vdso.c

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/*
 *  linux/arch/ppc64/kernel/vdso.c
 *
 *    Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
 *			 <[e-mail]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/bootmem.h>

#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/sections.h>
#include <asm/vdso.h>

#undef DEBUG

#ifdef DEBUG
#define DBG(fmt...) printk(fmt)
#else
#define DBG(fmt...)
#endif


/*
 * The vDSOs themselves are here
 */
extern char vdso64_start, vdso64_end;
extern char vdso32_start, vdso32_end;

static void *vdso64_kbase = &vdso64_start;
static void *vdso32_kbase = &vdso32_start;

unsigned int vdso64_pages;
unsigned int vdso32_pages;

/* Signal trampolines user addresses */

unsigned long vdso64_rt_sigtramp;
unsigned long vdso32_sigtramp;
unsigned long vdso32_rt_sigtramp;

/* Format of the patch table */
struct vdso_patch_def
{
	u32		pvr_mask, pvr_value;
	const char	*gen_name;
	const char	*fix_name;
};

/* Table of functions to patch based on the CPU type/revision
 *
 * TODO: Improve by adding whole lists for each entry
 */
static struct vdso_patch_def vdso_patches[] = {
	{
		0xffff0000, 0x003a0000,		/* POWER5 */
		"__kernel_sync_dicache", "__kernel_sync_dicache_p5"
	},
	{
		0xffff0000, 0x003b0000,		/* POWER5 */
		"__kernel_sync_dicache", "__kernel_sync_dicache_p5"
	},
};

/*
 * Some infos carried around for each of them during parsing at
 * boot time.
 */
struct lib32_elfinfo
{
	Elf32_Ehdr	*hdr;		/* ptr to ELF */
	Elf32_Sym	*dynsym;	/* ptr to .dynsym section */
	unsigned long	dynsymsize;	/* size of .dynsym section */
	char		*dynstr;	/* ptr to .dynstr section */
	unsigned long	text;		/* offset of .text section in .so */
};

struct lib64_elfinfo
{
	Elf64_Ehdr	*hdr;
	Elf64_Sym	*dynsym;
	unsigned long	dynsymsize;
	char		*dynstr;
	unsigned long	text;
};


#ifdef __DEBUG
static void dump_one_vdso_page(struct page *pg, struct page *upg)
{
	printk("kpg: %p (c:%d,f:%08lx)", __va(page_to_pfn(pg) << PAGE_SHIFT),
	       page_count(pg),
	       pg->flags);
	if (upg/* && pg != upg*/) {
		printk(" upg: %p (c:%d,f:%08lx)", __va(page_to_pfn(upg) << PAGE_SHIFT),
		       page_count(upg),
		       upg->flags);
	}
	printk("\n");
}

static void dump_vdso_pages(struct vm_area_struct * vma)
{
	int i;

	if (!vma || test_thread_flag(TIF_32BIT)) {
		printk("vDSO32 @ %016lx:\n", (unsigned long)vdso32_kbase);
		for (i=0; i<vdso32_pages; i++) {
			struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
			struct page *upg = (vma && vma->vm_mm) ?
				follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
				: NULL;
			dump_one_vdso_page(pg, upg);
		}
	}
	if (!vma || !test_thread_flag(TIF_32BIT)) {
		printk("vDSO64 @ %016lx:\n", (unsigned long)vdso64_kbase);
		for (i=0; i<vdso64_pages; i++) {
			struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
			struct page *upg = (vma && vma->vm_mm) ?
				follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
				: NULL;
			dump_one_vdso_page(pg, upg);
		}
	}
}
#endif /* DEBUG */

/*
 * Keep a dummy vma_close for now, it will prevent VMA merging.
 */
static void vdso_vma_close(struct vm_area_struct * vma)
{
}

/*
 * Our nopage() function, maps in the actual vDSO kernel pages, they will
 * be mapped read-only by do_no_page(), and eventually COW'ed, either
 * right away for an initial write access, or by do_wp_page().
 */
static struct page * vdso_vma_nopage(struct vm_area_struct * vma,
				     unsigned long address, int *type)
{
	unsigned long offset = address - vma->vm_start;
	struct page *pg;
	void *vbase = test_thread_flag(TIF_32BIT) ? vdso32_kbase : vdso64_kbase;

	DBG("vdso_vma_nopage(current: %s, address: %016lx, off: %lx)\n",
	    current->comm, address, offset);

	if (address < vma->vm_start || address > vma->vm_end)
		return NOPAGE_SIGBUS;

	/*
	 * Last page is systemcfg, special handling here, no get_page() a
	 * this is a reserved page
	 */
	if ((vma->vm_end - address) <= PAGE_SIZE)
		return virt_to_page(systemcfg);

	pg = virt_to_page(vbase + offset);
	get_page(pg);
	DBG(" ->page count: %d\n", page_count(pg));

	return pg;
}

static struct vm_operations_struct vdso_vmops = {
	.close	= vdso_vma_close,
	.nopage	= vdso_vma_nopage,
};

/*
 * This is called from binfmt_elf, we create the special vma for the
 * vDSO and insert it into the mm struct tree
 */
int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long vdso_pages;
	unsigned long vdso_base;

	if (test_thread_flag(TIF_32BIT)) {
		vdso_pages = vdso32_pages;
		vdso_base = VDSO32_MBASE;
	} else {
		vdso_pages = vdso64_pages;
		vdso_base = VDSO64_MBASE;
	}

	current->thread.vdso_base = 0;

	/* vDSO has a problem and was disabled, just don't "enable" it for the
	 * process
	 */
	if (vdso_pages == 0)
		return 0;

	vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
	if (vma == NULL)
		return -ENOMEM;

	memset(vma, 0, sizeof(*vma));

	/*
	 * pick a base address for the vDSO in process space. We try to put it
	 * at vdso_base which is the "natural" base for it, but we might fail
	 * and end up putting it elsewhere.
	 */
	vdso_base = get_unmapped_area(NULL, vdso_base,
				      vdso_pages << PAGE_SHIFT, 0, 0);
	if (vdso_base & ~PAGE_MASK) {
		kmem_cache_free(vm_area_cachep, vma);
		return (int)vdso_base;
	}

	current->thread.vdso_base = vdso_base;

	vma->vm_mm = mm;
	vma->vm_start = current->thread.vdso_base;

	/*
	 * the VMA size is one page more than the vDSO since systemcfg
	 * is mapped in the last one
	 */
	vma->vm_end = vma->vm_start + ((vdso_pages + 1) << PAGE_SHIFT);

	/*
	 * our vma flags don't have VM_WRITE so by default, the process isn't allowed
	 * to write those pages.
	 * gdb can break that with ptrace interface, and thus trigger COW on those
	 * pages but it's then your responsibility to never do that on the "data" page
	 * of the vDSO or you'll stop getting kernel updates and your nice userland
	 * gettimeofday will be totally dead. It's fine to use that for setting
	 * breakpoints in the vDSO code pages though
	 */
	vma->vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
	vma->vm_flags |= mm->def_flags;
	vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
	vma->vm_ops = &vdso_vmops;

	down_write(&mm->mmap_sem);
	if (insert_vm_struct(mm, vma)) {
		up_write(&mm->mmap_sem);
		kmem_cache_free(vm_area_cachep, vma);
		return -ENOMEM;
	}
	mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
	up_write(&mm->mmap_sem);

	return 0;
}

static void * __init find_section32(Elf32_Ehdr *ehdr, const char *secname,
				  unsigned long *size)
{
	Elf32_Shdr *sechdrs;
	unsigned int i;
	char *secnames;

	/* Grab section headers and strings so we can tell who is who */
	sechdrs = (void *)ehdr + ehdr->e_shoff;
	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;

	/* Find the section they want */
	for (i = 1; i < ehdr->e_shnum; i++) {
		if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
			if (size)
				*size = sechdrs[i].sh_size;
			return (void *)ehdr + sechdrs[i].sh_offset;
		}
	}
	*size = 0;
	return NULL;
}

static void * __init find_section64(Elf64_Ehdr *ehdr, const char *secname,
				  unsigned long *size)
{
	Elf64_Shdr *sechdrs;
	unsigned int i;
	char *secnames;

	/* Grab section headers and strings so we can tell who is who */
	sechdrs = (void *)ehdr + ehdr->e_shoff;
	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;