[RFC 2/2] Selective MMU identity mapping for kexec
Per Fransson
per.xx.fransson at stericsson.com
Mon Nov 8 03:42:37 EST 2010
Signed-off-by: Per Fransson <per.xx.fransson at stericsson.com>
---
arch/arm/kernel/machine_kexec.c | 27 +++++++++++++++++++++-
arch/arm/kernel/relocate_kernel.S | 23 +++++++++++++++++++
arch/arm/mm/mmu.c | 44 +++++++++++++++++++++++++++++++++++++
arch/arm/mm/proc-v7.S | 1 +
4 files changed, 94 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 3a8fd51..d5bb12f 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -17,12 +17,20 @@ extern const unsigned char relocate_new_kernel[];
extern const unsigned int relocate_new_kernel_size;
extern void setup_mm_for_reboot(char mode);
+extern void identity_map(unsigned long, pgd_t*, pgd_t**);
extern unsigned long kexec_start_address;
extern unsigned long kexec_indirection_page;
extern unsigned long kexec_mach_type;
extern unsigned long kexec_boot_atags;
+typedef struct {
+ pgd_t *ptr;
+ pgd_t store;
+} kexec_mmu_ent_t;
+
+extern kexec_mmu_ent_t kexec_mmu_ents[4];
+
/*
* Provide a dummy crash_notes definition while crash dump arrives to arm.
* This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@@ -51,6 +59,7 @@ void machine_kexec(struct kimage *image)
unsigned long reboot_code_buffer_phys;
void *reboot_code_buffer;
+ unsigned long cpu_reset_phys;
page_list = image->head & PAGE_MASK;
@@ -65,18 +74,34 @@ void machine_kexec(struct kimage *image)
kexec_mach_type = machine_arch_type;
kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
+ /* Identity map the code which turns off the mmu (cpu_reset) and
+ the code which will be executed immediately afterwards
+ (relocate_new_kernel).
+ Store the old entries so they can be restored. */
+ /* cpu_reset cannot be used directly when MULTI_CPU is true, see
+ cpu-multi32.h, instead processor.reset will have to be used */
+ cpu_reset_phys = virt_to_phys(cpu_reset);
+ identity_map(cpu_reset_phys, &kexec_mmu_ents[0].store,
+ &kexec_mmu_ents[0].ptr);
+ identity_map(((char *)cpu_reset_phys)+PGDIR_SIZE,
+ &kexec_mmu_ents[1].store, &kexec_mmu_ents[1].ptr);
+ identity_map(reboot_code_buffer_phys,
+ &kexec_mmu_ents[2].store, &kexec_mmu_ents[2].ptr);
+ identity_map(((char *)reboot_code_buffer_phys)+PGDIR_SIZE,
+ &kexec_mmu_ents[3].store, &kexec_mmu_ents[3].ptr);
+
/* copy our kernel relocation code to the control code page */
memcpy(reboot_code_buffer,
relocate_new_kernel, relocate_new_kernel_size);
+
flush_icache_range((unsigned long) reboot_code_buffer,
(unsigned long) reboot_code_buffer + KEXEC_CONTROL_PAGE_SIZE);
printk(KERN_INFO "Bye!\n");
local_irq_disable();
local_fiq_disable();
- setup_mm_for_reboot(0); /* mode is not used, so just pass 0*/
flush_cache_all();
outer_flush_all();
outer_disable();
diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S
index fd26f8d..36b1268 100644
--- a/arch/arm/kernel/relocate_kernel.S
+++ b/arch/arm/kernel/relocate_kernel.S
@@ -7,6 +7,23 @@
.globl relocate_new_kernel
relocate_new_kernel:
+ /* We get here when the MMU is in a transitional state.
+ Wait for the virtual address mapping to wear off before
+ overwriting the identity mappings (set up for the sake
+ of MMU disabling) with the previous mappings. */
+ ldr r0, =100
+0: subs r0, r0, #1
+ beq 0b
+
+ adr r0, kexec_mmu_ents
+ .rept 4
+ ldr r1, [r0], #4
+ ldr r2, [r0], #4
+ str r2, [r1], #4
+ ldr r2, [r0], #4
+ str r2, [r1], #4
+ .endr
+
ldr r0,kexec_indirection_page
ldr r1,kexec_start_address
@@ -67,6 +84,12 @@ kexec_start_address:
kexec_indirection_page:
.long 0x0
+
+ .globl kexec_mmu_ents
+kexec_mmu_ents:
+ .space 4*12, 0
+
+
.globl kexec_mach_type
kexec_mach_type:
.long 0x0
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index de3afc7..64f3f05 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1080,3 +1080,47 @@ void setup_mm_for_reboot(char mode)
local_flush_tlb_all();
}
+
+
+/*
+ * In order to soft-boot, we need to insert a 1:1 mapping in place of
+ * the user-mode pages. This will then ensure that we have predictable
+ * results when turning the mmu off
+ */
+void identity_map(unsigned long phys_addr, pmd_t *pmd_store, pmd_t **pmd_ptr)
+{
+ unsigned long base_pmdval;
+ pgd_t *pgd;
+ pmd_t *pmd;
+ int i;
+ unsigned long pmdval;
+
+ /*
+ * We need to access to user-mode page tables here. For kernel threads
+ * we don't have any user-mode mappings so we use the context that we
+ * "borrowed".
+ */
+ pgd = current->active_mm->pgd;
+
+ base_pmdval = PMD_SECT_AP_WRITE | PMD_SECT_AP_READ | PMD_TYPE_SECT;
+ if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale())
+ base_pmdval |= PMD_BIT4;
+
+ /* Where to modify */
+ pmd = pgd + (phys_addr >> PGDIR_SHIFT);
+
+ /* Save old value */
+ pmd_store[0] = pmd[0];
+ pmd_store[1] = pmd[1];
+
+ *pmd_ptr = virt_to_phys(pmd);
+
+ /* Set new value */
+ pmdval = ((phys_addr >> PGDIR_SHIFT) << PGDIR_SHIFT) | base_pmdval;
+ pmd[0] = __pmd(pmdval);
+ pmd[1] = __pmd(pmdval + (1 << (PGDIR_SHIFT - 1)));
+
+ flush_pmd_entry(pmd);
+ local_flush_tlb_all();
+}
+
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index b249143..37ee55b 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -61,6 +61,7 @@ ENDPROC(cpu_v7_proc_fin)
*/
.align 5
ENTRY(cpu_v7_reset)
+ sub pc, pc, #PAGE_OFFSET+4 @ go to physical addresses
mrc p15, 0, ip, c1, c0, 0 @ ctrl register
bic ip, ip, #0x0001 @ ...............m
mcr p15, 0, ip, c1, c0, 0 @ ctrl register
--
1.7.2.2
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