[linux-2.6-block.git] / arch / arm / kernel / vdso.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Adapted from arm64 version.
 *
 * Copyright (C) 2012 ARM Limited
 * Copyright (C) 2015 Mentor Graphics Corporation.
 */

#include <linux/cache.h>
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/of.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <asm/arch_timer.h>
#include <asm/barrier.h>
#include <asm/cacheflush.h>
#include <asm/page.h>
#include <asm/vdso.h>
#include <clocksource/arm_arch_timer.h>
#include <vdso/helpers.h>
#include <vdso/vsyscall.h>

#define MAX_SYMNAME	64

static struct page **vdso_text_pagelist;

extern char vdso_start[], vdso_end[];

/* Total number of pages needed for the data and text portions of the VDSO. */
unsigned int vdso_total_pages __ro_after_init;

static union vdso_data_store vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = vdso_data_store.data;

static struct page *vdso_data_page __ro_after_init;
static const struct vm_special_mapping vdso_data_mapping = {
	.name = "[vvar]",
	.pages = &vdso_data_page,
};

static int vdso_mremap(const struct vm_special_mapping *sm,
		struct vm_area_struct *new_vma)
{
	current->mm->context.vdso = new_vma->vm_start;

	return 0;
}

static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
	.name = "[vdso]",
	.mremap = vdso_mremap,
};

struct 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 */
};

/* Cached result of boot-time check for whether the arch timer exists,
 * and if so, whether the virtual counter is useable.
 */
bool cntvct_ok __ro_after_init;

static bool __init cntvct_functional(void)
{
	struct device_node *np;
	bool ret = false;

	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
		goto out;

	/* The arm_arch_timer core should export
	 * arch_timer_use_virtual or similar so we don't have to do
	 * this.
	 */
	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
	if (!np)
		np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
	if (!np)
		goto out_put;

	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
		goto out_put;

	ret = true;

out_put:
	of_node_put(np);
out:
	return ret;
}

static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
				  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, name) == 0) {
			if (size)
				*size = sechdrs[i].sh_size;
			return (void *)ehdr + sechdrs[i].sh_offset;
		}
	}

	if (size)
		*size = 0;
	return NULL;
}

static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
{
	unsigned int i;

	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
		char name[MAX_SYMNAME], *c;

		if (lib->dynsym[i].st_name == 0)
			continue;
		strscpy(name, lib->dynstr + lib->dynsym[i].st_name,
			MAX_SYMNAME);
		c = strchr(name, '@');
		if (c)
			*c = 0;
		if (strcmp(symname, name) == 0)
			return &lib->dynsym[i];
	}
	return NULL;
}

static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
{
	Elf32_Sym *sym;

	sym = find_symbol(lib, symname);
	if (!sym)
		return;

	sym->st_name = 0;
}

static void __init patch_vdso(void *ehdr)
{
	struct elfinfo einfo;

	einfo = (struct elfinfo) {
		.hdr = ehdr,
	};

	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);

	/* If the virtual counter is absent or non-functional we don't
	 * want programs to incur the slight additional overhead of
	 * dispatching through the VDSO only to fall back to syscalls.
	 */
	if (!cntvct_ok) {
		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
	}
}

static int __init vdso_init(void)
{
	unsigned int text_pages;
	int i;

	if (memcmp(vdso_start, "\177ELF", 4)) {
		pr_err("VDSO is not a valid ELF object!\n");
		return -ENOEXEC;
	}

	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;

	/* Allocate the VDSO text pagelist */
	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
				     GFP_KERNEL);
	if (vdso_text_pagelist == NULL)
		return -ENOMEM;

	/* Grab the VDSO data page. */
	vdso_data_page = virt_to_page(vdso_data);

	/* Grab the VDSO text pages. */
	for (i = 0; i < text_pages; i++) {
		struct page *page;

		page = virt_to_page(vdso_start + i * PAGE_SIZE);
		vdso_text_pagelist[i] = page;
	}

	vdso_text_mapping.pages = vdso_text_pagelist;

	vdso_total_pages = 1; /* for the data/vvar page */
	vdso_total_pages += text_pages;

	cntvct_ok = cntvct_functional();

	patch_vdso(vdso_start);

	return 0;
}
arch_initcall(vdso_init);

static int install_vvar(struct mm_struct *mm, unsigned long addr)
{
	struct vm_area_struct *vma;

	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
				       VM_READ | VM_MAYREAD,
				       &vdso_data_mapping);

	return PTR_ERR_OR_ZERO(vma);
}

/* assumes mmap_lock is write-locked */
void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
{
	struct vm_area_struct *vma;
	unsigned long len;

	mm->context.vdso = 0;

	if (vdso_text_pagelist == NULL)
		return;

	if (install_vvar(mm, addr))
		return;

	/* Account for vvar page. */
	addr += PAGE_SIZE;
	len = (vdso_total_pages - 1) << PAGE_SHIFT;

	vma = _install_special_mapping(mm, addr, len,
		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
		&vdso_text_mapping);

	if (!IS_ERR(vma))
		mm->context.vdso = addr;
}
Commit	Line	Data
caab277b	1	// SPDX-License-Identifier: GPL-2.0-only
ecf99a43 NL	2	/*
	3	* Adapted from arm64 version.
	4	*
	5	* Copyright (C) 2012 ARM Limited
	6	* Copyright (C) 2015 Mentor Graphics Corporation.
ecf99a43 NL	7	*/
ecf99a43 NL	8
92bb8d5d	9	#include <linux/cache.h>
ecf99a43 NL	10	#include <linux/elf.h>
	11	#include <linux/err.h>
	12	#include <linux/kernel.h>
	13	#include <linux/mm.h>
	14	#include <linux/of.h>
	15	#include <linux/printk.h>
	16	#include <linux/slab.h>
	17	#include <linux/timekeeper_internal.h>
	18	#include <linux/vmalloc.h>
	19	#include <asm/arch_timer.h>
	20	#include <asm/barrier.h>
	21	#include <asm/cacheflush.h>
	22	#include <asm/page.h>
	23	#include <asm/vdso.h>
ecf99a43	24	#include <clocksource/arm_arch_timer.h>
20e2fc42 VF	25	#include <vdso/helpers.h>
20e2fc42 VF	26	#include <vdso/vsyscall.h>
ecf99a43 NL	27
	28	#define MAX_SYMNAME 64
	29
	30	static struct page **vdso_text_pagelist;
	31
73b9160d JP	32	extern char vdso_start[], vdso_end[];
73b9160d JP	33
ecf99a43	34	/* Total number of pages needed for the data and text portions of the VDSO. */
92bb8d5d	35	unsigned int vdso_total_pages __ro_after_init;
ecf99a43	36
ecf99a43	37	static union vdso_data_store vdso_data_store __page_aligned_data;
20e2fc42	38	struct vdso_data *vdso_data = vdso_data_store.data;
ecf99a43	39
92bb8d5d JZ	40	static struct page *vdso_data_page __ro_after_init;
92bb8d5d JZ	41	static const struct vm_special_mapping vdso_data_mapping = {
ecf99a43 NL	42	.name = "[vvar]",
	43	.pages = &vdso_data_page,
	44	};
	45
280e87e9 DS	46	static int vdso_mremap(const struct vm_special_mapping *sm,
	47	struct vm_area_struct *new_vma)
	48	{
280e87e9 DS	49	current->mm->context.vdso = new_vma->vm_start;
	50
	51	return 0;
	52	}
	53
92bb8d5d	54	static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
ecf99a43	55	.name = "[vdso]",
280e87e9	56	.mremap = vdso_mremap,
ecf99a43 NL	57	};
	58
	59	struct elfinfo {
	60	Elf32_Ehdr hdr; / ptr to ELF */
	61	Elf32_Sym dynsym; / ptr to .dynsym section */
	62	unsigned long dynsymsize; /* size of .dynsym section */
	63	char dynstr; / ptr to .dynstr section */
	64	};
	65
	66	/* Cached result of boot-time check for whether the arch timer exists,
	67	* and if so, whether the virtual counter is useable.
	68	*/
20e2fc42	69	bool cntvct_ok __ro_after_init;
ecf99a43 NL	70
	71	static bool __init cntvct_functional(void)
	72	{
	73	struct device_node *np;
	74	bool ret = false;
	75
	76	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
	77	goto out;
	78
	79	/* The arm_arch_timer core should export
	80	* arch_timer_use_virtual or similar so we don't have to do
	81	* this.
	82	*/
	83	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
45939ce2 FF	84	if (!np)
45939ce2 FF	85	np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
ecf99a43 NL	86	if (!np)
	87	goto out_put;
	88
	89	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
	90	goto out_put;
	91
	92	ret = true;
	93
	94	out_put:
	95	of_node_put(np);
	96	out:
	97	return ret;
	98	}
	99
	100	static void * __init find_section(Elf32_Ehdr ehdr, const char name,
	101	unsigned long *size)
	102	{
	103	Elf32_Shdr *sechdrs;
	104	unsigned int i;
	105	char *secnames;
	106
	107	/* Grab section headers and strings so we can tell who is who */
	108	sechdrs = (void *)ehdr + ehdr->e_shoff;
	109	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
	110
	111	/* Find the section they want */
	112	for (i = 1; i < ehdr->e_shnum; i++) {
	113	if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
	114	if (size)
	115	*size = sechdrs[i].sh_size;
	116	return (void *)ehdr + sechdrs[i].sh_offset;
	117	}
	118	}
	119
	120	if (size)
	121	*size = 0;
	122	return NULL;
	123	}
	124
	125	static Elf32_Sym * __init find_symbol(struct elfinfo lib, const char symname)
	126	{
	127	unsigned int i;
	128
	129	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
	130	char name[MAX_SYMNAME], *c;
	131
	132	if (lib->dynsym[i].st_name == 0)
	133	continue;
7611b335	134	strscpy(name, lib->dynstr + lib->dynsym[i].st_name,
ecf99a43 NL	135	MAX_SYMNAME);
	136	c = strchr(name, '@');
	137	if (c)
	138	*c = 0;
	139	if (strcmp(symname, name) == 0)
	140	return &lib->dynsym[i];
	141	}
	142	return NULL;
	143	}
	144
	145	static void __init vdso_nullpatch_one(struct elfinfo lib, const char symname)
	146	{
	147	Elf32_Sym *sym;
	148
	149	sym = find_symbol(lib, symname);
	150	if (!sym)
	151	return;
	152
	153	sym->st_name = 0;
	154	}
	155
	156	static void __init patch_vdso(void *ehdr)
	157	{
	158	struct elfinfo einfo;
	159
	160	einfo = (struct elfinfo) {
	161	.hdr = ehdr,
	162	};
	163
	164	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
	165	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
	166
	167	/* If the virtual counter is absent or non-functional we don't
	168	* want programs to incur the slight additional overhead of
	169	* dispatching through the VDSO only to fall back to syscalls.
	170	*/
	171	if (!cntvct_ok) {
	172	vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
	173	vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
4405bdf3	174	vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
ecf99a43 NL	175	}
	176	}
	177
	178	static int __init vdso_init(void)
	179	{
	180	unsigned int text_pages;
	181	int i;
	182
73b9160d	183	if (memcmp(vdso_start, "\177ELF", 4)) {
ecf99a43 NL	184	pr_err("VDSO is not a valid ELF object!\n");
	185	return -ENOEXEC;
	186	}
	187
73b9160d	188	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
ecf99a43 NL	189
	190	/* Allocate the VDSO text pagelist */
	191	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
	192	GFP_KERNEL);
	193	if (vdso_text_pagelist == NULL)
	194	return -ENOMEM;
	195
	196	/* Grab the VDSO data page. */
	197	vdso_data_page = virt_to_page(vdso_data);
	198
	199	/* Grab the VDSO text pages. */
	200	for (i = 0; i < text_pages; i++) {
	201	struct page *page;
	202
73b9160d	203	page = virt_to_page(vdso_start + i * PAGE_SIZE);
ecf99a43 NL	204	vdso_text_pagelist[i] = page;
	205	}
	206
	207	vdso_text_mapping.pages = vdso_text_pagelist;
	208
	209	vdso_total_pages = 1; /* for the data/vvar page */
	210	vdso_total_pages += text_pages;
	211
	212	cntvct_ok = cntvct_functional();
	213
73b9160d	214	patch_vdso(vdso_start);
ecf99a43 NL	215
	216	return 0;
	217	}
	218	arch_initcall(vdso_init);
	219
	220	static int install_vvar(struct mm_struct *mm, unsigned long addr)
	221	{
	222	struct vm_area_struct *vma;
	223
	224	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
	225	VM_READ \| VM_MAYREAD,
	226	&vdso_data_mapping);
	227
38fc2f6c	228	return PTR_ERR_OR_ZERO(vma);
ecf99a43 NL	229	}
ecf99a43 NL	230
c1e8d7c6	231	/* assumes mmap_lock is write-locked */
ecf99a43 NL	232	void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
	233	{
	234	struct vm_area_struct *vma;
	235	unsigned long len;
	236
	237	mm->context.vdso = 0;
	238
	239	if (vdso_text_pagelist == NULL)
	240	return;
	241
	242	if (install_vvar(mm, addr))
	243	return;
	244
	245	/* Account for vvar page. */
	246	addr += PAGE_SIZE;
	247	len = (vdso_total_pages - 1) << PAGE_SHIFT;
	248
	249	vma = _install_special_mapping(mm, addr, len,
	250	VM_READ \| VM_EXEC \| VM_MAYREAD \| VM_MAYWRITE \| VM_MAYEXEC,
	251	&vdso_text_mapping);
	252
	253	if (!IS_ERR(vma))
	254	mm->context.vdso = addr;
	255	}
	256