coredump: Ensure proper size of sparse core files
If the last section of a core file ends with an unmapped or zero page,
the size of the file does not correspond with the last dump_skip() call.
gdb complains that the file is truncated and can be confusing to users.
After all of the vma sections are written, make sure that the file size
is no smaller than the current file position.
This problem can be demonstrated with gdb's bigcore testcase on the
sparc architecture.
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 29a02da..4223702 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2298,6 +2298,7 @@
goto end_coredump;
}
}
+ dump_truncate(cprm);
if (!elf_core_write_extra_data(cprm))
goto end_coredump;
diff --git a/fs/coredump.c b/fs/coredump.c
index e525b60..ae6b056 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -833,3 +833,21 @@
return mod ? dump_skip(cprm, align - mod) : 1;
}
EXPORT_SYMBOL(dump_align);
+
+/*
+ * Ensures that file size is big enough to contain the current file
+ * postion. This prevents gdb from complaining about a truncated file
+ * if the last "write" to the file was dump_skip.
+ */
+void dump_truncate(struct coredump_params *cprm)
+{
+ struct file *file = cprm->file;
+ loff_t offset;
+
+ if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
+ offset = file->f_op->llseek(file, 0, SEEK_CUR);
+ if (i_size_read(file->f_mapping->host) < offset)
+ do_truncate(file->f_path.dentry, offset, 0, file);
+ }
+}
+EXPORT_SYMBOL(dump_truncate);