[PATCH v3] ARM: module.lds: fix unwind metadata for merged .text sections

[Egg12138]

From: Xiao Junzhe <egg12138@xxxxxxxxxxx>

Commit 1ba9f8979426 ("vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN,
and related macros") made scripts/module.lds.S merge module input
.text.* sections into the output .text section.

On ARM, the paired unwind input sections keep their original names.  A
module can therefore contain .ARM.exidx.text.unlikely with sh_link
pointing at .text, while .text.unlikely no longer exists.

This is a valid ELF relationship, but ARM module_finalize() does not use
sh_link when registering module unwind tables.  It derives the target
text section from the exidx section name instead:

  .ARM.exidx.text.unlikely -> .text.unlikely

The lookup fails and the unwind table is not registered for the actual
.text range.  This can make module stack unwinding fail with:

  unwind: Index not found

Keep the ARM module unwind output names in sync with the text sections
that scripts/module.lds.S now produces.  Coalesce the .ARM.exidx/.ARM.extab
section associated with .text.*, into the
stable output names expected by the existing ARM module unwind code.

Fixes: 1ba9f8979426 ("vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN, and related macros")
Signed-off-by: Xiao Junzhe <egg12138@xxxxxxxxxxx>
---
Changes in v3:
  - Apply the ARM unwind section coalescing under CONFIG_ARM_UNWIND.
  - Remove quotes around linker-script wildcard patterns so GNU ld expands
    them correctly.
  - Use conventional linker-script wildcard syntax, i.e. *(...) without a
    space after the wildcard.

 arch/arm/include/asm/module.lds.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm/include/asm/module.lds.h b/arch/arm/include/asm/module.lds.h
index 0e7cb4e314b4..1d56c0375c18 100644
--- a/arch/arm/include/asm/module.lds.h
+++ b/arch/arm/include/asm/module.lds.h
@@ -1,4 +1,16 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+
+#ifdef CONFIG_ARM_UNWIND
+SECTIONS {
+	.ARM.extab		0 : {
+		*(.ARM.extab .ARM.extab.text .ARM.extab.text.[0-9a-zA-Z_]*)
+	}
+	.ARM.exidx		0 : {
+		*(.ARM.exidx .ARM.exidx.text .ARM.exidx.text.[0-9a-zA-Z_]*)
+	}
+}
+#endif
+
 #ifdef CONFIG_ARM_MODULE_PLTS
 SECTIONS {
 	.plt : { BYTE(0) }
-- 
2.43.0