From a895dc8f2a17f7dac9d3d63de1cea4720557625d Mon Sep 17 00:00:00 2001
From: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Date: Thu, 12 Dec 2013 16:40:12 +0900
Subject: [PATCH 1/2] [PATCH] Add --non-mmap option to disable mmap() manually.

When --non-mmap option is specified, makedumpfile doesn't use
mmap() even if /proc/vmcore supports mmap().

Signed-off-by: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
---
 makedumpfile.8 | 11 +++++++++++
 makedumpfile.c | 29 +++++++++++++++++++----------
 makedumpfile.h |  9 +++++++++
 print_info.c   |  6 ++++++
 4 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/makedumpfile-1.5.4/makedumpfile.8 b/makedumpfile-1.5.4/makedumpfile.8
index f50a011..227b6f7 100644
--- a/makedumpfile-1.5.4/makedumpfile.8
+++ b/makedumpfile-1.5.4/makedumpfile.8
@@ -395,6 +395,17 @@ If you feel the cyclic mode is too slow, please try this mode.
 # makedumpfile \-\-non\-cyclic \-d 31 \-x vmlinux /proc/vmcore dumpfile
 
 .TP
+\fB\-\-non\-mmap\fR
+Never use \fBmmap(2)\fR to read \fIVMCORE\fR even if it supports \fBmmap(2)\fR.
+Generally, reading \fIVMCORE\fR with \fBmmap(2)\fR is faster than without it,
+so ordinary users don't need to specify this option.
+This option is mainly for debugging.
+.br
+.B Example:
+.br
+# makedumpfile \-\-non\-mmap \-d 31 \-x vmlinux /proc/vmcore dumpfile
+
+.TP
 \fB\-\-xen-syms\fR \fIXEN-SYMS\fR
 Specify the \fIXEN-SYMS\fR with debug information to analyze the xen's memory usage.
 This option extracts the part of xen and domain-0.
diff --git a/makedumpfile-1.5.4/makedumpfile.c b/makedumpfile-1.5.4/makedumpfile.c
index 600fb5d..b3af28b 100644
--- a/makedumpfile-1.5.4/makedumpfile.c
+++ b/makedumpfile-1.5.4/makedumpfile.c
@@ -272,7 +272,7 @@ update_mmap_range(off_t offset, int initial) {
 static int
 is_mapped_with_mmap(off_t offset) {
 
-	if (info->flag_usemmap
+	if (info->flag_usemmap == MMAP_ENABLE
 	    && offset >= info->mmap_start_offset
 	    && offset < info->mmap_end_offset)
 		return TRUE;
@@ -320,7 +320,7 @@ read_from_vmcore(off_t offset, void *bufptr, unsigned long size)
 {
 	const off_t failed = (off_t)-1;
 
-	if (info->flag_usemmap) {
+	if (info->flag_usemmap == MMAP_ENABLE) {
 		if (!read_with_mmap(offset, bufptr, size)) {
 			ERRMSG("Can't read the dump memory(%s) with mmap().\n",
 			       info->name_memory);
@@ -3175,14 +3175,14 @@ out:
 	if (info->dump_level & DL_EXCLUDE_FREE)
 		setup_page_is_buddy();
 
-	if (!initialize_mmap()) {
-		/* this kernel does not support mmap of vmcore */
-		DEBUG_MSG("Kernel can't mmap vmcore, using reads.\n");
-		info->flag_usemmap = FALSE;
+	if (info->flag_usemmap == MMAP_TRY && initialize_mmap()) {
+		DEBUG_MSG("mmap() is available on the kernel.\n");
+		info->flag_usemmap = MMAP_ENABLE;
 	} else {
-		DEBUG_MSG("read %s with mmap()\n", info->name_memory);
-		info->flag_usemmap = TRUE;
-	}
+		DEBUG_MSG("The kernel doesn't support mmap(),");
+		DEBUG_MSG("read() will be used instead.\n");
+		info->flag_usemmap = MMAP_DISABLE;
+        }
 
 	return TRUE;
 }
@@ -8947,6 +8947,7 @@ static struct option longopts[] = {
 	{"non-cyclic", no_argument, NULL, OPT_NON_CYCLIC},
 	{"cyclic-buffer", required_argument, NULL, OPT_CYCLIC_BUFFER},
 	{"eppic", required_argument, NULL, OPT_EPPIC},
+	{"non-mmap", no_argument, NULL, OPT_NON_MMAP},
 	{0, 0, 0, 0}
 };
 
@@ -8972,7 +8973,12 @@ main(int argc, char *argv[])
 	 * By default, makedumpfile works in constant memory space.
 	 */
 	info->flag_cyclic = TRUE;
-	
+
+	/*
+	 * By default, makedumpfile try to use mmap(2) to read /proc/vmcore.
+	 */
+	info->flag_usemmap = MMAP_TRY;
+
 	info->block_order = DEFAULT_ORDER;
 	message_level = DEFAULT_MSG_LEVEL;
 	while ((opt = getopt_long(argc, argv, "b:cDd:EFfg:hi:lpRvXx:", longopts,
@@ -9069,6 +9075,9 @@ main(int argc, char *argv[])
 		case OPT_NON_CYCLIC:
 			info->flag_cyclic = FALSE;
 			break;
+		case OPT_NON_MMAP:
+			info->flag_usemmap = MMAP_DISABLE;
+			break;
 		case OPT_XEN_VMCOREINFO:
 			info->flag_read_vmcoreinfo = 1;
 			info->name_vmcoreinfo = optarg;
diff --git a/makedumpfile-1.5.4/makedumpfile.h b/makedumpfile-1.5.4/makedumpfile.h
index 517e16e..fe88eff 100644
--- a/makedumpfile-1.5.4/makedumpfile.h
+++ b/makedumpfile-1.5.4/makedumpfile.h
@@ -128,6 +128,14 @@ enum {
 	MADDR_XEN
 };
 
+/*
+ * State of mmap(2)
+ */
+enum {
+	MMAP_DISABLE,
+	MMAP_TRY,
+	MMAP_ENABLE,
+};
 
 static inline int
 test_bit(int nr, unsigned long addr)
@@ -1741,6 +1749,7 @@ struct elf_prstatus {
 #define OPT_NON_CYCLIC          OPT_START+10
 #define OPT_CYCLIC_BUFFER       OPT_START+11
 #define OPT_EPPIC               OPT_START+12
+#define OPT_NON_MMAP            OPT_START+13
 
 /*
  * Function Prototype.
diff --git a/makedumpfile-1.5.4/print_info.c b/makedumpfile-1.5.4/print_info.c
index d7a8600..90b6cee 100644
--- a/makedumpfile-1.5.4/print_info.c
+++ b/makedumpfile-1.5.4/print_info.c
@@ -196,6 +196,12 @@ print_usage(void)
 	MSG("      same as v1.4.4 or before.\n");
 	MSG("      If you feel the cyclic mode is too slow, please try this mode.\n");
 	MSG("\n");
+	MSG("  [--non-mmap]:\n");
+	MSG("      Never use mmap(2) to read VMCORE even if it supports mmap(2).\n");
+	MSG("      Generally, reading VMCORE with mmap(2) is faster than without it,\n");
+	MSG("      so ordinary users don't need to specify this option.\n");
+	MSG("      This option is mainly for debugging.\n");
+	MSG("\n");
 	MSG("  [--xen-syms XEN-SYMS]:\n");
 	MSG("      Specify the XEN-SYMS to analyze Xen's memory usage.\n");
 	MSG("\n");
-- 
1.8.4.2