[PATCH 2/2] makedumpfile: make the incomplete vmcore generated by ENOSPC error analyzable

["Wang, Xiao/Wang Xiao" <wangx.fnst@cn.fujitsu.com>]

Since the incomplete vmcore 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 vmcore file to make it analyzable
by crash utility. As there are two formats of the vmcore file, different
methods are needed to deal with each of them,

elf:
Modify the value of the PT_LOAD program header to reflect the actual size
of the incomplete vmcore file. This method can't be used to modify the
vmcore written in flattened mode.

kdump-compressed:
Dump the bitmap before any page header and page data.

Signed-of-by: Wang Xiao <wangx.fnst@cn.fujitsu.com>
---
  makedumpfile.c |  150 
+++++++++++++++++++++++++++++++++++++++++++++++++++++---
  1 files changed, 143 insertions(+), 7 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index ce4a866..debc15b 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3621,6 +3621,128 @@ write_cache(struct cache_data *cd, void *buf, 
size_t size)
  }

  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;
+
+	if (start_offset >= end_offset) {
+		ERRMSG("The start offset of diskspace to be reserved must smaller than "
+		       "the end offset.\n");
+		return FALSE;
+	}
+
+	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;
+}
+
+int
+check_and_modify_elf_header() {
+	int i, phnum;
+	off_t file_end, offset, end_offset;
+	Elf64_Ehdr ehdr64;
+	Elf32_Ehdr ehdr32;
+	Elf64_Phdr phdr64;
+	Elf32_Phdr phdr32;
+
+	/*
+	 * the is_elf64_memory() function still can be used.
+	 */
+	if (is_elf64_memory()) { /* ELF64 */
+		if (!get_elf64_ehdr(info->fd_dumpfile, info->name_dumpfile, &ehdr64)) {
+			ERRMSG("Can't get ehdr64.\n");
+			return FALSE;
+		}
+		phnum = ehdr64.e_phnum;
+	} else { /* ELF32 */
+		if (!get_elf32_ehdr(info->fd_dumpfile, info->name_dumpfile, &ehdr32)) {
+			ERRMSG("Can't get ehdr32.\n");
+			return FALSE;
+		}
+		phnum = ehdr32.e_phnum;
+	}
+
+	file_end = lseek(info->fd_dumpfile, 0, SEEK_END);
+	if (file_end < 0) {
+		ERRMSG("Can't detect the size of %s. %s\n",
+		       info->name_dumpfile,
+		       strerror(errno));
+		return FALSE;
+	}
+
+	for (i = 0; i < phnum; i++) {
+		if (is_elf64_memory()) {
+			if (!get_elf64_phdr(info->fd_dumpfile,
+			                    info->name_dumpfile,
+			                    i, &phdr64)) {
+				ERRMSG("Can't find Phdr %d.\n", i);
+				return FALSE;
+			}
+
+			offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) * i;
+			end_offset = phdr64.p_offset + phdr64.p_filesz;
+
+			/*
+			 * Check the program header and modify its value according
+			 * to the actual written size.
+			 */
+			if (file_end >= end_offset)
+				continue;
+			else if (file_end >= phdr64.p_offset && file_end < end_offset)
+				phdr64.p_filesz = file_end - phdr64.p_offset;
+			else if (file_end < phdr64.p_offset)
+				memset(&phdr64, 0, sizeof(Elf64_Phdr));
+
+			if (!write_buffer(info->fd_dumpfile, offset, &phdr64,
+			                  sizeof(Elf64_Phdr), info->name_dumpfile))
+				return FALSE;
+		} else {
+			if (!get_elf32_phdr(info->fd_dumpfile,
+			                    info->name_dumpfile,
+			                    i, &phdr32)) {
+				ERRMSG("Can't find Phdr %d.\n", i);
+				return FALSE;
+			}
+
+			offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr) * i;
+			end_offset = phdr32.p_offset + phdr32.p_filesz;
+
+			if (file_end >= end_offset)
+				continue;
+			else if (file_end >= phdr32.p_offset && file_end < end_offset)
+				phdr32.p_filesz = file_end - phdr32.p_offset;
+			else if (file_end < phdr32.p_offset)
+				memset(&phdr32, 0, sizeof(Elf32_Phdr));
+
+			if (!write_buffer(info->fd_dumpfile, offset, &phdr32,
+			                  sizeof(Elf32_Phdr), info->name_dumpfile))
+				return FALSE;
+		}
+	}
+
+	return TRUE;
+}
+
+int
  write_cache_bufsz(struct cache_data *cd)
  {
  	if (!cd->buf_size)
@@ -5432,6 +5554,13 @@ 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.
  	 */
@@ -6956,11 +7085,11 @@ write_kdump_pages_and_bitmap_cyclic(struct 
cache_data *cd_header, struct cache_d
  		if (!exclude_unnecessary_pages_cyclic(&cycle))
  			return FALSE;

-		if (!write_kdump_pages_cyclic(cd_header, cd_page, &pd_zero,
-					&offset_data, &cycle))
+		if (!write_kdump_bitmap2_cyclic(&cycle))
  			return FALSE;

-		if (!write_kdump_bitmap2_cyclic(&cycle))
+		if (!write_kdump_pages_cyclic(cd_header, cd_page, &pd_zero,
+					&offset_data, &cycle))
  			return FALSE;
  	}

@@ -7906,10 +8035,10 @@ writeout_dumpfile(void)
  			goto out;
  		if (info->flag_cyclic) {
  			if (!write_elf_pages_cyclic(&cd_header, &cd_page))
-				goto out;
+				goto chk_enospc;
  		} else {
  			if (!write_elf_pages(&cd_header, &cd_page))
-				goto out;
+				goto chk_enospc;
  		}
  		if (!write_elf_eraseinfo(&cd_header))
  			goto out;
@@ -7923,12 +8052,12 @@ writeout_dumpfile(void)
  	} else {
  		if (!write_kdump_header())
  			goto out;
+		if (!write_kdump_bitmap())
+			goto out;
  		if (!write_kdump_pages(&cd_header, &cd_page))
  			goto out;
  		if (!write_kdump_eraseinfo(&cd_page))
  			goto out;
-		if (!write_kdump_bitmap())
-			goto out;
  	}
  	if (info->flag_flatten) {
  		if (!write_end_flat_header())
@@ -7936,6 +8065,13 @@ writeout_dumpfile(void)
  	}

  	ret = TRUE;
+chk_enospc:
+	if ((ret == FALSE) && info->flag_nospace && !info->flag_flatten) {
+		if (!write_cache_bufsz(&cd_header))
+			goto out;
+		if (!check_and_modify_elf_header())
+			ERRMSG("Can't modify the elf header.\n");
+	}
  out:
  	free_cache_data(&cd_header);
  	free_cache_data(&cd_page);
-- 
1.7.1


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