[LLD] - Improve handling of AT> linker script commands

Patch by Konstantin Schwarz!

The condition to create a new phdr must also check the usage of "AT>" 
linker script command, and create a new PT_LOAD header if a new LMARegion is used.

This fixes PR38307

Differential revision: https://reviews.llvm.org/D50052

llvm-svn: 338679

lld/ELF/Writer.cpp

@@ -1815,12 +1815,14 @@ template <class ELFT> std::vector<PhdrEntry *> Writer<ELFT>::createPhdrs() {
     // Segments are contiguous memory regions that has the same attributes
     // (e.g. executable or writable). There is one phdr for each segment.
     // Therefore, we need to create a new phdr when the next section has
-    // different flags or is loaded at a discontiguous address using AT linker
-    // script command. At the same time, we don't want to create a separate
-    // load segment for the headers, even if the first output section has
-    // an AT attribute.
+    // different flags or is loaded at a discontiguous address or memory
+    // region using AT or AT> linker script command, respectively. At the same
+    // time, we don't want to create a separate load segment for the headers,
+    // even if the first output section has an AT or AT> attribute.
     uint64_t NewFlags = computeFlags(Sec->getPhdrFlags());
-    if ((Sec->LMAExpr && Load->LastSec != Out::ProgramHeaders) ||
+    if (((Sec->LMAExpr ||
+          (Sec->LMARegion && (Sec->LMARegion != Load->FirstSec->LMARegion))) &&
+         Load->LastSec != Out::ProgramHeaders) ||
         Sec->MemRegion != Load->FirstSec->MemRegion || Flags != NewFlags) {
 
       Load = AddHdr(PT_LOAD, NewFlags);

lld/test/ELF/linkerscript/Inputs/at6.s

@@ -0,0 +1,11 @@
+.global _start
+.text
+_start:
+nop
+
+.section .sec1,"aw",@progbits
+.long 1
+
+.section .sec2,"aw",@progbits
+.long 2
+

lld/test/ELF/linkerscript/at6.test

@@ -0,0 +1,30 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/at6.s -o %t.o
+# RUN: ld.lld %t.o --script %s -o %t
+# RUN: llvm-readelf -sections -program-headers %t | FileCheck %s
+
+MEMORY {
+  FLASH : ORIGIN = 0x08000000, LENGTH = 0x100
+  RAM   : ORIGIN = 0x20000000, LENGTH = 0x200
+}
+
+SECTIONS {
+ .text : { *(.text) } > FLASH
+ .sec1 : { *(.sec1) } > RAM
+ .sec2 : { *(.sec2) } > RAM AT > FLASH
+}
+
+# Make sure we create a separate PT_LOAD entry for .sec2. Previously,
+# it was added to the PT_LOAD entry of .sec1
+
+# CHECK: Name              Type            Address          Off
+# CHECK: .text             PROGBITS        0000000008000000 001000
+# CHECK: .sec1             PROGBITS        0000000020000000 002000
+# CHECK: .sec2             PROGBITS        0000000020000004 002004
+
+# CHECK: Program Headers:
+# CHECK:      Type  Offset   VirtAddr           PhysAddr
+# CHECK-NEXT: LOAD  0x001000 0x0000000008000000 0x0000000008000000
+# CHECK-NEXT: LOAD  0x002000 0x0000000020000000 0x0000000020000000
+# CHECK-NEXT: LOAD  0x002004 0x0000000020000004 0x0000000008000001
+# CHECK-NOT: LOAD