[PATCH 2/2] Support for relocatable kdump kernel
Mohan Kumar M
mohan at in.ibm.com
Tue Sep 30 08:53:27 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.
Now for kdump, both CONFIG_RELOCATABLE and CONFIG_CRASH_DUMP should be
enabled and 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 | 17 +++++++--
arch/powerpc/include/asm/kexec.h | 6 +++
arch/powerpc/kernel/head_64.S | 60 +++++++++++++++++++++++++++++---
arch/powerpc/kernel/iommu.c | 2 +-
arch/powerpc/kernel/machine_kexec_64.c | 12 ++++--
arch/powerpc/kernel/misc_64.S | 10 ++++--
6 files changed, 90 insertions(+), 17 deletions(-)
diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 0705040..95a9c95 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -104,12 +104,14 @@ Build the system and dump-capture kernels
There are two possible methods of using Kdump.
1) Build a separate custom dump-capture kernel for capturing the
- kernel core dump.
+ kernel core dump. Legacy kdump kernel build support(i.e separate kdump
+ kernel) for ppc64 is not available.
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 +209,15 @@ 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/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 3736d9b..765b318 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -24,6 +24,12 @@
#define KEXEC_CONTROL_PAGE_SIZE 4096
+/*
+ * Used to differentiate between relocatable kdump kernel and other
+ * kernels
+ */
+#define KDUMP_SIGNATURE 0xfeed1234
+
/* The native architecture */
#ifdef __powerpc64__
#define KEXEC_ARCH KEXEC_ARCH_PPC64
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 84856be..bbe1617 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)
li r3,0 /* 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 6724820..251f5c2 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -493,7 +493,7 @@ 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_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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