Support for relocatable kdump kernel
Subsystems (4)
PATCH 1/1 Support for relocatable kdump kernel
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
CONFIG_CRASH_DUMP depends on CONFIG_RELOCATABLE option to build kdump kernel as relocatable. So the same kernel can be used as production and kdump kernel.
This patch incorporates the changes suggested by Paul Mackerrass to avoid GOT use and to avoid two copies of the code.
Signed-off-by Mohan Kumar M <[email protected]>
--- Documentation/kdump/kdump.txt | 14 ++++++++++--- arch/powerpc/Kconfig | 8 ++----- arch/powerpc/include/asm/kdump.h | 16 +++++++++++++++ arch/powerpc/kernel/crash_dump.c | 2 + arch/powerpc/kernel/head_64.S | 34 ++++++++++++++++++++++++++++----- 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, 79 insertions(+), 21 deletions(-)
Documentation/kdump/kdump.txt +11 -3
@@ -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) ----------------------------------------------------------
arch/powerpc/Kconfig +3 -5
@@ -321,11 +321,11 @@ config KEXEC config CRASH_DUMP bool "Build a kdump crash kernel" - depends on PPC_MULTIPLATFORM && PPC64 + depends on PPC_MULTIPLATFORM && PPC64 && RELOCATABLE help Build a kernel suitable for use as a kdump capture kernel. - The kernel will be linked at a different address than normal, and - so can only be used for Kdump. + The same kernel binary can be used as production kernel and dump capture + kernel Don't change this unless you know what you are doing.
@@ -824,11 +824,9 @@ config PAGE_OFFSET default "0xc000000000000000" config KERNEL_START hex - default "0xc000000002000000" if CRASH_DUMP default "0xc000000000000000" config PHYSICAL_START hex - default "0x02000000" if CRASH_DUMP default "0x00000000" endif
arch/powerpc/include/asm/kdump.h +16 -0
@@ -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 ) { ; }
arch/powerpc/kernel/crash_dump.c +2 -0
@@ -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)
arch/powerpc/kernel/head_64.S +29 -5
@@ -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.
@@ -1384,8 +1392,13 @@ _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 +#ifdef CONFIG_CRASH_DUMP + ld r7,__kdump_flag-_stext(r26) + cmpldi cr0,r7,1 /* relocatable kernel ? */ + bne 1f add r25,r25,r26 - mr r3,r25 +#endif +1: mr r3,r25 bl .relocate #endif
@@ -1401,9 +1414,21 @@ _STATIC(__after_prom_start) beq 9f /* have already put us at zero */ 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-_stext(r26) + cmpldi cr0,r7,1 + bne regular + li r5,__end_interrupts - _stext /* just copy interrupts */ -#else + b 5f +regular: +#endif lis r5,(copy_to_here - _stext)@ha addi r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
@@ -1420,8 +1445,7 @@ 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 - bl .copy_and_flush /* copy the rest */ +5: bl .copy_and_flush /* copy the rest */ 9: b .start_here_multiplatform
arch/powerpc/kernel/iommu.c +1 -1
@@ -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 ;
arch/powerpc/kernel/machine_kexec.c +2 -0
@@ -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 ;
arch/powerpc/kernel/machine_kexec_64.c +8 -4
@@ -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 */ }
arch/powerpc/kernel/misc_64.S +7 -3
@@ -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 */
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arch/powerpc/kernel/head_64.S _STATIC(__after_prom_start) · line 1418
Quoted 9 lines · Mohan Kumar M
Support for relocatable kdump kernel
arch/powerpc/kernel/head_64.S +2
-1@@ -1401,9 +1414,21 @@ _STATIC(__after_prom_start) beq 9f /* have already put us at zero */ li r6,0x100 /* Start offset, the first 0x100 */ /* bytes were copied earlier. */ -#ifdef CONFIG_RELOCATABLE + +#ifdef CONFIG_CRASH_DUMP
What tree is this patch against? No tree that I can find has a line saying "#ifdef CONFIG_RELOCATABLE" at that point. Or is there a prerequisite patch that I haven't seen yet?
Paul.
Quoted 4 lines · Paul Mackerras
Quoted 1 line · Mohan Kumar M
Support for relocatable kdump kernel
Quoted 11 lines
arch/powerpc/kernel/head_64.S _STATIC(__after_prom_start) · line 1418
Quoted 7 lines
arch/powerpc/kernel/head_64.S +2
-1@@ -1401,9 +1414,21 @@ _STATIC(__after_prom_start) beq 9f /* have already put us at zero */ li r6,0x100 /* Start offset, the first 0x100 */ /* bytes were copied earlier. */ -#ifdef CONFIG_RELOCATABLE + +#ifdef CONFIG_CRASH_DUMPWhat tree is this patch against? No tree that I can find has a line saying "#ifdef
CONFIG_RELOCATABLE" at that point. Or is there a prerequisite patch that I haven't seen yet?
Hi Paul,
My patch is based on your PATCH 5 of relocatable kernel patchset (which demonstrates kernel can be relocatable).
Do I need to resend the patch by generating the diff with your patch5 also?
Regards,
Mohan.
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