[PATCH] D125410: [ELF] Align the end of PT_GNU_RELRO to max-page-size instead of common-page-size

[Fangrui Song via Phabricator via llvm-commits]

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The resolution to GNU ld https://sourceware.org/bugzilla/show_bug.cgi?id=28824
(milestone: binutils 2.39) switched to max-page-size so that the last page can
be protected by RELRO (x86-64 has been updated as well on 2022-02-14).

Thanks to the two RW PT_LOAD scheme, switching to max-page-size does not change
file size for us. We used common-page-size just for some compatibility.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125410

Files:
  lld/ELF/Writer.cpp
  lld/test/ELF/aarch64-relro.s
  lld/test/ELF/basic-ppc64.s


Index: lld/test/ELF/basic-ppc64.s
===================================================================
--- lld/test/ELF/basic-ppc64.s
+++ lld/test/ELF/basic-ppc64.s
@@ -336,7 +336,7 @@
 // CHECK-NEXT:    VirtualAddress: 0x20238
 // CHECK-NEXT:    PhysicalAddress: 0x20238
 // CHECK-NEXT:    FileSize: 96
-// CHECK-NEXT:    MemSize: 3528
+// CHECK-NEXT:    MemSize: 64968
 // CHECK-NEXT:    Flags [ (0x4)
 // CHECK-NEXT:      PF_R (0x4)
 // CHECK-NEXT:    ]
Index: lld/test/ELF/aarch64-relro.s
===================================================================
--- lld/test/ELF/aarch64-relro.s
+++ lld/test/ELF/aarch64-relro.s
@@ -8,7 +8,7 @@
 # CHECK-NEXT: VirtualAddress: 0x220190
 # CHECK-NEXT: PhysicalAddress:
 # CHECK-NEXT: FileSize:
-# CHECK-NEXT: MemSize: 3696
+# CHECK-NEXT: MemSize: 65136
 
 .section .data.rel.ro,"aw",%progbits
 .byte 1
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -2638,11 +2638,10 @@
 
     if (p->p_type == PT_GNU_RELRO) {
       p->p_align = 1;
-      // musl/glibc ld.so rounds the size down, so we need to round up
-      // to protect the last page. This is a no-op on FreeBSD which always
-      // rounds up.
-      p->p_memsz = alignTo(p->p_offset + p->p_memsz, config->commonPageSize) -
-                   p->p_offset;
+      // musl/glibc/FreeBSD ld.so rounds the size down, so we need to round up
+      // to protect the last page.
+      p->p_memsz =
+          alignTo(p->p_offset + p->p_memsz, config->maxPageSize) - p->p_offset;
     }
   }
 }


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