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authorTakahiro Akashi <takahiro.akashi@linaro.org>2017-04-03 11:24:34 +0900
committerAKASHI Takahiro <takahiro.akashi@linaro.org>2017-06-08 19:16:43 +0900
commit9670bd73fdfc08fa1b26cc131f1435ab22fb2968 (patch)
treec17eda4dddf7be234ed7a3acf98591fb6b2c33c6
parent3f4224f2f566c451c6a8ca5127df096a696c30cf (diff)
downloadlinux-aarch64-9670bd73fdfc08fa1b26cc131f1435ab22fb2968.tar.gz
arm64: kdump: protect crash dump kernel memory
arch_kexec_protect_crashkres() and arch_kexec_unprotect_crashkres() are meant to be called by kexec_load() in order to protect the memory allocated for crash dump kernel once the image is loaded. The protection is implemented by unmapping the relevant segments in crash dump kernel memory, rather than making it read-only as other archs do, to prevent coherency issues due to potential cache aliasing (with mismatched attributes). Page-level mappings are consistently used here so that we can change the attributes of segments in page granularity as well as shrink the region also in page granularity through /sys/kernel/kexec_crash_size, putting the freed memory back to buddy system. Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/kernel/machine_kexec.c32
-rw-r--r--arch/arm64/mm/mmu.c89
2 files changed, 72 insertions, 49 deletions
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index bc96c8a7fc79..b63baa749609 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -14,7 +14,9 @@
#include <asm/cacheflush.h>
#include <asm/cpu_ops.h>
+#include <asm/mmu.h>
#include <asm/mmu_context.h>
+#include <asm/page.h>
#include "cpu-reset.h"
@@ -22,8 +24,6 @@
extern const unsigned char arm64_relocate_new_kernel[];
extern const unsigned long arm64_relocate_new_kernel_size;
-static unsigned long kimage_start;
-
/**
* kexec_image_info - For debugging output.
*/
@@ -64,8 +64,6 @@ void machine_kexec_cleanup(struct kimage *kimage)
*/
int machine_kexec_prepare(struct kimage *kimage)
{
- kimage_start = kimage->start;
-
kexec_image_info(kimage);
if (kimage->type != KEXEC_TYPE_CRASH && cpus_are_stuck_in_kernel()) {
@@ -183,7 +181,7 @@ void machine_kexec(struct kimage *kimage)
kexec_list_flush(kimage);
/* Flush the new image if already in place. */
- if (kimage->head & IND_DONE)
+ if ((kimage != kexec_crash_image) && (kimage->head & IND_DONE))
kexec_segment_flush(kimage);
pr_info("Bye!\n");
@@ -201,7 +199,7 @@ void machine_kexec(struct kimage *kimage)
*/
cpu_soft_restart(1, reboot_code_buffer_phys, kimage->head,
- kimage_start, 0);
+ kimage->start, 0);
BUG(); /* Should never get here. */
}
@@ -210,3 +208,25 @@ void machine_crash_shutdown(struct pt_regs *regs)
{
/* Empty routine needed to avoid build errors. */
}
+
+void arch_kexec_protect_crashkres(void)
+{
+ int i;
+
+ kexec_segment_flush(kexec_crash_image);
+
+ for (i = 0; i < kexec_crash_image->nr_segments; i++)
+ set_memory_valid(
+ __phys_to_virt(kexec_crash_image->segment[i].mem),
+ kexec_crash_image->segment[i].memsz >> PAGE_SHIFT, 0);
+}
+
+void arch_kexec_unprotect_crashkres(void)
+{
+ int i;
+
+ for (i = 0; i < kexec_crash_image->nr_segments; i++)
+ set_memory_valid(
+ __phys_to_virt(kexec_crash_image->segment[i].mem),
+ kexec_crash_image->segment[i].memsz >> PAGE_SHIFT, 1);
+}
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 05615a3fdc6f..b6c838e9fa4d 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -22,6 +22,8 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/kexec.h>
#include <linux/libfdt.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
@@ -317,56 +319,32 @@ static void create_mapping_late(phys_addr_t phys, unsigned long virt,
NULL, !debug_pagealloc_enabled());
}
-static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
+static void __init __map_memblock(pgd_t *pgd, phys_addr_t start,
+ phys_addr_t end, pgprot_t prot,
+ bool allow_block_mappings)
+{
+ __create_pgd_mapping(pgd, start, __phys_to_virt(start), end - start,
+ prot, early_pgtable_alloc, allow_block_mappings);
+}
+
+static void __init map_mem(pgd_t *pgd)
{
unsigned long kernel_start = __pa(_text);
unsigned long kernel_end = __pa(__init_begin);
+ struct memblock_region *reg;
/*
* Take care not to create a writable alias for the
* read-only text and rodata sections of the kernel image.
+ * So temporarily mark them as NOMAP to skip mappings in
+ * the following for-loop
*/
-
- /* No overlap with the kernel text/rodata */
- if (end < kernel_start || start >= kernel_end) {
- __create_pgd_mapping(pgd, start, __phys_to_virt(start),
- end - start, PAGE_KERNEL,
- early_pgtable_alloc,
- !debug_pagealloc_enabled());
- return;
- }
-
- /*
- * This block overlaps the kernel text/rodata mappings.
- * Map the portion(s) which don't overlap.
- */
- if (start < kernel_start)
- __create_pgd_mapping(pgd, start,
- __phys_to_virt(start),
- kernel_start - start, PAGE_KERNEL,
- early_pgtable_alloc,
- !debug_pagealloc_enabled());
- if (kernel_end < end)
- __create_pgd_mapping(pgd, kernel_end,
- __phys_to_virt(kernel_end),
- end - kernel_end, PAGE_KERNEL,
- early_pgtable_alloc,
- !debug_pagealloc_enabled());
-
- /*
- * Map the linear alias of the [_text, __init_begin) interval as
- * read-only/non-executable. This makes the contents of the
- * region accessible to subsystems such as hibernate, but
- * protects it from inadvertent modification or execution.
- */
- __create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start),
- kernel_end - kernel_start, PAGE_KERNEL_RO,
- early_pgtable_alloc, !debug_pagealloc_enabled());
-}
-
-static void __init map_mem(pgd_t *pgd)
-{
- struct memblock_region *reg;
+ memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
+#ifdef CONFIG_KEXEC_CORE
+ if (crashk_res.end)
+ memblock_mark_nomap(crashk_res.start,
+ resource_size(&crashk_res));
+#endif
/* map all the memory banks */
for_each_memblock(memory, reg) {
@@ -378,8 +356,33 @@ static void __init map_mem(pgd_t *pgd)
if (memblock_is_nomap(reg))
continue;
- __map_memblock(pgd, start, end);
+ __map_memblock(pgd, start, end,
+ PAGE_KERNEL, !debug_pagealloc_enabled());
+ }
+
+ /*
+ * Map the linear alias of the [_text, __init_begin) interval as
+ * read-only/non-executable. This makes the contents of the
+ * region accessible to subsystems such as hibernate, but
+ * protects it from inadvertent modification or execution.
+ */
+ __map_memblock(pgd, kernel_start, kernel_end,
+ PAGE_KERNEL_RO, !debug_pagealloc_enabled());
+ memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
+
+#ifdef CONFIG_KEXEC_CORE
+ /*
+ * Use page-level mappings here so that we can shrink the region
+ * in page granularity and put back unused memory to buddy system
+ * through /sys/kernel/kexec_crash_size interface.
+ */
+ if (crashk_res.end) {
+ __map_memblock(pgd, crashk_res.start, crashk_res.end + 1,
+ PAGE_KERNEL, false);
+ memblock_clear_nomap(crashk_res.start,
+ resource_size(&crashk_res));
}
+#endif
}
void mark_rodata_ro(void)