// 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/crash_core.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/notifier.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/uaccess.h>
#include <asm/io.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/memory.h>
#include <linux/sched/task.h>
#include <asm/sections.h>
#include "internal.h"

#define CORE_STR "CORE"

#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

static LIST_HEAD(kclist_head);
static DECLARE_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 size_t get_kcore_size(int *nphdr, size_t *phdrs_len, size_t *notes_len,
                             size_t *data_offset)
{
        size_t try, size;
        struct kcore_list *m;

        *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;
                *nphdr = *nphdr + 1;
        }

        *phdrs_len = *nphdr * sizeof(struct elf_phdr);
        *notes_len = (4 * sizeof(struct elf_note) +
                      3 * ALIGN(sizeof(CORE_STR), 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));
        *data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + *phdrs_len +
                                  *notes_len);
        return *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(sizeof(*ent), GFP_KERNEL);
        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(sizeof(*vmm), GFP_KERNEL);
                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);
        if (!memmap_valid_within(pfn, p, page_zone(p)))
                return 1;

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

        if (!virt_addr_valid(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 inialized....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);
        int nphdr;
        size_t phdrs_len, notes_len, data_offset;
        struct kcore_list *tmp, *pos;
        int ret = 0;

        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);

        proc_root_kcore->size = get_kcore_size(&nphdr, &phdrs_len, &notes_len,
                                               &data_offset);

out:
        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(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
{
        char *buf = file->private_data;
        size_t phdrs_offset, notes_offset, data_offset;
        size_t phdrs_len, notes_len;
        struct kcore_list *m;
        size_t tsz;
        int nphdr;
        unsigned long start;
        size_t orig_buflen = buflen;
        int ret = 0;

        down_read(&kclist_lock);

        get_kcore_size(&nphdr, &phdrs_len, &notes_len, &data_offset);
        phdrs_offset = sizeof(struct elfhdr);
        notes_offset = phdrs_offset + 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 = nphdr,
                };

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

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

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

                phdrs = kzalloc(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 = 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) + data_offset;
                        if (m->type == KCORE_REMAP)
                                phdr->p_vaddr = (size_t)m->vaddr;
                        else
                                phdr->p_vaddr = (size_t)m->addr;
                        if (m->type == KCORE_RAM || m->type == KCORE_REMAP)
                                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 + phdrs_len - *fpos);
                if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset,
                                 tsz)) {
                        kfree(phdrs);
                        ret = -EFAULT;
                        goto out;
                }
                kfree(phdrs);

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

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

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

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

                append_kcore_note(notes, &i, CORE_STR, NT_PRSTATUS, &prstatus,
                                  sizeof(prstatus));
                append_kcore_note(notes, &i, CORE_STR, NT_PRPSINFO, &prpsinfo,
                                  sizeof(prpsinfo));
                append_kcore_note(notes, &i, CORE_STR, 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, notes_len - i));

                tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos);
                if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) {
                        kfree(notes);
                        ret = -EFAULT;
                        goto out;
                }
                kfree(notes);

                buffer += tsz;
                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 - data_offset);
        if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
                tsz = buflen;

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

                if (&m->list == &kclist_head) {
                        if (clear_user(buffer, tsz)) {
                                ret = -EFAULT;
                                goto out;
                        }
                        m = NULL;       /* skip the list anchor */
                } else if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) {
                        if (clear_user(buffer, tsz)) {
                                ret = -EFAULT;
                                goto out;
                        }
                } else if (m->type == KCORE_VMALLOC) {
                        vread(buf, (char *)start, tsz);
                        /* we have to zero-fill user buffer even if no read */
                        if (copy_to_user(buffer, buf, tsz)) {
                                ret = -EFAULT;
                                goto out;
                        }
                } else if (m->type == KCORE_USER) {
                        /* User page is handled prior to normal kernel page: */
                        if (copy_to_user(buffer, (char *)start, tsz)) {
                                ret = -EFAULT;
                                goto out;
                        }
                } else {
                        if (kern_addr_valid(start)) {
                                /*
                                 * Using bounce buffer to bypass the
                                 * hardened user copy kernel text checks.
                                 */
                                if (probe_kernel_read(buf, (void *) start, tsz)) {
                                        if (clear_user(buffer, tsz)) {
                                                ret = -EFAULT;
                                                goto out;
                                        }
                                } else {
                                        if (copy_to_user(buffer, buf, tsz)) {
                                                ret = -EFAULT;
                                                goto out;
                                        }
                                }
                        } else {
                                if (clear_user(buffer, tsz)) {
                                        ret = -EFAULT;
                                        goto out;
                                }
                        }
                }
                buflen -= tsz;
                *fpos += tsz;
                buffer += tsz;
                start += tsz;
                tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
        }

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

static int open_kcore(struct inode *inode, struct file *filp)
{
        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        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 file_operations proc_kcore_operations = {
        .read           = read_kcore,
        .open           = open_kcore,
        .release        = release_kcore,
        .llseek         = 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 notifier_block kcore_callback_nb __meminitdata = {
        .notifier_call = kcore_callback,
        .priority = 0,
};

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,
                                      &proc_kcore_operations);
        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();
        register_hotmemory_notifier(&kcore_callback_nb);

        return 0;
}
fs_initcall(proc_kcore_init);