// SPDX-License-Identifier: GPL-2.0
/*
 *      fs/proc/kcore.c kernel ELF core dumper
 *
 *      Modelled on fs/exec.c:aout_core_dump()
 *      Jeremy Fitzhardinge <jeremy@sw.oz.au>
 *      ELF version written by David Howells <David.Howells@nexor.co.uk>
 *      Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
 *      Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
 *      Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
 */

#include <linux/vmcore_info.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/kcore.h>
#include <linux/user.h>
#include <linux/capability.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/vmalloc.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <linux/memblock.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <asm/io.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/memory.h>
#include <linux/sched/task.h>
#include <linux/security.h>
#include <asm/sections.h>
#include "internal.h"

#ifndef ELF_CORE_EFLAGS
#define ELF_CORE_EFLAGS 0
#endif

static struct proc_dir_entry *proc_root_kcore;


#ifndef kc_vaddr_to_offset
#define kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
#endif
#ifndef kc_offset_to_vaddr
#define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
#endif

#ifndef kc_xlate_dev_mem_ptr
#define kc_xlate_dev_mem_ptr kc_xlate_dev_mem_ptr
static inline void *kc_xlate_dev_mem_ptr(phys_addr_t phys)
{
        return __va(phys);
}
#endif
#ifndef kc_unxlate_dev_mem_ptr
#define kc_unxlate_dev_mem_ptr kc_unxlate_dev_mem_ptr
static inline void kc_unxlate_dev_mem_ptr(phys_addr_t phys, void *virt)
{
}
#endif

static LIST_HEAD(kclist_head);
static int kcore_nphdr;
static size_t kcore_phdrs_len;
static size_t kcore_notes_len;
static size_t kcore_data_offset;
DEFINE_STATIC_PERCPU_RWSEM(kclist_lock);
static int kcore_need_update = 1;

/*
 * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
 * Same as oldmem_pfn_is_ram in vmcore
 */
static int (*mem_pfn_is_ram)(unsigned long pfn);

int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn))
{
        if (mem_pfn_is_ram)
                return -EBUSY;
        mem_pfn_is_ram = fn;
        return 0;
}

static int pfn_is_ram(unsigned long pfn)
{
        if (mem_pfn_is_ram)
                return mem_pfn_is_ram(pfn);
        else
                return 1;
}

/* This doesn't grab kclist_lock, so it should only be used at init time. */
void __init kclist_add(struct kcore_list *new, void *addr, size_t size,
                       int type)
{
        new->addr = (unsigned long)addr;
        new->size = size;
        new->type = type;

        list_add_tail(&new->list, &kclist_head);
}

static void update_kcore_size(void)
{
        size_t try, size;
        struct kcore_list *m;

        kcore_nphdr = 1; /* PT_NOTE */
        size = 0;

        list_for_each_entry(m, &kclist_head, list) {
                try = kc_vaddr_to_offset((size_t)m->addr + m->size);
                if (try > size)
                        size = try;
                kcore_nphdr++;
        }

        kcore_phdrs_len = kcore_nphdr * sizeof(struct elf_phdr);
        kcore_notes_len = (4 * sizeof(struct elf_note) +
                           ALIGN(sizeof(NN_PRSTATUS), 4) +
                           ALIGN(sizeof(NN_PRPSINFO), 4) +
                           ALIGN(sizeof(NN_TASKSTRUCT), 4) +
                           VMCOREINFO_NOTE_NAME_BYTES +
                           ALIGN(sizeof(struct elf_prstatus), 4) +
                           ALIGN(sizeof(struct elf_prpsinfo), 4) +
                           ALIGN(arch_task_struct_size, 4) +
                           ALIGN(vmcoreinfo_size, 4));
        kcore_data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + kcore_phdrs_len +
                                       kcore_notes_len);
        proc_root_kcore->size = kcore_data_offset + size;
}

#ifdef CONFIG_HIGHMEM
/*
 * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
 * because memory hole is not as big as !HIGHMEM case.
 * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
 */
static int kcore_ram_list(struct list_head *head)
{
        struct kcore_list *ent;

        ent = kmalloc_obj(*ent);
        if (!ent)
                return -ENOMEM;
        ent->addr = (unsigned long)__va(0);
        ent->size = max_low_pfn << PAGE_SHIFT;
        ent->type = KCORE_RAM;
        list_add(&ent->list, head);
        return 0;
}

#else /* !CONFIG_HIGHMEM */

#ifdef CONFIG_SPARSEMEM_VMEMMAP
/* calculate vmemmap's address from given system ram pfn and register it */
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
        unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
        unsigned long nr_pages = ent->size >> PAGE_SHIFT;
        unsigned long start, end;
        struct kcore_list *vmm, *tmp;


        start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
        end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
        end = PAGE_ALIGN(end);
        /* overlap check (because we have to align page */
        list_for_each_entry(tmp, head, list) {
                if (tmp->type != KCORE_VMEMMAP)
                        continue;
                if (start < tmp->addr + tmp->size)
                        if (end > tmp->addr)
                                end = tmp->addr;
        }
        if (start < end) {
                vmm = kmalloc_obj(*vmm);
                if (!vmm)
                        return 0;
                vmm->addr = start;
                vmm->size = end - start;
                vmm->type = KCORE_VMEMMAP;
                list_add_tail(&vmm->list, head);
        }
        return 1;

}
#else
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
        return 1;
}

#endif

static int
kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
{
        struct list_head *head = (struct list_head *)arg;
        struct kcore_list *ent;
        struct page *p;

        if (!pfn_valid(pfn))
                return 1;

        p = pfn_to_page(pfn);

        ent = kmalloc_obj(*ent);
        if (!ent)
                return -ENOMEM;
        ent->addr = (unsigned long)page_to_virt(p);
        ent->size = nr_pages << PAGE_SHIFT;

        if (!virt_addr_valid((void *)ent->addr))
                goto free_out;

        /* cut not-mapped area. ....from ppc-32 code. */
        if (ULONG_MAX - ent->addr < ent->size)
                ent->size = ULONG_MAX - ent->addr;

        /*
         * We've already checked virt_addr_valid so we know this address
         * is a valid pointer, therefore we can check against it to determine
         * if we need to trim
         */
        if (VMALLOC_START > ent->addr) {
                if (VMALLOC_START - ent->addr < ent->size)
                        ent->size = VMALLOC_START - ent->addr;
        }

        ent->type = KCORE_RAM;
        list_add_tail(&ent->list, head);

        if (!get_sparsemem_vmemmap_info(ent, head)) {
                list_del(&ent->list);
                goto free_out;
        }

        return 0;
free_out:
        kfree(ent);
        return 1;
}

static int kcore_ram_list(struct list_head *list)
{
        int nid, ret;
        unsigned long end_pfn;

        /* Not initialized....update now */
        /* find out "max pfn" */
        end_pfn = 0;
        for_each_node_state(nid, N_MEMORY) {
                unsigned long node_end;
                node_end = node_end_pfn(nid);
                if (end_pfn < node_end)
                        end_pfn = node_end;
        }
        /* scan 0 to max_pfn */
        ret = walk_system_ram_range(0, end_pfn, list, kclist_add_private);
        if (ret)
                return -ENOMEM;
        return 0;
}
#endif /* CONFIG_HIGHMEM */

static int kcore_update_ram(void)
{
        LIST_HEAD(list);
        LIST_HEAD(garbage);
        struct kcore_list *tmp, *pos;
        int ret = 0;

        percpu_down_write(&kclist_lock);
        if (!xchg(&kcore_need_update, 0))
                goto out;

        ret = kcore_ram_list(&list);
        if (ret) {
                /* Couldn't get the RAM list, try again next time. */
                WRITE_ONCE(kcore_need_update, 1);
                list_splice_tail(&list, &garbage);
                goto out;
        }

        list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
                if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP)
                        list_move(&pos->list, &garbage);
        }
        list_splice_tail(&list, &kclist_head);

        update_kcore_size();

out:
        percpu_up_write(&kclist_lock);
        list_for_each_entry_safe(pos, tmp, &garbage, list) {
                list_del(&pos->list);
                kfree(pos);
        }
        return ret;
}

static void append_kcore_note(char *notes, size_t *i, const char *name,
                              unsigned int type, const void *desc,
                              size_t descsz)
{
        struct elf_note *note = (struct elf_note *)&notes[*i];

        note->n_namesz = strlen(name) + 1;
        note->n_descsz = descsz;
        note->n_type = type;
        *i += sizeof(*note);
        memcpy(&notes[*i], name, note->n_namesz);
        *i = ALIGN(*i + note->n_namesz, 4);
        memcpy(&notes[*i], desc, descsz);
        *i = ALIGN(*i + descsz, 4);
}

static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
{
        struct file *file = iocb->ki_filp;
        char *buf = file->private_data;
        loff_t *fpos = &iocb->ki_pos;
        size_t phdrs_offset, notes_offset;
        size_t page_offline_frozen = 1;
        struct kcore_list *m;
        size_t tsz;
        unsigned long start;
        size_t buflen = iov_iter_count(iter);
        size_t orig_buflen = buflen;
        int ret = 0;

        percpu_down_read(&kclist_lock);
        /*
         * Don't race against drivers that set PageOffline() and expect no
         * further page access.
         */
        page_offline_freeze();

        phdrs_offset = sizeof(struct elfhdr);
        notes_offset = phdrs_offset + kcore_phdrs_len;

        /* ELF file header. */
        if (buflen && *fpos < sizeof(struct elfhdr)) {
                struct elfhdr ehdr = {
                        .e_ident = {
                                [EI_MAG0] = ELFMAG0,
                                [EI_MAG1] = ELFMAG1,
                                [EI_MAG2] = ELFMAG2,
                                [EI_MAG3] = ELFMAG3,
                                [EI_CLASS] = ELF_CLASS,
                                [EI_DATA] = ELF_DATA,
                                [EI_VERSION] = EV_CURRENT,
                                [EI_OSABI] = ELF_OSABI,
                        },
                        .e_type = ET_CORE,
                        .e_machine = ELF_ARCH,
                        .e_version = EV_CURRENT,
                        .e_phoff = sizeof(struct elfhdr),
                        .e_flags = ELF_CORE_EFLAGS,
                        .e_ehsize = sizeof(struct elfhdr),
                        .e_phentsize = sizeof(struct elf_phdr),
                        .e_phnum = kcore_nphdr,
                };

                tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
                if (copy_to_iter((char *)&ehdr + *fpos, tsz, iter) != tsz) {
                        ret = -EFAULT;
                        goto out;
                }

                buflen -= tsz;
                *fpos += tsz;
        }

        /* ELF program headers. */
        if (buflen && *fpos < phdrs_offset + kcore_phdrs_len) {
                struct elf_phdr *phdrs, *phdr;

                phdrs = kzalloc(kcore_phdrs_len, GFP_KERNEL);
                if (!phdrs) {
                        ret = -ENOMEM;
                        goto out;
                }

                phdrs[0].p_type = PT_NOTE;
                phdrs[0].p_offset = notes_offset;
                phdrs[0].p_filesz = kcore_notes_len;

                phdr = &phdrs[1];
                list_for_each_entry(m, &kclist_head, list) {
                        phdr->p_type = PT_LOAD;
                        phdr->p_flags = PF_R | PF_W | PF_X;
                        phdr->p_offset = kc_vaddr_to_offset(m->addr)
                                         + kcore_data_offset;
                        phdr->p_vaddr = (size_t)m->addr;
                        if (m->type == KCORE_RAM)
                                phdr->p_paddr = __pa(m->addr);
                        else if (m->type == KCORE_TEXT)
                                phdr->p_paddr = __pa_symbol(m->addr);
                        else
                                phdr->p_paddr = (elf_addr_t)-1;
                        phdr->p_filesz = phdr->p_memsz = m->size;
                        phdr->p_align = PAGE_SIZE;
                        phdr++;
                }

                tsz = min_t(size_t, buflen,
                            phdrs_offset + kcore_phdrs_len - *fpos);
                if (copy_to_iter((char *)phdrs + *fpos - phdrs_offset, tsz,
                                 iter) != tsz) {
                        kfree(phdrs);
                        ret = -EFAULT;
                        goto out;
                }
                kfree(phdrs);

                buflen -= tsz;
                *fpos += tsz;
        }

        /* ELF note segment. */
        if (buflen && *fpos < notes_offset + kcore_notes_len) {
                struct elf_prstatus prstatus = {};
                struct elf_prpsinfo prpsinfo = {
                        .pr_sname = 'R',
                        .pr_fname = "vmlinux",
                };
                char *notes;
                size_t i = 0;

                strscpy(prpsinfo.pr_psargs, saved_command_line,
                        sizeof(prpsinfo.pr_psargs));

                notes = kzalloc(kcore_notes_len, GFP_KERNEL);
                if (!notes) {
                        ret = -ENOMEM;
                        goto out;
                }

                append_kcore_note(notes, &i, NN_PRSTATUS, NT_PRSTATUS, &prstatus,
                                  sizeof(prstatus));
                append_kcore_note(notes, &i, NN_PRPSINFO, NT_PRPSINFO, &prpsinfo,
                                  sizeof(prpsinfo));
                append_kcore_note(notes, &i, NN_TASKSTRUCT, NT_TASKSTRUCT, current,
                                  arch_task_struct_size);
                /*
                 * vmcoreinfo_size is mostly constant after init time, but it
                 * can be changed by crash_save_vmcoreinfo(). Racing here with a
                 * panic on another CPU before the machine goes down is insanely
                 * unlikely, but it's better to not leave potential buffer
                 * overflows lying around, regardless.
                 */
                append_kcore_note(notes, &i, VMCOREINFO_NOTE_NAME, 0,
                                  vmcoreinfo_data,
                                  min(vmcoreinfo_size, kcore_notes_len - i));

                tsz = min_t(size_t, buflen,
                            notes_offset + kcore_notes_len - *fpos);
                if (copy_to_iter(notes + *fpos - notes_offset, tsz, iter) != tsz) {
                        kfree(notes);
                        ret = -EFAULT;
                        goto out;
                }
                kfree(notes);

                buflen -= tsz;
                *fpos += tsz;
        }

        /*
         * Check to see if our file offset matches with any of
         * the addresses in the elf_phdr on our list.
         */
        start = kc_offset_to_vaddr(*fpos - kcore_data_offset);
        if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
                tsz = buflen;

        m = NULL;
        while (buflen) {
                struct page *page;
                unsigned long pfn;
                phys_addr_t phys;
                void *__start;

                /*
                 * If this is the first iteration or the address is not within
                 * the previous entry, search for a matching entry.
                 */
                if (!m || start < m->addr || start >= m->addr + m->size) {
                        struct kcore_list *pos;

                        m = NULL;
                        list_for_each_entry(pos, &kclist_head, list) {
                                if (start >= pos->addr &&
                                    start < pos->addr + pos->size) {
                                        m = pos;
                                        break;
                                }
                        }
                }

                if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) {
                        page_offline_thaw();
                        cond_resched();
                        page_offline_freeze();
                }

                if (!m) {
                        if (iov_iter_zero(tsz, iter) != tsz) {
                                ret = -EFAULT;
                                goto out;
                        }
                        goto skip;
                }

                switch (m->type) {
                case KCORE_VMALLOC:
                {
                        const char *src = (char *)start;
                        size_t read = 0, left = tsz;

                        /*
                         * vmalloc uses spinlocks, so we optimistically try to
                         * read memory. If this fails, fault pages in and try
                         * again until we are done.
                         */
                        while (true) {
                                read += vread_iter(iter, src, left);
                                if (read == tsz)
                                        break;

                                src += read;
                                left -= read;

                                if (fault_in_iov_iter_writeable(iter, left)) {
                                        ret = -EFAULT;
                                        goto out;
                                }
                        }
                        break;
                }
                case KCORE_USER:
                        /* User page is handled prior to normal kernel page: */
                        if (copy_to_iter((char *)start, tsz, iter) != tsz) {
                                ret = -EFAULT;
                                goto out;
                        }
                        break;
                case KCORE_RAM:
                        phys = __pa(start);
                        pfn =  phys >> PAGE_SHIFT;
                        page = pfn_to_online_page(pfn);

                        /*
                         * Don't read offline sections, logically offline pages
                         * (e.g., inflated in a balloon), hwpoisoned pages,
                         * and explicitly excluded physical ranges.
                         */
                        if (!page || PageOffline(page) ||
                            is_page_hwpoison(page) || !pfn_is_ram(pfn) ||
                            pfn_is_unaccepted_memory(pfn)) {
                                if (iov_iter_zero(tsz, iter) != tsz) {
                                        ret = -EFAULT;
                                        goto out;
                                }
                                break;
                        }
                        fallthrough;
                case KCORE_VMEMMAP:
                case KCORE_TEXT:
                        if (m->type == KCORE_RAM) {
                                __start = kc_xlate_dev_mem_ptr(phys);
                                if (!__start) {
                                        ret = -ENOMEM;
                                        if (iov_iter_zero(tsz, iter) != tsz)
                                                ret = -EFAULT;
                                        goto out;
                                }
                        } else {
                                __start = (void *)start;
                        }

                        /*
                         * Sadly we must use a bounce buffer here to be able to
                         * make use of copy_from_kernel_nofault(), as these
                         * memory regions might not always be mapped on all
                         * architectures.
                         */
                        ret = copy_from_kernel_nofault(buf, __start, tsz);
                        if (m->type == KCORE_RAM)
                                kc_unxlate_dev_mem_ptr(phys, __start);
                        if (ret) {
                                if (iov_iter_zero(tsz, iter) != tsz) {
                                        ret = -EFAULT;
                                        goto out;
                                }
                                ret = 0;
                        /*
                         * We know the bounce buffer is safe to copy from, so
                         * use _copy_to_iter() directly.
                         */
                        } else if (_copy_to_iter(buf, tsz, iter) != tsz) {
                                ret = -EFAULT;
                                goto out;
                        }
                        break;
                default:
                        pr_warn_once("Unhandled KCORE type: %d\n", m->type);
                        if (iov_iter_zero(tsz, iter) != tsz) {
                                ret = -EFAULT;
                                goto out;
                        }
                }
skip:
                buflen -= tsz;
                *fpos += tsz;
                start += tsz;
                tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
        }

out:
        page_offline_thaw();
        percpu_up_read(&kclist_lock);
        if (ret)
                return ret;
        return orig_buflen - buflen;
}

static int open_kcore(struct inode *inode, struct file *filp)
{
        int ret = security_locked_down(LOCKDOWN_KCORE);

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        if (ret)
                return ret;

        filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!filp->private_data)
                return -ENOMEM;

        if (kcore_need_update)
                kcore_update_ram();
        if (i_size_read(inode) != proc_root_kcore->size) {
                inode_lock(inode);
                i_size_write(inode, proc_root_kcore->size);
                inode_unlock(inode);
        }
        return 0;
}

static int release_kcore(struct inode *inode, struct file *file)
{
        kfree(file->private_data);
        return 0;
}

static const struct proc_ops kcore_proc_ops = {
        .proc_flags     = PROC_ENTRY_PERMANENT,
        .proc_read_iter = read_kcore_iter,
        .proc_open      = open_kcore,
        .proc_release   = release_kcore,
        .proc_lseek     = default_llseek,
};

/* just remember that we have to update kcore */
static int __meminit kcore_callback(struct notifier_block *self,
                                    unsigned long action, void *arg)
{
        switch (action) {
        case MEM_ONLINE:
        case MEM_OFFLINE:
                kcore_need_update = 1;
                break;
        }
        return NOTIFY_OK;
}


static struct kcore_list kcore_vmalloc;

#ifdef CONFIG_ARCH_PROC_KCORE_TEXT
static struct kcore_list kcore_text;
/*
 * If defined, special segment is used for mapping kernel text instead of
 * direct-map area. We need to create special TEXT section.
 */
static void __init proc_kcore_text_init(void)
{
        kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
}
#else
static void __init proc_kcore_text_init(void)
{
}
#endif

#if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
/*
 * MODULES_VADDR has no intersection with VMALLOC_ADDR.
 */
static struct kcore_list kcore_modules;
static void __init add_modules_range(void)
{
        if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
                kclist_add(&kcore_modules, (void *)MODULES_VADDR,
                        MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
        }
}
#else
static void __init add_modules_range(void)
{
}
#endif

static int __init proc_kcore_init(void)
{
        proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &kcore_proc_ops);
        if (!proc_root_kcore) {
                pr_err("couldn't create /proc/kcore\n");
                return 0; /* Always returns 0. */
        }
        /* Store text area if it's special */
        proc_kcore_text_init();
        /* Store vmalloc area */
        kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
                VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
        add_modules_range();
        /* Store direct-map area from physical memory map */
        kcore_update_ram();
        hotplug_memory_notifier(kcore_callback, DEFAULT_CALLBACK_PRI);

        return 0;
}
fs_initcall(proc_kcore_init);