[PATCH] kdump: Parse elf32 headers and export through /proc/vmcore

o Adds support for parsing core ELF32 headers.
o I am expecting ELF32 support to go away down the line. This patch has been
  introduced for testing purposes as gdb can not parse ELF64 headers for
  i386. When a decent user space solution is available, ELF32 support
  can go away.

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>

1 files changed, 218 insertions, 0 deletions

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 8ad467855845..3b2e7b69e63a 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -202,6 +202,23 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
         return size;
 }
 
+static u64 __init get_vmcore_size_elf32(char *elfptr)
+{
+        int i;
+        u64 size;
+        Elf32_Ehdr *ehdr_ptr;
+        Elf32_Phdr *phdr_ptr;
+
+        ehdr_ptr = (Elf32_Ehdr *)elfptr;
+        phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
+        size = sizeof(Elf32_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf32_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)
@@ -283,6 +300,87 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
         return 0;
 }
 
+/* Merges all the PT_NOTE headers into one. */
+static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
+                                                struct list_head *vc_list)
+{
+        int i, nr_ptnote=0, rc=0;
+        char *tmp;
+        Elf32_Ehdr *ehdr_ptr;
+        Elf32_Phdr phdr, *phdr_ptr;
+        Elf32_Nhdr *nhdr_ptr;
+        u64 phdr_sz = 0, note_off;
+
+        ehdr_ptr = (Elf32_Ehdr *)elfptr;
+        phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_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(Elf32_Nhdr) +
+                                ((nhdr_ptr->n_namesz + 3) & ~3) +
+                                ((nhdr_ptr->n_descsz + 3) & ~3);
+                        real_sz += sz;
+                        nhdr_ptr = (Elf32_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(Elf32_Ehdr) +
+                        (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_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(Elf32_Ehdr);
+        memcpy(tmp, &phdr, sizeof(phdr));
+        tmp += sizeof(phdr);
+
+        /* Remove unwanted PT_NOTE program headers. */
+        i = (nr_ptnote - 1) * sizeof(Elf32_Phdr);
+        *elfsz = *elfsz - i;
+        memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_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,
@@ -322,6 +420,43 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
         return 0;
 }
 
+static int __init process_ptload_program_headers_elf32(char *elfptr,
+                                                size_t elfsz,
+                                                struct list_head *vc_list)
+{
+        int i;
+        Elf32_Ehdr *ehdr_ptr;
+        Elf32_Phdr *phdr_ptr;
+        loff_t vmcore_off;
+        struct vmcore *new;
+
+        ehdr_ptr = (Elf32_Ehdr *)elfptr;
+        phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */
+
+        /* First program header is PT_NOTE header. */
+        vmcore_off = sizeof(Elf32_Ehdr) +
+                        (ehdr_ptr->e_phnum) * sizeof(Elf32_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)
@@ -342,6 +477,26 @@ static void __init set_vmcore_list_offsets_elf64(char *elfptr,
         }
 }
 
+/* Sets offset fields of vmcore elements. */
+static void __init set_vmcore_list_offsets_elf32(char *elfptr,
+                                                struct list_head *vc_list)
+{
+        loff_t vmcore_off;
+        Elf32_Ehdr *ehdr_ptr;
+        struct vmcore *m;
+
+        ehdr_ptr = (Elf32_Ehdr *)elfptr;
+
+        /* Skip Elf header and program headers. */
+        vmcore_off = sizeof(Elf32_Ehdr) +
+                        (ehdr_ptr->e_phnum) * sizeof(Elf32_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;
@@ -398,6 +553,62 @@ static int __init parse_crash_elf64_headers(void)
         return 0;
 }
 
+static int __init parse_crash_elf32_headers(void)
+{
+        int rc=0;
+        Elf32_Ehdr ehdr;
+        u64 addr;
+
+        addr = elfcorehdr_addr;
+
+        /* Read Elf header */
+        rc = read_from_oldmem((char*)&ehdr, sizeof(Elf32_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] != ELFCLASS32||
+                ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
+                ehdr.e_version != EV_CURRENT ||
+                ehdr.e_ehsize != sizeof(Elf32_Ehdr) ||
+                ehdr.e_phentsize != sizeof(Elf32_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(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_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_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
+        if (rc) {
+                kfree(elfcorebuf);
+                return rc;
+        }
+        rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
+                                                                &vmcore_list);
+        if (rc) {
+                kfree(elfcorebuf);
+                return rc;
+        }
+        set_vmcore_list_offsets_elf32(elfcorebuf, &vmcore_list);
+        return 0;
+}
+
 static int __init parse_crash_elf_headers(void)
 {
         unsigned char e_ident[EI_NIDENT];
@@ -421,6 +632,13 @@ static int __init parse_crash_elf_headers(void)
 
                 /* Determine vmcore size. */
                 vmcore_size = get_vmcore_size_elf64(elfcorebuf);
+        } else if (e_ident[EI_CLASS] == ELFCLASS32) {
+                rc = parse_crash_elf32_headers();
+                if (rc)
+                        return rc;
+
+                /* Determine vmcore size. */
+                vmcore_size = get_vmcore_size_elf32(elfcorebuf);
         } else {
                 printk(KERN_WARNING "Warning: Core image elf header is not"
                                         " sane\n");