Commit 8903826d authored by Will Deacon's avatar Will Deacon
Browse files

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: default avatarDave Martin <dave.martin@linaro.org>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Tested-by: default avatarLorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent ba8bb18a

arch/arm/include/asm/idmap.h

0 → 100644
+17 −0
Original line number Diff line number Diff line 
#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 */

arch/arm/include/asm/pgtable.h

+0 −3
Original line number Diff line number Diff line
@@ -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 */

arch/arm/kernel/smp.c

+1 −0
Original line number Diff line number Diff line
@@ -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>

arch/arm/kernel/vmlinux.lds.S

+7 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/mm/idmap.c

+26 −0
Original line number Diff line number Diff line 
#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

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