coredump: extend core dump note section to contain file names of mapped files

This note has the following format:

long count     -- how many files are mapped
long page_size -- units for file_ofs
array of [COUNT] elements of
   long start
   long end
   long file_ofs
followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: "Jonathan M. Foote" <jmfoote@cert.org>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 106 insertions, 4 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 865f9be6a2d3..28a64e769527 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -27,6 +27,7 @@
 #include <linux/compiler.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
+#include <linux/vmalloc.h>
 #include <linux/security.h>
 #include <linux/random.h>
 #include <linux/elf.h>
@@ -37,6 +38,9 @@
 #include <asm/page.h>
 #include <asm/exec.h>
 
+#ifndef user_long_t
+#define user_long_t long
+#endif
 #ifndef user_siginfo_t
 #define user_siginfo_t siginfo_t
 #endif
@@ -1386,6 +1390,93 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata,
         fill_note(note, "CORE", NT_SIGINFO, sizeof(*csigdata), csigdata);
 }
 
+#define MAX_FILE_NOTE_SIZE (4*1024*1024)
+/*
+ * Format of NT_FILE note:
+ *
+ * long count     -- how many files are mapped
+ * long page_size -- units for file_ofs
+ * array of [COUNT] elements of
+ *   long start
+ *   long end
+ *   long file_ofs
+ * followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
+ */
+static void fill_files_note(struct memelfnote *note)
+{
+        struct vm_area_struct *vma;
+        unsigned count, size, names_ofs, remaining, n;
+        user_long_t *data;
+        user_long_t *start_end_ofs;
+        char *name_base, *name_curpos;
+
+        /* *Estimated* file count and total data size needed */
+        count = current->mm->map_count;
+        size = count * 64;
+
+        names_ofs = (2 + 3 * count) * sizeof(data[0]);
+ alloc:
+        if (size >= MAX_FILE_NOTE_SIZE) /* paranoia check */
+                goto err;
+        size = round_up(size, PAGE_SIZE);
+        data = vmalloc(size);
+        if (!data)
+                goto err;
+
+        start_end_ofs = data + 2;
+        name_base = name_curpos = ((char *)data) + names_ofs;
+        remaining = size - names_ofs;
+        count = 0;
+        for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
+                struct file *file;
+                const char *filename;
+
+                file = vma->vm_file;
+                if (!file)
+                        continue;
+                filename = d_path(&file->f_path, name_curpos, remaining);
+                if (IS_ERR(filename)) {
+                        if (PTR_ERR(filename) == -ENAMETOOLONG) {
+                                vfree(data);
+                                size = size * 5 / 4;
+                                goto alloc;
+                        }
+                        continue;
+                }
+
+                /* d_path() fills at the end, move name down */
+                /* n = strlen(filename) + 1: */
+                n = (name_curpos + remaining) - filename;
+                remaining = filename - name_curpos;
+                memmove(name_curpos, filename, n);
+                name_curpos += n;
+
+                *start_end_ofs++ = vma->vm_start;
+                *start_end_ofs++ = vma->vm_end;
+                *start_end_ofs++ = vma->vm_pgoff;
+                count++;
+        }
+
+        /* Now we know exact count of files, can store it */
+        data[0] = count;
+        data[1] = PAGE_SIZE;
+        /*
+         * Count usually is less than current->mm->map_count,
+         * we need to move filenames down.
+         */
+        n = current->mm->map_count - count;
+        if (n != 0) {
+                unsigned shift_bytes = n * 3 * sizeof(data[0]);
+                memmove(name_base - shift_bytes, name_base,
+                        name_curpos - name_base);
+                name_curpos -= shift_bytes;
+        }
+
+        size = name_curpos - (char *)data;
+        fill_note(note, "CORE", NT_FILE, size, data);
+ err: ;
+}
+
 #ifdef CORE_DUMP_USE_REGSET
 #include <linux/regset.h>
 
@@ -1401,6 +1492,7 @@ struct elf_note_info {
         struct memelfnote psinfo;
         struct memelfnote signote;
         struct memelfnote auxv;
+        struct memelfnote files;
         user_siginfo_t csigdata;
         size_t size;
         int thread_notes;
@@ -1581,6 +1673,9 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
         fill_auxv_note(&info->auxv, current->mm);
         info->size += notesize(&info->auxv);
 
+        fill_files_note(&info->files);
+        info->size += notesize(&info->files);
+
         return 1;
 }
 
@@ -1611,6 +1706,8 @@ static int write_note_info(struct elf_note_info *info,
                         return 0;
                 if (first && !writenote(&info->auxv, file, foffset))
                         return 0;
+                if (first && !writenote(&info->files, file, foffset))
+                        return 0;
 
                 for (i = 1; i < info->thread_notes; ++i)
                         if (t->notes[i].data &&
@@ -1637,6 +1734,7 @@ static void free_note_info(struct elf_note_info *info)
                 kfree(t);
         }
         kfree(info->psinfo.data);
+        vfree(info->files.data);
 }
 
 #else
@@ -1713,7 +1811,7 @@ static int elf_note_info_init(struct elf_note_info *info)
         INIT_LIST_HEAD(&info->thread_list);
 
         /* Allocate space for ELF notes */
-        info->notes = kmalloc(7 * sizeof(struct memelfnote), GFP_KERNEL);
+        info->notes = kmalloc(8 * sizeof(struct memelfnote), GFP_KERNEL);
         if (!info->notes)
                 return 0;
         info->psinfo = kmalloc(sizeof(*info->psinfo), GFP_KERNEL);
@@ -1783,10 +1881,11 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
         fill_note(info->notes + 1, "CORE", NT_PRPSINFO,
                   sizeof(*info->psinfo), info->psinfo);
 
-        info->numnote = 2;
+        fill_siginfo_note(info->notes + 2, &info->csigdata, siginfo);
+        fill_auxv_note(info->notes + 3, current->mm);
+        fill_files_note(info->notes + 4);
 
-        fill_siginfo_note(&info->notes[info->numnote++], &info->csigdata, siginfo);
-        fill_auxv_note(&info->notes[info->numnote++], current->mm);
+        info->numnote = 5;
 
         /* Try to dump the FPU. */
         info->prstatus->pr_fpvalid = elf_core_copy_task_fpregs(current, regs,
@@ -1848,6 +1947,9 @@ static void free_note_info(struct elf_note_info *info)
                 kfree(list_entry(tmp, struct elf_thread_status, list));
         }
 
+        /* Free data allocated by fill_files_note(): */
+        vfree(info->notes[4].data);
+
         kfree(info->prstatus);
         kfree(info->psinfo);
         kfree(info->notes);