arm64: mte: Dump the MTE tags in the core file

For each vma mapped with PROT_MTE (the VM_MTE flag set), generate a
PT_ARM_MEMTAG_MTE segment in the core file and dump the corresponding
tags. The in-file size for such segments is 128 bytes per page.

For pages in a VM_MTE vma which are not present in the user page tables
or don't have the PG_mte_tagged flag set (e.g. execute-only), just write
zeros in the core file.

An example of program headers for two vmas, one 2-page, the other 4-page
long:

  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
  ...
  LOAD           0x030000 0x0000ffff80034000 0x0000000000000000 0x000000 0x002000 RW  0x1000
  LOAD           0x030000 0x0000ffff80036000 0x0000000000000000 0x004000 0x004000 RW  0x1000
  ...
  LOPROC+0x1     0x05b000 0x0000ffff80034000 0x0000000000000000 0x000100 0x002000     0
  LOPROC+0x1     0x05b100 0x0000ffff80036000 0x0000000000000000 0x000200 0x004000     0

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Luis Machado <luis.machado@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220131165456.2160675-5-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index cbcd42decb2add4924f5b4801d388da90d65404c..b55c11796fad283bf45fe3185c153da18ec6acb9 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -10,6 +10,7 @@ config ARM64
        select ACPI_SPCR_TABLE if ACPI
        select ACPI_PPTT if ACPI
        select ARCH_HAS_DEBUG_WX
+       select ARCH_BINFMT_ELF_EXTRA_PHDRS
        select ARCH_BINFMT_ELF_STATE
        select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
        select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 88b3e2a214084522f079a7928f44abdac2c2ba40..986837d7ec82dc1863f06b0906575674d32a628e 100644 (file)
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_ARM64_ACPI_PARKING_PROTOCOL)     += acpi_parking_protocol.o
 obj-$(CONFIG_PARAVIRT)                 += paravirt.o
 obj-$(CONFIG_RANDOMIZE_BASE)           += kaslr.o
 obj-$(CONFIG_HIBERNATION)              += hibernate.o hibernate-asm.o
+obj-$(CONFIG_ELF_CORE)                 += elfcore.o
 obj-$(CONFIG_KEXEC_CORE)               += machine_kexec.o relocate_kernel.o    \
                                           cpu-reset.o
 obj-$(CONFIG_KEXEC_FILE)               += machine_kexec_file.o kexec_image.o

diff --git a/arch/arm64/kernel/elfcore.c b/arch/arm64/kernel/elfcore.c
new file mode 100644 (file)
index 0000000..3455ee4
--- /dev/null
+++ b/arch/arm64/kernel/elfcore.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/coredump.h>
+#include <linux/elfcore.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+
+#include <asm/cpufeature.h>
+#include <asm/mte.h>
+
+#define for_each_mte_vma(tsk, vma)                                     \
+       if (system_supports_mte())                                      \
+               for (vma = tsk->mm->mmap; vma; vma = vma->vm_next)      \
+                       if (vma->vm_flags & VM_MTE)
+
+static unsigned long mte_vma_tag_dump_size(struct vm_area_struct *vma)
+{
+       if (vma->vm_flags & VM_DONTDUMP)
+               return 0;
+
+       return vma_pages(vma) * MTE_PAGE_TAG_STORAGE;
+}
+
+/* Derived from dump_user_range(); start/end must be page-aligned */
+static int mte_dump_tag_range(struct coredump_params *cprm,
+                             unsigned long start, unsigned long end)
+{
+       unsigned long addr;
+
+       for (addr = start; addr < end; addr += PAGE_SIZE) {
+               char tags[MTE_PAGE_TAG_STORAGE];
+               struct page *page = get_dump_page(addr);
+
+               /*
+                * get_dump_page() returns NULL when encountering an empty
+                * page table entry that would otherwise have been filled with
+                * the zero page. Skip the equivalent tag dump which would
+                * have been all zeros.
+                */
+               if (!page) {
+                       dump_skip(cprm, MTE_PAGE_TAG_STORAGE);
+                       continue;
+               }
+
+               /*
+                * Pages mapped in user space as !pte_access_permitted() (e.g.
+                * PROT_EXEC only) may not have the PG_mte_tagged flag set.
+                */
+               if (!test_bit(PG_mte_tagged, &page->flags)) {
+                       put_page(page);
+                       dump_skip(cprm, MTE_PAGE_TAG_STORAGE);
+                       continue;
+               }
+
+               mte_save_page_tags(page_address(page), tags);
+               put_page(page);
+               if (!dump_emit(cprm, tags, MTE_PAGE_TAG_STORAGE))
+                       return 0;
+       }
+
+       return 1;
+}
+
+Elf_Half elf_core_extra_phdrs(void)
+{
+       struct vm_area_struct *vma;
+       int vma_count = 0;
+
+       for_each_mte_vma(current, vma)
+               vma_count++;
+
+       return vma_count;
+}
+
+int elf_core_write_extra_phdrs(struct coredump_params *cprm, loff_t offset)
+{
+       struct vm_area_struct *vma;
+
+       for_each_mte_vma(current, vma) {
+               struct elf_phdr phdr;
+
+               phdr.p_type = PT_ARM_MEMTAG_MTE;
+               phdr.p_offset = offset;
+               phdr.p_vaddr = vma->vm_start;
+               phdr.p_paddr = 0;
+               phdr.p_filesz = mte_vma_tag_dump_size(vma);
+               phdr.p_memsz = vma->vm_end - vma->vm_start;
+               offset += phdr.p_filesz;
+               phdr.p_flags = 0;
+               phdr.p_align = 0;
+
+               if (!dump_emit(cprm, &phdr, sizeof(phdr)))
+                       return 0;
+       }
+
+       return 1;
+}
+
+size_t elf_core_extra_data_size(void)
+{
+       struct vm_area_struct *vma;
+       size_t data_size = 0;
+
+       for_each_mte_vma(current, vma)
+               data_size += mte_vma_tag_dump_size(vma);
+
+       return data_size;
+}
+
+int elf_core_write_extra_data(struct coredump_params *cprm)
+{
+       struct vm_area_struct *vma;
+
+       for_each_mte_vma(current, vma) {
+               if (vma->vm_flags & VM_DONTDUMP)
+                       continue;
+
+               if (!mte_dump_tag_range(cprm, vma->vm_start, vma->vm_end))
+                       return 0;
+       }
+
+       return 1;
+}