked-by: Dave Martin <dave.martin@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm/include/asm/idmap.h b/arch/arm/include/asm/idmap.h
new file mode 100644 (file)
index 0000000..62e3d19
--- /dev/null
+++ b/arch/arm/include/asm/idmap.h
@@ -0,0 +1,17 @@
+#ifndef __ASM_IDMAP_H
+#define __ASM_IDMAP_H
+
+#include <linux/compiler.h>
+#include <asm/pgtable.h>
+
+/* Tag a function as requiring to be executed via an identity mapping. */
+#define __idmap __section(.idmap.text) noinline notrace
+
+extern pgd_t *idmap_pgd;
+
+void identity_mapping_add(pgd_t *, unsigned long, unsigned long);
+void identity_mapping_del(pgd_t *, unsigned long, unsigned long);
+
+void setup_mm_for_reboot(void);
+
+#endif /* __ASM_IDMAP_H */

diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 9451dce3a5530f9c50c9a34d9ef84e2366a9bbab..03893a55e6804598fa74844f8c44d876b5a2abd3 100644 (file)
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -346,9 +346,6 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 
 #define pgtable_cache_init() do { } while (0)
 
-void identity_mapping_add(pgd_t *, unsigned long, unsigned long);
-void identity_mapping_del(pgd_t *, unsigned long, unsigned long);
-
 #endif /* !__ASSEMBLY__ */
 
 #endif /* CONFIG_MMU */

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index ef5640b9e218fae4cd3b32cdf1e6482c2ea0cdbf..8afadda374593d2dc112c41d21b59684193a20fb 100644 (file)
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -31,6 +31,7 @@
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/exception.h>
+#include <asm/idmap.h>
 #include <asm/topology.h>
 #include <asm/mmu_context.h>
 #include <asm/pgtable.h>

diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 20b3041e0860f7c743f4e453a38c9ce738a10e75..f76e75548670e97eeac9112a8e48b53e37f9cc91 100644 (file)
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -13,6 +13,12 @@
        *(.proc.info.init)                                              \
        VMLINUX_SYMBOL(__proc_info_end) = .;
 
+#define IDMAP_TEXT                                                     \
+       ALIGN_FUNCTION();                                               \
+       VMLINUX_SYMBOL(__idmap_text_start) = .;                         \
+       *(.idmap.text)                                                  \
+       VMLINUX_SYMBOL(__idmap_text_end) = .;
+
 #ifdef CONFIG_HOTPLUG_CPU
 #define ARM_CPU_DISCARD(x)
 #define ARM_CPU_KEEP(x)                x
@@ -92,6 +98,7 @@ SECTIONS
                        SCHED_TEXT
                        LOCK_TEXT
                        KPROBES_TEXT
+                       IDMAP_TEXT
 #ifdef CONFIG_MMU
                        *(.fixup)
 #endif

diff --git a/arch/arm/mm/idmap.c b/arch/arm/mm/idmap.c
index 296ad2eaddb0565f3a14f4ab94b957a0d87c17e5..cda5ea3157a7d393fb67eff8381bf3db2bc970ce 100644 (file)
--- a/arch/arm/mm/idmap.c
+++ b/arch/arm/mm/idmap.c
@@ -1,8 +1,12 @@
 #include <linux/kernel.h>
 
 #include <asm/cputype.h>
+#include <asm/idmap.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
+#include <asm/sections.h>
+
+pgd_t *idmap_pgd;
 
 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
        unsigned long prot)
@@ -73,6 +77,28 @@ void identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)
 }
 #endif
 
+extern char  __idmap_text_start[], __idmap_text_end[];
+
+static int __init init_static_idmap(void)
+{
+       phys_addr_t idmap_start, idmap_end;
+
+       idmap_pgd = pgd_alloc(&init_mm);
+       if (!idmap_pgd)
+               return -ENOMEM;
+
+       /* Add an identity mapping for the physical address of the section. */
+       idmap_start = virt_to_phys((void *)__idmap_text_start);
+       idmap_end = virt_to_phys((void *)__idmap_text_end);
+
+       pr_info("Setting up static identity map for 0x%llx - 0x%llx\n",
+               (long long)idmap_start, (long long)idmap_end);
+       identity_mapping_add(idmap_pgd, idmap_start, idmap_end);
+
+       return 0;
+}
+arch_initcall(init_static_idmap);
+
 /*
  * In order to soft-boot, we need to insert a 1:1 mapping in place of
  * the user-mode pages.  This will then ensure that we have predictable