Merging r371013:

zmodem · zmodem · commit de934bf68968 · 2019-09-06T11:20:15.000Z
------------------------------------------------------------------------ r371013 | ruiu | 2019-09-05 07:30:24 +0200 (Thu, 05 Sep 2019) | 13 lines Align output segments correctly Previously, segments were aligned according to their first section's alignment requirements. That was not correct, but segments are also aligned to a page boundary, and a page boundary is usually much larger than a section alignment requirement, so no one noticed this bug before. Now, lld has --nmagic option which sets maxPageSize to 1 to effectively disable page alignment, which reveals the issue. Fixes https://bugs.llvm.org/show_bug.cgi?id=43212 Differential Revision: https://reviews.llvm.org/D67152 ------------------------------------------------------------------------ llvm-svn: 371197
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
@@ -2233,7 +2233,8 @@ static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {
   // The first section in a PT_LOAD has to have congruent offset and address
   // module the page size.
   if (os->ptLoad && os->ptLoad->firstSec == os) {
-    uint64_t alignment = std::max<uint64_t>(os->alignment, config->maxPageSize);
+    uint64_t alignment =
+        std::max<uint64_t>(os->ptLoad->p_align, config->maxPageSize);
     return alignTo(off, alignment, os->addr);
   }
 
diff --git a/lld/test/ELF/nmagic.s b/lld/test/ELF/nmagic.s
@@ -0,0 +1,23 @@
+# REQUIRES: x86
+# Verify that .rodata is aligned to a 8 byte boundary.
+
+# RUN: llvm-mc -filetype=obj -triple=i386 %s -o %t.o
+# RUN: ld.lld %t.o -o %t.exe -n -Ttext 0
+# RUN: llvm-readelf --section-headers %t.exe | FileCheck %s
+
+# CHECK: [ 0]           NULL     00000000 000000 000000 00      0   0  0
+# CHECK: [ 1] .text     PROGBITS 00000000 0000d4 000001 00  AX  0   0  4
+# CHECK: [ 2] .rodata   PROGBITS 00000008 0000d8 000008 00   A  0   0  8
+# CHECK: [ 3] .comment  PROGBITS 00000000 0000e0 000008 01  MS  0   0  1
+# CHECK: [ 4] .symtab   SYMTAB   00000000 0000e8 000020 10      6   1  4
+# CHECK: [ 5] .shstrtab STRTAB   00000000 000108 000032 00      0   0  1
+# CHECK: [ 6] .strtab   STRTAB   00000000 00013a 000008 00      0   0  1
+
+.globl _start
+.text
+_start:
+  ret
+
+.rodata
+.align 8
+.quad 42

Original file line number	Diff line number	Diff line change
`@@ -2233,7 +2233,8 @@ static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {`
`2233`	`2233`	`// The first section in a PT_LOAD has to have congruent offset and address`
`2234`	`2234`	`// module the page size.`
`2235`	`2235`	`if (os->ptLoad && os->ptLoad->firstSec == os) {`
`2236`		`- uint64_t alignment = std::max<uint64_t>(os->alignment, config->maxPageSize);`
	`2236`	`+ uint64_t alignment =`
	`2237`	`+ std::max<uint64_t>(os->ptLoad->p_align, config->maxPageSize);`
`2237`	`2238`	`return alignTo(off, alignment, os->addr);`
`2238`	`2239`	`}`
`2239`	`2240`