linux/include/asm-generic
Josh Poimboeuf f7ba52f302 vmlinux.lds.h: Discard .note.gnu.property section
When tooling reads ELF notes, it assumes each note entry is aligned to
the value listed in the .note section header's sh_addralign field.

The kernel-created ELF notes in the .note.Linux and .note.Xen sections
are aligned to 4 bytes.  This causes the toolchain to set those
sections' sh_addralign values to 4.

On the other hand, the GCC-created .note.gnu.property section has an
sh_addralign value of 8 for some reason, despite being based on struct
Elf32_Nhdr which only needs 4-byte alignment.

When the mismatched input sections get linked together into the vmlinux
.notes output section, the higher alignment "wins", resulting in an
sh_addralign of 8, which confuses tooling.  For example:

  $ readelf -n .tmp_vmlinux.btf
  ...
  readelf: .tmp_vmlinux.btf: Warning: note with invalid namesz and/or descsz found at offset 0x170
  readelf: .tmp_vmlinux.btf: Warning:  type: 0x4, namesize: 0x006e6558, descsize: 0x00008801, alignment: 8

In this case readelf thinks there's alignment padding where there is
none, so it starts reading an ELF note in the middle.

With newer toolchains (e.g., latest Fedora Rawhide), a similar mismatch
triggers a build failure when combined with CONFIG_X86_KERNEL_IBT:

  btf_encoder__encode: btf__dedup failed!
  Failed to encode BTF
  libbpf: failed to find '.BTF' ELF section in vmlinux
  FAILED: load BTF from vmlinux: No data available
  make[1]: *** [scripts/Makefile.vmlinux:35: vmlinux] Error 255

This latter error was caused by pahole crashing when it encountered the
corrupt .notes section.  This crash has been fixed in dwarves version
1.25.  As Tianyi Liu describes:

  "Pahole reads .notes to look for LINUX_ELFNOTE_BUILD_LTO. When LTO is
   enabled, pahole needs to call cus__merge_and_process_cu to merge
   compile units, at which point there should only be one unspecified
   type (used to represent some compilation information) in the global
   context.

   However, when the kernel is compiled without LTO, if pahole calls
   cus__merge_and_process_cu due to alignment issues with notes,
   multiple unspecified types may appear after merging the cus, and
   older versions of pahole only support up to one. This is why pahole
   1.24 crashes, while newer versions support multiple. However, the
   latest version of pahole still does not solve the problem of
   incorrect LTO recognition, so compiling the kernel may be slower
   than normal."

Even with the newer pahole, the note section misaligment issue still
exists and pahole is misinterpreting the LTO note.  Fix it by discarding
the .note.gnu.property section.  While GNU properties are important for
user space (and VDSO), they don't seem to have any use for vmlinux.

(In fact, they're already getting (inadvertently) stripped from vmlinux
when CONFIG_DEBUG_INFO_BTF is enabled.  The BTF data is extracted from
vmlinux.o with "objcopy --only-section=.BTF" into .btf.vmlinux.bin.o.
That file doesn't have .note.gnu.property, so when it gets modified and
linked back into the main object, the linker automatically strips it
(see "How GNU properties are merged" in the ld man page).)

Reported-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lkml.kernel.org/bpf/57830c30-cd77-40cf-9cd1-3bb608aa602e@app.fastmail.com
Debugged-by: Tianyi Liu <i.pear@outlook.com>
Suggested-by: Joan Bruguera Micó <joanbrugueram@gmail.com>
Link: https://lore.kernel.org/r/20230418214925.ay3jpf2zhw75kgmd@treble
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2023-05-16 06:30:50 -07:00
..
bitops wait_on_bit: add an acquire memory barrier 2022-08-26 09:30:25 -07:00
vdso lib/vdso: Avoid highres update if clocksource is not VDSO capable 2020-02-17 20:12:17 +01:00
access_ok.h uaccess: remove CONFIG_SET_FS 2022-02-25 09:36:06 +01:00
agp.h char/agp: introduce asm-generic/agp.h 2023-02-13 22:13:29 +01:00
archrandom.h random: handle archrandom with multiple longs 2022-07-25 13:26:14 +02:00
asm-offsets.h
asm-prototypes.h
atomic64.h locking/atomic: delete !ARCH_ATOMIC remnants 2021-05-26 13:20:52 +02:00
atomic.h asm-generic: avoid __generic_cmpxchg_local warnings 2023-04-04 17:58:11 +02:00
audit_change_attr.h
audit_dir_write.h
audit_read.h
audit_signal.h
audit_write.h
barrier.h asm-generic: Add memory barrier dma_mb() 2022-06-23 18:34:58 +01:00
bitops.h include: move find.h from asm_generic to linux 2022-01-15 08:47:31 -08:00
bitsperlong.h lib: extend the scope of small_const_nbits() macro 2021-05-06 19:24:11 -07:00
bug.h treewide: Drop WARN_ON_FUNCTION_MISMATCH 2022-09-26 10:13:14 -07:00
bugs.h
cache.h
cacheflush.h asm-generic: instrument usercopy in cacheflush.h 2022-10-03 14:03:18 -07:00
checksum.h unify generic instances of csum_partial_copy_nocheck() 2020-08-20 15:45:14 -04:00
cmpxchg-local.h asm-generic: avoid __generic_cmpxchg_local warnings 2023-04-04 17:58:11 +02:00
cmpxchg.h asm-generic: avoid __generic_cmpxchg_local warnings 2023-04-04 17:58:11 +02:00
compat.h asm-generic: compat: fix compat_arg_u64() and compat_arg_u64_dual() 2022-11-01 10:20:11 +11:00
current.h
delay.h
device.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
div64.h ARM: 9117/1: asm-generic: div64: Remove always-true __div64_const32_is_OK() 2021-08-20 11:39:28 +01:00
dma-mapping.h dma-mapping: no need to pass a bus_type into get_arch_dma_ops() 2023-02-15 12:35:20 +01:00
dma.h
early_ioremap.h mm/early_ioremap.c: remove redundant early_ioremap_shutdown() 2021-09-08 11:50:24 -07:00
emergency-restart.h
error-injection.h docs: fault-injection: add requirements of error injectable functions 2023-02-02 22:50:00 -08:00
exec.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
export.h kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS 2022-05-24 16:33:20 +09:00
extable.h
fb.h
fixmap.h
flat.h binfmt_flat: remove the persistent argument from flat_get_addr_from_rp 2019-06-24 09:16:47 +10:00
ftrace.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
futex.h futex: Fix additional regressions 2021-12-11 23:31:51 +01:00
getorder.h asm-generic: force inlining of get_order() to work around gcc10 poor decision 2020-12-15 22:46:15 -08:00
hardirq.h irqstat: Move declaration into asm-generic/hardirq.h 2020-11-23 10:31:06 +01:00
hugetlb.h mm/uffd: always wr-protect pte in pte|pmd_mkuffd_wp() 2023-01-18 17:12:37 -08:00
hw_irq.h
hyperv-tlfs.h x86/hyperv: Add VTL specific structs and hypercalls 2023-04-18 17:29:51 +00:00
ide_iops.h
int-ll64.h
io.h asm-generic/io.h: suppress endianness warnings for relaxed accessors 2023-04-04 17:58:11 +02:00
ioctl.h
iomap.h parisc: Declare pci_iounmap() parisc version only when CONFIG_PCI enabled 2021-09-19 10:36:09 -07:00
irq_regs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
irq_work.h
irq.h
irqflags.h
Kbuild xen: branch for v6.0-rc1 2022-08-04 15:10:55 -07:00
kdebug.h
kmap_size.h mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL 2020-11-24 14:42:08 +01:00
kprobes.h treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
kvm_para.h
kvm_types.h KVM: Move x86's version of struct kvm_mmu_memory_cache to common code 2020-07-09 13:29:42 -04:00
linkage.h
local64.h locking/generic: Wire up local{,64}_try_cmpxchg() 2023-04-29 09:09:09 +02:00
local.h locking/generic: Wire up local{,64}_try_cmpxchg() 2023-04-29 09:09:09 +02:00
logic_io.h logic_io instance of iounmap() needs volatile on argument 2021-12-21 21:31:08 +01:00
mcs_spinlock.h
memory_model.h mm, arch: add generic implementation of pfn_valid() for FLATMEM 2023-02-09 16:51:41 -08:00
mm_hooks.h mm: remove arch_bprm_mm_init() hook 2020-01-23 10:41:16 -08:00
mmiowb_types.h asm-generic/mmiowb: Add generic implementation of mmiowb() tracking 2019-04-08 11:59:39 +01:00
mmiowb.h asm-generic/mmiowb: Allow mmiowb_set_pending() when preemptible() 2020-07-17 10:02:03 +01:00
mmu_context.h asm-generic: add generic MMU versions of mmu context functions 2020-10-26 16:45:03 +01:00
mmu.h
module.h
module.lds.h kbuild: preprocess module linker script 2020-09-25 00:36:41 +09:00
mshyperv.h x86/hyperv: Add callback filter to cpumask_to_vpset() 2023-04-17 19:19:05 +00:00
msi.h genirq: Get rid of GENERIC_MSI_IRQ_DOMAIN 2022-11-17 15:15:20 +01:00
nommu_context.h asm-generic: add generic MMU versions of mmu context functions 2020-10-26 16:45:03 +01:00
numa.h numa: Move numa implementation to common code 2021-01-14 15:08:55 -08:00
page.h mm, arch: add generic implementation of pfn_valid() for FLATMEM 2023-02-09 16:51:41 -08:00
param.h
parport.h
pci_iomap.h PCI: Stub __pci_ioport_map() for arches that don't support it at all 2022-07-29 12:01:00 -05:00
pci.h asm-generic: Add new pci.h and use it 2022-07-22 17:34:57 -05:00
percpu.h asm-generic: percpu: avoid Wshadow warning 2020-10-26 23:54:48 +00:00
pgalloc.h mm: prefer xxx_page() alloc/free functions for order-0 pages 2023-03-28 16:20:16 -07:00
pgtable_uffd.h userfaultfd: wp: add pmd_swp_*uffd_wp() helpers 2020-04-07 10:43:39 -07:00
pgtable-nop4d.h mm: rename p4d_page_vaddr to p4d_pgtable and make it return pud_t * 2021-07-08 11:48:22 -07:00
pgtable-nopmd.h riscv/mm: fix two page table check related issues 2022-05-19 14:08:48 -07:00
pgtable-nopud.h mm: rename p4d_page_vaddr to p4d_pgtable and make it return pud_t * 2021-07-08 11:48:22 -07:00
preempt.h sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
qrwlock_types.h locking/qrwlock: Change "queue rwlock" to "queued rwlock" 2022-05-11 16:27:04 +02:00
qrwlock.h asm-generic changes for 5.19 2022-05-26 10:50:30 -07:00
qspinlock_types.h locking/qspinlock: Do not include atomic.h from qspinlock_types.h 2020-07-29 16:14:19 +02:00
qspinlock.h asm-generic: qspinlock: Indicate the use of mixed-size atomics 2022-05-11 11:49:47 -07:00
resource.h
rwonce.h asm/rwonce: Don't pull <asm/barrier.h> into 'asm-generic/rwonce.h' 2020-07-21 10:50:36 +01:00
seccomp.h seccomp: Use -1 marker for end of mode 1 syscall list 2020-07-10 16:01:52 -07:00
sections.h asm-generic: sections: refactor memory_intersects 2022-08-28 14:02:45 -07:00
serial.h
set_memory.h
shmparam.h treewide: remove SPDX "WITH Linux-syscall-note" from kernel-space headers 2019-05-14 19:52:48 -07:00
signal.h asm-generic: Remove empty #ifdef SA_RESTORER 2022-09-10 09:56:53 +02:00
simd.h
softirq_stack.h asm-generic: Conditionally enable do_softirq_own_stack() via Kconfig. 2022-09-05 17:20:55 +02:00
spinlock_types.h asm-generic: ticket-lock: New generic ticket-based spinlock 2022-05-11 11:49:38 -07:00
spinlock.h asm-generic: ticket-lock: New generic ticket-based spinlock 2022-05-11 11:49:38 -07:00
statfs.h
string.h
switch_to.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
syscall.h ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h 2022-03-10 13:35:08 -06:00
syscalls.h
timex.h
tlb.h mm: delay page_remove_rmap() until after the TLB has been flushed 2022-11-30 15:58:50 -08:00
tlbflush.h
topology.h mm: replace CONFIG_NEED_MULTIPLE_NODES with CONFIG_NUMA 2021-06-29 10:53:55 -07:00
trace_clock.h
uaccess.h uaccess: remove CONFIG_SET_FS 2022-02-25 09:36:06 +01:00
unaligned.h asm-generic: make parameter types consistent in _unaligned_be48() 2022-09-11 21:55:12 -07:00
user.h
vermagic.h arch: split MODULE_ARCH_VERMAGIC definitions out to <asm/vermagic.h> 2020-04-23 10:50:26 +09:00
vga.h
vmlinux.lds.h vmlinux.lds.h: Discard .note.gnu.property section 2023-05-16 06:30:50 -07:00
vtime.h
word-at-a-time.h
xor.h lib/xor: make xor prototypes more friendly to compiler vectorization 2022-02-11 20:39:39 +11:00