[PATCH] ppc64: Support for relocatable kernel in kexec-tools

[PATCH] ppc64: Support for relocatable kernel in kexec-tools

[M. Mohan Kumar]

Support for relocatable kernel in kexec-tools

This patch is based on the  patch sent by Milton Miller with the subject [PATCH 1/2
 kexec-tools] ppc64: new relocatble kernel activation ABI

http://patchwork.ozlabs.org/patch/5378/

Even with the above patch, the relocatable kernel always move to physical
address 0 (ie PHYSICAL_START). Following patch fixes this problem by marking
a local variable to 1 in purgatory during kdump kernel load time (kexec -p).
After a crash, purgatory sets __run_at_load variable location in the kernel
to 1 if the local variable is set to 1. So that the kernel will be running
as a relocatable kernel.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Milton Miller <miltonm@bga.com>
---
 kexec/arch/ppc64/crashdump-ppc64.h |    2 ++
 kexec/arch/ppc64/kexec-elf-ppc64.c |   17 +++++++++++++++++
 purgatory/arch/ppc64/v2wrap.S      |   25 ++++++++++++-------------
 3 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/kexec/arch/ppc64/crashdump-ppc64.h b/kexec/arch/ppc64/crashdump-ppc64.h
index 9608782..be02213 100644
--- a/kexec/arch/ppc64/crashdump-ppc64.h
+++ b/kexec/arch/ppc64/crashdump-ppc64.h
@@ -23,6 +23,8 @@ void add_usable_mem_rgns(unsigned long long base, unsigned long long size);
 #define _ALIGN_UP(addr,size)	(((addr)+((size)-1))&(~((size)-1)))
 #define _ALIGN_DOWN(addr,size)	((addr)&(~((size)-1)))
 
+#define KERNEL_RUN_AT_ZERO_MAGIC 0x72756e30	/* "run0" */
+
 extern uint64_t crash_base;
 extern uint64_t crash_size;
 extern unsigned int rtas_base;
diff --git a/kexec/arch/ppc64/kexec-elf-ppc64.c b/kexec/arch/ppc64/kexec-elf-ppc64.c
index d72550d..870315e 100644
--- a/kexec/arch/ppc64/kexec-elf-ppc64.c
+++ b/kexec/arch/ppc64/kexec-elf-ppc64.c
@@ -93,6 +93,7 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
 	uint64_t my_stack, my_backup_start;
 	uint64_t toc_addr;
 	unsigned int slave_code[256/sizeof (unsigned int)], master_entry;
+	unsigned int run_at_load;
 
 #define OPT_APPEND     (OPT_ARCH_MAX+0)
 #define OPT_RAMDISK     (OPT_ARCH_MAX+1)
@@ -307,6 +308,18 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
 		my_backup_start = info->backup_start;
 		elf_rel_set_symbol(&info->rhdr, "backup_start",
 				&my_backup_start, sizeof(my_backup_start));
+
+		/* Tell relocatable kernel to run at load address
+		 * via word before slave code in purgatory
+		 */
+
+		elf_rel_get_symbol(&info->rhdr, "run_at_load", &run_at_load,
+				sizeof(run_at_load));
+		if (run_at_load == KERNEL_RUN_AT_ZERO_MAGIC)
+			run_at_load = 1;
+			/* else it should be a fixed offset image */
+		elf_rel_set_symbol(&info->rhdr, "run_at_load", &run_at_load,
+				sizeof(run_at_load));
 	}
 
 	/* Set stack address */
@@ -325,10 +338,13 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
 	my_backup_start = 0;
 	my_stack = 0;
 	toc_addr = 0;
+	run_at_load = 0;
 
 	elf_rel_get_symbol(&info->rhdr, "kernel", &my_kernel, sizeof(my_kernel));
 	elf_rel_get_symbol(&info->rhdr, "dt_offset", &my_dt_offset,
 				sizeof(my_dt_offset));
+	elf_rel_get_symbol(&info->rhdr, "run_at_load", &run_at_load,
+				sizeof(run_at_load));
 	elf_rel_get_symbol(&info->rhdr, "panic_kernel", &my_panic_kernel,
 				sizeof(my_panic_kernel));
 	elf_rel_get_symbol(&info->rhdr, "backup_start", &my_backup_start,
@@ -341,6 +357,7 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
 	fprintf(stderr, "kernel is %llx\n", (unsigned long long)my_kernel);
 	fprintf(stderr, "dt_offset is %llx\n",
 		(unsigned long long)my_dt_offset);
+	fprintf(stderr, "run_at_load flag is %x\n", run_at_load);
 	fprintf(stderr, "panic_kernel is %x\n", my_panic_kernel);
 	fprintf(stderr, "backup_start is %llx\n",
 		(unsigned long long)my_backup_start);
diff --git a/purgatory/arch/ppc64/v2wrap.S b/purgatory/arch/ppc64/v2wrap.S
index f69dad2..78b6eec 100644
--- a/purgatory/arch/ppc64/v2wrap.S
+++ b/purgatory/arch/ppc64/v2wrap.S
@@ -45,11 +45,14 @@
 	oris    rn,rn,name##@h;         \
 	ori     rn,rn,name##@l
 
-#define KDUMP_SIGNATURE 0xfeed1234
-
 	.machine ppc64
 	.globl purgatory_start
 purgatory_start:	b	master
+	.org purgatory_start + 0x5c     # ABI: possible run_at_load flag at 0x5c
+run_at_load:
+	.globl run_at_load
+	.long 0
+	.size run_at_load, . - run_at_load
 	.org purgatory_start + 0x60     # ABI: slaves start at 60 with r3=phys
 slave:	b $
 	.org purgatory_start + 0x100    # ABI: end of copied region
@@ -65,7 +68,6 @@ master:
 	isync
 	mr      17,3            # save cpu id to r17
 	mr      15,4            # save physical address in reg15
-	mr      18,6            # save kdump flag in reg18
 
 	LOADADDR(6,my_toc)
 	ld      2,0(6)          #setup toc
@@ -96,14 +98,11 @@ master:
 	mtctr	4		# prepare branch too
 	mr      3,16            # restore dt address
 
-	LOADADDR(6,KDUMP_SIGNATURE)
-	cmpd	18,6
-	bne	regular
-	li	7,1
-	std	7,24(4)		# mark kdump flag at kernel
-regular:
-	lwz	7,0(4)		# get the first instruction that we stole
-	stw	7,0(0)		# and put it in the slave loop at 0
-				# skip cache flush, do we care?
-
+	LOADADDR(6,run_at_load) # load the run_at_load address
+	lwz     18,0(6)		# it will be 1 for kdump kernel
+	cmpwi	18,1
+	bne	skip
+	li	7,1		# if its kdump kernel, mark it
+	stw	7,92(4)		# in kernel
+skip:
 	bctr			# start kernel
-- 
1.6.0.6

Re: [PATCH] ppc64: Support for relocatable kernel in kexec-tools

[Milton Miller]

On Jan 2, 2009, at 8:08 AM, M. Mohan Kumar wrote:

> Support for relocatable kernel in kexec-tools
>
> This patch is based on the  patch sent by Milton Miller with the 
> subject [PATCH 1/2
>  kexec-tools] ppc64: new relocatble kernel activation ABI
>
> http://patchwork.ozlabs.org/patch/5378/
>
> Even with the above patch, the relocatable kernel always move to 
> physical
> address 0 (ie PHYSICAL_START). Following patch fixes this problem by 
> marking
> a local variable to 1 in purgatory during kdump kernel load time 
> (kexec -p).
> After a crash, purgatory sets __run_at_load variable location in the 
> kernel
> to 1 if the local variable is set to 1. So that the kernel will be 
> running
> as a relocatable kernel.
>
> Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
> Signed-off-by: Milton Miller <miltonm@bga.com>

your sign-off should have been after mine as you were making changes to 
my patch.

I actually completed my own testing last night with a slightly 
different version:

(1) I unconditionally store the purgatory value to the kernel (less 
maintence if we decide to define further flags in the future).

(2) I use less registers in asm (no need for r18)

(3) I renamed the variable in the c code to be my_run_at_load to be 
more consistent  with the other names.

Also, I have some cleanup patches on top of this one.  I'm in the 
process of setting up a new email client to send my patches, so it will 
be a few hours yet until I get them posted.  But I would appreciate 
waiting for my series so I don't have to rediff the later patches.

thanks,
milton