diff options
| -rw-r--r-- | arch/arm/kernel/process.c | 17 | ||||
| -rw-r--r-- | arch/arm/kernel/vdso.c | 337 |
2 files changed, 351 insertions, 3 deletions
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index fdfa3a78ec8c..c50fe212fd89 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -41,6 +41,7 @@ #include <asm/system_misc.h> #include <asm/mach/time.h> #include <asm/tls.h> +#include <asm/vdso.h> #ifdef CONFIG_CC_STACKPROTECTOR #include <linux/stackprotector.h> @@ -475,7 +476,7 @@ const char *arch_vma_name(struct vm_area_struct *vma) } /* If possible, provide a placement hint at a random offset from the - * stack for the signal page. + * stack for the sigpage and vdso pages. */ static unsigned long sigpage_addr(const struct mm_struct *mm, unsigned int npages) @@ -519,6 +520,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; + unsigned long npages; unsigned long addr; unsigned long hint; int ret = 0; @@ -528,9 +530,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) if (!signal_page) return -ENOMEM; + npages = 1; /* for sigpage */ + npages += vdso_total_pages; + down_write(&mm->mmap_sem); - hint = sigpage_addr(mm, 1); - addr = get_unmapped_area(NULL, hint, PAGE_SIZE, 0, 0); + hint = sigpage_addr(mm, npages); + addr = get_unmapped_area(NULL, hint, npages << PAGE_SHIFT, 0, 0); if (IS_ERR_VALUE(addr)) { ret = addr; goto up_fail; @@ -547,6 +552,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) mm->context.sigpage = addr; + /* Unlike the sigpage, failure to install the vdso is unlikely + * to be fatal to the process, so no error check needed + * here. + */ + arm_install_vdso(mm, addr + PAGE_SIZE); + up_fail: up_write(&mm->mmap_sem); return ret; diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c new file mode 100644 index 000000000000..0d31d3ccab81 --- /dev/null +++ b/arch/arm/kernel/vdso.c @@ -0,0 +1,337 @@ +/* + * Adapted from arm64 version. + * + * Copyright (C) 2012 ARM Limited + * Copyright (C) 2015 Mentor Graphics Corporation. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#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; + +/* Total number of pages needed for the data and text portions of the VDSO. */ +unsigned int vdso_total_pages __read_mostly; + +/* + * 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; +static struct vm_special_mapping vdso_data_mapping = { + .name = "[vvar]", + .pages = &vdso_data_page, +}; + +static struct vm_special_mapping vdso_text_mapping = { + .name = "[vdso]", +}; + +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 __read_mostly; + +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 IS_ERR(vma) ? PTR_ERR(vma) : 0; +} + +/* 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 (strcmp(tk->tkr.clock->name, "arch_sys_counter") != 0) + 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 timespec xtime_coarse; + 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); + + xtime_coarse = __current_kernel_time(); + vdso_data->tk_is_cntvct = tk_is_cntvct(tk); + vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec; + vdso_data->xtime_coarse_nsec = xtime_coarse.tv_nsec; + 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.cycle_last; + vdso_data->xtime_clock_sec = tk->xtime_sec; + vdso_data->xtime_clock_snsec = tk->tkr.xtime_nsec; + vdso_data->cs_mult = tk->tkr.mult; + vdso_data->cs_shift = tk->tkr.shift; + vdso_data->cs_mask = tk->tkr.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)); +} |
