[lld] [ELF] Include sharded relocations in RelocationBaseSection::getSize (PR #173285)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lld-elf

Author: Jessica Clarke (jrtc27)

<details>
<summary>Changes</summary>

Although mergeRels is called prior to using this size for final layout,
Writer::setReservedSymbolSections uses this in order to set the value of
__rel[a]_iplt_end and, downstream in Morello LLVM, __rel[a]_dyn_end.
Currently none of the relocations that can exist when static linking (as
the case when these symbols are defined) are sharded, but a future
commit will change this for R_AARCH64_AUTH_RELATIVE, and similarly
R_MORELLO_RELATIVE is sharded downstream in Morello LLVM. Make sure we
compute the right size when called prior to mergeRels, and add a
regression test to demonstrate that R_AARCH64_AUTH_RELATIVE still gets
the right __rel[a]_ipt_end in future even when sharding is adopted.


---
Full diff: https://github.com/llvm/llvm-project/pull/173285.diff


2 Files Affected:

- (modified) lld/ELF/SyntheticSections.h (+6-1) 
- (added) lld/test/ELF/aarch64-pauth-rela-iplt-end.s (+20) 


``````````diff
diff --git a/lld/ELF/SyntheticSections.h b/lld/ELF/SyntheticSections.h
index 16bdda8ef75bb..47d87e76357f3 100644
--- a/lld/ELF/SyntheticSections.h
+++ b/lld/ELF/SyntheticSections.h
@@ -528,7 +528,12 @@ class RelocationBaseSection : public SyntheticSection {
     return !relocs.empty() ||
            llvm::any_of(relocsVec, [](auto &v) { return !v.empty(); });
   }
-  size_t getSize() const override { return relocs.size() * this->entsize; }
+  size_t getSize() const override {
+    size_t count = relocs.size();
+    for (const auto &v : relocsVec)
+      count += v.size();
+    return count * this->entsize;
+  }
   size_t getRelativeRelocCount() const { return numRelativeRelocs; }
   void mergeRels();
   void partitionRels();
diff --git a/lld/test/ELF/aarch64-pauth-rela-iplt-end.s b/lld/test/ELF/aarch64-pauth-rela-iplt-end.s
new file mode 100644
index 0000000000000..b2c7fe0c61c99
--- /dev/null
+++ b/lld/test/ELF/aarch64-pauth-rela-iplt-end.s
@@ -0,0 +1,20 @@
+# REQUIRES: aarch64
+# RUN: llvm-mc -filetype=obj -triple=aarch64 %s -o %t.o
+# RUN: ld.lld --static %t.o -o %t
+# RUN: llvm-readelf -S -s -d %t | FileCheck %s
+
+## Verify that R_AARCH64_AUTH_RELATIVE relocations are included within the
+## bounds of __rela_iplt_start/end, as relative relocations still emitted for
+## static PDEs due to needing run-time signing. Historically this would not be
+## the case if added to .rela.dyn with sharding.
+
+# CHECK: .rela.dyn         RELA            0000000000200158 000158 000018 18   A  0   0  8
+# CHECK: 0000000000200158     0 NOTYPE  LOCAL  HIDDEN      1 __rela_iplt_start
+# CHECK: 0000000000200170     0 NOTYPE  LOCAL  HIDDEN      1 __rela_iplt_end
+
+adrp x0, __rela_iplt_start
+adrp x0, __rela_iplt_end
+
+.data
+foo:
+.quad foo at AUTH(da,42)

``````````

</details>


https://github.com/llvm/llvm-project/pull/173285