[PATCH v3 2/3] make the incomplete dumpfile generated by ENOSPC error analyzable

[Zhou Wenjian]

From: Wang Xiao <wangx.fnst at cn.fujitsu.com>

Since the incomplete dumpfile generated by ENOSPC error can't be anylyzed
by crash utility, but sometimes this file may contain important information
and the panic problem won't be reproduced, then we came up with an idea to
modify the exist data of the incomplete dumpfile to make it analyzable by
crash utility. And each of those dumpfiles has a flag to indicate that it
has been modified. As there are two formats of these dumpfiles, different
methods and flags are needed to deal with each of them,

elf:
This format use the "e_flags" of "elf header" to indicate that it has been
modified.

The method of dealing with "kdump-compressed" format dumpfiles is
implemented
in the next patch.

Signed-of-by: Wang Xiao <wangx.fnst at cn.fujitsu.com>
Singed-of-by: Zhou Wenjian <zhouwj-fnst at cn.fujitsu.com>
---
 makedumpfile.c |  115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 111 insertions(+), 4 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index b4d43d8..141d290 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -24,6 +24,7 @@
 #include <ctype.h>
 #include <sys/time.h>
 #include <limits.h>
+#include <assert.h>
 
 struct symbol_table	symbol_table;
 struct size_table	size_table;
@@ -3768,6 +3769,93 @@ read_flat_data_header(struct makedumpfile_data_header *fdh)
 }
 
 int
+reserve_diskspace(int fd, off_t start_offset, off_t end_offset, char *file_name)
+{
+	size_t buf_size;
+	char *buf = NULL;
+
+	int ret = FALSE;
+
+	assert(start_offset < end_offset);
+	buf_size = end_offset - start_offset;
+
+	if ((buf = malloc(buf_size)) == NULL) {
+		ERRMSG("Can't allocate memory for the size of reserved diskspace. %s\n",
+		       strerror(errno));
+		return FALSE;
+	}
+
+	memset(buf, 0, buf_size);
+	if (!write_buffer(fd, start_offset, buf, buf_size, file_name))
+		goto out;
+
+	ret = TRUE;
+out:
+	if (buf != NULL) {
+		free(buf);
+	}
+
+	return ret;
+}
+
+#define DUMP_ELF_INCOMPLETE 0x1
+int
+check_and_modify_elf_headers(char *filename)
+{
+	int fd, ret = FALSE;
+	Elf64_Ehdr ehdr64;
+	Elf32_Ehdr ehdr32;
+
+	if ((fd = open(filename, O_RDWR)) < 0) {
+		ERRMSG("Can't open the dump file(%s). %s\n",
+		       filename, strerror(errno));
+		return FALSE;
+	}
+
+	/*
+	 * the is_elf64_memory() function still can be used.
+	 */
+	/*
+	 * Set the incomplete flag to the e_flags of elf header.
+	 */
+	if (is_elf64_memory()) { /* ELF64 */
+		if (!get_elf64_ehdr(fd, filename, &ehdr64)) {
+			ERRMSG("Can't get ehdr64.\n");
+			goto out_close_file;
+		}
+		ehdr64.e_flags |= DUMP_ELF_INCOMPLETE;
+		if (!write_buffer(fd, 0, &ehdr64, sizeof(Elf64_Ehdr), filename))
+			goto out_close_file;
+
+	} else { /* ELF32 */
+		if (!get_elf32_ehdr(fd, filename, &ehdr32)) {
+			ERRMSG("Can't get ehdr32.\n");
+			goto out_close_file;
+		}
+		ehdr32.e_flags |= DUMP_ELF_INCOMPLETE;
+		if (!write_buffer(fd, 0, &ehdr32, sizeof(Elf32_Ehdr), filename))
+			goto out_close_file;
+
+	}
+	ret = TRUE;
+out_close_file:
+	if (close(fd) < 0) {
+		ERRMSG("Can't close the dump file(%s). %s\n",
+		       filename, strerror(errno));
+	}
+	return ret;
+}
+
+int
+check_and_modify_headers()
+{
+	if (info->flag_elf_dumpfile)
+		return check_and_modify_elf_headers(info->name_dumpfile);
+	return FALSE;
+}
+
+
+int
 rearrange_dumpdata(void)
 {
 	int read_size, tmp_read_size;
@@ -5498,6 +5586,13 @@ write_elf_header(struct cache_data *cd_header)
 	size_note          = note.p_filesz;
 
 	/*
+	 * Reserve a space to store the whole program headers.
+	 */
+	if (!reserve_diskspace(cd_header->fd, cd_header->offset,
+				offset_note_dumpfile, cd_header->file_name))
+		goto out;
+
+	/*
 	 * Modify the note size in PT_NOTE header to accomodate eraseinfo data.
 	 * Eraseinfo will be written later.
 	 */
@@ -8015,10 +8110,10 @@ writeout_dumpfile(void)
 			goto out;
 		if (info->flag_cyclic) {
 			if (!write_elf_pages_cyclic(&cd_header, &cd_page))
-				goto out;
+				goto write_cache_enospc;
 		} else {
 			if (!write_elf_pages(&cd_header, &cd_page))
-				goto out;
+				goto write_cache_enospc;
 		}
 		if (!write_elf_eraseinfo(&cd_header))
 			goto out;
@@ -8045,6 +8140,11 @@ writeout_dumpfile(void)
 	}
 
 	ret = TRUE;
+write_cache_enospc:
+	if ((ret == FALSE) && info->flag_nospace && !info->flag_flatten) {
+		if (!write_cache_bufsz(&cd_header))
+			ERRMSG("This dumpfile may lost some important data.\n");
+	}
 out:
 	free_cache_data(&cd_header);
 	free_cache_data(&cd_page);
@@ -8237,8 +8337,15 @@ retry:
 		 * to create a dumpfile with it again.
 		 */
 		num_retry++;
-		if ((info->dump_level = get_next_dump_level(num_retry)) < 0)
- 			return FALSE;
+		if ((info->dump_level = get_next_dump_level(num_retry)) < 0) {
+			if (!info->flag_flatten) {
+				if (check_and_modify_headers())
+					MSG("This is an incomplete dumpfile,"
+						" but might analyzable.\n");
+			}
+
+			return FALSE;
+		}
 		MSG("Retry to create a dumpfile by dump_level(%d).\n",
 		    info->dump_level);
 		if (!delete_dumpfile())
-- 
1.7.1