This is always true for a non-relocatable kernel. Otherwise the kernel
would get stuck. But for a relocatable kernel, it seems a little
complicated. When booting a relocatable kernel, we just align the
kernel start addr to 64M and map the PAGE_OFFSET from there. The
relocation will base on this virtual address. But if this address
is not the same as the memstart_addr, we will have to change the
map of PAGE_OFFSET to the real memstart_addr and do another relocation
again.
Signed-off-by: Kevin Hao <haoke...@gmail.com>
---
v3:
* Typo fix.
* Refactor relocate_init, no function change.
* Map only 64M memory before the second relocation.
* Comments update.
v2: A new patch in v2.
arch/powerpc/kernel/head_fsl_booke.S | 75 +++++++++++++++++++++++++++++++++---
arch/powerpc/mm/fsl_booke_mmu.c | 37 +++++++++++++++---
arch/powerpc/mm/mmu_decl.h | 2 +-
3 files changed, 102 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/kernel/head_fsl_booke.S
b/arch/powerpc/kernel/head_fsl_booke.S
index 7e9724e..c3989d9 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -84,6 +84,39 @@ _ENTRY(_start);
mr r23,r3
mr r25,r4
+ bl 0f
+0: mflr r8
+ addis r3,r8,(is_second_reloc - 0b)@ha
+ lwz r19,(is_second_reloc - 0b)@l(r3)
+
+ /* Check if this is the second relocation. */
+ cmpwi r19,1
+ bne 1f
+
+ /*
+ * For the second relocation, we already get the real memstart_addr
+ * from device tree. So we will map PAGE_OFFSET to memstart_addr,
+ * then the virtual address of start kernel should be:
+ * PAGE_OFFSET + (kernstart_addr - memstart_addr)
+ * Since the offset between kernstart_addr and memstart_addr should
+ * never be beyond 1G, so we can just use the lower 32bit of them
+ * for the calculation.
+ */
+ lis r3,PAGE_OFFSET@h
+
+ addis r4,r8,(kernstart_addr - 0b)@ha
+ addi r4,r4,(kernstart_addr - 0b)@l
+ lwz r5,4(r4)
+
+ addis r6,r8,(memstart_addr - 0b)@ha
+ addi r6,r6,(memstart_addr - 0b)@l
+ lwz r7,4(r6)
+
+ subf r5,r7,r5
+ add r3,r3,r5
+ b 2f
+
+1:
/*
* We have the runtime (virutal) address of our base.
* We calculate our shift of offset from a 64M page.
@@ -97,7 +130,7 @@ _ENTRY(_start);
subf r3,r5,r6 /* r3 = r6 - r5 */
add r3,r4,r3 /* Required Virtual Address */
- bl relocate
+2: bl relocate
#endif
/* We try to not make any assumptions about how the boot loader
@@ -121,10 +154,19 @@ _ENTRY(_start);
_ENTRY(__early_start)
+#ifdef CONFIG_RELOCATABLE
+ /*
+ * For the second relocation, we already set the right tlb entries
+ * for the kernel space, so skip the code in fsl_booke_entry_mapping.S
+ */
+ cmpwi r19,1
+ beq set_ivor
+#endif
#define ENTRY_MAPPING_BOOT_SETUP
#include "fsl_booke_entry_mapping.S"
#undef ENTRY_MAPPING_BOOT_SETUP
+set_ivor:
/* Establish the interrupt vector offsets */
SET_IVOR(0, CriticalInput);
SET_IVOR(1, MachineCheck);
@@ -210,11 +252,13 @@ _ENTRY(__early_start)
bl early_init
#ifdef CONFIG_RELOCATABLE
+ mr r3,r30
+ mr r4,r31
#ifdef CONFIG_PHYS_64BIT
- mr r3,r23
- mr r4,r25
+ mr r5,r23
+ mr r6,r25
#else
- mr r3,r25
+ mr r5,r25
#endif
bl relocate_init
#endif
@@ -1220,6 +1264,9 @@ _GLOBAL(switch_to_as1)
/*
* Restore to the address space 0 and also invalidate the tlb entry created
* by switch_to_as1.
+ * r3 - the tlb entry which should be invalidated
+ * r4 - __pa(PAGE_OFFSET in AS0) - __pa(PAGE_OFFSET in AS1)
+ * r5 - device tree virtual address. If r4 is 0, r5 is ignored.
*/
_GLOBAL(restore_to_as0)
mflr r0
@@ -1228,7 +1275,15 @@ _GLOBAL(restore_to_as0)
0: mflr r9
addi r9,r9,1f - 0b
- mfmsr r7
+ /*
+ * We may map the PAGE_OFFSET in AS0 to a different physical address,
+ * so we need calculate the right jump and device tree address based
+ * on the offset passed by r4.
+ */
+ subf r9,r4,r9
+ subf r5,r4,r5
+
+2: mfmsr r7
li r8,(MSR_IS | MSR_DS)
andc r7,r7,r8
@@ -1247,9 +1302,19 @@ _GLOBAL(restore_to_as0)
mtspr SPRN_MAS1,r9
tlbwe
isync
+
+ cmpwi r4,0
+ bne 3f
mtlr r0
blr
+ /*
+ * The PAGE_OFFSET will map to a different physical address,
+ * jump to _start to do another relocation again.
+ */
+3: mr r3,r5
+ bl _start
+
/*
* We put a few things here that have to be page-aligned. This stuff
* goes at the beginning of the data segment, which is page-aligned.
diff --git a/arch/powerpc/mm/fsl_booke_mmu.c b/arch/powerpc/mm/fsl_booke_mmu.c
index 1d54f6d..048d716 100644
--- a/arch/powerpc/mm/fsl_booke_mmu.c
+++ b/arch/powerpc/mm/fsl_booke_mmu.c
@@ -224,7 +224,7 @@ void __init adjust_total_lowmem(void)
i = switch_to_as1();
__max_low_memory = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM);
- restore_to_as0(i);
+ restore_to_as0(i, 0, 0);
pr_info("Memory CAM mapping: ");
for (i = 0; i < tlbcam_index - 1; i++)
@@ -245,17 +245,25 @@ void setup_initial_memory_limit(phys_addr_t
first_memblock_base,
}
#ifdef CONFIG_RELOCATABLE
-notrace void __init relocate_init(phys_addr_t start)
+int __initdata is_second_reloc;
+notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
{
unsigned long base = KERNELBASE;
+ kernstart_addr = start;
+ if (is_second_reloc) {
+ virt_phys_offset = PAGE_OFFSET - memstart_addr;
+ return;
+ }
+
/*
* Relocatable kernel support based on processing of dynamic
- * relocation entries.
- * Compute the virt_phys_offset :
+ * relocation entries. Before we get the real memstart_addr,
+ * We will compute the virt_phys_offset like this:
* virt_phys_offset = stext.run - kernstart_addr
*
- * stext.run = (KERNELBASE & ~0x3ffffff) + (kernstart_addr & 0x3ffffff)
+ * stext.run = (KERNELBASE & ~0x3ffffff) +
+ * (kernstart_addr & 0x3ffffff)
* When we relocate, we have :
*
* (kernstart_addr & 0x3ffffff) = (stext.run & 0x3ffffff)
@@ -265,10 +273,27 @@ notrace void __init relocate_init(phys_addr_t start)
* (kernstart_addr & ~0x3ffffff)
*
*/
- kernstart_addr = start;
start &= ~0x3ffffff;
base &= ~0x3ffffff;
virt_phys_offset = base - start;
+ early_get_first_memblock_info(__va(dt_ptr), NULL);
+ /*
+ * We now get the memstart_addr, then we should check if this
+ * address is the same as what the PAGE_OFFSET map to now. If
+ * not we have to change the map of PAGE_OFFSET to memstart_addr
+ * and do a second relocation.
+ */
+ if (start != memstart_addr) {
+ int n, offset = memstart_addr - start;
+
+ is_second_reloc = 1;
+ n = switch_to_as1();
+ /* map a 64M area for the second relocation */
+ map_mem_in_cams(0x4000000UL, CONFIG_LOWMEM_CAM_NUM);
+ restore_to_as0(n, offset, __va(dt_ptr));
+ /* We should never reach here */
+ panic("Relocation error");
+ }
}
#endif
#endif
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index eefbf7b..91da910 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -149,7 +149,7 @@ extern void MMU_init_hw(void);
extern unsigned long mmu_mapin_ram(unsigned long top);
extern void adjust_total_lowmem(void);
extern int switch_to_as1(void);
-extern void restore_to_as0(int esel);
+extern void restore_to_as0(int esel, int offset, void *dt_ptr);
#endif
extern void loadcam_entry(unsigned int index);
--
1.8.3.1
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