[PATCH] elf: Fix the arm64 MTE ELF segment name and value

From: Catalin Marinas
Date: Mon Apr 25 2022 - 11:18:46 EST

Unfortunately, the name/value choice for the MTE ELF segment type
(PT_ARM_MEMTAG_MTE) was pretty poor: LOPROC+1 is already in use by
PT_AARCH64_UNWIND, as defined in the AArch64 ELF ABI

Update the ELF segment type value to LOPROC+2 and also change the define
to PT_AARCH64_MEMTAG_MTE to match the AArch64 ELF ABI namespace. The
AArch64 ELF ABI document is updating accordingly (segment type not
previously mentioned in the document).

Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Fixes: 761b9b366cec ("elf: Introduce the ARM MTE ELF segment type")
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Luis Machado <luis.machado@xxxxxxx>
Cc: Richard Earnshaw <Richard.Earnshaw@xxxxxxx>

Luckily, the commit being fixed here only went in for 5.18-rc1, so there is no
ABI change in a mainline release.

FYI, the corresponding pull request for the AArch64 ELF ABI:


I don't expect any further change to the segment name/value.

Documentation/arm64/memory-tagging-extension.rst | 4 ++--
arch/arm64/kernel/elfcore.c | 2 +-
include/uapi/linux/elf.h | 2 +-
3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Documentation/arm64/memory-tagging-extension.rst b/Documentation/arm64/memory-tagging-extension.rst
index dd27f78d7608..dbae47bba25e 100644
--- a/Documentation/arm64/memory-tagging-extension.rst
+++ b/Documentation/arm64/memory-tagging-extension.rst
@@ -228,10 +228,10 @@ 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
+in the core file as additional ``PT_AARCH64_MEMTAG_MTE`` segments. The
program header for such segment is defined as:

-:``p_type``: ``PT_ARM_MEMTAG_MTE``
+:``p_type``: ``PT_AARCH64_MEMTAG_MTE``
:``p_flags``: 0
:``p_offset``: segment file offset
:``p_vaddr``: segment virtual address, same as the corresponding
diff --git a/arch/arm64/kernel/elfcore.c b/arch/arm64/kernel/elfcore.c
index 2b3f3d0544b9..98d67444a5b6 100644
--- a/arch/arm64/kernel/elfcore.c
+++ b/arch/arm64/kernel/elfcore.c
@@ -95,7 +95,7 @@ int elf_core_write_extra_phdrs(struct coredump_params *cprm, loff_t offset)
for_each_mte_vma(current, vma) {
struct elf_phdr phdr;

- phdr.p_type = PT_ARM_MEMTAG_MTE;
+ phdr.p_type = PT_AARCH64_MEMTAG_MTE;
phdr.p_offset = offset;
phdr.p_vaddr = vma->vm_start;
phdr.p_paddr = 0;
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 787c657bfae8..7ce993e6786c 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -42,7 +42,7 @@ typedef __s64 Elf64_Sxword;

/* ARM MTE memory tag segment type */
-#define PT_ARM_MEMTAG_MTE (PT_LOPROC + 0x1)
+#define PT_AARCH64_MEMTAG_MTE (PT_LOPROC + 0x2)

* Extended Numbering