[lld] e21b9ca - [ELF] Respect output section alignment for AT> (non-null lmaRegion)

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-02-12T08:19:42-08:00
New Revision: e21b9ca751c525f5927ad313482be9a9c9e4dc9d

URL: https://github.com/llvm/llvm-project/commit/e21b9ca751c525f5927ad313482be9a9c9e4dc9d
DIFF: https://github.com/llvm/llvm-project/commit/e21b9ca751c525f5927ad313482be9a9c9e4dc9d.diff

LOG: [ELF] Respect output section alignment for AT> (non-null lmaRegion)

When lmaRegion is non-null, respect `sec->alignment`
This rule is analogous to `switchTo(sec)` which advances sh_addr (VMA).

This fixes the p_paddr misalignment issue as reported by
https://android-review.googlesource.com/c/trusty/external/trusted-firmware-a/+/1230058

Note, `sec->alignment` is the maximum of ALIGN and input section alignments. We may overalign LMA than GNU ld.

linkerscript/align-lma.s has a FIXME that demonstrates another bug:
`.bss ... >RAM` should be placed in a different PT_LOAD (GNU ld
behavior) because its lmaRegion (nullptr) is different from the previous
section's lmaRegion (ROM).

Reviewed By: psmith

Differential Revision: https://reviews.llvm.org/D74286

Added: 
    lld/test/ELF/linkerscript/lma-align.test

Modified: 
    lld/ELF/LinkerScript.cpp

Removed: 
    


################################################################################
diff  --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index b5f4644ee03b..a859e8262d55 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -835,7 +835,7 @@ void LinkerScript::assignOffsets(OutputSection *sec) {
     ctx->lmaOffset = sec->lmaExpr().getValue() - dot;
 
   if (MemoryRegion *mr = sec->lmaRegion)
-    ctx->lmaOffset = mr->curPos - dot;
+    ctx->lmaOffset = alignTo(mr->curPos, sec->alignment) - dot;
 
   // If neither AT nor AT> is specified for an allocatable section, the linker
   // will set the LMA such that the 
diff erence between VMA and LMA for the

diff  --git a/lld/test/ELF/linkerscript/lma-align.test b/lld/test/ELF/linkerscript/lma-align.test
new file mode 100644
index 000000000000..d2f039a5caf3
--- /dev/null
+++ b/lld/test/ELF/linkerscript/lma-align.test
@@ -0,0 +1,32 @@
+# REQUIRES: x86
+# RUN: echo 'ret; .data.rel.ro; .balign 16; .byte 0; .data; .byte 0; .bss; .byte 0' | \
+# RUN:   llvm-mc -filetype=obj -triple=x86_64 - -o %t.o
+# RUN: ld.lld -T %s %t.o -o %t
+# RUN: llvm-readelf -S -l %t | FileCheck %s
+
+# CHECK:      Name         Type     Address          Off    Size   ES Flg Lk Inf Al
+# CHECK-NEXT:              NULL     0000000000000000 000000 000000 00      0   0  0
+# CHECK-NEXT: .text        PROGBITS 0000000000001000 001000 000001 00  AX  0   0  4
+# CHECK-NEXT: .data.rel.ro PROGBITS 0000000000011000 002000 000001 00  WA  0   0 16
+# CHECK-NEXT: .data        PROGBITS 0000000000011010 002010 000001 00  WA  0   0 16
+# CHECK-NEXT: .bss         NOBITS   0000000000011040 002011 000001 00  WA  0   0 64
+
+# CHECK:      Type  Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
+# CHECK-NEXT: LOAD  0x001000 0x0000000000001000 0x0000000000001000 0x000001 0x000001 R E 0x1000
+# CHECK-NEXT: LOAD  0x002000 0x0000000000011000 0x0000000000001010 0x000001 0x000001 RW  0x1000
+## FIXME .data and .bss should be placed in 
diff erent PT_LOAD segments
+## because their LMA regions are 
diff erent.
+# CHECK-NEXT: LOAD  0x002010 0x0000000000011010 0x0000000000001020 0x000001 0x000031 RW  0x1000
+
+MEMORY {
+  ROM : ORIGIN = 0x1000, LENGTH = 1K
+  RAM : ORIGIN = 0x11000, LENGTH = 1K
+}
+SECTIONS {
+  .text 0x1000 : { *(.text*) } >ROM
+  ## Input section alignment decides output section alignment.
+  .data.rel.ro 0x11000 : { *(.data.rel.ro) } >RAM AT>ROM
+  ## ALIGN decides output section alignment.
+  .data . : ALIGN(16) { *(.data*) } >RAM AT>ROM
+  .bss . : ALIGN(64) { *(.bss*) } >RAM
+}