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From: Mikulas Patocka <mpatocka@redhat.com>
To: Luis Chamberlain <mcgrof@kernel.org>,
	Petr Pavlu <petr.pavlu@suse.com>,
	 Sami Tolvanen <samitolvanen@google.com>,
	 Daniel Gomez <da.gomez@samsung.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	 Helge Deller <deller@gmx.de>,
	linux-modules@vger.kernel.org,  linux-kernel@vger.kernel.org,
	linux-parisc@vger.kernel.org
Subject: Unaligned accesses when loading modules
Date: Tue, 14 Jan 2025 19:07:30 +0100 (CET)	[thread overview]
Message-ID: <1665d54c-178f-ff72-e627-776e7c76798b@redhat.com> (raw)

Hi

On PA-RISC, with the kernel 6.12.9, I get unaligned pointer warnings when 
a module is loaded. The warnings are caused by the fact that the 
.gnu.linkonce.this_module section is not aligned to the appropriate 
boundary. If I dump the module content with "objdump -h configs.ko", I get 
this. Note that the .gnu.linkonce.this_module has "File off 000042d2" and 
"Algn 2**4".

On x86-64, the same misalignment can be seen, but it doesn't cause 
warnings because unaligned pointers are handled in hardware.

This seems to be a bug in the linker, because when I compile an old kernel 
with a new linker, I also get the misalignment. Do you have an idea how to 
work around this bug?

Mikulas


kernel-6.12.9, binutils from Debian ports:

configs.ko:     file format elf64-hppa-linux

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         00000040  0000000000000000  0000000000000000  00000040  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  1 .init.text    00000070  0000000000000000  0000000000000000  00000080  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  2 .exit.text    00000028  0000000000000000  0000000000000000  000000f0  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  3 .rodata       00004015  0000000000000000  0000000000000000  00000118  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .rodata.str1.8 00000010  0000000000000000  0000000000000000  0000412d  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .PARISC.unwind 00000030  0000000000000000  0000000000000000  0000413d  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  6 .modinfo      000000a1  0000000000000000  0000000000000000  0000416d  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 .note.gnu.build-id 00000024  0000000000000000  0000000000000000  0000420e  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 .note.Linux   00000030  0000000000000000  0000000000000000  00004232  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 .data         00000000  0000000000000030  0000000000000030  00004262  2**0
                  CONTENTS, ALLOC, LOAD, DATA
 10 .exit.data    00000008  0000000000000000  0000000000000000  00004262  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 11 .init.data    00000008  0000000000000000  0000000000000000  0000426a  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 12 .data.rel.ro  00000060  0000000000000000  0000000000000000  00004272  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 13 .gnu.linkonce.this_module 000002d0  0000000000000000  0000000000000000  000042d2  2**4
                  CONTENTS, ALLOC, LOAD, RELOC, DATA, LINK_ONCE_DISCARD
 14 .bss          00000000  0000000000000000  0000000000000000  000045a2  2**0
                  ALLOC
 15 .comment      00000039  0000000000000000  0000000000000000  000045a2  2**0
                  CONTENTS, READONLY
 16 .note.GNU-stack 00000000  0000000000000000  0000000000000000  000045db  2**0
                  CONTENTS, READONLY

With the kernel 6.10, I get this - the ".gnu.linkonce.this_module" 
sections has "File off 00004210" and "Algn 2**4" - so, it is properly 
aligned.

kernel 6.10, older binutils:

configs.ko:     file format elf64-hppa-linux

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .note.gnu.build-id 00000024  0000000000000000  0000000000000000  00000040  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  1 .note.Linux   00000030  0000000000000000  0000000000000000  00000064  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .text         00000040  0000000000000000  0000000000000000  00000098  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  3 .init.text    00000070  0000000000000000  0000000000000000  000000d8  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  4 .exit.text    00000028  0000000000000000  0000000000000000  00000148  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  5 .rodata       00003f45  0000000000000000  0000000000000000  00000170  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 .rodata.str1.8 00000010  0000000000000000  0000000000000000  000040b8  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 .PARISC.unwind 00000030  0000000000000000  0000000000000000  000040c8  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  8 .modinfo      000000a1  0000000000000000  0000000000000000  000040f8  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 .data         00000007  00000000000000a1  00000000000000a1  00004199  2**0
                  CONTENTS, ALLOC, LOAD, DATA
 10 .exit.data    00000008  0000000000000000  0000000000000000  000041a0  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 11 .init.data    00000008  0000000000000000  0000000000000000  000041a8  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 12 .data.rel.ro  00000060  0000000000000000  0000000000000000  000041b0  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
 13 .gnu.linkonce.this_module 000002d0  0000000000000000  0000000000000000  00004210  2**4
                  CONTENTS, ALLOC, LOAD, RELOC, DATA, LINK_ONCE_DISCARD
 14 .bss          00000000  0000000000000000  0000000000000000  000044e0  2**0
                  ALLOC
 15 .comment      00000026  0000000000000000  0000000000000000  000044e0  2**0
                  CONTENTS, READONLY
 16 .note.GNU-stack 00000000  0000000000000000  0000000000000000  00004506  2**0
                  CONTENTS, READONLY


             reply	other threads:[~2025-01-14 18:07 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-01-14 18:07 Mikulas Patocka [this message]
2025-01-14 22:37 ` Unaligned accesses when loading modules Sami Tolvanen
2025-01-15 18:02   ` Mikulas Patocka
2025-01-16  7:59     ` Jan Beulich
2025-01-16 15:29       ` Mikulas Patocka
2025-01-16 16:00         ` Jan Beulich
2025-01-17  2:00           ` Maciej W. Rozycki

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