vmcore: allocate buffer for ELF headers on page-size alignment

Allocate ELF headers on page-size boundary using __get_free_pages()
instead of kmalloc().

Later patch will merge PT_NOTE entries into a single unique one and
decrease the buffer size actually used.  Keep original buffer size in
variable elfcorebuf_sz_orig to kfree the buffer later and actually used
buffer size with rounded up to page-size boundary in variable
elfcorebuf_sz separately.

The size of part of the ELF buffer exported from /proc/vmcore is
elfcorebuf_sz.

The merged, removed PT_NOTE entries, i.e.  the range [elfcorebuf_sz,
elfcorebuf_sz_orig], is filled with 0.

Use size of the ELF headers as an initial offset value in
set_vmcore_list_offsets_elf{64,32} and
process_ptload_program_headers_elf{64,32} in order to indicate that the
offset includes the holes towards the page boundary.

As a result, both set_vmcore_list_offsets_elf{64,32} have the same
definition.  Merge them as set_vmcore_list_offsets.

[akpm@linux-foundation.org: add free_elfcorebuf(), cleanups]
Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Lisa Mitchell <lisa.mitchell@hp.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 51 insertions, 68 deletions

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index ab0c92e64411..0b1c04e5e2c5 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -32,6 +32,7 @@ static LIST_HEAD(vmcore_list);
 /* Stores the pointer to the buffer containing kernel elf core headers. */
 static char *elfcorebuf;
 static size_t elfcorebuf_sz;
+static size_t elfcorebuf_sz_orig;
 
 /* Total size of vmcore file. */
 static u64 vmcore_size;
@@ -186,7 +187,7 @@ static struct vmcore* __init get_new_element(void)
         return kzalloc(sizeof(struct vmcore), GFP_KERNEL);
 }
 
-static u64 __init get_vmcore_size_elf64(char *elfptr)
+static u64 __init get_vmcore_size_elf64(char *elfptr, size_t elfsz)
 {
         int i;
         u64 size;
@@ -195,7 +196,7 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
 
         ehdr_ptr = (Elf64_Ehdr *)elfptr;
         phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
-        size = sizeof(Elf64_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr));
+        size = elfsz;
         for (i = 0; i < ehdr_ptr->e_phnum; i++) {
                 size += phdr_ptr->p_memsz;
                 phdr_ptr++;
@@ -203,7 +204,7 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
         return size;
 }
 
-static u64 __init get_vmcore_size_elf32(char *elfptr)
+static u64 __init get_vmcore_size_elf32(char *elfptr, size_t elfsz)
 {
         int i;
         u64 size;
@@ -212,7 +213,7 @@ static u64 __init get_vmcore_size_elf32(char *elfptr)
 
         ehdr_ptr = (Elf32_Ehdr *)elfptr;
         phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
-        size = sizeof(Elf32_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr));
+        size = elfsz;
         for (i = 0; i < ehdr_ptr->e_phnum; i++) {
                 size += phdr_ptr->p_memsz;
                 phdr_ptr++;
@@ -294,6 +295,8 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
         i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
         *elfsz = *elfsz - i;
         memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
+        memset(elfptr + *elfsz, 0, i);
+        *elfsz = roundup(*elfsz, PAGE_SIZE);
 
         /* Modify e_phnum to reflect merged headers. */
         ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
@@ -375,6 +378,8 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
         i = (nr_ptnote - 1) * sizeof(Elf32_Phdr);
         *elfsz = *elfsz - i;
         memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_Phdr)));
+        memset(elfptr + *elfsz, 0, i);
+        *elfsz = roundup(*elfsz, PAGE_SIZE);
 
         /* Modify e_phnum to reflect merged headers. */
         ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
@@ -398,8 +403,7 @@ static int __init process_ptload_program_headers_elf64(char *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) +
+        vmcore_off = elfsz +
                         phdr_ptr->p_memsz; /* Note sections */
 
         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
@@ -435,8 +439,7 @@ static int __init process_ptload_program_headers_elf32(char *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) +
+        vmcore_off = elfsz +
                         phdr_ptr->p_memsz; /* Note sections */
 
         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
@@ -459,18 +462,14 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
 }
 
 /* Sets offset fields of vmcore elements. */
-static void __init set_vmcore_list_offsets_elf64(char *elfptr,
-                                                struct list_head *vc_list)
+static void __init set_vmcore_list_offsets(size_t elfsz,
+                                           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);
+        vmcore_off = elfsz;
 
         list_for_each_entry(m, vc_list, list) {
                 m->offset = vmcore_off;
@@ -478,24 +477,10 @@ 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)
+static void free_elfcorebuf(void)
 {
-        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;
-        }
+        free_pages((unsigned long)elfcorebuf, get_order(elfcorebuf_sz_orig));
+        elfcorebuf = NULL;
 }
 
 static int __init parse_crash_elf64_headers(void)
@@ -526,31 +511,31 @@ static int __init parse_crash_elf64_headers(void)
         }
 
         /* Read in all elf headers. */
-        elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
-        elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
+        elfcorebuf_sz_orig = sizeof(Elf64_Ehdr) +
+                                ehdr.e_phnum * sizeof(Elf64_Phdr);
+        elfcorebuf_sz = elfcorebuf_sz_orig;
+        elfcorebuf = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+                                              get_order(elfcorebuf_sz_orig));
         if (!elfcorebuf)
                 return -ENOMEM;
         addr = elfcorehdr_addr;
-        rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
-        if (rc < 0) {
-                kfree(elfcorebuf);
-                return rc;
-        }
+        rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0);
+        if (rc < 0)
+                goto fail;
 
         /* Merge all PT_NOTE headers into one. */
         rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
-        if (rc) {
-                kfree(elfcorebuf);
-                return rc;
-        }
+        if (rc)
+                goto fail;
         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);
+        if (rc)
+                goto fail;
+        set_vmcore_list_offsets(elfcorebuf_sz, &vmcore_list);
         return 0;
+fail:
+        free_elfcorebuf();
+        return rc;
 }
 
 static int __init parse_crash_elf32_headers(void)
@@ -581,31 +566,30 @@ static int __init parse_crash_elf32_headers(void)
         }
 
         /* Read in all elf headers. */
-        elfcorebuf_sz = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
-        elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
+        elfcorebuf_sz_orig = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
+        elfcorebuf_sz = elfcorebuf_sz_orig;
+        elfcorebuf = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+                                              get_order(elfcorebuf_sz_orig));
         if (!elfcorebuf)
                 return -ENOMEM;
         addr = elfcorehdr_addr;
-        rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
-        if (rc < 0) {
-                kfree(elfcorebuf);
-                return rc;
-        }
+        rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0);
+        if (rc < 0)
+                goto fail;
 
         /* Merge all PT_NOTE headers into one. */
         rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
-        if (rc) {
-                kfree(elfcorebuf);
-                return rc;
-        }
+        if (rc)
+                goto fail;
         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);
+        if (rc)
+                goto fail;
+        set_vmcore_list_offsets(elfcorebuf_sz, &vmcore_list);
         return 0;
+fail:
+        free_elfcorebuf();
+        return rc;
 }
 
 static int __init parse_crash_elf_headers(void)
@@ -629,14 +613,14 @@ static int __init parse_crash_elf_headers(void)
                         return rc;
 
                 /* Determine vmcore size. */
-                vmcore_size = get_vmcore_size_elf64(elfcorebuf);
+                vmcore_size = get_vmcore_size_elf64(elfcorebuf, elfcorebuf_sz);
         } 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);
+                vmcore_size = get_vmcore_size_elf32(elfcorebuf, elfcorebuf_sz);
         } else {
                 pr_warn("Warning: Core image elf header is not sane\n");
                 return -EINVAL;
@@ -683,7 +667,6 @@ void vmcore_cleanup(void)
                 list_del(&m->list);
                 kfree(m);
         }
-        kfree(elfcorebuf);
-        elfcorebuf = NULL;
+        free_elfcorebuf();
 }
 EXPORT_SYMBOL_GPL(vmcore_cleanup);