Documentation/arm64/tagged-address-abi.rst and above. The corresponding
``regset`` is 1 element of 8 bytes (``sizeof(long))``).
+Core dump support
+-----------------
+
+The allocation tags for user memory mapped with ``PROT_MTE`` are dumped
+in the core file as additional ``PT_ARM_MEMTAG_MTE`` segments. The
+program header for such segment is defined as:
+
+:``p_type``: ``PT_ARM_MEMTAG_MTE``
+:``p_flags``: 0
+:``p_offset``: segment file offset
+:``p_vaddr``: segment virtual address, same as the corresponding
+ ``PT_LOAD`` segment
+:``p_paddr``: 0
+:``p_filesz``: segment size in file, calculated as ``p_mem_sz / 32``
+ (two 4-bit tags cover 32 bytes of memory)
+:``p_memsz``: segment size in memory, same as the corresponding
+ ``PT_LOAD`` segment
+:``p_align``: 0
+
+The tags are stored in the core file at ``p_offset`` as two 4-bit tags
+in a byte. With the tag granule of 16 bytes, a 4K page requires 128
+bytes in the core file.
+
Example of correct usage
========================
--- /dev/null
+// 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>
+
+#ifndef VMA_ITERATOR
+#define VMA_ITERATOR(name, mm, addr) \
+ struct mm_struct *name = mm
+#define for_each_vma(vmi, vma) \
+ for (vma = vmi->mmap; vma; vma = vma->vm_next)
+#endif
+
+#define for_each_mte_vma(vmi, vma) \
+ if (system_supports_mte()) \
+ for_each_vma(vmi, vma) \
+ 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;
+ VMA_ITERATOR(vmi, current->mm, 0);
+
+ for_each_mte_vma(vmi, vma)
+ vma_count++;
+
+ return vma_count;
+}
+
+int elf_core_write_extra_phdrs(struct coredump_params *cprm, loff_t offset)
+{
+ struct vm_area_struct *vma;
+ VMA_ITERATOR(vmi, current->mm, 0);
+
+ for_each_mte_vma(vmi, 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;
+ VMA_ITERATOR(vmi, current->mm, 0);
+
+ for_each_mte_vma(vmi, 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;
+ VMA_ITERATOR(vmi, current->mm, 0);
+
+ for_each_mte_vma(vmi, vma) {
+ if (vma->vm_flags & VM_DONTDUMP)
+ continue;
+
+ if (!mte_dump_tag_range(cprm, vma->vm_start, vma->vm_end))
+ return 0;
+ }
+
+ return 1;
+}
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