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-rw-r--r--arch/arm/kernel/vdso.c260
1 files changed, 260 insertions, 0 deletions
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
new file mode 100644
index 0000000000..f297d66a8a
--- /dev/null
+++ b/arch/arm/kernel/vdso.c
@@ -0,0 +1,260 @@
+// 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>
+#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;
+
+/*
+ * The VDSO data page.
+ */
+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;
+}
+