Commit 26ecb6c4 authored by Suzuki Poulose's avatar Suzuki Poulose Committed by Josh Boyer
Browse files

powerpc/44x: Enable CONFIG_RELOCATABLE for PPC44x 



The following patch adds relocatable kernel support - based on processing
of dynamic relocations - for PPC44x kernel.

We find the runtime address of _stext and relocate ourselves based
on the following calculation.

	virtual_base = ALIGN(KERNELBASE,256M) +
			MODULO(_stext.run,256M)

relocate() is called with the Effective Virtual Base Address (as
shown below)

            | Phys. Addr| Virt. Addr |
Page (256M) |------------------------|
Boundary    |           |            |
            |           |            |
            |           |            |
Kernel Load |___________|_ __ _ _ _ _|<- Effective
Addr(_stext)|           |      ^     |Virt. Base Addr
            |           |      |     |
            |           |      |     |
            |           |reloc_offset|
            |           |      |     |
            |           |      |     |
            |           |______v_____|<-(KERNELBASE)%256M
            |           |            |
            |           |            |
            |           |            |
Page(256M)  |-----------|------------|
Boundary    |           |            |

The virt_phys_offset is updated accordingly, i.e,

	virt_phys_offset = effective. kernel virt base - kernstart_addr

I have tested the patches on 440x platforms only. However this should
work fine for PPC_47x also, as we only depend on the runtime address
and the current TLB XLAT entry for the startup code, which is available
in r25. I don't have access to a 47x board yet. So, it would be great if
somebody could test this on 47x.

Signed-off-by: default avatarSuzuki K. Poulose <suzuki@in.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Tony Breeds <tony@bakeyournoodle.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Signed-off-by: default avatarJosh Boyer <jwboyer@gmail.com>
parent 368ff8f1

arch/powerpc/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -851,7 +851,7 @@ config DYNAMIC_MEMSTART 


config RELOCATABLE

	bool "Build a relocatable kernel (EXPERIMENTAL)"

	depends on EXPERIMENTAL && ADVANCED_OPTIONS && FLATMEM

	depends on EXPERIMENTAL && ADVANCED_OPTIONS && FLATMEM && 44x

	select NONSTATIC_KERNEL

	help

	  This builds a kernel image that is capable of running at the

arch/powerpc/kernel/head_44x.S

+93 −2
Original line number Diff line number Diff line
@@ -64,6 +64,35 @@ _ENTRY(_start); 
	mr	r31,r3		/* save device tree ptr */

	li	r24,0		/* CPU number */



#ifdef CONFIG_RELOCATABLE

/*

 * Relocate ourselves to the current runtime address.

 * This is called only by the Boot CPU.

 * "relocate" is called with our current runtime virutal

 * address.

 * r21 will be loaded with the physical runtime address of _stext

 */

	bl	0f				/* Get our runtime address */

0:	mflr	r21				/* Make it accessible */

	addis	r21,r21,(_stext - 0b)@ha

	addi	r21,r21,(_stext - 0b)@l 	/* Get our current runtime base */



	/*

	 * We have the runtime (virutal) address of our base.

	 * We calculate our shift of offset from a 256M page.

	 * We could map the 256M page we belong to at PAGE_OFFSET and

	 * get going from there.

	 */

	lis	r4,KERNELBASE@h

	ori	r4,r4,KERNELBASE@l

	rlwinm	r6,r21,0,4,31			/* r6 = PHYS_START % 256M */

	rlwinm	r5,r4,0,4,31			/* r5 = KERNELBASE % 256M */

	subf	r3,r5,r6			/* r3 = r6 - r5 */

	add	r3,r4,r3			/* Required Virutal Address */



	bl	relocate

#endif



	bl	init_cpu_state



	/*
@@ -86,7 +115,64 @@ _ENTRY(_start); 


	bl	early_init



#ifdef CONFIG_DYNAMIC_MEMSTART

#ifdef CONFIG_RELOCATABLE

	/*

	 * Relocatable kernel support based on processing of dynamic

	 * relocation entries.

	 *

	 * r25 will contain RPN/ERPN for the start address of memory

	 * r21 will contain the current offset of _stext

	 */

	lis	r3,kernstart_addr@ha

	la	r3,kernstart_addr@l(r3)



	/*

	 * Compute the kernstart_addr.

	 * kernstart_addr => (r6,r8)

	 * kernstart_addr & ~0xfffffff => (r6,r7)

	 */

	rlwinm	r6,r25,0,28,31	/* ERPN. Bits 32-35 of Address */

	rlwinm	r7,r25,0,0,3	/* RPN - assuming 256 MB page size */

	rlwinm	r8,r21,0,4,31	/* r8 = (_stext & 0xfffffff) */

	or	r8,r7,r8	/* Compute the lower 32bit of kernstart_addr */



	/* Store kernstart_addr */

	stw	r6,0(r3)	/* higher 32bit */

	stw	r8,4(r3)	/* lower 32bit  */



	/*

	 * Compute the virt_phys_offset :

	 * virt_phys_offset = stext.run - kernstart_addr

	 *

	 * stext.run = (KERNELBASE & ~0xfffffff) + (kernstart_addr & 0xfffffff)

	 * When we relocate, we have :

	 *

	 *	(kernstart_addr & 0xfffffff) = (stext.run & 0xfffffff)

	 *

	 * hence:

	 *  virt_phys_offset = (KERNELBASE & ~0xfffffff) - (kernstart_addr & ~0xfffffff)

	 *

	 */



	/* KERNELBASE&~0xfffffff => (r4,r5) */

	li	r4, 0		/* higer 32bit */

	lis	r5,KERNELBASE@h

	rlwinm	r5,r5,0,0,3	/* Align to 256M, lower 32bit */



	/*

	 * 64bit subtraction.

	 */

	subfc	r5,r7,r5

	subfe	r4,r6,r4



	/* Store virt_phys_offset */

	lis	r3,virt_phys_offset@ha

	la	r3,virt_phys_offset@l(r3)



	stw	r4,0(r3)

	stw	r5,4(r3)



#elif defined(CONFIG_DYNAMIC_MEMSTART)

	/*

	 * Mapping based, page aligned dynamic kernel loading.

	 *
@@ -804,7 +890,12 @@ skpinv: addi r4,r4,1 /* Increment */ 
/*

 * Configure and load pinned entry into TLB slot 63.

 */

#ifdef CONFIG_DYNAMIC_MEMSTART

#ifdef CONFIG_NONSTATIC_KERNEL

	/*

	 * In case of a NONSTATIC_KERNEL we reuse the TLB XLAT

	 * entries of the initial mapping set by the boot loader.

	 * The XLAT entry is stored in r25

	 */



	/* Read the XLAT entry for our current mapping */

	tlbre	r25,r23,PPC44x_TLB_XLAT

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