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authorSuzuki Poulose <suzuki@in.ibm.com>2011-12-14 22:59:24 +0000
committerJosh Boyer <jwboyer@gmail.com>2011-12-20 10:21:57 -0500
commit26ecb6c44bb33afc62905ba01b636dde70fc2dc6 (patch)
tree1e2a12510dcc81b40705ed04a1f4e1470856b041 /arch/powerpc/kernel/head_44x.S
parent368ff8f14d6ed8e9fd3b7c2156f2607719bf5a7a (diff)
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>
Diffstat (limited to 'arch/powerpc/kernel/head_44x.S')
-rw-r--r--arch/powerpc/kernel/head_44x.S95
1 files changed, 93 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 0878bf5d8a6..7dd2981bcc5 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