kexec-hardboot for LG Nexus 4 (mako)

mako-aosp-Implement-kexec-hardboot.patch

From a5c71c50da839c6932af1903bcc0036daa033f7e Mon Sep 17 00:00:00 2001
From: Vojtech Bocek <[email protected]>
Date: Mon, 30 Sep 2013 18:02:43 +0200
Subject: [PATCH] Implement kexec-hardboot

"Allows hard booting (i.e., with a full hardware reboot) to a kernel
previously loaded in memory by kexec.  This works around the problem of
soft-booted kernel hangs due to improper device shutdown and/or
reinitialization."
More info in /arch/arm/Kconfig.

Original author: Mike Kasick <[email protected]>

Vojtech Bocek <[email protected]>:
  I've ported it to mako and flo, it is based of my grouper port, which is
  based of Asus TF201 patche ported by Jens Andersen <[email protected]>

  I've moved atags copying from guest to the host kernel, which means there
  is no need to patch the guest kernel, assuming the --mem-min in kexec call
  is within the first 256MB of System RAM, otherwise it will take a long time
  to load. I've also fixed /proc/atags entry, which would give the kexec-tools
  userspace binary only the first 1024 bytes of atags,
  see arch/arm/kernel/atags.c for more details.

  Other than that, memory-reservation code for the hardboot page and
  some assembler to do the watchdog reset on MSM chip are new for this device.

ayysir <[email protected]>:
  kexec: use mem_text_write_kernel_word to set reboot_code_buffer args
  in order to avoid protection faults (writes to read-only
  kernel memory) when CONFIG_STRICT_MEMORY_RWX is enabled.

Signed-off-by: Vojtech Bocek <[email protected]>
---
 arch/arm/Kconfig                        | 26 +++++++++
 arch/arm/boot/compressed/head.S         | 96 +++++++++++++++++++++++++++++++++
 arch/arm/include/asm/kexec.h            |  8 +++
 arch/arm/kernel/atags.c                 | 51 ++++++++++++------
 arch/arm/kernel/machine_kexec.c         | 22 ++++++--
 arch/arm/kernel/relocate_kernel.S       | 55 +++++++++++++++++++
 arch/arm/mach-msm/include/mach/memory.h | 10 ++++
 arch/arm/mach-msm/lge/devices_lge.c     | 15 ++++++
 arch/arm/mach-msm/restart.c             | 16 ++++++
 include/linux/kexec.h                   | 19 +++++--
 kernel/kexec.c                          |  4 ++
 11 files changed, 298 insertions(+), 24 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c450e1d..a577ae7 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2180,6 +2180,32 @@ config ATAGS_PROC
 	  Should the atags used to boot the kernel be exported in an "atags"
 	  file in procfs. Useful with kexec.
 
+config KEXEC_HARDBOOT
+	bool "Support hard booting to a kexec kernel"
+	depends on KEXEC
+	help
+	  Allows hard booting (i.e., with a full hardware reboot) to a kernel
+	  previously loaded in memory by kexec.  This works around the problem of
+	  soft-booted kernel hangs due to improper device shutdown and/or
+	  reinitialization.  Support is comprised of two components:
+
+	  First, a "hardboot" flag is added to the kexec syscall to force a hard
+	  reboot in relocate_new_kernel() (which requires machine-specific assembly
+	  code).  This also requires the kexec userspace tool to load the kexec'd
+	  kernel in memory region left untouched by the bootloader (i.e., not
+	  explicitly cleared and not overwritten by the boot kernel).  Just prior
+	  to reboot, the kexec kernel arguments are stashed in a machine-specific
+	  memory page that must also be preserved.  Note that this hardboot page
+	  need not be reserved during regular kernel execution.
+
+	  Second, the zImage decompresor of the boot (bootloader-loaded) kernel is
+	  modified to check the hardboot page for fresh kexec arguments, and if
+	  present, attempts to jump to the kexec'd kernel preserved in memory.
+
+	  Note that hardboot support is only required in the boot kernel and any
+	  kernel capable of performing a hardboot kexec.  It is _not_ required by a
+	  kexec'd kernel.
+
 config CRASH_DUMP
 	bool "Build kdump crash kernel (EXPERIMENTAL)"
 	depends on EXPERIMENTAL
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 64a6d6f..c7f1e64 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -10,6 +10,11 @@
  */
 #include <linux/linkage.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+  #include <asm/kexec.h>
+  #include <asm/memory.h>
+#endif
+
 /*
  * Debugging stuff
  *
@@ -135,6 +140,97 @@ start:
 1:		mov	r7, r1			@ save architecture ID
 		mov	r8, r2			@ save atags pointer
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+		/* Check hardboot page for a kexec kernel. */
+		ldr	r3, =KEXEC_HB_PAGE_ADDR
+		ldr	r0, [r3]
+		ldr	r1, =KEXEC_HB_PAGE_MAGIC
+		teq	r0, r1
+		bne	not_booting_other
+
+		/* Clear hardboot page magic to avoid boot loop. */
+		mov	r0, #0
+		str	r0, [r3]
+
+/* Copy the kernel tagged list (atags):
+ *
+ * The kernel requires atags to be located in a direct-mapped region,
+ * usually below the kernel in the first 16 kB of RAM.  If they're above
+ * (the start of) the kernel, they need to be copied to a suitable
+ * location, e.g., the machine-defined params_phys.
+ *
+ * The assumption is that the tags will only be "out of place" if the
+ * decompressor code is also, so copying is implemented only in the "won't
+ * overwrite" case (which should be fixed).  Still need to make sure that
+ * the copied tags don't overwrite either the kernel or decompressor code
+ * (or rather, the remainder of it since everything up to here has already
+ * been executed).
+ *
+ * Vojtech Bocek <[email protected]>: I've moved atags copying from guest
+ * kernel to the host and rewrote it from C to assembler in order to remove
+ * the need for guest kernel to be patched. I don't know assembler very well,
+ * so it doesn't look very good and I have no idea if I didn't accidentally
+ * break something, causing problems down the road. It's worked every time
+ * and I didn't notice any problems so far though.
+ *
+ * r4: zreladdr (kernel start)
+ * r8: kexec_boot_atags
+ * r2: boot_atags */
+		ldr	r8, [r3, #12]			@ kexec_boot_atags (r2: boot_atags)
+		ldr	r4, =zreladdr			@ zreladdr
+
+		/* No need to copy atags if they're already below kernel */
+		cmp	r8, r4
+		blo	no_atags_cpy
+
+		/* r0: min(zreladdr, pc) */
+		mov	r0, pc
+		cmp	r4, r0
+		movlo	r0, r4
+
+		/* Compute max space for atags, if max <= 0 don't copy. */
+		subs	r5, r0, r2			@ max = min(zreladdr, pc) - dest
+		bls	no_atags_cpy
+
+		/* Copy atags to params_phys. */
+		/* r8 src, r2 dest, r5 max */
+
+		ldr	r0, [r8]				@ first tag size
+		cmp	r0, #0
+		moveq	r4, #8
+		beq	catags_empty
+		mov	r4, r8
+
+catags_foreach:
+		lsl	r0, r0, #2				@ Multiply by 4
+		ldr	r0, [r4, r0]!			@ Load next tag size to r0 and address to r4
+		cmp	r0, #0
+		bne	catags_foreach
+
+		rsb	r4, r8, r4				@ r4 -= r8 (get only size)
+		add	r4, r4, #8				@ add size of the last tag
+catags_empty:
+		cmp	r5, r4					@ if(max <= size)
+		bcc	no_atags_cpy
+
+		mov	r5, #0					@ iterator
+catags_cpy:
+		ldr	r0, [r8, r5]
+		str	r0, [r2, r5]
+		add	r5, r5, #4
+		cmp	r5, r4
+		blo	catags_cpy
+
+no_atags_cpy:
+		/* Load boot arguments and jump to kexec kernel. */
+		ldr	r1, [r3, #8]			@ kexec_mach_type
+		ldr	pc, [r3, #4]			@ kexec_start_address
+
+		.ltorg
+
+not_booting_other:
+#endif
+
 #ifndef __ARM_ARCH_2__
 		/*
 		 * Booting from Angel - need to enter SVC mode and disable
diff --git a/arch/arm/include/asm/kexec.h b/arch/arm/include/asm/kexec.h
index c2b9b4b..564c55b 100644
--- a/arch/arm/include/asm/kexec.h
+++ b/arch/arm/include/asm/kexec.h
@@ -17,6 +17,10 @@
 #define KEXEC_ARM_ATAGS_OFFSET  0x1000
 #define KEXEC_ARM_ZIMAGE_OFFSET 0x8000
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+  #define KEXEC_HB_PAGE_MAGIC 0x4a5db007
+#endif
+
 #ifndef __ASSEMBLY__
 
 /**
@@ -53,6 +57,10 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
 /* Function pointer to optional machine-specific reinitialization */
 extern void (*kexec_reinit)(void);
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+extern void (*kexec_hardboot_hook)(void);
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* CONFIG_KEXEC */
diff --git a/arch/arm/kernel/atags.c b/arch/arm/kernel/atags.c
index 42a1a14..0cfd7e4 100644
--- a/arch/arm/kernel/atags.c
+++ b/arch/arm/kernel/atags.c
@@ -4,29 +4,45 @@
 #include <asm/types.h>
 #include <asm/page.h>
 
+/*
+ * [PATCH] Backport arch/arm/kernel/atags.c from 3.10
+ *
+ * There is a bug in older kernels, causing kexec-tools binary to
+ * only read first 1024 bytes from /proc/atags. I guess the bug is
+ * somewhere in /fs/proc/, since I don't think the callback in atags.c
+ * does something wrong. It might affect all procfs files using that
+ * old read callback instead of fops. Doesn't matter though, since it
+ * was accidentally fixed when 3.10 removed it.
+ *
+ * This might have no particular effect on real devices, because the
+ * atags _might_ be organized "just right", but it might be very hard
+ * to track down on a device where it causes problems.
+ *
+ */
+
 struct buffer {
 	size_t size;
 	char data[];
 };
 
-static int
-read_buffer(char* page, char** start, off_t off, int count,
-	int* eof, void* data)
-{
-	struct buffer *buffer = (struct buffer *)data;
-
-	if (off >= buffer->size) {
-		*eof = 1;
-		return 0;
-	}
-
-	count = min((int) (buffer->size - off), count);
+static struct buffer* atags_buffer = NULL;
 
-	memcpy(page, &buffer->data[off], count);
-
-	return count;
+static ssize_t atags_read(struct file *file, char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	// These are introduced in kernel 3.10. I don't want to backport
+	// the whole chunk, and other things (ram_console) use static
+	// variable to keep data too, so I guess it's okay.
+	//struct buffer *b = PDE_DATA(file_inode(file));
+	struct buffer *b = atags_buffer;
+	return simple_read_from_buffer(buf, count, ppos, b->data, b->size);
 }
 
+static const struct file_operations atags_fops = {
+	.read = atags_read,
+	.llseek = default_llseek,
+};
+
 #define BOOT_PARAMS_SIZE 1536
 static char __initdata atags_copy[BOOT_PARAMS_SIZE];
 
@@ -66,12 +82,13 @@ static int __init init_atags_procfs(void)
 	b->size = size;
 	memcpy(b->data, atags_copy, size);
 
-	tags_entry = create_proc_read_entry("atags", 0400,
-			NULL, read_buffer, b);
+	tags_entry = proc_create_data("atags", 0400, NULL, &atags_fops, b);
 
 	if (!tags_entry)
 		goto nomem;
 
+	atags_buffer = b;
+
 	return 0;
 
 nomem:
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index c355aeb..449394d 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -14,6 +14,7 @@
 #include <asm/cacheflush.h>
 #include <asm/mach-types.h>
 #include <asm/system_misc.h>
+#include <asm/mmu_writeable.h>
 
 extern const unsigned char relocate_new_kernel[];
 extern const unsigned int relocate_new_kernel_size;
@@ -22,6 +23,10 @@ extern unsigned long kexec_start_address;
 extern unsigned long kexec_indirection_page;
 extern unsigned long kexec_mach_type;
 extern unsigned long kexec_boot_atags;
+#ifdef CONFIG_KEXEC_HARDBOOT
+extern unsigned long kexec_hardboot;
+void (*kexec_hardboot_hook)(void);
+#endif
 
 static atomic_t waiting_for_crash_ipi;
 
@@ -120,10 +125,13 @@ void machine_kexec(struct kimage *image)
 	reboot_code_buffer = page_address(image->control_code_page);
 
 	/* Prepare parameters for reboot_code_buffer*/
-	kexec_start_address = image->start;
-	kexec_indirection_page = page_list;
-	kexec_mach_type = machine_arch_type;
-	kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
+	mem_text_write_kernel_word(&kexec_start_address, image->start);
+	mem_text_write_kernel_word(&kexec_indirection_page, page_list);
+	mem_text_write_kernel_word(&kexec_mach_type, machine_arch_type);
+	mem_text_write_kernel_word(&kexec_boot_atags, image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET);
+#ifdef CONFIG_KEXEC_HARDBOOT
+	mem_text_write_kernel_word(&kexec_hardboot, image->hardboot);
+#endif
 
 	/* copy our kernel relocation code to the control code page */
 	memcpy(reboot_code_buffer,
@@ -137,5 +145,11 @@ void machine_kexec(struct kimage *image)
 	if (kexec_reinit)
 		kexec_reinit();
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	/* Run any final machine-specific shutdown code. */
+	if (image->hardboot && kexec_hardboot_hook)
+		kexec_hardboot_hook();
+#endif
+
 	soft_restart(reboot_code_buffer_phys);
 }
diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S
index d0cdedf..f534293 100644
--- a/arch/arm/kernel/relocate_kernel.S
+++ b/arch/arm/kernel/relocate_kernel.S
@@ -4,6 +4,15 @@
 
 #include <asm/kexec.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/memory.h>
+#if defined(CONFIG_ARCH_TEGRA_2x_SOC) || defined(CONFIG_ARCH_TEGRA_3x_SOC)
+  #include <mach/iomap.h>
+#elif defined(CONFIG_ARCH_APQ8064)
+  #include <mach/msm_iomap.h>
+#endif
+#endif
+
 	.globl relocate_new_kernel
 relocate_new_kernel:
 
@@ -52,6 +61,12 @@ relocate_new_kernel:
 	b 0b
 
 2:
+#ifdef CONFIG_KEXEC_HARDBOOT
+	ldr	r0, kexec_hardboot
+	teq	r0, #0
+	bne	hardboot
+#endif
+
 	/* Jump to relocated kernel */
 	mov lr,r1
 	mov r0,#0
@@ -60,6 +75,40 @@ relocate_new_kernel:
  ARM(	mov pc, lr	)
  THUMB(	bx lr		)
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+hardboot:
+	/* Stash boot arguments in hardboot page:
+	 *  0: KEXEC_HB_PAGE_MAGIC
+	 *  4: kexec_start_address
+	 *  8: kexec_mach_type
+	 * 12: kexec_boot_atags */
+	ldr	r0, =KEXEC_HB_PAGE_ADDR
+	str	r1, [r0, #4]
+	ldr	r1, kexec_mach_type
+	str	r1, [r0, #8]
+	ldr	r1, kexec_boot_atags
+	str	r1, [r0, #12]
+	ldr	r1, =KEXEC_HB_PAGE_MAGIC
+	str	r1, [r0]
+
+#if defined(CONFIG_ARCH_TEGRA_2x_SOC) || defined(CONFIG_ARCH_TEGRA_3x_SOC)
+	ldr     r0, =TEGRA_PMC_BASE
+	ldr	r1, [r0]
+	orr	r1, r1, #0x10
+	str	r1, [r0]
+loop:	b	loop
+#elif defined(CONFIG_ARCH_APQ8064)
+	/* Restart using the PMIC chip, see mach-msm/restart.c */
+	ldr	r0, =APQ8064_TLMM_PHYS
+	mov	r1, #0
+	str	r1, [r0, #0x820]  @ PSHOLD_CTL_SU
+loop:	b	loop
+#else
+#error "No reboot method defined for hardboot."
+#endif
+
+	.ltorg
+#endif
 	.align
 
 	.globl kexec_start_address
@@ -79,6 +128,12 @@ kexec_mach_type:
 kexec_boot_atags:
 	.long	0x0
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	.globl kexec_hardboot
+kexec_hardboot:
+	.long	0x0
+#endif
+
 relocate_new_kernel_end:
 
 	.globl relocate_new_kernel_size
diff --git a/arch/arm/mach-msm/include/mach/memory.h b/arch/arm/mach-msm/include/mach/memory.h
index 8329611..d9f6b78 100644
--- a/arch/arm/mach-msm/include/mach/memory.h
+++ b/arch/arm/mach-msm/include/mach/memory.h
@@ -20,6 +20,16 @@
 /* physical offset of RAM */
 #define PLAT_PHYS_OFFSET UL(CONFIG_PHYS_OFFSET)
 
+#if defined(CONFIG_KEXEC_HARDBOOT)
+#if defined(CONFIG_MACH_APQ8064_FLO)
+#define KEXEC_HB_PAGE_ADDR		UL(0x88C00000)
+#elif defined(CONFIG_MACH_APQ8064_MAKO)
+#define KEXEC_HB_PAGE_ADDR		UL(0x88600000)
+#else
+#error "Adress for kexec hardboot page not defined"
+#endif
+#endif
+
 #define MAX_PHYSMEM_BITS 32
 #define SECTION_SIZE_BITS 28
 
diff --git a/arch/arm/mach-msm/lge/devices_lge.c b/arch/arm/mach-msm/lge/devices_lge.c
index 504cc1e..f74e4e7 100644
--- a/arch/arm/mach-msm/lge/devices_lge.c
+++ b/arch/arm/mach-msm/lge/devices_lge.c
@@ -26,6 +26,10 @@
 
 #include <ram_console.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <linux/memblock.h>
+#endif
+
 /* setting whether uart console is enalbed or disabled */
 static int uart_console_mode = 0;
 
@@ -187,6 +191,17 @@ void __init lge_add_persistent_ram(void)
 
 void __init lge_reserve(void)
 {
+#ifdef CONFIG_KEXEC_HARDBOOT
+	// Reserve space for hardboot page, just before the ram_console
+	struct membank* bank = &meminfo.bank[0];
+	phys_addr_t start = bank->start + bank->size - SZ_1M - LGE_PERSISTENT_RAM_SIZE;
+	int ret = memblock_remove(start, SZ_1M);
+	if(!ret)
+		pr_info("Hardboot page reserved at 0x%X\n", start);
+	else
+		pr_err("Failed to reserve space for hardboot page at 0x%X!\n", start);
+#endif
+
 	lge_add_persistent_ram();
 }
 
diff --git a/arch/arm/mach-msm/restart.c b/arch/arm/mach-msm/restart.c
index 8fac40c..74ef77a 100644
--- a/arch/arm/mach-msm/restart.c
+++ b/arch/arm/mach-msm/restart.c
@@ -35,6 +35,10 @@
 #include "msm_watchdog.h"
 #include "timer.h"
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/kexec.h>
+#endif
+
 #define WDT0_RST	0x38
 #define WDT0_EN		0x40
 #define WDT0_BARK_TIME	0x4C
@@ -322,6 +326,14 @@ static int __init msm_pmic_restart_init(void)
 
 late_initcall(msm_pmic_restart_init);
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+static void msm_kexec_hardboot_hook(void)
+{
+	// Set PMIC to restart-on-poweroff
+	pm8xxx_reset_pwr_off(1);
+}
+#endif
+
 static int __init msm_restart_init(void)
 {
 #ifdef CONFIG_MSM_DLOAD_MODE
@@ -337,6 +349,10 @@ static int __init msm_restart_init(void)
 	restart_reason = MSM_IMEM_BASE + RESTART_REASON_ADDR;
 	pm_power_off = msm_power_off;
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	kexec_hardboot_hook = msm_kexec_hardboot_hook;
+#endif
+
 	return 0;
 }
 early_initcall(msm_restart_init);
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index af84a25..a4509ad 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -111,6 +111,10 @@ struct kimage {
 #define KEXEC_TYPE_CRASH   1
 	unsigned int preserve_context : 1;
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	unsigned int hardboot : 1;
+#endif
+
 #ifdef ARCH_HAS_KIMAGE_ARCH
 	struct kimage_arch arch;
 #endif
@@ -178,6 +182,11 @@ extern struct kimage *kexec_crash_image;
 
 #define KEXEC_ON_CRASH		0x00000001
 #define KEXEC_PRESERVE_CONTEXT	0x00000002
+
+#ifdef CONFIG_KEXEC_HARDBOOT
+#define KEXEC_HARDBOOT		0x00000004
+#endif
+
 #define KEXEC_ARCH_MASK		0xffff0000
 
 /* These values match the ELF architecture values.
@@ -196,10 +205,14 @@ extern struct kimage *kexec_crash_image;
 #define KEXEC_ARCH_MIPS    ( 8 << 16)
 
 /* List of defined/legal kexec flags */
-#ifndef CONFIG_KEXEC_JUMP
-#define KEXEC_FLAGS    KEXEC_ON_CRASH
-#else
+#if defined(CONFIG_KEXEC_JUMP) && defined(CONFIG_KEXEC_HARDBOOT)
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_HARDBOOT)
+#elif defined(CONFIG_KEXEC_JUMP)
 #define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT)
+#elif defined(CONFIG_KEXEC_HARDBOOT)
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_HARDBOOT)
+#else
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH)
 #endif
 
 #define VMCOREINFO_BYTES           (4096)
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 4e2e472..aef7893 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1004,6 +1004,10 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 
 		if (flags & KEXEC_PRESERVE_CONTEXT)
 			image->preserve_context = 1;
+#ifdef CONFIG_KEXEC_HARDBOOT
+		if (flags & KEXEC_HARDBOOT)
+			image->hardboot = 1;
+#endif
 		result = machine_kexec_prepare(image);
 		if (result)
 			goto out;
-- 
1.8.4.rc3

mako-cm-Implement-kexec-hardboot.patch

From e133376adb4140dd11772f143ad1790dcbbe37cf Mon Sep 17 00:00:00 2001
From: Vojtech Bocek <[email protected]>
Date: Sun, 6 Oct 2013 16:35:23 +0200
Subject: [PATCH] Implement kexec-hardboot

"Allows hard booting (i.e., with a full hardware reboot) to a kernel
previously loaded in memory by kexec.  This works around the problem of
soft-booted kernel hangs due to improper device shutdown and/or
reinitialization."
More info in /arch/arm/Kconfig.

Original author: Mike Kasick <[email protected]>

Vojtech Bocek <[email protected]>:
  I've ported it to mako and flo, it is based of my grouper port, which is
  based of Asus TF201 patche ported by Jens Andersen <[email protected]>

  I've moved atags copying from guest to the host kernel, which means there
  is no need to patch the guest kernel, assuming the --mem-min in kexec call
  is within the first 256MB of System RAM, otherwise it will take a long time
  to load. I've also fixed /proc/atags entry, which would give the kexec-tools
  userspace binary only the first 1024 bytes of atags,
  see arch/arm/kernel/atags.c for more details.

  Other than that, memory-reservation code for the hardboot page and
  some assembler to do the watchdog reset on MSM chip are new for this device.

ayysir <[email protected]>:
  kexec: use mem_text_write_kernel_word to set reboot_code_buffer args
  in order to avoid protection faults (writes to read-only
  kernel memory) when CONFIG_STRICT_MEMORY_RWX is enabled.

Signed-off-by: Vojtech Bocek <[email protected]>
---
 arch/arm/Kconfig                            | 26 ++++++++
 arch/arm/boot/compressed/head.S             | 96 +++++++++++++++++++++++++++++
 arch/arm/include/asm/kexec.h                |  8 +++
 arch/arm/kernel/atags.c                     | 51 ++++++++++-----
 arch/arm/kernel/machine_kexec.c             | 22 +++++--
 arch/arm/kernel/relocate_kernel.S           | 55 +++++++++++++++++
 arch/arm/mach-msm/asustek/devices_asustek.c | 15 +++++
 arch/arm/mach-msm/include/mach/memory.h     | 10 +++
 arch/arm/mach-msm/lge/devices_lge.c         | 15 +++++
 arch/arm/mach-msm/restart.c                 | 16 +++++
 include/linux/kexec.h                       | 19 +++++-
 kernel/kexec.c                              |  4 ++
 12 files changed, 313 insertions(+), 24 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b3b7d18..3bad5f7 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2205,6 +2205,32 @@ config ATAGS_PROC
 	  Should the atags used to boot the kernel be exported in an "atags"
 	  file in procfs. Useful with kexec.
 
+config KEXEC_HARDBOOT
+	bool "Support hard booting to a kexec kernel"
+	depends on KEXEC
+	help
+	  Allows hard booting (i.e., with a full hardware reboot) to a kernel
+	  previously loaded in memory by kexec.  This works around the problem of
+	  soft-booted kernel hangs due to improper device shutdown and/or
+	  reinitialization.  Support is comprised of two components:
+
+	  First, a "hardboot" flag is added to the kexec syscall to force a hard
+	  reboot in relocate_new_kernel() (which requires machine-specific assembly
+	  code).  This also requires the kexec userspace tool to load the kexec'd
+	  kernel in memory region left untouched by the bootloader (i.e., not
+	  explicitly cleared and not overwritten by the boot kernel).  Just prior
+	  to reboot, the kexec kernel arguments are stashed in a machine-specific
+	  memory page that must also be preserved.  Note that this hardboot page
+	  need not be reserved during regular kernel execution.
+
+	  Second, the zImage decompresor of the boot (bootloader-loaded) kernel is
+	  modified to check the hardboot page for fresh kexec arguments, and if
+	  present, attempts to jump to the kexec'd kernel preserved in memory.
+
+	  Note that hardboot support is only required in the boot kernel and any
+	  kernel capable of performing a hardboot kexec.  It is _not_ required by a
+	  kexec'd kernel.
+
 config CRASH_DUMP
 	bool "Build kdump crash kernel (EXPERIMENTAL)"
 	depends on EXPERIMENTAL
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 576e623..a2f492c 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -10,6 +10,11 @@
  */
 #include <linux/linkage.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+  #include <asm/kexec.h>
+  #include <asm/memory.h>
+#endif
+
 	.arch	armv7-a
 /*
  * Debugging stuff
@@ -136,6 +141,97 @@ start:
 1:		mov	r7, r1			@ save architecture ID
 		mov	r8, r2			@ save atags pointer
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+		/* Check hardboot page for a kexec kernel. */
+		ldr	r3, =KEXEC_HB_PAGE_ADDR
+		ldr	r0, [r3]
+		ldr	r1, =KEXEC_HB_PAGE_MAGIC
+		teq	r0, r1
+		bne	not_booting_other
+
+		/* Clear hardboot page magic to avoid boot loop. */
+		mov	r0, #0
+		str	r0, [r3]
+
+/* Copy the kernel tagged list (atags):
+ *
+ * The kernel requires atags to be located in a direct-mapped region,
+ * usually below the kernel in the first 16 kB of RAM.  If they're above
+ * (the start of) the kernel, they need to be copied to a suitable
+ * location, e.g., the machine-defined params_phys.
+ *
+ * The assumption is that the tags will only be "out of place" if the
+ * decompressor code is also, so copying is implemented only in the "won't
+ * overwrite" case (which should be fixed).  Still need to make sure that
+ * the copied tags don't overwrite either the kernel or decompressor code
+ * (or rather, the remainder of it since everything up to here has already
+ * been executed).
+ *
+ * Vojtech Bocek <[email protected]>: I've moved atags copying from guest
+ * kernel to the host and rewrote it from C to assembler in order to remove
+ * the need for guest kernel to be patched. I don't know assembler very well,
+ * so it doesn't look very good and I have no idea if I didn't accidentally
+ * break something, causing problems down the road. It's worked every time
+ * and I didn't notice any problems so far though.
+ *
+ * r4: zreladdr (kernel start)
+ * r8: kexec_boot_atags
+ * r2: boot_atags */
+		ldr	r8, [r3, #12]			@ kexec_boot_atags (r2: boot_atags)
+		ldr	r4, =zreladdr			@ zreladdr
+
+		/* No need to copy atags if they're already below kernel */
+		cmp	r8, r4
+		blo	no_atags_cpy
+
+		/* r0: min(zreladdr, pc) */
+		mov	r0, pc
+		cmp	r4, r0
+		movlo	r0, r4
+
+		/* Compute max space for atags, if max <= 0 don't copy. */
+		subs	r5, r0, r2			@ max = min(zreladdr, pc) - dest
+		bls	no_atags_cpy
+
+		/* Copy atags to params_phys. */
+		/* r8 src, r2 dest, r5 max */
+
+		ldr	r0, [r8]				@ first tag size
+		cmp	r0, #0
+		moveq	r4, #8
+		beq	catags_empty
+		mov	r4, r8
+
+catags_foreach:
+		lsl	r0, r0, #2				@ Multiply by 4
+		ldr	r0, [r4, r0]!			@ Load next tag size to r0 and address to r4
+		cmp	r0, #0
+		bne	catags_foreach
+
+		rsb	r4, r8, r4				@ r4 -= r8 (get only size)
+		add	r4, r4, #8				@ add size of the last tag
+catags_empty:
+		cmp	r5, r4					@ if(max <= size)
+		bcc	no_atags_cpy
+
+		mov	r5, #0					@ iterator
+catags_cpy:
+		ldr	r0, [r8, r5]
+		str	r0, [r2, r5]
+		add	r5, r5, #4
+		cmp	r5, r4
+		blo	catags_cpy
+
+no_atags_cpy:
+		/* Load boot arguments and jump to kexec kernel. */
+		ldr	r1, [r3, #8]			@ kexec_mach_type
+		ldr	pc, [r3, #4]			@ kexec_start_address
+
+		.ltorg
+
+not_booting_other:
+#endif
+
 #ifndef __ARM_ARCH_2__
 		/*
 		 * Booting from Angel - need to enter SVC mode and disable
diff --git a/arch/arm/include/asm/kexec.h b/arch/arm/include/asm/kexec.h
index c2b9b4b..564c55b 100644
--- a/arch/arm/include/asm/kexec.h
+++ b/arch/arm/include/asm/kexec.h
@@ -17,6 +17,10 @@
 #define KEXEC_ARM_ATAGS_OFFSET  0x1000
 #define KEXEC_ARM_ZIMAGE_OFFSET 0x8000
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+  #define KEXEC_HB_PAGE_MAGIC 0x4a5db007
+#endif
+
 #ifndef __ASSEMBLY__
 
 /**
@@ -53,6 +57,10 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
 /* Function pointer to optional machine-specific reinitialization */
 extern void (*kexec_reinit)(void);
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+extern void (*kexec_hardboot_hook)(void);
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* CONFIG_KEXEC */
diff --git a/arch/arm/kernel/atags.c b/arch/arm/kernel/atags.c
index 42a1a14..0cfd7e4 100644
--- a/arch/arm/kernel/atags.c
+++ b/arch/arm/kernel/atags.c
@@ -4,29 +4,45 @@
 #include <asm/types.h>
 #include <asm/page.h>
 
+/*
+ * [PATCH] Backport arch/arm/kernel/atags.c from 3.10
+ *
+ * There is a bug in older kernels, causing kexec-tools binary to
+ * only read first 1024 bytes from /proc/atags. I guess the bug is
+ * somewhere in /fs/proc/, since I don't think the callback in atags.c
+ * does something wrong. It might affect all procfs files using that
+ * old read callback instead of fops. Doesn't matter though, since it
+ * was accidentally fixed when 3.10 removed it.
+ *
+ * This might have no particular effect on real devices, because the
+ * atags _might_ be organized "just right", but it might be very hard
+ * to track down on a device where it causes problems.
+ *
+ */
+
 struct buffer {
 	size_t size;
 	char data[];
 };
 
-static int
-read_buffer(char* page, char** start, off_t off, int count,
-	int* eof, void* data)
-{
-	struct buffer *buffer = (struct buffer *)data;
-
-	if (off >= buffer->size) {
-		*eof = 1;
-		return 0;
-	}
-
-	count = min((int) (buffer->size - off), count);
+static struct buffer* atags_buffer = NULL;
 
-	memcpy(page, &buffer->data[off], count);
-
-	return count;
+static ssize_t atags_read(struct file *file, char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	// These are introduced in kernel 3.10. I don't want to backport
+	// the whole chunk, and other things (ram_console) use static
+	// variable to keep data too, so I guess it's okay.
+	//struct buffer *b = PDE_DATA(file_inode(file));
+	struct buffer *b = atags_buffer;
+	return simple_read_from_buffer(buf, count, ppos, b->data, b->size);
 }
 
+static const struct file_operations atags_fops = {
+	.read = atags_read,
+	.llseek = default_llseek,
+};
+
 #define BOOT_PARAMS_SIZE 1536
 static char __initdata atags_copy[BOOT_PARAMS_SIZE];
 
@@ -66,12 +82,13 @@ static int __init init_atags_procfs(void)
 	b->size = size;
 	memcpy(b->data, atags_copy, size);
 
-	tags_entry = create_proc_read_entry("atags", 0400,
-			NULL, read_buffer, b);
+	tags_entry = proc_create_data("atags", 0400, NULL, &atags_fops, b);
 
 	if (!tags_entry)
 		goto nomem;
 
+	atags_buffer = b;
+
 	return 0;
 
 nomem:
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index c355aeb..449394d 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -14,6 +14,7 @@
 #include <asm/cacheflush.h>
 #include <asm/mach-types.h>
 #include <asm/system_misc.h>
+#include <asm/mmu_writeable.h>
 
 extern const unsigned char relocate_new_kernel[];
 extern const unsigned int relocate_new_kernel_size;
@@ -22,6 +23,10 @@ extern unsigned long kexec_start_address;
 extern unsigned long kexec_indirection_page;
 extern unsigned long kexec_mach_type;
 extern unsigned long kexec_boot_atags;
+#ifdef CONFIG_KEXEC_HARDBOOT
+extern unsigned long kexec_hardboot;
+void (*kexec_hardboot_hook)(void);
+#endif
 
 static atomic_t waiting_for_crash_ipi;
 
@@ -120,10 +125,13 @@ void machine_kexec(struct kimage *image)
 	reboot_code_buffer = page_address(image->control_code_page);
 
 	/* Prepare parameters for reboot_code_buffer*/
-	kexec_start_address = image->start;
-	kexec_indirection_page = page_list;
-	kexec_mach_type = machine_arch_type;
-	kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
+	mem_text_write_kernel_word(&kexec_start_address, image->start);
+	mem_text_write_kernel_word(&kexec_indirection_page, page_list);
+	mem_text_write_kernel_word(&kexec_mach_type, machine_arch_type);
+	mem_text_write_kernel_word(&kexec_boot_atags, image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET);
+#ifdef CONFIG_KEXEC_HARDBOOT
+	mem_text_write_kernel_word(&kexec_hardboot, image->hardboot);
+#endif
 
 	/* copy our kernel relocation code to the control code page */
 	memcpy(reboot_code_buffer,
@@ -137,5 +145,11 @@ void machine_kexec(struct kimage *image)
 	if (kexec_reinit)
 		kexec_reinit();
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	/* Run any final machine-specific shutdown code. */
+	if (image->hardboot && kexec_hardboot_hook)
+		kexec_hardboot_hook();
+#endif
+
 	soft_restart(reboot_code_buffer_phys);
 }
diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S
index d0cdedf..f534293 100644
--- a/arch/arm/kernel/relocate_kernel.S
+++ b/arch/arm/kernel/relocate_kernel.S
@@ -4,6 +4,15 @@
 
 #include <asm/kexec.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/memory.h>
+#if defined(CONFIG_ARCH_TEGRA_2x_SOC) || defined(CONFIG_ARCH_TEGRA_3x_SOC)
+  #include <mach/iomap.h>
+#elif defined(CONFIG_ARCH_APQ8064)
+  #include <mach/msm_iomap.h>
+#endif
+#endif
+
 	.globl relocate_new_kernel
 relocate_new_kernel:
 
@@ -52,6 +61,12 @@ relocate_new_kernel:
 	b 0b
 
 2:
+#ifdef CONFIG_KEXEC_HARDBOOT
+	ldr	r0, kexec_hardboot
+	teq	r0, #0
+	bne	hardboot
+#endif
+
 	/* Jump to relocated kernel */
 	mov lr,r1
 	mov r0,#0
@@ -60,6 +75,40 @@ relocate_new_kernel:
  ARM(	mov pc, lr	)
  THUMB(	bx lr		)
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+hardboot:
+	/* Stash boot arguments in hardboot page:
+	 *  0: KEXEC_HB_PAGE_MAGIC
+	 *  4: kexec_start_address
+	 *  8: kexec_mach_type
+	 * 12: kexec_boot_atags */
+	ldr	r0, =KEXEC_HB_PAGE_ADDR
+	str	r1, [r0, #4]
+	ldr	r1, kexec_mach_type
+	str	r1, [r0, #8]
+	ldr	r1, kexec_boot_atags
+	str	r1, [r0, #12]
+	ldr	r1, =KEXEC_HB_PAGE_MAGIC
+	str	r1, [r0]
+
+#if defined(CONFIG_ARCH_TEGRA_2x_SOC) || defined(CONFIG_ARCH_TEGRA_3x_SOC)
+	ldr     r0, =TEGRA_PMC_BASE
+	ldr	r1, [r0]
+	orr	r1, r1, #0x10
+	str	r1, [r0]
+loop:	b	loop
+#elif defined(CONFIG_ARCH_APQ8064)
+	/* Restart using the PMIC chip, see mach-msm/restart.c */
+	ldr	r0, =APQ8064_TLMM_PHYS
+	mov	r1, #0
+	str	r1, [r0, #0x820]  @ PSHOLD_CTL_SU
+loop:	b	loop
+#else
+#error "No reboot method defined for hardboot."
+#endif
+
+	.ltorg
+#endif
 	.align
 
 	.globl kexec_start_address
@@ -79,6 +128,12 @@ kexec_mach_type:
 kexec_boot_atags:
 	.long	0x0
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	.globl kexec_hardboot
+kexec_hardboot:
+	.long	0x0
+#endif
+
 relocate_new_kernel_end:
 
 	.globl relocate_new_kernel_size
diff --git a/arch/arm/mach-msm/asustek/devices_asustek.c b/arch/arm/mach-msm/asustek/devices_asustek.c
index 85ed946..43ab567 100644
--- a/arch/arm/mach-msm/asustek/devices_asustek.c
+++ b/arch/arm/mach-msm/asustek/devices_asustek.c
@@ -17,6 +17,10 @@
 #include <linux/memory.h>
 #include <linux/persistent_ram.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <linux/memblock.h>
+#endif
+
 #include <asm/setup.h>
 #include <asm/sizes.h>
 #include <asm/system_info.h>
@@ -56,6 +60,17 @@ void __init asustek_add_persistent_ram(void)
 
 void __init asustek_reserve(void)
 {
+#ifdef CONFIG_KEXEC_HARDBOOT
+	// Reserve space for hardboot page, just before the ram_console
+	struct membank* bank = &meminfo.bank[0];
+	phys_addr_t start = bank->start + bank->size - SZ_1M - ASUSTEK_PERSISTENT_RAM_SIZE;
+	int ret = memblock_remove(start, SZ_1M);
+	if(!ret)
+		pr_info("Hardboot page reserved at 0x%X\n", start);
+	else
+		pr_err("Failed to reserve space for hardboot page at 0x%X!\n", start);
+#endif
+
 	asustek_add_persistent_ram();
 }
 
diff --git a/arch/arm/mach-msm/include/mach/memory.h b/arch/arm/mach-msm/include/mach/memory.h
index 33fe673..daee9e6 100644
--- a/arch/arm/mach-msm/include/mach/memory.h
+++ b/arch/arm/mach-msm/include/mach/memory.h
@@ -20,6 +20,16 @@
 /* physical offset of RAM */
 #define PLAT_PHYS_OFFSET UL(CONFIG_PHYS_OFFSET)
 
+#if defined(CONFIG_KEXEC_HARDBOOT)
+#if defined(CONFIG_MACH_APQ8064_FLO)
+#define KEXEC_HB_PAGE_ADDR		UL(0x88C00000)
+#elif defined(CONFIG_MACH_APQ8064_MAKO)
+#define KEXEC_HB_PAGE_ADDR		UL(0x88600000)
+#else
+#error "Adress for kexec hardboot page not defined"
+#endif
+#endif
+
 #define MAX_PHYSMEM_BITS 32
 #define SECTION_SIZE_BITS 28
 
diff --git a/arch/arm/mach-msm/lge/devices_lge.c b/arch/arm/mach-msm/lge/devices_lge.c
index 504cc1e..f74e4e7 100644
--- a/arch/arm/mach-msm/lge/devices_lge.c
+++ b/arch/arm/mach-msm/lge/devices_lge.c
@@ -26,6 +26,10 @@
 
 #include <ram_console.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <linux/memblock.h>
+#endif
+
 /* setting whether uart console is enalbed or disabled */
 static int uart_console_mode = 0;
 
@@ -187,6 +191,17 @@ void __init lge_add_persistent_ram(void)
 
 void __init lge_reserve(void)
 {
+#ifdef CONFIG_KEXEC_HARDBOOT
+	// Reserve space for hardboot page, just before the ram_console
+	struct membank* bank = &meminfo.bank[0];
+	phys_addr_t start = bank->start + bank->size - SZ_1M - LGE_PERSISTENT_RAM_SIZE;
+	int ret = memblock_remove(start, SZ_1M);
+	if(!ret)
+		pr_info("Hardboot page reserved at 0x%X\n", start);
+	else
+		pr_err("Failed to reserve space for hardboot page at 0x%X!\n", start);
+#endif
+
 	lge_add_persistent_ram();
 }
 
diff --git a/arch/arm/mach-msm/restart.c b/arch/arm/mach-msm/restart.c
index 369f70d..bc49721 100644
--- a/arch/arm/mach-msm/restart.c
+++ b/arch/arm/mach-msm/restart.c
@@ -35,6 +35,10 @@
 #include "msm_watchdog.h"
 #include "timer.h"
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/kexec.h>
+#endif
+
 extern unsigned get_cable_status(void);
 
 #define WDT0_RST	0x38
@@ -337,6 +341,14 @@ static int __init msm_pmic_restart_init(void)
 
 late_initcall(msm_pmic_restart_init);
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+static void msm_kexec_hardboot_hook(void)
+{
+	// Set PMIC to restart-on-poweroff
+	pm8xxx_reset_pwr_off(1);
+}
+#endif
+
 static int __init msm_restart_init(void)
 {
 #ifdef CONFIG_MSM_DLOAD_MODE
@@ -352,6 +364,10 @@ static int __init msm_restart_init(void)
 	restart_reason = MSM_IMEM_BASE + RESTART_REASON_ADDR;
 	pm_power_off = msm_power_off;
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	kexec_hardboot_hook = msm_kexec_hardboot_hook;
+#endif
+
 	return 0;
 }
 early_initcall(msm_restart_init);
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index af84a25..a4509ad 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -111,6 +111,10 @@ struct kimage {
 #define KEXEC_TYPE_CRASH   1
 	unsigned int preserve_context : 1;
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+	unsigned int hardboot : 1;
+#endif
+
 #ifdef ARCH_HAS_KIMAGE_ARCH
 	struct kimage_arch arch;
 #endif
@@ -178,6 +182,11 @@ extern struct kimage *kexec_crash_image;
 
 #define KEXEC_ON_CRASH		0x00000001
 #define KEXEC_PRESERVE_CONTEXT	0x00000002
+
+#ifdef CONFIG_KEXEC_HARDBOOT
+#define KEXEC_HARDBOOT		0x00000004
+#endif
+
 #define KEXEC_ARCH_MASK		0xffff0000
 
 /* These values match the ELF architecture values.
@@ -196,10 +205,14 @@ extern struct kimage *kexec_crash_image;
 #define KEXEC_ARCH_MIPS    ( 8 << 16)
 
 /* List of defined/legal kexec flags */
-#ifndef CONFIG_KEXEC_JUMP
-#define KEXEC_FLAGS    KEXEC_ON_CRASH
-#else
+#if defined(CONFIG_KEXEC_JUMP) && defined(CONFIG_KEXEC_HARDBOOT)
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_HARDBOOT)
+#elif defined(CONFIG_KEXEC_JUMP)
 #define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT)
+#elif defined(CONFIG_KEXEC_HARDBOOT)
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_HARDBOOT)
+#else
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH)
 #endif
 
 #define VMCOREINFO_BYTES           (4096)
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 4e2e472..aef7893 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1004,6 +1004,10 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 
 		if (flags & KEXEC_PRESERVE_CONTEXT)
 			image->preserve_context = 1;
+#ifdef CONFIG_KEXEC_HARDBOOT
+		if (flags & KEXEC_HARDBOOT)
+			image->hardboot = 1;
+#endif
 		result = machine_kexec_prepare(image);
 		if (result)
 			goto out;
-- 
1.8.4.rc3

hi i'm interested of using those patches, can you please point me to an article or instruct me how to?

@spider623 commented on May 17, 2014, 5:22 AM PDT:

hi i'm interested of using those patches, can you please point me to an article or instruct me how to?

https://github.com/Tasssadar/multirom/wiki/Porting-MultiROM
https://github.com/Tasssadar/multirom/wiki/Porting-kexec-hardboot