From 26ecb6c44bb33afc62905ba01b636dde70fc2dc6 Mon Sep 17 00:00:00 2001 From: Suzuki Poulose Date: Wed, 14 Dec 2011 22:59:24 +0000 Subject: [PATCH] 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 Cc: Benjamin Herrenschmidt Cc: Kumar Gala Cc: Tony Breeds Cc: Josh Boyer Cc: linuxppc-dev Signed-off-by: Josh Boyer --- arch/powerpc/Kconfig | 2 +- arch/powerpc/kernel/head_44x.S | 95 +++++++++++++++++++++++++++++++++- 2 files changed, 94 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 2ad5ea827820..1703509649b0 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -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 diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S index 0878bf5d8a68..7dd2981bcc50 100644 --- a/arch/powerpc/kernel/head_44x.S +++ b/arch/powerpc/kernel/head_44x.S @@ -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 -- GitLab