[PATCH v1] GAS: Keep symbols in their own section [PR27566]

[Xiao Zeng]

Hi Jeff and Nelson, an issue has arisen in GCC, described here:
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115166>

Afterward, it was thought to be an ld issue, described here:
<https://sourceware.org/bugzilla/show_bug.cgi?id=27566>

Nelson has done some work on ld, but it hasn’t completely resolved the problem. I understand that this issue may actually stem from as. I have tested the following modification, which can resolve the current issue.

Here is the emails exchange I had with Alan:
<https://sourceware.org/pipermail/binutils/2024-October/137360.html>

Alan provided some excellent insights.

To help drive the resolution of this issue, could you also offer some advice when you have time?

Thank you both very much.

2024-10-22 17:43  Xiao Zeng <zengxiao@eswincomputing.com> wrote:
>
>PR27566 is categorized under ld:
><https://sourceware.org/bugzilla/show_bug.cgi?id=27566>
>but the root cause of this issue is in gas.
>
>The following assembly example is provided:
>        .section        .rodata
>        .globl Sym
>        .type  Sym, @object
>        .set   Sym, . + 0x1200
>        .size	Sym, 8
>
>readelf reads ELF information:
>Section Headers:
>  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
>  [ 4] .rodata           PROGBITS        0000000000000000 000040 000000 00   A  0   0  1
>
>Symbol table '.symtab' contains 7 entries:
>   Num:    Value          Size Type    Bind   Vis      Ndx Name
>     6: 0000000000001200     8 OBJECT  GLOBAL DEFAULT    4 Sym
>
>The Sym belongs to the .rodata section, but the size of .rodata is 0.
>
>        PR gas/27566
>	* write.c (size_seg): Update section size.
>	* testsuite/gas/elf/elf.exp: New test.
>	* testsuite/gas/elf/pr27566.d: New file.
>	* testsuite/gas/elf/pr27566.s: Likewise.
>
>Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
>---
> gas/testsuite/gas/elf/elf.exp   |  1 +
> gas/testsuite/gas/elf/pr27566.d | 11 +++++++++++
> gas/testsuite/gas/elf/pr27566.s |  5 +++++
> gas/write.c                     |  7 +++++++
> 4 files changed, 24 insertions(+)
> create mode 100644 gas/testsuite/gas/elf/pr27566.d
> create mode 100644 gas/testsuite/gas/elf/pr27566.s
>
>diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
>index c828c3af25c..6a69acbc109 100644
>--- a/gas/testsuite/gas/elf/elf.exp
>+++ b/gas/testsuite/gas/elf/elf.exp
>@@ -387,4 +387,5 @@ if { [is_elf_format] } then {
>     run_dump_test "bignums" $dump_opts
>     run_dump_test "section-symbol-redef"
>     run_dump_test "pr27228"
>+    run_dump_test "pr27566"
> }
>diff --git a/gas/testsuite/gas/elf/pr27566.d b/gas/testsuite/gas/elf/pr27566.d
>new file mode 100644
>index 00000000000..75268cefb20
>--- /dev/null
>+++ b/gas/testsuite/gas/elf/pr27566.d
>@@ -0,0 +1,11 @@
>+#as:
>+#name: Keep symbols in their own section (PR 27566)
>+#readelf: -S --wide
>+
>+There are [0-9]+ section headers, starting at offset 0x[0-9a-f]+:
>+
>+Section Headers:
>+ +\[Nr\] Name +Type +Addr(ess|) +Off +Size +ES +Flg +Lk +Inf +Al
>+#...
>+ *\[ [1-9]\] *\.rodata +PROGBITS +0*0 +0[0-9a-f]* +0*1208 .*
>+#pass
>diff --git a/gas/testsuite/gas/elf/pr27566.s b/gas/testsuite/gas/elf/pr27566.s
>new file mode 100644
>index 00000000000..4232df21494
>--- /dev/null
>+++ b/gas/testsuite/gas/elf/pr27566.s
>@@ -0,0 +1,5 @@
>+        .section        .rodata
>+        .globl Sym
>+        .type  Sym, @object
>+        .set   Sym, . + 0x1200
>+        .size	Sym, 8
>diff --git a/gas/write.c b/gas/write.c
>index 18cf18fc830..7f69d7aad44 100644
>--- a/gas/write.c
>+++ b/gas/write.c
>@@ -559,6 +559,7 @@ size_seg (bfd *abfd ATTRIBUTE_UNUSED, asection *sec, void *xxx ATTRIBUTE_UNUSED)
>   segment_info_type *seginfo;
>   int x;
>   valueT size, newsize;
>+  symbolS *symp;
>
>   subseg_change (sec, 0);
>
>@@ -577,6 +578,12 @@ size_seg (bfd *abfd ATTRIBUTE_UNUSED, asection *sec, void *xxx ATTRIBUTE_UNUSED)
>   else
>     size = 0;
>
>+  /* Keep symbols in their own section.  */
>+  for (symp = symbol_rootP; symp; symp = symbol_next (symp))
>+    if (S_GET_SEGMENT (symp) == sec
>+	&& size < (S_GET_VALUE (symp) + S_GET_SIZE (symp)))
>+      size = S_GET_VALUE (symp) + S_GET_SIZE (symp);
>+
>   flags = bfd_section_flags (sec);
>   if (size == 0 && bfd_section_size (sec) != 0 &&
>     (flags & SEC_HAS_CONTENTS) != 0)
>--
>2.17.1
Thanks
Xiao Zeng