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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: Suzuki 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: Josh Boyer <jwboyer@gmail.com>
This commit is contained in:
Suzuki Poulose 2011-12-14 22:59:24 +00:00 committed by Josh Boyer
parent 368ff8f14d
commit 26ecb6c44b
2 changed files with 94 additions and 3 deletions
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2
arch/powerpc/Kconfig
View File

@ -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

95
arch/powerpc/kernel/head_44x.S
View File

@ -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