[PATCH] kdump: Access dump file in elf format (/proc/vmcore)

From: "Vivek Goyal" <vgoyal@in.ibm.com>

o Support for /proc/vmcore interface. This interface exports elf core image
  either in ELF32 or ELF64 format, depending on the format in which elf headers
  have been stored by crashed kernel.
o Added support for CONFIG_VMCORE config option.
o Removed the dependency on /proc/kcore.

From: "Eric W. Biederman" <ebiederm@xmission.com>

This patch has been refactored to more closely match the prevailing style in
the affected files.  And to clearly indicate the dependency between
/proc/kcore and proc/vmcore.c

From: Hariprasad Nellitheertha <hari@in.ibm.com>

This patch contains the code that provides an ELF format interface to the
previous kernel's memory post kexec reboot.

Signed off by Hariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 458 insertions, 0 deletions

diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index 738b9b602932..7431d7ba2d09 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -11,4 +11,5 @@ proc-y       += inode.o root.o base.o generic.o array.o \
                 kmsg.o proc_tty.o proc_misc.o
 
 proc-$(CONFIG_PROC_KCORE)       += kcore.o
+proc-$(CONFIG_PROC_VMCORE)      += vmcore.o
 proc-$(CONFIG_PROC_DEVICETREE)  += proc_devtree.o
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 94b570ad037d..a3453555a94e 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -44,6 +44,7 @@
 #include <linux/jiffies.h>
 #include <linux/sysrq.h>
 #include <linux/vmalloc.h>
+#include <linux/crash_dump.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/io.h>
@@ -618,6 +619,11 @@ void __init proc_misc_init(void)
                                 (size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;
         }
 #endif
+#ifdef CONFIG_PROC_VMCORE
+        proc_vmcore = create_proc_entry("vmcore", S_IRUSR, NULL);
+        if (proc_vmcore)
+                proc_vmcore->proc_fops = &proc_vmcore_operations;
+#endif
 #ifdef CONFIG_MAGIC_SYSRQ
         entry = create_proc_entry("sysrq-trigger", S_IWUSR, NULL);
         if (entry)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
new file mode 100644
index 000000000000..8ad467855845
--- /dev/null
+++ b/fs/proc/vmcore.c
@@ -0,0 +1,451 @@
+/*
+ *      fs/proc/vmcore.c Interface for accessing the crash
+ *                               dump from the system's previous life.
+ *      Heavily borrowed from fs/proc/kcore.c
+ *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
+ *      Copyright (C) IBM Corporation, 2004. All rights reserved
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/user.h>
+#include <linux/a.out.h>
+#include <linux/elf.h>
+#include <linux/elfcore.h>
+#include <linux/proc_fs.h>
+#include <linux/highmem.h>
+#include <linux/bootmem.h>
+#include <linux/init.h>
+#include <linux/crash_dump.h>
+#include <linux/list.h>
+#include <asm/uaccess.h>
+#include <asm/io.h>
+
+/* List representing chunks of contiguous memory areas and their offsets in
+ * vmcore file.
+ */
+static LIST_HEAD(vmcore_list);
+
+/* Stores the pointer to the buffer containing kernel elf core headers. */
+static char *elfcorebuf;
+static size_t elfcorebuf_sz;
+
+/* Total size of vmcore file. */
+static u64 vmcore_size;
+
+struct proc_dir_entry *proc_vmcore = NULL;
+
+/* Reads a page from the oldmem device from given offset. */
+static ssize_t read_from_oldmem(char *buf, size_t count,
+                             loff_t *ppos, int userbuf)
+{
+        unsigned long pfn, offset;
+        size_t nr_bytes;
+        ssize_t read = 0, tmp;
+
+        if (!count)
+                return 0;
+
+        offset = (unsigned long)(*ppos % PAGE_SIZE);
+        pfn = (unsigned long)(*ppos / PAGE_SIZE);
+        if (pfn > saved_max_pfn)
+                return -EINVAL;
+
+        do {
+                if (count > (PAGE_SIZE - offset))
+                        nr_bytes = PAGE_SIZE - offset;
+                else
+                        nr_bytes = count;
+
+                tmp = copy_oldmem_page(pfn, buf, nr_bytes, offset, userbuf);
+                if (tmp < 0)
+                        return tmp;
+                *ppos += nr_bytes;
+                count -= nr_bytes;
+                buf += nr_bytes;
+                read += nr_bytes;
+                ++pfn;
+                offset = 0;
+        } while (count);
+
+        return read;
+}
+
+/* Maps vmcore file offset to respective physical address in memroy. */
+static u64 map_offset_to_paddr(loff_t offset, struct list_head *vc_list,
+                                        struct vmcore **m_ptr)
+{
+        struct vmcore *m;
+        u64 paddr;
+
+        list_for_each_entry(m, vc_list, list) {
+                u64 start, end;
+                start = m->offset;
+                end = m->offset + m->size - 1;
+                if (offset >= start && offset <= end) {
+                        paddr = m->paddr + offset - start;
+                        *m_ptr = m;
+                        return paddr;
+                }
+        }
+        *m_ptr = NULL;
+        return 0;
+}
+
+/* Read from the ELF header and then the crash dump. On error, negative value is
+ * returned otherwise number of bytes read are returned.
+ */
+static ssize_t read_vmcore(struct file *file, char __user *buffer,
+                                size_t buflen, loff_t *fpos)
+{
+        ssize_t acc = 0, tmp;
+        size_t tsz, nr_bytes;
+        u64 start;
+        struct vmcore *curr_m = NULL;
+
+        if (buflen == 0 || *fpos >= vmcore_size)
+                return 0;
+
+        /* trim buflen to not go beyond EOF */
+        if (buflen > vmcore_size - *fpos)
+                buflen = vmcore_size - *fpos;
+
+        /* Read ELF core header */
+        if (*fpos < elfcorebuf_sz) {
+                tsz = elfcorebuf_sz - *fpos;
+                if (buflen < tsz)
+                        tsz = buflen;
+                if (copy_to_user(buffer, elfcorebuf + *fpos, tsz))
+                        return -EFAULT;
+                buflen -= tsz;
+                *fpos += tsz;
+                buffer += tsz;
+                acc += tsz;
+
+                /* leave now if filled buffer already */
+                if (buflen == 0)
+                        return acc;
+        }
+
+        start = map_offset_to_paddr(*fpos, &vmcore_list, &curr_m);
+        if (!curr_m)
+                return -EINVAL;
+        if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
+                tsz = buflen;
+
+        /* Calculate left bytes in current memory segment. */
+        nr_bytes = (curr_m->size - (start - curr_m->paddr));
+        if (tsz > nr_bytes)
+                tsz = nr_bytes;
+
+        while (buflen) {
+                tmp = read_from_oldmem(buffer, tsz, &start, 1);
+                if (tmp < 0)
+                        return tmp;
+                buflen -= tsz;
+                *fpos += tsz;
+                buffer += tsz;
+                acc += tsz;
+                if (start >= (curr_m->paddr + curr_m->size)) {
+                        if (curr_m->list.next == &vmcore_list)
+                                return acc;     /*EOF*/
+                        curr_m = list_entry(curr_m->list.next,
+                                                struct vmcore, list);
+                        start = curr_m->paddr;
+                }
+                if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
+                        tsz = buflen;
+                /* Calculate left bytes in current memory segment. */
+                nr_bytes = (curr_m->size - (start - curr_m->paddr));
+                if (tsz > nr_bytes)
+                        tsz = nr_bytes;
+        }
+        return acc;
+}
+
+static int open_vmcore(struct inode *inode, struct file *filp)
+{
+        return 0;
+}
+
+struct file_operations proc_vmcore_operations = {
+        .read           = read_vmcore,
+        .open           = open_vmcore,
+};
+
+static struct vmcore* __init get_new_element(void)
+{
+        struct vmcore *p;
+
+        p = kmalloc(sizeof(*p), GFP_KERNEL);
+        if (p)
+                memset(p, 0, sizeof(*p));
+        return p;
+}
+
+static u64 __init get_vmcore_size_elf64(char *elfptr)
+{
+        int i;
+        u64 size;
+        Elf64_Ehdr *ehdr_ptr;
+        Elf64_Phdr *phdr_ptr;
+
+        ehdr_ptr = (Elf64_Ehdr *)elfptr;
+        phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
+        size = sizeof(Elf64_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr));
+        for (i = 0; i < ehdr_ptr->e_phnum; i++) {
+                size += phdr_ptr->p_memsz;
+                phdr_ptr++;
+        }
+        return size;
+}
+
+/* Merges all the PT_NOTE headers into one. */
+static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
+                                                struct list_head *vc_list)
+{
+        int i, nr_ptnote=0, rc=0;
+        char *tmp;
+        Elf64_Ehdr *ehdr_ptr;
+        Elf64_Phdr phdr, *phdr_ptr;
+        Elf64_Nhdr *nhdr_ptr;
+        u64 phdr_sz = 0, note_off;
+
+        ehdr_ptr = (Elf64_Ehdr *)elfptr;
+        phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
+        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
+                int j;
+                void *notes_section;
+                struct vmcore *new;
+                u64 offset, max_sz, sz, real_sz = 0;
+                if (phdr_ptr->p_type != PT_NOTE)
+                        continue;
+                nr_ptnote++;
+                max_sz = phdr_ptr->p_memsz;
+                offset = phdr_ptr->p_offset;
+                notes_section = kmalloc(max_sz, GFP_KERNEL);
+                if (!notes_section)
+                        return -ENOMEM;
+                rc = read_from_oldmem(notes_section, max_sz, &offset, 0);
+                if (rc < 0) {
+                        kfree(notes_section);
+                        return rc;
+                }
+                nhdr_ptr = notes_section;
+                for (j = 0; j < max_sz; j += sz) {
+                        if (nhdr_ptr->n_namesz == 0)
+                                break;
+                        sz = sizeof(Elf64_Nhdr) +
+                                ((nhdr_ptr->n_namesz + 3) & ~3) +
+                                ((nhdr_ptr->n_descsz + 3) & ~3);
+                        real_sz += sz;
+                        nhdr_ptr = (Elf64_Nhdr*)((char*)nhdr_ptr + sz);
+                }
+
+                /* Add this contiguous chunk of notes section to vmcore list.*/
+                new = get_new_element();
+                if (!new) {
+                        kfree(notes_section);
+                        return -ENOMEM;
+                }
+                new->paddr = phdr_ptr->p_offset;
+                new->size = real_sz;
+                list_add_tail(&new->list, vc_list);
+                phdr_sz += real_sz;
+                kfree(notes_section);
+        }
+
+        /* Prepare merged PT_NOTE program header. */
+        phdr.p_type    = PT_NOTE;
+        phdr.p_flags   = 0;
+        note_off = sizeof(Elf64_Ehdr) +
+                        (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr);
+        phdr.p_offset  = note_off;
+        phdr.p_vaddr   = phdr.p_paddr = 0;
+        phdr.p_filesz  = phdr.p_memsz = phdr_sz;
+        phdr.p_align   = 0;
+
+        /* Add merged PT_NOTE program header*/
+        tmp = elfptr + sizeof(Elf64_Ehdr);
+        memcpy(tmp, &phdr, sizeof(phdr));
+        tmp += sizeof(phdr);
+
+        /* Remove unwanted PT_NOTE program headers. */
+        i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
+        *elfsz = *elfsz - i;
+        memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
+
+        /* Modify e_phnum to reflect merged headers. */
+        ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
+
+        return 0;
+}
+
+/* Add memory chunks represented by program headers to vmcore list. Also update
+ * the new offset fields of exported program headers. */
+static int __init process_ptload_program_headers_elf64(char *elfptr,
+                                                size_t elfsz,
+                                                struct list_head *vc_list)
+{
+        int i;
+        Elf64_Ehdr *ehdr_ptr;
+        Elf64_Phdr *phdr_ptr;
+        loff_t vmcore_off;
+        struct vmcore *new;
+
+        ehdr_ptr = (Elf64_Ehdr *)elfptr;
+        phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
+
+        /* First program header is PT_NOTE header. */
+        vmcore_off = sizeof(Elf64_Ehdr) +
+                        (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) +
+                        phdr_ptr->p_memsz; /* Note sections */
+
+        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
+                if (phdr_ptr->p_type != PT_LOAD)
+                        continue;
+
+                /* Add this contiguous chunk of memory to vmcore list.*/
+                new = get_new_element();
+                if (!new)
+                        return -ENOMEM;
+                new->paddr = phdr_ptr->p_offset;
+                new->size = phdr_ptr->p_memsz;
+                list_add_tail(&new->list, vc_list);
+
+                /* Update the program header offset. */
+                phdr_ptr->p_offset = vmcore_off;
+                vmcore_off = vmcore_off + phdr_ptr->p_memsz;
+        }
+        return 0;
+}
+
+/* Sets offset fields of vmcore elements. */
+static void __init set_vmcore_list_offsets_elf64(char *elfptr,
+                                                struct list_head *vc_list)
+{
+        loff_t vmcore_off;
+        Elf64_Ehdr *ehdr_ptr;
+        struct vmcore *m;
+
+        ehdr_ptr = (Elf64_Ehdr *)elfptr;
+
+        /* Skip Elf header and program headers. */
+        vmcore_off = sizeof(Elf64_Ehdr) +
+                        (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr);
+
+        list_for_each_entry(m, vc_list, list) {
+                m->offset = vmcore_off;
+                vmcore_off += m->size;
+        }
+}
+
+static int __init parse_crash_elf64_headers(void)
+{
+        int rc=0;
+        Elf64_Ehdr ehdr;
+        u64 addr;
+
+        addr = elfcorehdr_addr;
+
+        /* Read Elf header */
+        rc = read_from_oldmem((char*)&ehdr, sizeof(Elf64_Ehdr), &addr, 0);
+        if (rc < 0)
+                return rc;
+
+        /* Do some basic Verification. */
+        if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
+                (ehdr.e_type != ET_CORE) ||
+                !elf_check_arch(&ehdr) ||
+                ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
+                ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
+                ehdr.e_version != EV_CURRENT ||
+                ehdr.e_ehsize != sizeof(Elf64_Ehdr) ||
+                ehdr.e_phentsize != sizeof(Elf64_Phdr) ||
+                ehdr.e_phnum == 0) {
+                printk(KERN_WARNING "Warning: Core image elf header is not"
+                                        "sane\n");
+                return -EINVAL;
+        }
+
+        /* Read in all elf headers. */
+        elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
+        elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
+        if (!elfcorebuf)
+                return -ENOMEM;
+        addr = elfcorehdr_addr;
+        rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
+        if (rc < 0) {
+                kfree(elfcorebuf);
+                return rc;
+        }
+
+        /* Merge all PT_NOTE headers into one. */
+        rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
+        if (rc) {
+                kfree(elfcorebuf);
+                return rc;
+        }
+        rc = process_ptload_program_headers_elf64(elfcorebuf, elfcorebuf_sz,
+                                                        &vmcore_list);
+        if (rc) {
+                kfree(elfcorebuf);
+                return rc;
+        }
+        set_vmcore_list_offsets_elf64(elfcorebuf, &vmcore_list);
+        return 0;
+}
+
+static int __init parse_crash_elf_headers(void)
+{
+        unsigned char e_ident[EI_NIDENT];
+        u64 addr;
+        int rc=0;
+
+        addr = elfcorehdr_addr;
+        rc = read_from_oldmem(e_ident, EI_NIDENT, &addr, 0);
+        if (rc < 0)
+                return rc;
+        if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
+                printk(KERN_WARNING "Warning: Core image elf header"
+                                        " not found\n");
+                return -EINVAL;
+        }
+
+        if (e_ident[EI_CLASS] == ELFCLASS64) {
+                rc = parse_crash_elf64_headers();
+                if (rc)
+                        return rc;
+
+                /* Determine vmcore size. */
+                vmcore_size = get_vmcore_size_elf64(elfcorebuf);
+        } else {
+                printk(KERN_WARNING "Warning: Core image elf header is not"
+                                        " sane\n");
+                return -EINVAL;
+        }
+        return 0;
+}
+
+/* Init function for vmcore module. */
+static int __init vmcore_init(void)
+{
+        int rc = 0;
+
+        /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
+        if (!(elfcorehdr_addr < ELFCORE_ADDR_MAX))
+                return rc;
+        rc = parse_crash_elf_headers();
+        if (rc) {
+                printk(KERN_WARNING "Kdump: vmcore not initialized\n");
+                return rc;
+        }
+
+        /* Initialize /proc/vmcore size if proc is already up. */
+        if (proc_vmcore)
+                proc_vmcore->size = vmcore_size;
+        return 0;
+}
+module_init(vmcore_init)