Incorrect layout due to the use of incorrect symbol value when layout restarts in-between a layout pass

[parth-07]

We often have to restart the layout computation when some assumption changes such as the number of segments. When this layout re-computation restart happens, sometimes we end up using incorrect symbol values when evaluating some assignments. This can lead to incorrect layout.

Reproducible example:

#!/usr/bin/env bash

cat >1.c <<\EOF
int foo() { return 1; }

int u = 11;
EOF

cat >script.t <<\EOF
SECTIONS {
  u = v;
  .text.foo : { *(.text.foo) }
  v = 0x1000;
  .data : { *(.data) }
  .comment : { *(.comment) }
  v = 0x2000;
}
EOF

LDs=(ld.eld)
SFs=(eld)

clang -o 1.o -target aarch64-unknown-elf 1.c -c -ffunction-sections

for i in "${!SFs[@]}"; do
  ${LDs[$i]} -o 1.${SFs[$i]}.out 1.o -T script.t
done

llvm-readelf -s 1.eld.out

Outputs:

...
8: 0000000000000000     8 FUNC    GLOBAL DEFAULT     1 foo
9: 0000000000001000     4 OBJECT  GLOBAL DEFAULT   ABS u
...

The value of u should be 0x2000 instead of 0x1000.