[PATCH 2/2] Support for relocatable kdump kernel
From: Mohan Kumar M <hidden>
Date: 2008-09-30 12:53:35
Also in:
kexec
Subsystem:
documentation, linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Jonathan Corbet, Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
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 <redacted> --- 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@highest /* compute virtual base of kernel */ sldi r25,r25,32 - mr r3,r25 +#ifdef CONFIG_CRASH_DUMP + ld r7,__kdump_flag@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@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