[PATCH] Support for relocatable kdump kernel
Mohan Kumar M
mohan at in.ibm.com
Wed Oct 1 14:26:45 EDT 2008
Support for relocatable kdump kernel
This patch adds relocatable kernel support for kdump. With this one can
use the same regular kernel to capture the kdump. A signature (0xfeed1234)
is passed in r8 from panic code to the next kernel through kexec_sequence
and purgatory code. The signature is used to differentiate between
relocatable kdump kernel and non-kdump kernels.
The purgatory code compares the signature and sets the __kdump_flag in
head_64.S. During the boot up, kernel code checks __kdump_flag and if it
is set, the kernel will behave as relocatable kdump kernel. This kernel
will boot at the address where it was loaded by kexec-tools ie at the
address reserved through crashkernel boot parameter.
Enabling both CONFIG_RELOCATABLE and CONFIG_CRASH_DUMP options makes the
kdump kernel as relocatable. So the same kernel can be used as
production and kdump kernel.
Signed-off-by: Mohan Kumar M <mohan at in.ibm.com>
---
Documentation/kdump/kdump.txt | 14 ++++++--
arch/powerpc/Kconfig | 4 +-
arch/powerpc/include/asm/kdump.h | 16 ++++++++
arch/powerpc/kernel/crash_dump.c | 2 +
arch/powerpc/kernel/head_64.S | 60 +++++++++++++++++++++++++++++---
arch/powerpc/kernel/iommu.c | 2 +-
arch/powerpc/kernel/machine_kexec.c | 2 +
arch/powerpc/kernel/machine_kexec_64.c | 12 ++++--
arch/powerpc/kernel/misc_64.S | 10 ++++--
9 files changed, 104 insertions(+), 18 deletions(-)
diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 0705040..3f4bc84 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -109,7 +109,8 @@ There are two possible methods of using Kdump.
2) Or use the system kernel binary itself as dump-capture kernel and there is
no need to build a separate dump-capture kernel. This is possible
only with the architecutres which support a relocatable kernel. As
- of today, i386, x86_64 and ia64 architectures support relocatable kernel.
+ of today, i386, x86_64, ppc64 and ia64 architectures support relocatable
+ kernel.
Building a relocatable kernel is advantageous from the point of view that
one does not have to build a second kernel for capturing the dump. But
@@ -207,8 +208,15 @@ Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
Dump-capture kernel config options (Arch Dependent, ppc64)
----------------------------------------------------------
-* Make and install the kernel and its modules. DO NOT add this kernel
- to the boot loader configuration files.
+1) Enable "Build a kdump crash kernel" support under "Kernel" options:
+
+ CONFIG_CRASH_DUMP=y
+
+2) Enable "Build a relocatable kernel" support
+
+ CONFIG_RELOCATABLE=y
+
+ Make and install the kernel and its modules.
Dump-capture kernel config options (Arch Dependent, ia64)
----------------------------------------------------------
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 17c988b..f04a96a 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -824,11 +824,11 @@ config PAGE_OFFSET
default "0xc000000000000000"
config KERNEL_START
hex
- default "0xc000000002000000" if CRASH_DUMP
+ default "0xc000000002000000" if CRASH_DUMP && !RELOCATABLE
default "0xc000000000000000"
config PHYSICAL_START
hex
- default "0x02000000" if CRASH_DUMP
+ default "0x02000000" if CRASH_DUMP && !RELOCATABLE
default "0x00000000"
endif
diff --git a/arch/powerpc/include/asm/kdump.h b/arch/powerpc/include/asm/kdump.h
index f6c93c7..5308754 100644
--- a/arch/powerpc/include/asm/kdump.h
+++ b/arch/powerpc/include/asm/kdump.h
@@ -9,6 +9,12 @@
* Reserve to the end of the FWNMI area, see head_64.S */
#define KDUMP_RESERVE_LIMIT 0x10000 /* 64K */
+/*
+ * Used to differentiate between relocatable kdump kernel and other
+ * kernels
+ */
+#define KDUMP_SIGNATURE 0xfeed1234
+
#ifdef CONFIG_CRASH_DUMP
#define KDUMP_TRAMPOLINE_START 0x0100
@@ -19,11 +25,21 @@
#endif /* CONFIG_CRASH_DUMP */
#ifndef __ASSEMBLY__
+
+extern unsigned long long __kdump_flag;
+
#ifdef CONFIG_CRASH_DUMP
+#ifdef CONFIG_RELOCATABLE
+
+static inline void reserve_kdump_trampoline(void) { ; }
+static inline void setup_kdump_trampoline(void) { ; }
+
+#else
extern void reserve_kdump_trampoline(void);
extern void setup_kdump_trampoline(void);
+#endif /* CONFIG_RELOCATABLE */
#else /* !CONFIG_CRASH_DUMP */
static inline void reserve_kdump_trampoline(void) { ; }
diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index a323c9b..eaf9d6d 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -27,6 +27,7 @@
#define DBG(fmt...)
#endif
+#ifndef CONFIG_RELOCATABLE
void __init reserve_kdump_trampoline(void)
{
lmb_reserve(0, KDUMP_RESERVE_LIMIT);
@@ -65,6 +66,7 @@ void __init setup_kdump_trampoline(void)
DBG(" <- setup_kdump_trampoline()\n");
}
+#endif /* CONFIG_RELOCATABLE */
#ifdef CONFIG_PROC_VMCORE
static int __init parse_elfcorehdr(char *p)
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 8934500..29c2c34 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -97,6 +97,14 @@ __secondary_hold_spinloop:
__secondary_hold_acknowledge:
.llong 0x0
+ /* This flag is set only for kdump kernels so that */
+ /* it will be relocatable. Purgatory code user space kexec-tools */
+ /* sets this flag. Do not move this variable as purgatory code */
+ /* relies on the position of this variables */
+ .globl __kdump_flag
+__kdump_flag:
+ .llong 0x0
+
#ifdef CONFIG_PPC_ISERIES
/*
* At offset 0x20, there is a pointer to iSeries LPAR data.
@@ -1384,7 +1392,15 @@ _STATIC(__after_prom_start)
/* process relocations for the final address of the kernel */
lis r25,PAGE_OFFSET at highest /* compute virtual base of kernel */
sldi r25,r25,32
- mr r3,r25
+#ifdef CONFIG_CRASH_DUMP
+ ld r7,__kdump_flag at got(r2)
+ add r7,r7,r26
+ ld r7,0(r7)
+ cmpldi cr0,r7,1 /* relocatable kernel ? */
+ bne 1f
+ add r25,r25,r26
+#endif
+1: mr r3,r25
bl .relocate
#endif
@@ -1398,10 +1414,26 @@ _STATIC(__after_prom_start)
LOAD_REG_IMMEDIATE(r3, PHYSICAL_START) /* target addr */
mr. r4,r26 /* In some cases the loader may */
beq 9f /* have already put us at zero */
- lis r5,(copy_to_here - _stext)@ha
- addi r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
li r6,0x100 /* Start offset, the first 0x100 */
/* bytes were copied earlier. */
+#ifdef CONFIG_RELOCATABLE
+#ifdef CONFIG_CRASH_DUMP
+/*
+ * Check if the kernel has to be running as relocatable kernel based on the
+ * variable __kdump_flag, if it is set the kernel is treated as relocatble
+ * kernel, otherwise it will be moved to PHYSICAL_START
+ */
+ ld r7,__kdump_flag at got(r2)
+ ld r7,0(r7)
+ cmpldi cr0,r7,1
+ bne regular
+
+ li r5,__end_interrupts - _stext /* just copy interrupts */
+ b 5f
+regular:
+#endif
+ lis r5,(copy_to_here - _stext)@ha
+ addi r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
bl .copy_and_flush /* copy the first n bytes */
/* this includes the code being */
@@ -1411,15 +1443,33 @@ _STATIC(__after_prom_start)
mtctr r8
bctr
+p_end: .llong _end - _stext
+
4: /* Now copy the rest of the kernel up to _end */
addis r5,r26,(p_end - _stext)@ha
ld r5,(p_end - _stext)@l(r5) /* get _end */
- bl .copy_and_flush /* copy the rest */
+#else
+ lis r5,(copy_to_here - _stext)@ha
+ addi r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
-9: b .start_here_multiplatform
+ bl .copy_and_flush /* copy the first n bytes */
+ /* this includes the code being */
+ /* executed here. */
+ addis r8,r3,(4f - _stext)@ha /* Jump to the copy of this code */
+ addi r8,r8,(4f - _stext)@l /* that we just made */
+ mtctr r8
+ bctr
p_end: .llong _end - _stext
+4: /* Now copy the rest of the kernel up to _end */
+ addis r5,r26,(p_end - _stext)@ha
+ ld r5,(p_end - _stext)@l(r5) /* get _end */
+#endif
+5: bl .copy_and_flush /* copy the rest */
+
+9: b .start_here_multiplatform
+
/*
* Copy routine used to copy the kernel to start at physical address 0
* and flush and invalidate the caches as needed.
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 550a193..24f7797 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -494,7 +494,7 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
spin_lock_init(&tbl->it_lock);
#ifdef CONFIG_CRASH_DUMP
- if (ppc_md.tce_get) {
+ if (ppc_md.tce_get && __kdump_flag) {
unsigned long index;
unsigned long tceval;
unsigned long tcecount = 0;
diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
index aab7688..ac2a21f 100644
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -88,11 +88,13 @@ void __init reserve_crashkernel(void)
crash_size = crashk_res.end - crashk_res.start + 1;
+#ifndef CONFIG_RELOCATABLE
if (crashk_res.start != KDUMP_KERNELBASE)
printk("Crash kernel location must be 0x%x\n",
KDUMP_KERNELBASE);
crashk_res.start = KDUMP_KERNELBASE;
+#endif
crash_size = PAGE_ALIGN(crash_size);
crashk_res.end = crashk_res.start + crash_size - 1;
diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
index a168514..6a45a9e 100644
--- a/arch/powerpc/kernel/machine_kexec_64.c
+++ b/arch/powerpc/kernel/machine_kexec_64.c
@@ -255,11 +255,13 @@ static union thread_union kexec_stack
/* Our assembly helper, in kexec_stub.S */
extern NORET_TYPE void kexec_sequence(void *newstack, unsigned long start,
void *image, void *control,
- void (*clear_all)(void)) ATTRIB_NORET;
+ void (*clear_all)(void),
+ unsigned long long kdump_flag) ATTRIB_NORET;
/* too late to fail here */
void default_machine_kexec(struct kimage *image)
{
+ unsigned long long kdump_flag = 0;
/* prepare control code if any */
/*
@@ -270,8 +272,10 @@ void default_machine_kexec(struct kimage *image)
* using debugger IPI.
*/
- if (crashing_cpu == -1)
- kexec_prepare_cpus();
+ if (crashing_cpu == -1)
+ kexec_prepare_cpus();
+ else
+ kdump_flag = KDUMP_SIGNATURE;
/* switch to a staticly allocated stack. Based on irq stack code.
* XXX: the task struct will likely be invalid once we do the copy!
@@ -284,7 +288,7 @@ void default_machine_kexec(struct kimage *image)
*/
kexec_sequence(&kexec_stack, image->start, image,
page_address(image->control_code_page),
- ppc_md.hpte_clear_all);
+ ppc_md.hpte_clear_all, kdump_flag);
/* NOTREACHED */
}
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 4dd70cf..c93e5f7 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -609,10 +609,13 @@ real_mode: /* assume normal blr return */
/*
- * kexec_sequence(newstack, start, image, control, clear_all())
+ * kexec_sequence(newstack, start, image, control, clear_all(), kdump_flag)
*
* does the grungy work with stack switching and real mode switches
* also does simple calls to other code
+ *
+ * kdump_flag says whether the next kernel should be running at the reserved
+ * load address as needed for relocatable kdump kernel
*/
_GLOBAL(kexec_sequence)
@@ -645,7 +648,7 @@ _GLOBAL(kexec_sequence)
mr r29,r5 /* image (virt) */
mr r28,r6 /* control, unused */
mr r27,r7 /* clear_all() fn desc */
- mr r26,r8 /* spare */
+ mr r26,r8 /* kdump flag */
lhz r25,PACAHWCPUID(r13) /* get our phys cpu from paca */
/* disable interrupts, we are overwriting kernel data next */
@@ -707,5 +710,6 @@ _GLOBAL(kexec_sequence)
mr r4,r30 # start, aka phys mem offset
mtlr 4
li r5,0
- blr /* image->start(physid, image->start, 0); */
+ mr r6,r26 /* kdump_flag */
+ blr /* image->start(physid, image->start, 0, kdump_flag); */
#endif /* CONFIG_KEXEC */
--
1.5.5.1
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