[thirdparty/linux.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 <asm/vdso_datapage.h>
#include <clocksource/arm_arch_timer.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;

/*
 * The VDSO data page.
 */
static union vdso_data_store vdso_data_store __page_aligned_data;
static 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)
{
	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
	unsigned long vdso_size;

	/* without VVAR page */
	vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT;

	if (vdso_size != new_size)
		return -EINVAL;

	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.
 */
static 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)
		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;
		strlcpy(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");
	}
}

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;
	pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start);

	/* 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_sem 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;
}

static void vdso_write_begin(struct vdso_data *vdata)
{
	++vdso_data->seq_count;
	smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
}

static void vdso_write_end(struct vdso_data *vdata)
{
	smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
	++vdso_data->seq_count;
}

static bool tk_is_cntvct(const struct timekeeper *tk)
{
	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
		return false;

	if (!tk->tkr_mono.clock->archdata.vdso_direct)
		return false;

	return true;
}

/**
 * update_vsyscall - update the vdso data page
 *
 * Increment the sequence counter, making it odd, indicating to
 * userspace that an update is in progress.  Update the fields used
 * for coarse clocks and, if the architected system timer is in use,
 * the fields used for high precision clocks.  Increment the sequence
 * counter again, making it even, indicating to userspace that the
 * update is finished.
 *
 * Userspace is expected to sample seq_count before reading any other
 * fields from the data page.  If seq_count is odd, userspace is
 * expected to wait until it becomes even.  After copying data from
 * the page, userspace must sample seq_count again; if it has changed
 * from its previous value, userspace must retry the whole sequence.
 *
 * Calls to update_vsyscall are serialized by the timekeeping core.
 */
void update_vsyscall(struct timekeeper *tk)
{
	struct timespec64 *wtm = &tk->wall_to_monotonic;

	if (!cntvct_ok) {
		/* The entry points have been zeroed, so there is no
		 * point in updating the data page.
		 */
		return;
	}

	vdso_write_begin(vdso_data);

	vdso_data->tk_is_cntvct			= tk_is_cntvct(tk);
	vdso_data->xtime_coarse_sec		= tk->xtime_sec;
	vdso_data->xtime_coarse_nsec		= (u32)(tk->tkr_mono.xtime_nsec >>
							tk->tkr_mono.shift);
	vdso_data->wtm_clock_sec		= wtm->tv_sec;
	vdso_data->wtm_clock_nsec		= wtm->tv_nsec;

	if (vdso_data->tk_is_cntvct) {
		vdso_data->cs_cycle_last	= tk->tkr_mono.cycle_last;
		vdso_data->xtime_clock_sec	= tk->xtime_sec;
		vdso_data->xtime_clock_snsec	= tk->tkr_mono.xtime_nsec;
		vdso_data->cs_mult		= tk->tkr_mono.mult;
		vdso_data->cs_shift		= tk->tkr_mono.shift;
		vdso_data->cs_mask		= tk->tkr_mono.mask;
	}

	vdso_write_end(vdso_data);

	flush_dcache_page(virt_to_page(vdso_data));
}

void update_vsyscall_tz(void)
{
	vdso_data->tz_minuteswest	= sys_tz.tz_minuteswest;
	vdso_data->tz_dsttime		= sys_tz.tz_dsttime;
	flush_dcache_page(virt_to_page(vdso_data));
}
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>
	24	#include <asm/vdso_datapage.h>
	25	#include <clocksource/arm_arch_timer.h>
	26
	27	#define MAX_SYMNAME 64
	28
	29	static struct page **vdso_text_pagelist;
	30
73b9160d JP	31	extern char vdso_start[], vdso_end[];
73b9160d JP	32
ecf99a43	33	/* Total number of pages needed for the data and text portions of the VDSO. */
92bb8d5d	34	unsigned int vdso_total_pages __ro_after_init;
ecf99a43 NL	35
	36	/*
	37	* The VDSO data page.
	38	*/
	39	static union vdso_data_store vdso_data_store __page_aligned_data;
	40	static struct vdso_data *vdso_data = &vdso_data_store.data;
	41
92bb8d5d JZ	42	static struct page *vdso_data_page __ro_after_init;
92bb8d5d JZ	43	static const struct vm_special_mapping vdso_data_mapping = {
ecf99a43 NL	44	.name = "[vvar]",
	45	.pages = &vdso_data_page,
	46	};
	47
280e87e9 DS	48	static int vdso_mremap(const struct vm_special_mapping *sm,
	49	struct vm_area_struct *new_vma)
	50	{
	51	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
	52	unsigned long vdso_size;
	53
	54	/* without VVAR page */
	55	vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT;
	56
	57	if (vdso_size != new_size)
	58	return -EINVAL;
	59
	60	current->mm->context.vdso = new_vma->vm_start;
	61
	62	return 0;
	63	}
	64
92bb8d5d	65	static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
ecf99a43	66	.name = "[vdso]",
280e87e9	67	.mremap = vdso_mremap,
ecf99a43 NL	68	};
	69
	70	struct elfinfo {
	71	Elf32_Ehdr hdr; / ptr to ELF */
	72	Elf32_Sym dynsym; / ptr to .dynsym section */
	73	unsigned long dynsymsize; /* size of .dynsym section */
	74	char dynstr; / ptr to .dynstr section */
	75	};
	76
	77	/* Cached result of boot-time check for whether the arch timer exists,
	78	* and if so, whether the virtual counter is useable.
	79	*/
92bb8d5d	80	static bool cntvct_ok __ro_after_init;
ecf99a43 NL	81
	82	static bool __init cntvct_functional(void)
	83	{
	84	struct device_node *np;
	85	bool ret = false;
	86
	87	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
	88	goto out;
	89
	90	/* The arm_arch_timer core should export
	91	* arch_timer_use_virtual or similar so we don't have to do
	92	* this.
	93	*/
	94	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
	95	if (!np)
	96	goto out_put;
	97
	98	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
	99	goto out_put;
	100
	101	ret = true;
	102
	103	out_put:
	104	of_node_put(np);
	105	out:
	106	return ret;
	107	}
	108
	109	static void * __init find_section(Elf32_Ehdr ehdr, const char name,
	110	unsigned long *size)
	111	{
	112	Elf32_Shdr *sechdrs;
	113	unsigned int i;
	114	char *secnames;
	115
	116	/* Grab section headers and strings so we can tell who is who */
	117	sechdrs = (void *)ehdr + ehdr->e_shoff;
	118	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
	119
	120	/* Find the section they want */
	121	for (i = 1; i < ehdr->e_shnum; i++) {
	122	if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
	123	if (size)
	124	*size = sechdrs[i].sh_size;
	125	return (void *)ehdr + sechdrs[i].sh_offset;
	126	}
	127	}
	128
	129	if (size)
	130	*size = 0;
	131	return NULL;
	132	}
	133
	134	static Elf32_Sym * __init find_symbol(struct elfinfo lib, const char symname)
	135	{
	136	unsigned int i;
	137
	138	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
	139	char name[MAX_SYMNAME], *c;
	140
	141	if (lib->dynsym[i].st_name == 0)
	142	continue;
	143	strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
	144	MAX_SYMNAME);
145	c = strchr(name, '@');
146	if (c)
147	*c = 0;
148	if (strcmp(symname, name) == 0)
149	return &lib->dynsym[i];
150	}
151	return NULL;
152	}
153
154	static void __init vdso_nullpatch_one(struct elfinfo lib, const char symname)
155	{
156	Elf32_Sym *sym;
157
158	sym = find_symbol(lib, symname);
159	if (!sym)
160	return;
161
162	sym->st_name = 0;
163	}
164
165	static void __init patch_vdso(void *ehdr)
166	{
167	struct elfinfo einfo;
168
169	einfo = (struct elfinfo) {
170	.hdr = ehdr,
171	};
172
173	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
174	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
175
176	/* If the virtual counter is absent or non-functional we don't
177	* want programs to incur the slight additional overhead of
178	* dispatching through the VDSO only to fall back to syscalls.
179	*/
180	if (!cntvct_ok) {
181	vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
182	vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
183	}
184	}
185
186	static int __init vdso_init(void)
187	{
188	unsigned int text_pages;
189	int i;
190
73b9160d	191	if (memcmp(vdso_start, "\177ELF", 4)) {
ecf99a43 NL	192	pr_err("VDSO is not a valid ELF object!\n");
	193	return -ENOEXEC;
	194	}
	195
73b9160d JP	196	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
73b9160d JP	197	pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start);
ecf99a43 NL	198
	199	/* Allocate the VDSO text pagelist */
	200	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
	201	GFP_KERNEL);
	202	if (vdso_text_pagelist == NULL)
	203	return -ENOMEM;
	204
	205	/* Grab the VDSO data page. */
	206	vdso_data_page = virt_to_page(vdso_data);
	207
	208	/* Grab the VDSO text pages. */
	209	for (i = 0; i < text_pages; i++) {
	210	struct page *page;
	211
73b9160d	212	page = virt_to_page(vdso_start + i * PAGE_SIZE);
ecf99a43 NL	213	vdso_text_pagelist[i] = page;
	214	}
	215
	216	vdso_text_mapping.pages = vdso_text_pagelist;
	217
	218	vdso_total_pages = 1; /* for the data/vvar page */
	219	vdso_total_pages += text_pages;
	220
	221	cntvct_ok = cntvct_functional();
	222
73b9160d	223	patch_vdso(vdso_start);
ecf99a43 NL	224
	225	return 0;
	226	}
	227	arch_initcall(vdso_init);
	228
	229	static int install_vvar(struct mm_struct *mm, unsigned long addr)
	230	{
	231	struct vm_area_struct *vma;
	232
	233	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
	234	VM_READ \| VM_MAYREAD,
	235	&vdso_data_mapping);
	236
38fc2f6c	237	return PTR_ERR_OR_ZERO(vma);
ecf99a43 NL	238	}
	239
	240	/* assumes mmap_sem is write-locked */
	241	void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
	242	{
	243	struct vm_area_struct *vma;
	244	unsigned long len;
	245
	246	mm->context.vdso = 0;
	247
	248	if (vdso_text_pagelist == NULL)
	249	return;
	250
	251	if (install_vvar(mm, addr))
	252	return;
	253
	254	/* Account for vvar page. */
	255	addr += PAGE_SIZE;
	256	len = (vdso_total_pages - 1) << PAGE_SHIFT;
	257
	258	vma = _install_special_mapping(mm, addr, len,
	259	VM_READ \| VM_EXEC \| VM_MAYREAD \| VM_MAYWRITE \| VM_MAYEXEC,
	260	&vdso_text_mapping);
	261
	262	if (!IS_ERR(vma))
	263	mm->context.vdso = addr;
	264	}
	265
	266	static void vdso_write_begin(struct vdso_data *vdata)
	267	{
	268	++vdso_data->seq_count;
	269	smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
	270	}
	271
	272	static void vdso_write_end(struct vdso_data *vdata)
	273	{
	274	smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
	275	++vdso_data->seq_count;
	276	}
	277
	278	static bool tk_is_cntvct(const struct timekeeper *tk)
	279	{
	280	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
	281	return false;
	282
1d8f51d4	283	if (!tk->tkr_mono.clock->archdata.vdso_direct)
ecf99a43 NL	284	return false;
	285
	286	return true;
	287	}
	288
	289	/**
	290	* update_vsyscall - update the vdso data page
	291	*
	292	* Increment the sequence counter, making it odd, indicating to
	293	* userspace that an update is in progress. Update the fields used
	294	* for coarse clocks and, if the architected system timer is in use,
	295	* the fields used for high precision clocks. Increment the sequence
	296	* counter again, making it even, indicating to userspace that the
	297	* update is finished.
	298	*
	299	* Userspace is expected to sample seq_count before reading any other
	300	* fields from the data page. If seq_count is odd, userspace is
	301	* expected to wait until it becomes even. After copying data from
	302	* the page, userspace must sample seq_count again; if it has changed
	303	* from its previous value, userspace must retry the whole sequence.
	304	*
	305	* Calls to update_vsyscall are serialized by the timekeeping core.
	306	*/
	307	void update_vsyscall(struct timekeeper *tk)
	308	{
ecf99a43 NL	309	struct timespec64 *wtm = &tk->wall_to_monotonic;
	310
	311	if (!cntvct_ok) {
	312	/* The entry points have been zeroed, so there is no
	313	* point in updating the data page.
	314	*/
	315	return;
	316	}
	317
	318	vdso_write_begin(vdso_data);
	319
ecf99a43	320	vdso_data->tk_is_cntvct = tk_is_cntvct(tk);
09edea4f NL	321	vdso_data->xtime_coarse_sec = tk->xtime_sec;
	322	vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >>
	323	tk->tkr_mono.shift);
ecf99a43 NL	324	vdso_data->wtm_clock_sec = wtm->tv_sec;
	325	vdso_data->wtm_clock_nsec = wtm->tv_nsec;
	326
	327	if (vdso_data->tk_is_cntvct) {
bb0fd7ab	328	vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last;
ecf99a43	329	vdso_data->xtime_clock_sec = tk->xtime_sec;
bb0fd7ab LT	330	vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec;
	331	vdso_data->cs_mult = tk->tkr_mono.mult;
	332	vdso_data->cs_shift = tk->tkr_mono.shift;
	333	vdso_data->cs_mask = tk->tkr_mono.mask;
ecf99a43 NL	334	}
	335
	336	vdso_write_end(vdso_data);
	337
	338	flush_dcache_page(virt_to_page(vdso_data));
	339	}
	340
	341	void update_vsyscall_tz(void)
	342	{
	343	vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
	344	vdso_data->tz_dsttime = sys_tz.tz_dsttime;
	345	flush_dcache_page(virt_to_page(vdso_data));
	346	}