https://sourceware.org/bugzilla/show_bug.cgi?id=28686
Nick Clifton <nickc at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-12-16
Assignee|unassigned at sourceware dot org |nickc at redhat dot com
CC| |nickc at redhat dot com
Status|UNCONFIRMED |ASSIGNED
Ever confirmed|0 |1
--- Comment #1 from Nick Clifton <nickc at redhat dot com> ---
Hi Joerg,
The root cause for this problem is the assembler. When it assembles
the test file it created a relocation for the LDI instruction which
references the .text section:
% objdump -dr main.o
[...]
4b2: f0 e0 ldi r31, 0x00 ; 0
4b2: R_AVR_HI8_LDI .text+0x500
So when the relaxation happens the code adjusts the relocation
eventually ending up with .text+0x2ab which then translates into
a value of 2 (the top 8 bits of the addition) for LDI instruction.
This error of course is that the relocation should not be against
an offset from the .text section, but rather against the matrix
symbol itself. Since this symbol stays aligned, it does not move
as far back as the .text+offset value.
I am currently testing a local patch which stops the assembler
from trying to optimize away symbol names in relocations if it
knows that linker relaxation is going to occur. With this patch
applied the object file looks like:
% objdump -dr main.o
[...]
4b2: f0 e0 ldi r31, 0x00 ; 0
4b2: R_AVR_HI8_LDI matrix
And when finally linked the correct value - 3 - is used by the
LDI instruction.
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