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Subject[PATCH v9 16/18] arm64: kexec: configure trans_pgd page table for kexec
Date
Configure a page table located in kexec-safe memory that has
the following mappings:

1. identity mapping for text of relocation function with executable
permission.
2. linear mappings for all source ranges
3. linear mappings for all destination ranges.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
arch/arm64/include/asm/kexec.h | 12 ++++
arch/arm64/kernel/asm-offsets.c | 6 ++
arch/arm64/kernel/machine_kexec.c | 92 ++++++++++++++++++++++++++++++-
3 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 0f758fd51518..8f4332ac607a 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -108,6 +108,12 @@ extern const unsigned long kexec_el2_vectors_offset;
* el2_vector If present means that relocation routine will go to EL1
* from EL2 to do the copy, and then back to EL2 to do the jump
* to new world.
+ * trans_ttbr0 idmap for relocation function and its argument
+ * trans_ttbr1 linear map for source/destination addresses.
+ * trans_t0sz t0sz for idmap page in trans_ttbr0
+ * src_addr linear map for source pages.
+ * dst_addr linear map for destination pages.
+ * copy_len Number of bytes that need to be copied
*/
struct kern_reloc_arg {
phys_addr_t head;
@@ -117,6 +123,12 @@ struct kern_reloc_arg {
phys_addr_t kern_arg2;
phys_addr_t kern_arg3;
phys_addr_t el2_vector;
+ phys_addr_t trans_ttbr0;
+ phys_addr_t trans_ttbr1;
+ unsigned long trans_t0sz;
+ unsigned long src_addr;
+ unsigned long dst_addr;
+ unsigned long copy_len;
};

#define ARCH_HAS_KIMAGE_ARCH
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index ff974b648347..58ad5b7816ab 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -137,6 +137,12 @@ int main(void)
DEFINE(KEXEC_KRELOC_KERN_ARG2, offsetof(struct kern_reloc_arg, kern_arg2));
DEFINE(KEXEC_KRELOC_KERN_ARG3, offsetof(struct kern_reloc_arg, kern_arg3));
DEFINE(KEXEC_KRELOC_EL2_VECTOR, offsetof(struct kern_reloc_arg, el2_vector));
+ DEFINE(KEXEC_KRELOC_TRANS_TTBR0, offsetof(struct kern_reloc_arg, trans_ttbr0));
+ DEFINE(KEXEC_KRELOC_TRANS_TTBR1, offsetof(struct kern_reloc_arg, trans_ttbr1));
+ DEFINE(KEXEC_KRELOC_TRANS_T0SZ, offsetof(struct kern_reloc_arg, trans_t0sz));
+ DEFINE(KEXEC_KRELOC_SRC_ADDR, offsetof(struct kern_reloc_arg, src_addr));
+ DEFINE(KEXEC_KRELOC_DST_ADDR, offsetof(struct kern_reloc_arg, dst_addr));
+ DEFINE(KEXEC_KRELOC_COPY_LEN, offsetof(struct kern_reloc_arg, copy_len));
#endif
return 0;
}
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index bd398def7627..db96d2fab8b2 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -20,6 +20,7 @@
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/page.h>
+#include <asm/trans_pgd.h>

#include "cpu-reset.h"

@@ -70,10 +71,90 @@ static void *kexec_page_alloc(void *arg)
return page_address(page);
}

+/*
+ * Map source segments starting from src_va, and map destination
+ * segments starting from dst_va, and return size of copy in
+ * *copy_len argument.
+ * Relocation function essentially needs to do:
+ * memcpy(dst_va, src_va, copy_len);
+ */
+static int map_segments(struct kimage *kimage, pgd_t *pgdp,
+ struct trans_pgd_info *info,
+ unsigned long src_va,
+ unsigned long dst_va,
+ unsigned long *copy_len)
+{
+ unsigned long *ptr = 0;
+ unsigned long dest = 0;
+ unsigned long len = 0;
+ unsigned long entry, addr;
+ int rc;
+
+ for (entry = kimage->head; !(entry & IND_DONE); entry = *ptr++) {
+ addr = entry & PAGE_MASK;
+
+ switch (entry & IND_FLAGS) {
+ case IND_DESTINATION:
+ dest = addr;
+ break;
+ case IND_INDIRECTION:
+ ptr = __va(addr);
+ if (rc)
+ return rc;
+ break;
+ case IND_SOURCE:
+ rc = trans_pgd_map_page(info, pgdp, __va(addr),
+ src_va, PAGE_KERNEL);
+ if (rc)
+ return rc;
+ rc = trans_pgd_map_page(info, pgdp, __va(dest),
+ dst_va, PAGE_KERNEL);
+ if (rc)
+ return rc;
+ dest += PAGE_SIZE;
+ src_va += PAGE_SIZE;
+ dst_va += PAGE_SIZE;
+ len += PAGE_SIZE;
+ }
+ }
+ *copy_len = len;
+
+ return 0;
+}
+
+static int mmu_relocate_setup(struct kimage *kimage, void *reloc_code,
+ struct kern_reloc_arg *kern_reloc_arg)
+{
+ struct trans_pgd_info info = {
+ .trans_alloc_page = kexec_page_alloc,
+ .trans_alloc_arg = kimage,
+ };
+ pgd_t *trans_pgd = kexec_page_alloc(kimage);
+ int rc;
+
+ if (!trans_pgd)
+ return -ENOMEM;
+
+ /* idmap relocation function */
+ rc = trans_pgd_idmap_page(&info, &kern_reloc_arg->trans_ttbr0,
+ &kern_reloc_arg->trans_t0sz, reloc_code);
+ if (rc)
+ return rc;
+
+ kern_reloc_arg->src_addr = _PAGE_OFFSET(VA_BITS_MIN);
+ kern_reloc_arg->dst_addr = _PAGE_OFFSET(VA_BITS_MIN - 1);
+ kern_reloc_arg->trans_ttbr1 = phys_to_ttbr(__pa(trans_pgd));
+
+ rc = map_segments(kimage, trans_pgd, &info, kern_reloc_arg->src_addr,
+ kern_reloc_arg->dst_addr, &kern_reloc_arg->copy_len);
+ return rc;
+}
+
int machine_kexec_post_load(struct kimage *kimage)
{
void *reloc_code = page_to_virt(kimage->control_code_page);
struct kern_reloc_arg *kern_reloc_arg = kexec_page_alloc(kimage);
+ int rc = 0;

if (!kern_reloc_arg)
return -ENOMEM;
@@ -89,9 +170,18 @@ int machine_kexec_post_load(struct kimage *kimage)
kern_reloc_arg->el2_vector = __pa(reloc_code)
+ kexec_el2_vectors_offset;
}
+
+ /*
+ * If relocation is not needed, we do not need to enable MMU in
+ * relocation routine, therefore do not create page tables for
+ * scenarios such as crash kernel
+ */
+ if (!(kimage->head & IND_DONE))
+ rc = mmu_relocate_setup(kimage, reloc_code, kern_reloc_arg);
+
kexec_image_info(kimage);

- return 0;
+ return rc;
}

/**
--
2.17.1
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