Exynos Kexec Hardboot Patch

0001-Implement-kexec-hardboot.patch

From f1190e69caac8087c201951b01f50baeb5da5ec7 Mon Sep 17 00:00:00 2001
From: Vojtech Bocek <[email protected]>
Date: Mon, 23 Sep 2013 22:30:02 +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 flo, it is based of my grouper port, which is based of
  Asus TF201 patches 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.

Signed-off-by: Vojtech Bocek <[email protected]>

Change-Id: I4b53b59cf61ee77cdc3369b3f5c579fba70837dc
---
 arch/arm/Kconfig                             | 26 ++++++++
 arch/arm/boot/compressed/head.S              | 96 ++++++++++++++++++++++++++++
 arch/arm/configs/cyanogenmod_i9500_defconfig |  4 +-
 arch/arm/include/asm/kexec.h                 |  8 +++
 arch/arm/kernel/atags.c                      | 51 ++++++++++-----
 arch/arm/kernel/machine_kexec.c              | 13 ++++
 arch/arm/kernel/relocate_kernel.S            | 41 ++++++++++++
 arch/arm/mach-exynos/include/mach/memory.h   |  4 ++
 arch/arm/mach-exynos/mach-universal5410.c    | 15 ++++-
 arch/arm/mach-exynos/sec-reboot.c            | 19 ++++++
 include/linux/kexec.h                        | 19 +++++-
 kernel/kexec.c                               |  4 ++
 12 files changed, 278 insertions(+), 22 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 20911e0..b551dca 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2152,6 +2152,32 @@ 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 ace2dee..4ffcac2 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/configs/cyanogenmod_i9500_defconfig b/arch/arm/configs/cyanogenmod_i9500_defconfig
index 7807840..61fb87c 100644
--- a/arch/arm/configs/cyanogenmod_i9500_defconfig
+++ b/arch/arm/configs/cyanogenmod_i9500_defconfig
@@ -674,7 +674,9 @@ CONFIG_CMDLINE="console=ttySAC2,115200n8 vmalloc=512M androidboot.console=ttySAC
 CONFIG_CMDLINE_EXTEND=y
 # CONFIG_CMDLINE_FORCE is not set
 # CONFIG_XIP_KERNEL is not set
-# CONFIG_KEXEC is not set
+CONFIG_KEXEC=y
+CONFIG_KEXEC_HARDBOOT=y
+CONFIG_ATAGS_PROC=y
 # CONFIG_CRASH_DUMP is not set
 # CONFIG_AUTO_ZRELADDR is not set
 
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 dfcdb9f..98bdae3 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -22,6 +22,10 @@ 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;
 
@@ -123,6 +127,9 @@ void machine_kexec(struct kimage *image)
 	kexec_indirection_page = page_list;
 	kexec_mach_type = machine_arch_type;
 	kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
+#ifdef CONFIG_KEXEC_HARDBOOT
+	kexec_hardboot = image->hardboot;
+#endif
 
 	/* copy our kernel relocation code to the control code page */
 	memcpy(reboot_code_buffer,
@@ -136,5 +143,11 @@ 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..e28cc6d 100644
--- a/arch/arm/kernel/relocate_kernel.S
+++ b/arch/arm/kernel/relocate_kernel.S
@@ -4,6 +4,12 @@
 
 #include <asm/kexec.h>
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/memory.h>
+#include <mach/map.h>
+#include <mach/regs-pmu.h>
+#endif
+
 	.globl relocate_new_kernel
 relocate_new_kernel:
 
@@ -52,6 +58,12 @@ 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 +72,29 @@ 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]
+
+	ldr	r0, =EXYNOS5_PA_PMU
+	mov	r1, #1
+	str	r1, [r0, #EXYNOS_SWRESET-EXYNOS_PMUREG(0)]
+loop:	b	loop
+
+	.ltorg
+#endif
 	.align
 
 	.globl kexec_start_address
@@ -79,6 +114,12 @@ 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-exynos/include/mach/memory.h b/arch/arm/mach-exynos/include/mach/memory.h
index 7bd7765..c688a3e 100644
--- a/arch/arm/mach-exynos/include/mach/memory.h
+++ b/arch/arm/mach-exynos/include/mach/memory.h
@@ -21,4 +21,8 @@
 
 #define ARCH_HAS_SG_CHAIN
 
+#if defined(CONFIG_KEXEC_HARDBOOT)
+#define KEXEC_HB_PAGE_ADDR		UL(0xbfd00000)
+#endif
+
 #endif /* __ASM_ARCH_MEMORY_H */
diff --git a/arch/arm/mach-exynos/mach-universal5410.c b/arch/arm/mach-exynos/mach-universal5410.c
index 787204b..547294e 100644
--- a/arch/arm/mach-exynos/mach-universal5410.c
+++ b/arch/arm/mach-exynos/mach-universal5410.c
@@ -48,6 +48,10 @@
 
 #include "mach/sec_debug.h"
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/kexec.h>
+#endif
+
 extern phys_addr_t bootloaderfb_start;
 extern phys_addr_t bootloaderfb_size;
 
@@ -193,10 +197,19 @@ static struct notifier_block exynos5_reboot_notifier = {
 	.notifier_call = exynos5_notifier_call,
 };
 
+#define RAMCONSOLE_PHYS_ADDR  PLAT_PHYS_OFFSET + SZ_512M
 static struct persistent_ram_descriptor universal5410_prd[] __initdata = {
 	{
 		.name = "ram_console",
+#ifdef CONFIG_KEXEC_HARDBOOT
+                .size = KEXEC_HB_PAGE_ADDR - RAMCONSOLE_PHYS_ADDR,
+       },
+       {
+                .name = "kexec_hb_page",
+                .size = SZ_2M - (KEXEC_HB_PAGE_ADDR - RAMCONSOLE_PHYS_ADDR),
+#else
 		.size = SZ_2M,
+#endif
 	},
 #ifdef CONFIG_PERSISTENT_TRACER
 	{
@@ -209,7 +222,7 @@ static struct persistent_ram_descriptor universal5410_prd[] __initdata = {
 static struct persistent_ram universal5410_pr __initdata = {
 	.descs		= universal5410_prd,
 	.num_descs	= ARRAY_SIZE(universal5410_prd),
-	.start		= PLAT_PHYS_OFFSET + SZ_512M,
+	.start		= RAMCONSOLE_PHYS_ADDR,
 #ifdef CONFIG_PERSISTENT_TRACER
 	.size		= 3 * SZ_1M,
 #else
diff --git a/arch/arm/mach-exynos/sec-reboot.c b/arch/arm/mach-exynos/sec-reboot.c
index a4cd30f..750ebde 100644
--- a/arch/arm/mach-exynos/sec-reboot.c
+++ b/arch/arm/mach-exynos/sec-reboot.c
@@ -7,6 +7,10 @@
 #include <linux/gpio.h>
 #include "common.h"
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+#include <asm/kexec.h>
+#endif
+
 static void sec_power_off(void)
 {
 	int poweroff_try = 0;
@@ -133,10 +137,25 @@ static void sec_reboot(char str, const char *cmd)
 		;
 }
 
+#ifdef CONFIG_KEXEC_HARDBOOT
+static void sec_kexec_hardboot(void)
+{
+	/* Don't enter lpm mode */
+	writel(0x12345678, EXYNOS_INFORM2);
+
+	/* Reboot with boot kernel */
+	writel(REBOOT_MODE_PREFIX|REBOOT_MODE_NONE, EXYNOS_INFORM3);
+}
+#endif
+
 static int __init sec_reboot_init(void)
 {
 	pm_power_off = sec_power_off;
 	arm_pm_restart = sec_reboot;
+#ifdef CONFIG_KEXEC_HARDBOOT
+	kexec_hardboot_hook = sec_kexec_hardboot;
+#endif
+
 	return 0;
 }
 
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 0d7d6a1..6af4224 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
@@ -177,6 +181,11 @@ 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.
@@ -195,10 +204,14 @@ 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;
-- 
1.9.1