[PATCH v2] bfd: xtensa: keep property tables without linker script KEEP
Alexey Lapshin
alexey.lapshin@espressif.com
Tue Aug 25 07:52:04 GMT 2026
Property sections are unreferenced, so linker scripts kept them alive
with KEEP(). That does not work: gas puts .xt.prop/.xt.lit for a COMDAT
function into that function's group, and _bfd_elf_gc_mark marks every
member of a group when one member is marked. KEEP() on the property
section therefore resurrected the code, literals, rodata and exception
tables of unused C++ template instantiations and inline functions.
Dropping KEEP() instead loses the property tables of live code, because
non-COMDAT objects share one .xt.prop that nothing references.
Mark property tables from the gc_mark_extra_sections hook, once the
sections they describe have been marked, using the existing
xtensa_get_property_section lookup. Set gc_mark directly rather than
calling _bfd_elf_gc_mark, so a property section that belongs to a COMDAT
group does not drag in the rest of the group. Linker scripts no longer
need KEEP() for .xt.prop/.xt.lit. Warn once if KEEP is still used for a
property section base name.
bfd/
* elf32-xtensa.c (elf_xtensa_gc_mark_extra_sections): New
function. Warn if KEEP is used for a property section.
(elf_backend_gc_mark_extra_sections): Define.
(elf_xtensa_gc_mark_hook): Update comment.
include/
* elf/xtensa.h (XTENSA_PROPERTY_SEC_NAMES): New macro.
ld/
* testsuite/ld-xtensa/gc-prop.d: New test.
* testsuite/ld-xtensa/gc-prop.map: New test map check.
* testsuite/ld-xtensa/gc-prop.s: New test source.
* testsuite/ld-xtensa/gc-prop.t: New test script.
* testsuite/ld-xtensa/xtensa.exp: Run it.
---
bfd/elf32-xtensa.c | 76 ++++++++++++++++++++++++++----
include/elf/xtensa.h | 3 ++
ld/testsuite/ld-xtensa/gc-prop.d | 7 +++
ld/testsuite/ld-xtensa/gc-prop.map | 9 ++++
ld/testsuite/ld-xtensa/gc-prop.s | 9 ++++
ld/testsuite/ld-xtensa/gc-prop.t | 7 +++
ld/testsuite/ld-xtensa/xtensa.exp | 1 +
7 files changed, 102 insertions(+), 10 deletions(-)
create mode 100644 ld/testsuite/ld-xtensa/gc-prop.d
create mode 100644 ld/testsuite/ld-xtensa/gc-prop.map
create mode 100644 ld/testsuite/ld-xtensa/gc-prop.s
create mode 100644 ld/testsuite/ld-xtensa/gc-prop.t
diff --git a/bfd/elf32-xtensa.c b/bfd/elf32-xtensa.c
index b1733345fc8..ef40af97053 100644
--- a/bfd/elf32-xtensa.c
+++ b/bfd/elf32-xtensa.c
@@ -1325,16 +1325,12 @@ elf_xtensa_gc_mark_hook (asection *sec,
struct elf_link_hash_entry *h,
unsigned int symndx)
{
- /* Property sections are marked "KEEP" in the linker scripts, but they
- should not cause other sections to be marked. (This approach relies
- on elf_xtensa_discard_info to remove property table entries that
- describe discarded sections. Alternatively, it might be more
- efficient to avoid using "KEEP" in the linker scripts and instead use
- the gc_mark_extra_sections hook to mark only the property sections
- that describe marked sections. That alternative does not work well
- with the current property table sections, which do not correspond
- one-to-one with the sections they describe, but that should be fixed
- someday.) */
+ /* Nothing refers to a property section, so it is kept alive by
+ elf_xtensa_gc_mark_extra_sections instead, and its relocations must
+ not cause other sections to be marked. (This relies on
+ elf_xtensa_discard_info to remove property table entries that
+ describe discarded sections, which is needed anyway because a
+ property section may describe more than one section.) */
if (xtensa_is_property_section (sec))
return NULL;
@@ -1350,6 +1346,65 @@ elf_xtensa_gc_mark_hook (asection *sec,
}
+/* Property sections are not referenced by anything, so this pass marks
+ the ones describing sections that have been marked. */
+
+static bool
+elf_xtensa_gc_mark_extra_sections (struct bfd_link_info *info,
+ elf_gc_mark_hook_fn gc_mark_hook)
+{
+ static const char *const prop_names[] = XTENSA_PROPERTY_SEC_NAMES;
+ bfd *sub;
+ bool warned = false;
+
+ _bfd_elf_gc_mark_extra_sections (info, gc_mark_hook);
+
+ for (sub = info->input_bfds; sub != NULL; sub = sub->link.next)
+ {
+ asection *sec;
+
+ if (!is_xtensa_elf (sub))
+ continue;
+
+ for (sec = sub->sections; sec != NULL; sec = sec->next)
+ {
+ size_t i;
+
+ if (!sec->gc_mark
+ || (sec->flags & SEC_ALLOC) == 0
+ || xtensa_is_property_section (sec))
+ continue;
+
+ for (i = 0; i < sizeof (prop_names) / sizeof (prop_names[0]); i++)
+ {
+ asection *prop_sec =
+ xtensa_get_property_section (sec, prop_names[i]);
+
+ /* Set "gc_mark" directly rather than calling _bfd_elf_gc_mark:
+ a property section can be a member of the COMDAT group of
+ the section it describes, and marking a group member retains
+ the entire group. Nothing else needs to be marked because
+ elf_xtensa_gc_mark_hook ignores relocations in property
+ sections. */
+ if (prop_sec != NULL)
+ {
+ if (!warned && (prop_sec->flags & SEC_KEEP) != 0)
+ {
+ info->callbacks->einfo
+ (_("%P: warning: KEEP should not be used for Xtensa "
+ "property section %s\n"), prop_names[i]);
+ warned = true;
+ }
+ prop_sec->gc_mark = 1;
+ }
+ }
+ }
+ }
+
+ return true;
+}
+
+
/* Create all the dynamic sections. */
static bool
@@ -11497,6 +11552,7 @@ static const struct bfd_elf_special_section elf_xtensa_special_sections[] =
#define elf_backend_finish_dynamic_sections elf_xtensa_finish_dynamic_sections
#define elf_backend_finish_dynamic_symbol elf_xtensa_finish_dynamic_symbol
#define elf_backend_gc_mark_hook elf_xtensa_gc_mark_hook
+#define elf_backend_gc_mark_extra_sections elf_xtensa_gc_mark_extra_sections
#define elf_backend_grok_prstatus elf_xtensa_grok_prstatus
#define elf_backend_grok_psinfo elf_xtensa_grok_psinfo
#define elf_backend_hide_symbol elf_xtensa_hide_symbol
diff --git a/include/elf/xtensa.h b/include/elf/xtensa.h
index 1a9bdf95cf7..339c8bf8ada 100644
--- a/include/elf/xtensa.h
+++ b/include/elf/xtensa.h
@@ -131,6 +131,9 @@ END_RELOC_NUMBERS (R_XTENSA_max)
#define XTENSA_LIT_SEC_NAME ".xt.lit"
#define XTENSA_PROP_SEC_NAME ".xt.prop"
+#define XTENSA_PROPERTY_SEC_NAMES \
+ { XTENSA_INSN_SEC_NAME, XTENSA_LIT_SEC_NAME, XTENSA_PROP_SEC_NAME }
+
typedef struct property_table_entry_t
{
bfd_vma address;
diff --git a/ld/testsuite/ld-xtensa/gc-prop.d b/ld/testsuite/ld-xtensa/gc-prop.d
new file mode 100644
index 00000000000..3e8d3a07186
--- /dev/null
+++ b/ld/testsuite/ld-xtensa/gc-prop.d
@@ -0,0 +1,7 @@
+#source: gc-prop.s
+#ld: -T gc-prop.t --gc-sections
+#map: gc-prop.map
+#readelf: -SW
+#...
+ +\[ *[0-9]+\] \.xt\.prop +PROGBITS +[0-9a-f]+ +[0-9a-f]+ +0*[1-9a-f][0-9a-f]* .*
+#pass
diff --git a/ld/testsuite/ld-xtensa/gc-prop.map b/ld/testsuite/ld-xtensa/gc-prop.map
new file mode 100644
index 00000000000..85ffa79dff0
--- /dev/null
+++ b/ld/testsuite/ld-xtensa/gc-prop.map
@@ -0,0 +1,9 @@
+#...
+Discarded input sections
+#...
+ \.text\.dead +0x[0-9a-f]+ +0x[0-9a-f]+ .*
+#...
+ \.xt\.prop\.dead +0x[0-9a-f]+ +0x[0-9a-f]+ .*
+#...
+\.xt\.prop +0x[0-9a-f]+ +0x0*[1-9a-f][0-9a-f]*
+#pass
diff --git a/ld/testsuite/ld-xtensa/gc-prop.s b/ld/testsuite/ld-xtensa/gc-prop.s
new file mode 100644
index 00000000000..56396206018
--- /dev/null
+++ b/ld/testsuite/ld-xtensa/gc-prop.s
@@ -0,0 +1,9 @@
+ .section .text.dead,"axG",@progbits,dead,comdat
+ .global dead
+dead:
+ ret
+
+ .text
+ .global _start
+_start:
+ ret
diff --git a/ld/testsuite/ld-xtensa/gc-prop.t b/ld/testsuite/ld-xtensa/gc-prop.t
new file mode 100644
index 00000000000..d493873cfce
--- /dev/null
+++ b/ld/testsuite/ld-xtensa/gc-prop.t
@@ -0,0 +1,7 @@
+ENTRY(_start)
+SECTIONS
+{
+ .text 0x1000 : { *(.literal .literal.* .text .text.*) }
+ .xt.prop 0 : { *(.xt.prop .xt.prop.* .gnu.linkonce.prop.*) }
+ .xt.lit 0 : { *(.xt.lit .xt.lit.* .gnu.linkonce.p.*) }
+}
diff --git a/ld/testsuite/ld-xtensa/xtensa.exp b/ld/testsuite/ld-xtensa/xtensa.exp
index 7173c6b21b2..97b7d159a68 100644
--- a/ld/testsuite/ld-xtensa/xtensa.exp
+++ b/ld/testsuite/ld-xtensa/xtensa.exp
@@ -26,6 +26,7 @@ if { !([istarget "xtensa*-*-*"]) } {
run_dump_test "call_overflow"
run_dump_test "coalesce"
run_dump_test "diff_overflow"
+run_dump_test "gc-prop"
run_dump_test "lcall"
run_dump_test "relax-diff1"
run_dump_test "relax-loc"
--
2.55.0
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