Commit 8d0e051c authored by Helge Deller's avatar Helge Deller
Browse files

parisc: Enable the ro_after_init feature 



This patch modifies the initial page mapping functions in the following way:

During bootup the init, text and data pages will be mapped RWX and if
supported, with huge pages.

At final stage of the bootup, the kernel calls free_initmem() and then all
pages will be remapped either R-X (for text and read-only data) or RW- (for
data). The __init pages will be dropped.

This reflects the behaviour of the x86 platform.

Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent e6eb5fe9

arch/parisc/include/asm/cache.h

+0 −3
Original line number Diff line number Diff line
@@ -24,9 +24,6 @@ 


#define __read_mostly __attribute__((__section__(".data..read_mostly")))



/* Read-only memory is marked before mark_rodata_ro() is called. */

#define __ro_after_init	__read_mostly



void parisc_cache_init(void);	/* initializes cache-flushing */

void disable_sr_hashing_asm(int); /* low level support for above */

void disable_sr_hashing(void);   /* turns off space register hashing */

arch/parisc/kernel/vmlinux.lds.S

+0 −3
Original line number Diff line number Diff line
@@ -18,9 +18,6 @@ 
				*(.data..vm0.pgd) \

				*(.data..vm0.pte)



/* No __ro_after_init data in the .rodata section - which will always be ro */

#define RO_AFTER_INIT_DATA



#include <asm-generic/vmlinux.lds.h>



/* needed for the processor specific cache alignment size */

arch/parisc/mm/init.c

+35 −32
Original line number Diff line number Diff line
@@ -345,16 +345,7 @@ static void __init setup_bootmem(void) 
	memblock_dump_all();

}



static int __init parisc_text_address(unsigned long vaddr)

{

	static unsigned long head_ptr __initdata;



	if (!head_ptr)

		head_ptr = PAGE_MASK & (unsigned long)

			dereference_function_descriptor(&parisc_kernel_start);



	return core_kernel_text(vaddr) || vaddr == head_ptr;

}

static bool kernel_set_to_readonly;



static void __init map_pages(unsigned long start_vaddr,

			     unsigned long start_paddr, unsigned long size,
@@ -372,10 +363,11 @@ static void __init map_pages(unsigned long start_vaddr, 
	unsigned long vaddr;

	unsigned long ro_start;

	unsigned long ro_end;

	unsigned long kernel_end;

	unsigned long kernel_start, kernel_end;



	ro_start = __pa((unsigned long)_text);

	ro_end   = __pa((unsigned long)&data_start);

	kernel_start = __pa((unsigned long)&__init_begin);

	kernel_end  = __pa((unsigned long)&_end);



	end_paddr = start_paddr + size;
@@ -438,26 +430,30 @@ static void __init map_pages(unsigned long start_vaddr, 
			pg_table = (pte_t *) __va(pg_table) + start_pte;

			for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++, pg_table++) {

				pte_t pte;



				if (force)

					pte =  __mk_pte(address, pgprot);

				else if (parisc_text_address(vaddr)) {

					pte = __mk_pte(address, PAGE_KERNEL_EXEC);

					if (address >= ro_start && address < kernel_end)

						pte = pte_mkhuge(pte);

				pgprot_t prot;

				bool huge = false;



				if (force) {

					prot = pgprot;

				} else if (address < kernel_start || address >= kernel_end) {

					/* outside kernel memory */

					prot = PAGE_KERNEL;

				} else if (!kernel_set_to_readonly) {

					/* still initializing, allow writing to RO memory */

					prot = PAGE_KERNEL_RWX;

					huge = true;

				} else if (address >= ro_start) {

					/* Code (ro) and Data areas */

					prot = (address < ro_end) ?

						PAGE_KERNEL_EXEC : PAGE_KERNEL;

					huge = true;

				} else {

					prot = PAGE_KERNEL;

				}

				else

#if defined(CONFIG_PARISC_PAGE_SIZE_4KB)

				if (address >= ro_start && address < ro_end) {

					pte = __mk_pte(address, PAGE_KERNEL_EXEC);

					pte = pte_mkhuge(pte);

				} else

#endif

				{

					pte = __mk_pte(address, pgprot);

					if (address >= ro_start && address < kernel_end)



				pte = __mk_pte(address, prot);

				if (huge)

					pte = pte_mkhuge(pte);

				}



				if (address >= end_paddr)

					break;
@@ -493,6 +489,12 @@ void __ref free_initmem(void) 
{

	unsigned long init_begin = (unsigned long)__init_begin;

	unsigned long init_end = (unsigned long)__init_end;

	unsigned long kernel_end  = (unsigned long)&_end;



	/* Remap kernel text and data, but do not touch init section yet. */

	kernel_set_to_readonly = true;

	map_pages(init_end, __pa(init_end), kernel_end - init_end,

		  PAGE_KERNEL, 0);



	/* The init text pages are marked R-X.  We have to

	 * flush the icache and mark them RW-
@@ -509,7 +511,7 @@ void __ref free_initmem(void) 
		  PAGE_KERNEL, 1);



	/* force the kernel to see the new TLB entries */

	__flush_tlb_range(0, init_begin, init_end);

	__flush_tlb_range(0, init_begin, kernel_end);



	/* finally dump all the instructions which were cached, since the

	 * pages are no-longer executable */
@@ -527,8 +529,9 @@ void mark_rodata_ro(void) 
{

	/* rodata memory was already mapped with KERNEL_RO access rights by

           pagetable_init() and map_pages(). No need to do additional stuff here */

	printk (KERN_INFO "Write protecting the kernel read-only data: %luk\n",

		(unsigned long)(__end_rodata - __start_rodata) >> 10);

	unsigned long roai_size = __end_ro_after_init - __start_ro_after_init;



	pr_info("Write protected read-only-after-init data: %luk\n", roai_size >> 10);

}

#endif

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