kexec: split crashkernel reservation code out from crash_core.c

Patch series "Split crash out from kexec and clean up related config
items", v3.

Motivation:
=============
Previously, LKP reported a building error. When investigating, it can't
be resolved reasonablly with the present messy kdump config items.

 https://lore.kernel.org/oe-kbuild-all/202312182200.Ka7MzifQ-lkp@intel.com/

The kdump (crash dumping) related config items could causes confusions:

Firstly,

CRASH_CORE enables codes including
 - crashkernel reservation;
 - elfcorehdr updating;
 - vmcoreinfo exporting;
 - crash hotplug handling;

Now fadump of powerpc, kcore dynamic debugging and kdump all selects
CRASH_CORE, while fadump
 - fadump needs crashkernel parsing, vmcoreinfo exporting, and accessing
   global variable 'elfcorehdr_addr';
 - kcore only needs vmcoreinfo exporting;
 - kdump needs all of the current kernel/crash_core.c.

So only enabling PROC_CORE or FA_DUMP will enable CRASH_CORE, this
mislead people that we enable crash dumping, actual it's not.

Secondly,

It's not reasonable to allow KEXEC_CORE select CRASH_CORE.

Because KEXEC_CORE enables codes which allocate control pages, copy
kexec/kdump segments, and prepare for switching. These codes are
shared by both kexec reboot and kdump. We could want kexec reboot,
but disable kdump. In that case, CRASH_CORE should not be selected.

 --------------------
 CONFIG_CRASH_CORE=y
 CONFIG_KEXEC_CORE=y
 CONFIG_KEXEC=y
 CONFIG_KEXEC_FILE=y
 ---------------------

Thirdly,

It's not reasonable to allow CRASH_DUMP select KEXEC_CORE.

That could make KEXEC_CORE, CRASH_DUMP are enabled independently from
KEXEC or KEXEC_FILE. However, w/o KEXEC or KEXEC_FILE, the KEXEC_CORE
code built in doesn't make any sense because no kernel loading or
switching will happen to utilize the KEXEC_CORE code.
 ---------------------
 CONFIG_CRASH_CORE=y
 CONFIG_KEXEC_CORE=y
 CONFIG_CRASH_DUMP=y
 ---------------------

In this case, what is worse, on arch sh and arm, KEXEC relies on MMU,
while CRASH_DUMP can still be enabled when !MMU, then compiling error is
seen as the lkp test robot reported in above link.

 ------arch/sh/Kconfig------
 config ARCH_SUPPORTS_KEXEC
         def_bool MMU

 config ARCH_SUPPORTS_CRASH_DUMP
         def_bool BROKEN_ON_SMP
 ---------------------------

Changes:
===========
1, split out crash_reserve.c from crash_core.c;
2, split out vmcore_infoc. from crash_core.c;
3, move crash related codes in kexec_core.c into crash_core.c;
4, remove dependency of FA_DUMP on CRASH_DUMP;
5, clean up kdump related config items;
6, wrap up crash codes in crash related ifdefs on all 8 arch-es
   which support crash dumping, except of ppc;

Achievement:
===========
With above changes, I can rearrange the config item logic as below (the right
item depends on or is selected by the left item):

    PROC_KCORE -----------> VMCORE_INFO

               |----------> VMCORE_INFO
    FA_DUMP----|
               |----------> CRASH_RESERVE

                                                    ---->VMCORE_INFO
                                                   /
                                                   |---->CRASH_RESERVE
    KEXEC      --|                                /|
                 |--> KEXEC_CORE--> CRASH_DUMP-->/-|---->PROC_VMCORE
    KEXEC_FILE --|                               \ |
                                                   \---->CRASH_HOTPLUG


    KEXEC      --|
                 |--> KEXEC_CORE (for kexec reboot only)
    KEXEC_FILE --|

Test
========
On all 8 architectures, including x86_64, arm64, s390x, sh, arm, mips,
riscv, loongarch, I did below three cases of config item setting and
building all passed. Take configs on x86_64 as exampmle here:

(1) Both CONFIG_KEXEC and KEXEC_FILE is unset, then all kexec/kdump
items are unset automatically:
# Kexec and crash features
# CONFIG_KEXEC is not set
# CONFIG_KEXEC_FILE is not set
# end of Kexec and crash features

(2) set CONFIG_KEXEC_FILE and 'make olddefconfig':
---------------
# Kexec and crash features
CONFIG_CRASH_RESERVE=y
CONFIG_VMCORE_INFO=y
CONFIG_KEXEC_CORE=y
CONFIG_KEXEC_FILE=y
CONFIG_CRASH_DUMP=y
CONFIG_CRASH_HOTPLUG=y
CONFIG_CRASH_MAX_MEMORY_RANGES=8192
# end of Kexec and crash features
---------------

(3) unset CONFIG_CRASH_DUMP in case 2 and execute 'make olddefconfig':
------------------------
# Kexec and crash features
CONFIG_KEXEC_CORE=y
CONFIG_KEXEC_FILE=y
# end of Kexec and crash features
------------------------

Note:
For ppc, it needs investigation to make clear how to split out crash
code in arch folder. Hope Hari and Pingfan can help have a look, see if
it's doable. Now, I make it either have both kexec and crash enabled, or
disable both of them altogether.


This patch (of 14):

Both kdump and fa_dump of ppc rely on crashkernel reservation.  Move the
relevant codes into separate files: crash_reserve.c,
include/linux/crash_reserve.h.

And also add config item CRASH_RESERVE to control its enabling of the
codes.  And update config items which has relationship with crashkernel
reservation.

And also change ifdeffery from CONFIG_CRASH_CORE to CONFIG_CRASH_RESERVE
when those scopes are only crashkernel reservation related.

And also rename arch/XXX/include/asm/{crash_core.h => crash_reserve.h} on
arm64, x86 and risc-v because those architectures' crash_core.h is only
related to crashkernel reservation.

[akpm@linux-foundation.org: s/CRASH_RESEERVE/CRASH_RESERVE/, per Klara Modin]
Link: https://lkml.kernel.org/r/20240124051254.67105-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20240124051254.67105-2-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Michael Kelley <mhklinux@outlook.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

4 files changed, 469 insertions, 439 deletions

diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index 946dffa048b7..8b7be71edd85 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -2,11 +2,15 @@
 
 menu "Kexec and crash features"
 
+config CRASH_RESERVE
+	bool
+
 config CRASH_CORE
 	bool
 
 config KEXEC_CORE
 	select CRASH_CORE
+	select CRASH_RESERVE
 	bool
 
 config KEXEC_ELF
@@ -96,7 +100,6 @@ config KEXEC_JUMP
 config CRASH_DUMP
 	bool "kernel crash dumps"
 	depends on ARCH_SUPPORTS_CRASH_DUMP
-	select CRASH_CORE
 	select KEXEC_CORE
 	help
 	  Generate crash dump after being started by kexec.
diff --git a/kernel/Makefile b/kernel/Makefile
index ce105a5558fc..05fa88b3ab74 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_KALLSYMS_SELFTEST) += kallsyms_selftest.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_CRASH_CORE) += crash_core.o
+obj-$(CONFIG_CRASH_RESERVE) += crash_reserve.o
 obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
 obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 49b31e59d3cc..ae0d1ce89b46 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -34,444 +34,6 @@ u32 *vmcoreinfo_note;
 /* trusted vmcoreinfo, e.g. we can make a copy in the crash memory */
 static unsigned char *vmcoreinfo_data_safecopy;
 
-/* Location of the reserved area for the crash kernel */
-struct resource crashk_res = {
-	.name  = "Crash kernel",
-	.start = 0,
-	.end   = 0,
-	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
-	.desc  = IORES_DESC_CRASH_KERNEL
-};
-struct resource crashk_low_res = {
-	.name  = "Crash kernel",
-	.start = 0,
-	.end   = 0,
-	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
-	.desc  = IORES_DESC_CRASH_KERNEL
-};
-
-/*
- * parsing the "crashkernel" commandline
- *
- * this code is intended to be called from architecture specific code
- */
-
-
-/*
- * This function parses command lines in the format
- *
- *   crashkernel=ramsize-range:size[,...][@offset]
- *
- * The function returns 0 on success and -EINVAL on failure.
- */
-static int __init parse_crashkernel_mem(char *cmdline,
-					unsigned long long system_ram,
-					unsigned long long *crash_size,
-					unsigned long long *crash_base)
-{
-	char *cur = cmdline, *tmp;
-	unsigned long long total_mem = system_ram;
-
-	/*
-	 * Firmware sometimes reserves some memory regions for its own use,
-	 * so the system memory size is less than the actual physical memory
-	 * size. Work around this by rounding up the total size to 128M,
-	 * which is enough for most test cases.
-	 */
-	total_mem = roundup(total_mem, SZ_128M);
-
-	/* for each entry of the comma-separated list */
-	do {
-		unsigned long long start, end = ULLONG_MAX, size;
-
-		/* get the start of the range */
-		start = memparse(cur, &tmp);
-		if (cur == tmp) {
-			pr_warn("crashkernel: Memory value expected\n");
-			return -EINVAL;
-		}
-		cur = tmp;
-		if (*cur != '-') {
-			pr_warn("crashkernel: '-' expected\n");
-			return -EINVAL;
-		}
-		cur++;
-
-		/* if no ':' is here, than we read the end */
-		if (*cur != ':') {
-			end = memparse(cur, &tmp);
-			if (cur == tmp) {
-				pr_warn("crashkernel: Memory value expected\n");
-				return -EINVAL;
-			}
-			cur = tmp;
-			if (end <= start) {
-				pr_warn("crashkernel: end <= start\n");
-				return -EINVAL;
-			}
-		}
-
-		if (*cur != ':') {
-			pr_warn("crashkernel: ':' expected\n");
-			return -EINVAL;
-		}
-		cur++;
-
-		size = memparse(cur, &tmp);
-		if (cur == tmp) {
-			pr_warn("Memory value expected\n");
-			return -EINVAL;
-		}
-		cur = tmp;
-		if (size >= total_mem) {
-			pr_warn("crashkernel: invalid size\n");
-			return -EINVAL;
-		}
-
-		/* match ? */
-		if (total_mem >= start && total_mem < end) {
-			*crash_size = size;
-			break;
-		}
-	} while (*cur++ == ',');
-
-	if (*crash_size > 0) {
-		while (*cur && *cur != ' ' && *cur != '@')
-			cur++;
-		if (*cur == '@') {
-			cur++;
-			*crash_base = memparse(cur, &tmp);
-			if (cur == tmp) {
-				pr_warn("Memory value expected after '@'\n");
-				return -EINVAL;
-			}
-		}
-	} else
-		pr_info("crashkernel size resulted in zero bytes\n");
-
-	return 0;
-}
-
-/*
- * That function parses "simple" (old) crashkernel command lines like
- *
- *	crashkernel=size[@offset]
- *
- * It returns 0 on success and -EINVAL on failure.
- */
-static int __init parse_crashkernel_simple(char *cmdline,
-					   unsigned long long *crash_size,
-					   unsigned long long *crash_base)
-{
-	char *cur = cmdline;
-
-	*crash_size = memparse(cmdline, &cur);
-	if (cmdline == cur) {
-		pr_warn("crashkernel: memory value expected\n");
-		return -EINVAL;
-	}
-
-	if (*cur == '@')
-		*crash_base = memparse(cur+1, &cur);
-	else if (*cur != ' ' && *cur != '\0') {
-		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-#define SUFFIX_HIGH 0
-#define SUFFIX_LOW  1
-#define SUFFIX_NULL 2
-static __initdata char *suffix_tbl[] = {
-	[SUFFIX_HIGH] = ",high",
-	[SUFFIX_LOW]  = ",low",
-	[SUFFIX_NULL] = NULL,
-};
-
-/*
- * That function parses "suffix"  crashkernel command lines like
- *
- *	crashkernel=size,[high|low]
- *
- * It returns 0 on success and -EINVAL on failure.
- */
-static int __init parse_crashkernel_suffix(char *cmdline,
-					   unsigned long long *crash_size,
-					   const char *suffix)
-{
-	char *cur = cmdline;
-
-	*crash_size = memparse(cmdline, &cur);
-	if (cmdline == cur) {
-		pr_warn("crashkernel: memory value expected\n");
-		return -EINVAL;
-	}
-
-	/* check with suffix */
-	if (strncmp(cur, suffix, strlen(suffix))) {
-		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
-		return -EINVAL;
-	}
-	cur += strlen(suffix);
-	if (*cur != ' ' && *cur != '\0') {
-		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-static __init char *get_last_crashkernel(char *cmdline,
-			     const char *name,
-			     const char *suffix)
-{
-	char *p = cmdline, *ck_cmdline = NULL;
-
-	/* find crashkernel and use the last one if there are more */
-	p = strstr(p, name);
-	while (p) {
-		char *end_p = strchr(p, ' ');
-		char *q;
-
-		if (!end_p)
-			end_p = p + strlen(p);
-
-		if (!suffix) {
-			int i;
-
-			/* skip the one with any known suffix */
-			for (i = 0; suffix_tbl[i]; i++) {
-				q = end_p - strlen(suffix_tbl[i]);
-				if (!strncmp(q, suffix_tbl[i],
-					     strlen(suffix_tbl[i])))
-					goto next;
-			}
-			ck_cmdline = p;
-		} else {
-			q = end_p - strlen(suffix);
-			if (!strncmp(q, suffix, strlen(suffix)))
-				ck_cmdline = p;
-		}
-next:
-		p = strstr(p+1, name);
-	}
-
-	return ck_cmdline;
-}
-
-static int __init __parse_crashkernel(char *cmdline,
-			     unsigned long long system_ram,
-			     unsigned long long *crash_size,
-			     unsigned long long *crash_base,
-			     const char *suffix)
-{
-	char *first_colon, *first_space;
-	char *ck_cmdline;
-	char *name = "crashkernel=";
-
-	BUG_ON(!crash_size || !crash_base);
-	*crash_size = 0;
-	*crash_base = 0;
-
-	ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
-	if (!ck_cmdline)
-		return -ENOENT;
-
-	ck_cmdline += strlen(name);
-
-	if (suffix)
-		return parse_crashkernel_suffix(ck_cmdline, crash_size,
-				suffix);
-	/*
-	 * if the commandline contains a ':', then that's the extended
-	 * syntax -- if not, it must be the classic syntax
-	 */
-	first_colon = strchr(ck_cmdline, ':');
-	first_space = strchr(ck_cmdline, ' ');
-	if (first_colon && (!first_space || first_colon < first_space))
-		return parse_crashkernel_mem(ck_cmdline, system_ram,
-				crash_size, crash_base);
-
-	return parse_crashkernel_simple(ck_cmdline, crash_size, crash_base);
-}
-
-/*
- * That function is the entry point for command line parsing and should be
- * called from the arch-specific code.
- *
- * If crashkernel=,high|low is supported on architecture, non-NULL values
- * should be passed to parameters 'low_size' and 'high'.
- */
-int __init parse_crashkernel(char *cmdline,
-			     unsigned long long system_ram,
-			     unsigned long long *crash_size,
-			     unsigned long long *crash_base,
-			     unsigned long long *low_size,
-			     bool *high)
-{
-	int ret;
-
-	/* crashkernel=X[@offset] */
-	ret = __parse_crashkernel(cmdline, system_ram, crash_size,
-				crash_base, NULL);
-#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
-	/*
-	 * If non-NULL 'high' passed in and no normal crashkernel
-	 * setting detected, try parsing crashkernel=,high|low.
-	 */
-	if (high && ret == -ENOENT) {
-		ret = __parse_crashkernel(cmdline, 0, crash_size,
-				crash_base, suffix_tbl[SUFFIX_HIGH]);
-		if (ret || !*crash_size)
-			return -EINVAL;
-
-		/*
-		 * crashkernel=Y,low can be specified or not, but invalid value
-		 * is not allowed.
-		 */
-		ret = __parse_crashkernel(cmdline, 0, low_size,
-				crash_base, suffix_tbl[SUFFIX_LOW]);
-		if (ret == -ENOENT) {
-			*low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
-			ret = 0;
-		} else if (ret) {
-			return ret;
-		}
-
-		*high = true;
-	}
-#endif
-	if (!*crash_size)
-		ret = -EINVAL;
-
-	return ret;
-}
-
-/*
- * Add a dummy early_param handler to mark crashkernel= as a known command line
- * parameter and suppress incorrect warnings in init/main.c.
- */
-static int __init parse_crashkernel_dummy(char *arg)
-{
-	return 0;
-}
-early_param("crashkernel", parse_crashkernel_dummy);
-
-#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
-static int __init reserve_crashkernel_low(unsigned long long low_size)
-{
-#ifdef CONFIG_64BIT
-	unsigned long long low_base;
-
-	low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
-	if (!low_base) {
-		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
-		return -ENOMEM;
-	}
-
-	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
-		low_base, low_base + low_size, low_size >> 20);
-
-	crashk_low_res.start = low_base;
-	crashk_low_res.end   = low_base + low_size - 1;
-#endif
-	return 0;
-}
-
-void __init reserve_crashkernel_generic(char *cmdline,
-			     unsigned long long crash_size,
-			     unsigned long long crash_base,
-			     unsigned long long crash_low_size,
-			     bool high)
-{
-	unsigned long long search_end = CRASH_ADDR_LOW_MAX, search_base = 0;
-	bool fixed_base = false;
-
-	/* User specifies base address explicitly. */
-	if (crash_base) {
-		fixed_base = true;
-		search_base = crash_base;
-		search_end = crash_base + crash_size;
-	} else if (high) {
-		search_base = CRASH_ADDR_LOW_MAX;
-		search_end = CRASH_ADDR_HIGH_MAX;
-	}
-
-retry:
-	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
-					       search_base, search_end);
-	if (!crash_base) {
-		/*
-		 * For crashkernel=size[KMG]@offset[KMG], print out failure
-		 * message if can't reserve the specified region.
-		 */
-		if (fixed_base) {
-			pr_warn("crashkernel reservation failed - memory is in use.\n");
-			return;
-		}
-
-		/*
-		 * For crashkernel=size[KMG], if the first attempt was for
-		 * low memory, fall back to high memory, the minimum required
-		 * low memory will be reserved later.
-		 */
-		if (!high && search_end == CRASH_ADDR_LOW_MAX) {
-			search_end = CRASH_ADDR_HIGH_MAX;
-			search_base = CRASH_ADDR_LOW_MAX;
-			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
-			goto retry;
-		}
-
-		/*
-		 * For crashkernel=size[KMG],high, if the first attempt was
-		 * for high memory, fall back to low memory.
-		 */
-		if (high && search_end == CRASH_ADDR_HIGH_MAX) {
-			search_end = CRASH_ADDR_LOW_MAX;
-			search_base = 0;
-			goto retry;
-		}
-		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
-			crash_size);
-		return;
-	}
-
-	if ((crash_base >= CRASH_ADDR_LOW_MAX) &&
-	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
-		memblock_phys_free(crash_base, crash_size);
-		return;
-	}
-
-	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
-		crash_base, crash_base + crash_size, crash_size >> 20);
-
-	/*
-	 * The crashkernel memory will be removed from the kernel linear
-	 * map. Inform kmemleak so that it won't try to access it.
-	 */
-	kmemleak_ignore_phys(crash_base);
-	if (crashk_low_res.end)
-		kmemleak_ignore_phys(crashk_low_res.start);
-
-	crashk_res.start = crash_base;
-	crashk_res.end = crash_base + crash_size - 1;
-}
-
-static __init int insert_crashkernel_resources(void)
-{
-	if (crashk_res.start < crashk_res.end)
-		insert_resource(&iomem_resource, &crashk_res);
-
-	if (crashk_low_res.start < crashk_low_res.end)
-		insert_resource(&iomem_resource, &crashk_low_res);
-
-	return 0;
-}
-early_initcall(insert_crashkernel_resources);
-#endif
-
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 			  void **addr, unsigned long *sz)
 {
diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
new file mode 100644
index 000000000000..bbb6c3cb00e4
--- /dev/null
+++ b/kernel/crash_reserve.c
@@ -0,0 +1,464 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * crash.c - kernel crash support code.
+ * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
+ */
+
+#include <linux/buildid.h>
+#include <linux/init.h>
+#include <linux/utsname.h>
+#include <linux/vmalloc.h>
+#include <linux/sizes.h>
+#include <linux/kexec.h>
+#include <linux/memory.h>
+#include <linux/cpuhotplug.h>
+#include <linux/memblock.h>
+#include <linux/kexec.h>
+#include <linux/kmemleak.h>
+
+#include <asm/page.h>
+#include <asm/sections.h>
+
+#include <crypto/sha1.h>
+
+#include "kallsyms_internal.h"
+#include "kexec_internal.h"
+
+/* Location of the reserved area for the crash kernel */
+struct resource crashk_res = {
+	.name  = "Crash kernel",
+	.start = 0,
+	.end   = 0,
+	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
+	.desc  = IORES_DESC_CRASH_KERNEL
+};
+struct resource crashk_low_res = {
+	.name  = "Crash kernel",
+	.start = 0,
+	.end   = 0,
+	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
+	.desc  = IORES_DESC_CRASH_KERNEL
+};
+
+/*
+ * parsing the "crashkernel" commandline
+ *
+ * this code is intended to be called from architecture specific code
+ */
+
+
+/*
+ * This function parses command lines in the format
+ *
+ *   crashkernel=ramsize-range:size[,...][@offset]
+ *
+ * The function returns 0 on success and -EINVAL on failure.
+ */
+static int __init parse_crashkernel_mem(char *cmdline,
+					unsigned long long system_ram,
+					unsigned long long *crash_size,
+					unsigned long long *crash_base)
+{
+	char *cur = cmdline, *tmp;
+	unsigned long long total_mem = system_ram;
+
+	/*
+	 * Firmware sometimes reserves some memory regions for its own use,
+	 * so the system memory size is less than the actual physical memory
+	 * size. Work around this by rounding up the total size to 128M,
+	 * which is enough for most test cases.
+	 */
+	total_mem = roundup(total_mem, SZ_128M);
+
+	/* for each entry of the comma-separated list */
+	do {
+		unsigned long long start, end = ULLONG_MAX, size;
+
+		/* get the start of the range */
+		start = memparse(cur, &tmp);
+		if (cur == tmp) {
+			pr_warn("crashkernel: Memory value expected\n");
+			return -EINVAL;
+		}
+		cur = tmp;
+		if (*cur != '-') {
+			pr_warn("crashkernel: '-' expected\n");
+			return -EINVAL;
+		}
+		cur++;
+
+		/* if no ':' is here, than we read the end */
+		if (*cur != ':') {
+			end = memparse(cur, &tmp);
+			if (cur == tmp) {
+				pr_warn("crashkernel: Memory value expected\n");
+				return -EINVAL;
+			}
+			cur = tmp;
+			if (end <= start) {
+				pr_warn("crashkernel: end <= start\n");
+				return -EINVAL;
+			}
+		}
+
+		if (*cur != ':') {
+			pr_warn("crashkernel: ':' expected\n");
+			return -EINVAL;
+		}
+		cur++;
+
+		size = memparse(cur, &tmp);
+		if (cur == tmp) {
+			pr_warn("Memory value expected\n");
+			return -EINVAL;
+		}
+		cur = tmp;
+		if (size >= total_mem) {
+			pr_warn("crashkernel: invalid size\n");
+			return -EINVAL;
+		}
+
+		/* match ? */
+		if (total_mem >= start && total_mem < end) {
+			*crash_size = size;
+			break;
+		}
+	} while (*cur++ == ',');
+
+	if (*crash_size > 0) {
+		while (*cur && *cur != ' ' && *cur != '@')
+			cur++;
+		if (*cur == '@') {
+			cur++;
+			*crash_base = memparse(cur, &tmp);
+			if (cur == tmp) {
+				pr_warn("Memory value expected after '@'\n");
+				return -EINVAL;
+			}
+		}
+	} else
+		pr_info("crashkernel size resulted in zero bytes\n");
+
+	return 0;
+}
+
+/*
+ * That function parses "simple" (old) crashkernel command lines like
+ *
+ *	crashkernel=size[@offset]
+ *
+ * It returns 0 on success and -EINVAL on failure.
+ */
+static int __init parse_crashkernel_simple(char *cmdline,
+					   unsigned long long *crash_size,
+					   unsigned long long *crash_base)
+{
+	char *cur = cmdline;
+
+	*crash_size = memparse(cmdline, &cur);
+	if (cmdline == cur) {
+		pr_warn("crashkernel: memory value expected\n");
+		return -EINVAL;
+	}
+
+	if (*cur == '@')
+		*crash_base = memparse(cur+1, &cur);
+	else if (*cur != ' ' && *cur != '\0') {
+		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+#define SUFFIX_HIGH 0
+#define SUFFIX_LOW  1
+#define SUFFIX_NULL 2
+static __initdata char *suffix_tbl[] = {
+	[SUFFIX_HIGH] = ",high",
+	[SUFFIX_LOW]  = ",low",
+	[SUFFIX_NULL] = NULL,
+};
+
+/*
+ * That function parses "suffix"  crashkernel command lines like
+ *
+ *	crashkernel=size,[high|low]
+ *
+ * It returns 0 on success and -EINVAL on failure.
+ */
+static int __init parse_crashkernel_suffix(char *cmdline,
+					   unsigned long long *crash_size,
+					   const char *suffix)
+{
+	char *cur = cmdline;
+
+	*crash_size = memparse(cmdline, &cur);
+	if (cmdline == cur) {
+		pr_warn("crashkernel: memory value expected\n");
+		return -EINVAL;
+	}
+
+	/* check with suffix */
+	if (strncmp(cur, suffix, strlen(suffix))) {
+		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
+		return -EINVAL;
+	}
+	cur += strlen(suffix);
+	if (*cur != ' ' && *cur != '\0') {
+		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static __init char *get_last_crashkernel(char *cmdline,
+			     const char *name,
+			     const char *suffix)
+{
+	char *p = cmdline, *ck_cmdline = NULL;
+
+	/* find crashkernel and use the last one if there are more */
+	p = strstr(p, name);
+	while (p) {
+		char *end_p = strchr(p, ' ');
+		char *q;
+
+		if (!end_p)
+			end_p = p + strlen(p);
+
+		if (!suffix) {
+			int i;
+
+			/* skip the one with any known suffix */
+			for (i = 0; suffix_tbl[i]; i++) {
+				q = end_p - strlen(suffix_tbl[i]);
+				if (!strncmp(q, suffix_tbl[i],
+					     strlen(suffix_tbl[i])))
+					goto next;
+			}
+			ck_cmdline = p;
+		} else {
+			q = end_p - strlen(suffix);
+			if (!strncmp(q, suffix, strlen(suffix)))
+				ck_cmdline = p;
+		}
+next:
+		p = strstr(p+1, name);
+	}
+
+	return ck_cmdline;
+}
+
+static int __init __parse_crashkernel(char *cmdline,
+			     unsigned long long system_ram,
+			     unsigned long long *crash_size,
+			     unsigned long long *crash_base,
+			     const char *suffix)
+{
+	char *first_colon, *first_space;
+	char *ck_cmdline;
+	char *name = "crashkernel=";
+
+	BUG_ON(!crash_size || !crash_base);
+	*crash_size = 0;
+	*crash_base = 0;
+
+	ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
+	if (!ck_cmdline)
+		return -ENOENT;
+
+	ck_cmdline += strlen(name);
+
+	if (suffix)
+		return parse_crashkernel_suffix(ck_cmdline, crash_size,
+				suffix);
+	/*
+	 * if the commandline contains a ':', then that's the extended
+	 * syntax -- if not, it must be the classic syntax
+	 */
+	first_colon = strchr(ck_cmdline, ':');
+	first_space = strchr(ck_cmdline, ' ');
+	if (first_colon && (!first_space || first_colon < first_space))
+		return parse_crashkernel_mem(ck_cmdline, system_ram,
+				crash_size, crash_base);
+
+	return parse_crashkernel_simple(ck_cmdline, crash_size, crash_base);
+}
+
+/*
+ * That function is the entry point for command line parsing and should be
+ * called from the arch-specific code.
+ *
+ * If crashkernel=,high|low is supported on architecture, non-NULL values
+ * should be passed to parameters 'low_size' and 'high'.
+ */
+int __init parse_crashkernel(char *cmdline,
+			     unsigned long long system_ram,
+			     unsigned long long *crash_size,
+			     unsigned long long *crash_base,
+			     unsigned long long *low_size,
+			     bool *high)
+{
+	int ret;
+
+	/* crashkernel=X[@offset] */
+	ret = __parse_crashkernel(cmdline, system_ram, crash_size,
+				crash_base, NULL);
+#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+	/*
+	 * If non-NULL 'high' passed in and no normal crashkernel
+	 * setting detected, try parsing crashkernel=,high|low.
+	 */
+	if (high && ret == -ENOENT) {
+		ret = __parse_crashkernel(cmdline, 0, crash_size,
+				crash_base, suffix_tbl[SUFFIX_HIGH]);
+		if (ret || !*crash_size)
+			return -EINVAL;
+
+		/*
+		 * crashkernel=Y,low can be specified or not, but invalid value
+		 * is not allowed.
+		 */
+		ret = __parse_crashkernel(cmdline, 0, low_size,
+				crash_base, suffix_tbl[SUFFIX_LOW]);
+		if (ret == -ENOENT) {
+			*low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+			ret = 0;
+		} else if (ret) {
+			return ret;
+		}
+
+		*high = true;
+	}
+#endif
+	if (!*crash_size)
+		ret = -EINVAL;
+
+	return ret;
+}
+
+/*
+ * Add a dummy early_param handler to mark crashkernel= as a known command line
+ * parameter and suppress incorrect warnings in init/main.c.
+ */
+static int __init parse_crashkernel_dummy(char *arg)
+{
+	return 0;
+}
+early_param("crashkernel", parse_crashkernel_dummy);
+
+#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+static int __init reserve_crashkernel_low(unsigned long long low_size)
+{
+#ifdef CONFIG_64BIT
+	unsigned long long low_base;
+
+	low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
+	if (!low_base) {
+		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
+		return -ENOMEM;
+	}
+
+	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
+		low_base, low_base + low_size, low_size >> 20);
+
+	crashk_low_res.start = low_base;
+	crashk_low_res.end   = low_base + low_size - 1;
+	insert_resource(&iomem_resource, &crashk_low_res);
+#endif
+	return 0;
+}
+
+void __init reserve_crashkernel_generic(char *cmdline,
+			     unsigned long long crash_size,
+			     unsigned long long crash_base,
+			     unsigned long long crash_low_size,
+			     bool high)
+{
+	unsigned long long search_end = CRASH_ADDR_LOW_MAX, search_base = 0;
+	bool fixed_base = false;
+
+	/* User specifies base address explicitly. */
+	if (crash_base) {
+		fixed_base = true;
+		search_base = crash_base;
+		search_end = crash_base + crash_size;
+	} else if (high) {
+		search_base = CRASH_ADDR_LOW_MAX;
+		search_end = CRASH_ADDR_HIGH_MAX;
+	}
+
+retry:
+	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
+					       search_base, search_end);
+	if (!crash_base) {
+		/*
+		 * For crashkernel=size[KMG]@offset[KMG], print out failure
+		 * message if can't reserve the specified region.
+		 */
+		if (fixed_base) {
+			pr_warn("crashkernel reservation failed - memory is in use.\n");
+			return;
+		}
+
+		/*
+		 * For crashkernel=size[KMG], if the first attempt was for
+		 * low memory, fall back to high memory, the minimum required
+		 * low memory will be reserved later.
+		 */
+		if (!high && search_end == CRASH_ADDR_LOW_MAX) {
+			search_end = CRASH_ADDR_HIGH_MAX;
+			search_base = CRASH_ADDR_LOW_MAX;
+			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+			goto retry;
+		}
+
+		/*
+		 * For crashkernel=size[KMG],high, if the first attempt was
+		 * for high memory, fall back to low memory.
+		 */
+		if (high && search_end == CRASH_ADDR_HIGH_MAX) {
+			search_end = CRASH_ADDR_LOW_MAX;
+			search_base = 0;
+			goto retry;
+		}
+		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
+			crash_size);
+		return;
+	}
+
+	if ((crash_base >= CRASH_ADDR_LOW_MAX) &&
+	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
+		memblock_phys_free(crash_base, crash_size);
+		return;
+	}
+
+	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
+		crash_base, crash_base + crash_size, crash_size >> 20);
+
+	/*
+	 * The crashkernel memory will be removed from the kernel linear
+	 * map. Inform kmemleak so that it won't try to access it.
+	 */
+	kmemleak_ignore_phys(crash_base);
+	if (crashk_low_res.end)
+		kmemleak_ignore_phys(crashk_low_res.start);
+
+	crashk_res.start = crash_base;
+	crashk_res.end = crash_base + crash_size - 1;
+}
+
+static __init int insert_crashkernel_resources(void)
+{
+	if (crashk_res.start < crashk_res.end)
+		insert_resource(&iomem_resource, &crashk_res);
+
+	if (crashk_low_res.start < crashk_low_res.end)
+		insert_resource(&iomem_resource, &crashk_low_res);
+
+	return 0;
+}
+early_initcall(insert_crashkernel_resources);
+#endif