[PATCH v2 4/5] makedumpfile: Add --non-mmap option to disable mmap() manually

[WANG Chao]

This is a backport of the following upstream commit:

commit a895dc8
Author: Atsushi Kumagai <kumagai-atsushi(a)mxc.nes.nec.co.jp&gt;
Date:   Thu Dec 12 16:40:12 2013 +0900

    [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(a)mxc.nes.nec.co.jp&gt;

Having this patch, user can switch between mmap() and read() when
accessing vmcore. Whenever user feels necessary to use readmem on vmcore
(buggy code in mmap path, debug purpose, etc.), --non-mmap can do this
favor.

Signed-off-by: WANG Chao <chaowang(a)redhat.com&gt;
---
 ...-non-mmap-option-to-disable-mmap-manually.patch | 161 +++++++++++++++++++++
 kexec-tools.spec                                   |   2 +
 2 files changed, 163 insertions(+)
 create mode 100644
kexec-tools-2.0.4-makedumpfile-Add-non-mmap-option-to-disable-mmap-manually.patch

diff --git
a/kexec-tools-2.0.4-makedumpfile-Add-non-mmap-option-to-disable-mmap-manually.patch
b/kexec-tools-2.0.4-makedumpfile-Add-non-mmap-option-to-disable-mmap-manually.patch
new file mode 100644
index 0000000..8a9ee47
--- /dev/null
+++ b/kexec-tools-2.0.4-makedumpfile-Add-non-mmap-option-to-disable-mmap-manually.patch
@@ -0,0 +1,161 @@
+From a895dc8f2a17f7dac9d3d63de1cea4720557625d Mon Sep 17 00:00:00 2001
+From: Atsushi Kumagai <kumagai-atsushi(a)mxc.nes.nec.co.jp&gt;
+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(a)mxc.nes.nec.co.jp&gt;
+---
+ 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
+
diff --git a/kexec-tools.spec b/kexec-tools.spec
index 1edd4ed..c83cc64 100644
--- a/kexec-tools.spec
+++ b/kexec-tools.spec
@@ -92,6 +92,7 @@ Patch610:
kexec-tools-2.0.4-makedumpfile-cache-Reuse-entry-in-pending-list.patch
 Patch612: kexec-tools-2.0.4-makedumpfile-Understand-v3.11-rc4-dmesg.patch
 Patch613:
kexec-tools-2.0.4-makedumpfile-Assign-non-printable-value-as-short-option.patch
 Patch614: kexec-tools-2.0.4-makedumpfile-Add-help-and-man-message-for-help.patch
+Patch615:
kexec-tools-2.0.4-makedumpfile-Add-non-mmap-option-to-disable-mmap-manually.patch
 
 %description
 kexec-tools provides /sbin/kexec binary that facilitates a new
@@ -137,6 +138,7 @@ tar -z -x -v -f %{SOURCE19}
 %patch302 -p1
 %patch613 -p1
 %patch614 -p1
+%patch615 -p1
 
 tar -z -x -v -f %{SOURCE13}
 
-- 
1.8.4.2