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Date: Tue, 16 Jan 2024 19:29:18 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: Cody Wetzel <codyawetzel@...il.com>
Cc: Natanael Copa <ncopa@...inelinux.org>, musl@...ts.openwall.com,
	Markus Wichmann <nullplan@....net>
Subject: Re: Segmentation fault musl 1.2.4

* Cody Wetzel <codyawetzel@...il.com> [2024-01-16 09:21:05 -0600]:
> Here is the output for the old
> ....
> >
> > / # /tmp/ld-musl-armhf.so.1 /usr/bin/readelf -lW /tmp/ld-musl-armhf.so.1
> >
> > Elf file type is DYN (Shared object file)
> > Entry point 0x359cd
> > There are 6 program headers, starting at offset 52
> >
> > Program Headers:
> >   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> >   EXIDX          0x07acec 0x0007acec 0x0007acec 0x00008 0x00008 R   0x4
> >   LOAD           0x000000 0x00000000 0x00000000 0x7acf4 0x7acf4 R E 0x10000
> >   LOAD           0x07fd6c 0x0008fd6c 0x0008fd6c 0x0054a 0x02258 RW  0x10000

this load segment is 64k aligned.

> >   DYNAMIC        0x07febc 0x0008febc 0x0008febc 0x000c0 0x000c0 RW  0x4
> >   GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x10
> >   GNU_RELRO      0x07fd6c 0x0008fd6c 0x0008fd6c 0x00294 0x00294 R   0x1
> >
> >  Section to Segment mapping:
> >   Segment Sections...
> >    00     .ARM.exidx
> >    01     .hash .gnu.hash .dynsym .dynstr .rel.dyn .rel.plt .plt .text
> > .rodata .ARM.exidx
> >    02     .data.rel.ro .dynamic .got .data .bss
> >    03     .dynamic
> >    04
> >    05     .data.rel.ro .dynamic .got
> >
> 
> And the new...
> 
> / # /tmp/ld-musl-armhf.so.1 /usr/bin/readelf -lW /lib/ld-musl-armhf.so.1
> >
> > Elf file type is DYN (Shared object file)
> > Entry point 0x362f1
> > There are 6 program headers, starting at offset 52
> >
> > Program Headers:
> >   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> >   EXIDX          0x07b81c 0x0007b81c 0x0007b81c 0x00008 0x00008 R   0x4
> >   LOAD           0x000000 0x00000000 0x00000000 0x7b824 0x7b824 R E 0x1000
> >   LOAD           0x07bd74 0x0007cd74 0x0007cd74 0x0054a 0x0225c RW  0x1000

this load segment is 4k aligned and offset vs addr is not congruent
modulo 64k, or 32k, so won't work on systems with such page size.

> >   DYNAMIC        0x07bebc 0x0007cebc 0x0007cebc 0x000c0 0x000c0 RW  0x4
> >   GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x10
> >   GNU_RELRO      0x07bd74 0x0007cd74 0x0007cd74 0x0028c 0x0028c R   0x1
> >
> >  Section to Segment mapping:
> >   Segment Sections...
> >    00     .ARM.exidx
> >    01     .hash .gnu.hash .dynsym .dynstr .rel.dyn .rel.plt .plt .text
> > .rodata .ARM.exidx
> >    02     .data.rel.ro .dynamic .got .data .bss
> >    03     .dynamic
> >    04
> >    05     .data.rel.ro .dynamic .got
> 
> 
> I hope that helps.

yes, this is a linking issue, not musl libc.

alpine linux links binaries for 4k pagesize only.

arm linkers were updated at some point to create binaries supporting
up to 64k pagesize.  i suspect some ppl ran into issues in practice
and decided the larger binaries are not worth it, if they dont work
reliably and forced 4k page size at link time.

you have to raise an issue with alpine linux, if you think 32k
oage size is useful and reliably supportable.

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