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authorDaisuke HATAYAMA <d.hatayama@jp.fujitsu.com>2010-03-05 13:44:05 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-06 11:26:45 -0800
commit05f47fda9fc5b17bfab189e9d54228025befc996 (patch)
treef42e4f13eed3d52022a629e6697c96f6155c9d66 /fs/binfmt_elf_fdpic.c
parent12bac0d9f4dbf3445a0319beee848d15fa32775e (diff)
downloadlinux-linaro-stable-05f47fda9fc5b17bfab189e9d54228025befc996.tar.gz
coredump: unify dump_seek() implementations for each binfmt_*.c
The current ELF dumper can produce broken corefiles if program headers exceed 65535. In particular, the program in 64-bit environment often demands more than 65535 mmaps. If you google max_map_count, then you can find many users facing this problem. Solaris has already dealt with this issue, and other OSes have also adopted the same method as in Solaris. Currently, Sun's document and AMD 64 ABI include the description for the extension, where they call the extension Extended Numbering. See Reference for further information. I believe that linux kernel should adopt the same way as they did, so I've written this patch. I am also preparing for patches of GDB and binutils. How to fix ========== In new dumping process, there are two cases according to weather or not the number of program headers is equal to or more than 65535. - if less than 65535, the produced corefile format is exactly the same as the ordinary one. - if equal to or more than 65535, then e_phnum field is set to newly introduced constant PN_XNUM(0xffff) and the actual number of program headers is set to sh_info field of the section header at index 0. Compatibility Concern ===================== * As already mentioned in Summary, Sun and AMD64 has already adopted this. See Reference. * There are four combinations according to whether kernel and userland tools are respectively modified or not. The next table summarizes shortly for each combination. --------------------------------------------- Original Kernel | Modified Kernel --------------------------------------------- < 65535 | >= 65535 | < 65535 | >= 65535 ------------------------------------------------------------- Original Tools | OK | broken | OK | broken (#) ------------------------------------------------------------- Modified Tools | OK | broken | OK | OK ------------------------------------------------------------- Note that there is no case that `OK' changes to `broken'. (#) Although this case remains broken, O-M behaves better than O-O. That is, while in O-O case e_phnum field would be extremely small due to integer overflow, in O-M case it is guaranteed to be at least 65535 by being set to PN_XNUM(0xFFFF), much closer to the actual correct value than the O-O case. Test Program ============ Here is a test program mkmmaps.c that is useful to produce the corefile with many mmaps. To use this, please take the following steps: $ ulimit -c unlimited $ sysctl vm.max_map_count=70000 # default 65530 is too small $ sysctl fs.file-max=70000 $ mkmmaps 65535 Then, the program will abort and a corefile will be generated. If failed, there are two cases according to the error message displayed. * ``out of memory'' means vm.max_map_count is still smaller * ``too many open files'' means fs.file-max is still smaller So, please change it to a larger value, and then retry it. mkmmaps.c == #include <stdio.h> #include <stdlib.h> #include <sys/mman.h> #include <fcntl.h> #include <unistd.h> int main(int argc, char **argv) { int maps_num; if (argc < 2) { fprintf(stderr, "mkmmaps [number of maps to be created]\n"); exit(1); } if (sscanf(argv[1], "%d", &maps_num) == EOF) { perror("sscanf"); exit(2); } if (maps_num < 0) { fprintf(stderr, "%d is invalid\n", maps_num); exit(3); } for (; maps_num > 0; --maps_num) { if (MAP_FAILED == mmap((void *)NULL, (size_t) 1, PROT_READ, MAP_SHARED | MAP_ANONYMOUS, (int) -1, (off_t) NULL)) { perror("mmap"); exit(4); } } abort(); { char buffer[128]; sprintf(buffer, "wc -l /proc/%u/maps", getpid()); system(buffer); } return 0; } Tested on i386, ia64 and um/sys-i386. Built on sh4 (which covers fs/binfmt_elf_fdpic.c) References ========== - Sun microsystems: Linker and Libraries. Part No: 817-1984-17, September 2008. URL: http://docs.sun.com/app/docs/doc/817-1984 - System V ABI AMD64 Architecture Processor Supplement Draft Version 0.99., May 11, 2009. URL: http://www.x86-64.org/ This patch: There are three different definitions for dump_seek() functions in binfmt_aout.c, binfmt_elf.c and binfmt_elf_fdpic.c, respectively. The only for binfmt_elf.c. My next patch will move dump_seek() into a header file in order to share the same implementations for dump_write() and dump_seek(). As the first step, this patch unify these three definitions for dump_seek() by applying the past commits that have been applied only for binfmt_elf.c. Specifically, the modification made here is part of the following commits: * d025c9db7f31fc0554ce7fb2dfc78d35a77f3487 * 7f14daa19ea36b200d237ad3ac5826ae25360461 This patch does not change a shape of corefiles. Signed-off-by: Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: David Howells <dhowells@redhat.com> Cc: Greg Ungerer <gerg@snapgear.com> Cc: Roland McGrath <roland@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andi Kleen <andi@firstfloor.org> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_elf_fdpic.c')
-rw-r--r--fs/binfmt_elf_fdpic.c59
1 files changed, 38 insertions, 21 deletions
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 18d77297ccc8..32d9b44c3cb9 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1226,11 +1226,22 @@ static int dump_write(struct file *file, const void *addr, int nr)
static int dump_seek(struct file *file, loff_t off)
{
- if (file->f_op->llseek) {
- if (file->f_op->llseek(file, off, SEEK_SET) != off)
+ if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
+ if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
return 0;
} else {
- file->f_pos = off;
+ char *buf = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!buf)
+ return 0;
+ while (off > 0) {
+ unsigned long n = off;
+ if (n > PAGE_SIZE)
+ n = PAGE_SIZE;
+ if (!dump_write(file, buf, n))
+ return 0;
+ off -= n;
+ }
+ free_page((unsigned long)buf);
}
return 1;
}
@@ -1313,30 +1324,35 @@ static int notesize(struct memelfnote *en)
/* #define DEBUG */
-#define DUMP_WRITE(addr, nr) \
- do { if (!dump_write(file, (addr), (nr))) return 0; } while(0)
-#define DUMP_SEEK(off) \
- do { if (!dump_seek(file, (off))) return 0; } while(0)
+#define DUMP_WRITE(addr, nr, foffset) \
+ do { if (!dump_write(file, (addr), (nr))) return 0; *foffset += (nr); } while(0)
-static int writenote(struct memelfnote *men, struct file *file)
+static int alignfile(struct file *file, loff_t *foffset)
{
- struct elf_note en;
+ static const char buf[4] = { 0, };
+ DUMP_WRITE(buf, roundup(*foffset, 4) - *foffset, foffset);
+ return 1;
+}
+static int writenote(struct memelfnote *men, struct file *file,
+ loff_t *foffset)
+{
+ struct elf_note en;
en.n_namesz = strlen(men->name) + 1;
en.n_descsz = men->datasz;
en.n_type = men->type;
- DUMP_WRITE(&en, sizeof(en));
- DUMP_WRITE(men->name, en.n_namesz);
- /* XXX - cast from long long to long to avoid need for libgcc.a */
- DUMP_SEEK(roundup((unsigned long)file->f_pos, 4)); /* XXX */
- DUMP_WRITE(men->data, men->datasz);
- DUMP_SEEK(roundup((unsigned long)file->f_pos, 4)); /* XXX */
+ DUMP_WRITE(&en, sizeof(en), foffset);
+ DUMP_WRITE(men->name, en.n_namesz, foffset);
+ if (!alignfile(file, foffset))
+ return 0;
+ DUMP_WRITE(men->data, men->datasz, foffset);
+ if (!alignfile(file, foffset))
+ return 0;
return 1;
}
#undef DUMP_WRITE
-#undef DUMP_SEEK
#define DUMP_WRITE(addr, nr) \
if ((size += (nr)) > cprm->limit || \
@@ -1552,7 +1568,7 @@ static int elf_fdpic_dump_segments(struct file *file, size_t *size,
err = -EIO;
kunmap(page);
page_cache_release(page);
- } else if (!dump_seek(file, file->f_pos + PAGE_SIZE))
+ } else if (!dump_seek(file, PAGE_SIZE))
err = -EFBIG;
if (err)
goto out;
@@ -1605,7 +1621,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
int i;
struct vm_area_struct *vma;
struct elfhdr *elf = NULL;
- loff_t offset = 0, dataoff;
+ loff_t offset = 0, dataoff, foffset;
int numnote;
struct memelfnote *notes = NULL;
struct elf_prstatus *prstatus = NULL; /* NT_PRSTATUS */
@@ -1730,6 +1746,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
DUMP_WRITE(elf, sizeof(*elf));
offset += sizeof(*elf); /* Elf header */
offset += (segs+1) * sizeof(struct elf_phdr); /* Program headers */
+ foffset = offset;
/* Write notes phdr entry */
{
@@ -1786,7 +1803,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
/* write out the notes section */
for (i = 0; i < numnote; i++)
- if (!writenote(notes + i, cprm->file))
+ if (!writenote(notes + i, cprm->file, &foffset))
goto end_coredump;
/* write out the thread status notes section */
@@ -1795,11 +1812,11 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
list_entry(t, struct elf_thread_status, list);
for (i = 0; i < tmp->num_notes; i++)
- if (!writenote(&tmp->notes[i], cprm->file))
+ if (!writenote(&tmp->notes[i], cprm->file, &foffset))
goto end_coredump;
}
- if (!dump_seek(cprm->file, dataoff))
+ if (!dump_seek(cprm->file, dataoff - foffset))
goto end_coredump;
if (elf_fdpic_dump_segments(cprm->file, &size, &cprm->limit,