[nanoMIPS][LLD] Change in linker script parsing

Changed parsing of the linker script, as some nanoMIPS linker scripts
require different set of rules for parsing:
- Dot operator can be used as section address expression, and its
  value should be determined by the latest value of dot, not the
  current position in the memory region
- Alignment for output section is not ignored for nanoMIPS if output
  section has got address expression
- SHT_NOBITS sections don't occupy load addresses
- OVERLAY sections can have a load region and assignment or byte
  commands in them.

lld/ELF/LinkerScript.cpp

@@ -169,7 +169,8 @@ void LinkerScript::expandMemoryRegions(uint64_t size) {
   if (state->memRegion)
     expandMemoryRegion(state->memRegion, size, state->outSec->name);
   // Only expand the LMARegion if it is different from memRegion.
-  if (state->lmaRegion && state->memRegion != state->lmaRegion)
+  if (state->lmaRegion && state->memRegion != state->lmaRegion &&
+      (config->emachine != EM_NANOMIPS || state->outSec->type != SHT_NOBITS))
     expandMemoryRegion(state->lmaRegion, size, state->outSec->name);
 }
 
@@ -948,7 +949,8 @@ LinkerScript::findMemoryRegion(OutputSection *sec, MemoryRegion *hint) {
 
 static OutputSection *findFirstSection(PhdrEntry *load) {
   for (OutputSection *sec : outputSections)
-    if (sec->ptLoad == load)
+    if (sec->ptLoad == load &&
+        (config->emachine != EM_NANOMIPS || sec->type != SHT_NOBITS))
       return sec;
   return nullptr;
 }
@@ -960,6 +962,7 @@ void LinkerScript::assignOffsets(OutputSection *sec) {
   const bool sameMemRegion = state->memRegion == sec->memRegion;
   const bool prevLMARegionIsDefault = state->lmaRegion == nullptr;
   const uint64_t savedDot = dot;
+  uint64_t savedOverlayCurPos = 0;
   state->memRegion = sec->memRegion;
   state->lmaRegion = sec->lmaRegion;
 
@@ -974,10 +977,20 @@ void LinkerScript::assignOffsets(OutputSection *sec) {
     else
       dot = state->tbssAddr;
   } else {
-    if (state->memRegion)
+    if (state->memRegion) {
       dot = state->memRegion->curPos;
-    if (sec->addrExpr)
+      savedOverlayCurPos = state->memRegion->curPos;
+    }
+    if (sec->addrExpr) {
+      // FIXME: nanoMIPS workaround for interpreting the dot symbol
+      if (config->emachine == EM_NANOMIPS)
+        dot = savedDot;
       setDot(sec->addrExpr, sec->location, false);
+    }
+
+    // FIXME: Seting the alignment is not ignored for nanoMIPS
+    if (config->emachine == EM_NANOMIPS)
+      dot = alignToPowerOf2(dot, sec->addralign);
 
     // If the address of the section has been moved forward by an explicit
     // expression so that it now starts past the current curPos of the enclosing
@@ -1073,6 +1086,12 @@ void LinkerScript::assignOffsets(OutputSection *sec) {
     state->tbssAddr = dot;
     dot = savedDot;
   }
+
+  if (config->emachine == EM_NANOMIPS && (sec->inOverlay)) {
+    dot = savedDot;
+    if (sec->memRegion)
+      sec->memRegion->curPos = savedOverlayCurPos;
+  }
 }
 
 static bool isDiscardable(const OutputSection &sec) {

lld/ELF/OutputSections.cpp

@@ -120,7 +120,13 @@ void OutputSection::commitSection(InputSection *isec) {
         // (e.g. https://github.com/ClangBuiltLinux/linux/issues/1597)
         // traditionally rely on the behavior. Issue a warning to not break
         // them. Other types get an error.
-        auto diagnose = type == SHT_NOBITS ? warn : errorOrWarn;
+        // FIXME: A .rel.dyn section may be mapped to a SHT_PROGBITS section in
+        // a nanoMIPS linker script, so this is a workaround to let it pass
+        auto diagnose =
+            ((type == SHT_NOBITS) ||
+             (isec->name == ".rel.dyn" && config->emachine == EM_NANOMIPS))
+                ? warn
+                : errorOrWarn;
         diagnose("section type mismatch for " + isec->name + "\n>>> " +
                  toString(isec) + ": " +
                  getELFSectionTypeName(config->emachine, isec->type) +

lld/ELF/ScriptParser.cpp

@@ -530,8 +530,15 @@ SmallVector<SectionCommand *, 0> ScriptParser::readOverlay() {
   // for first of all: to allow sections with overlapping VAs at different LMAs.
   Expr addrExpr = readExpr();
   expect(":");
-  expect("AT");
-  Expr lmaExpr = readParenExpr();
+  Expr lmaExpr;
+  // if (config->emachine == EM_NANOMIPS) {
+  if (consume("AT"))
+    lmaExpr = readParenExpr();
+  // }
+  // else {
+  // expect("AT");
+  // lmaExpr = readParenExpr();
+  // }
   expect("{");
 
   SmallVector<SectionCommand *, 0> v;
@@ -541,14 +548,38 @@ SmallVector<SectionCommand *, 0> ScriptParser::readOverlay() {
     // starting from the base load address specified.
     OutputDesc *osd = readOverlaySectionDescription();
     osd->osec.addrExpr = addrExpr;
-    if (prev)
-      osd->osec.lmaExpr = [=] { return prev->getLMA() + prev->size; };
-    else
-      osd->osec.lmaExpr = lmaExpr;
+    if (lmaExpr) {
+      if (prev)
+        osd->osec.lmaExpr = [=] { return prev->getLMA() + prev->size; };
+      else
+        osd->osec.lmaExpr = lmaExpr;
+    }
     v.push_back(osd);
     prev = &osd->osec;
   }
 
+  if (/* config->emachine == EM_NANOMIPS && */ consume(">")) {
+    StringRef tok = next();
+    for (SectionCommand *cmd : v)
+      cast<OutputDesc>(cmd)->osec.memoryRegionName = std::string(tok);
+  }
+
+  if (/* config->emachine == EM_NANOMIPS && */ consume("AT")) {
+    expect(">");
+    StringRef tok = next();
+    for (SectionCommand *cmd : v) {
+      OutputSection &osec = cast<OutputDesc>(cmd)->osec;
+      osec.lmaRegionName = std::string(tok);
+      if (osec.lmaExpr)
+        error("section can't have both LMA and a load region");
+    }
+  }
+
+  for (SectionCommand *cmd : v) {
+    OutputSection &osec = cast<OutputDesc>(cmd)->osec;
+    if (!osec.lmaExpr && osec.lmaRegionName.empty())
+      error("overlay section must have LMA or a load region");
+  }
   // According to the specification, at the end of the overlay, the location
   // counter should be equal to the overlay base address plus size of the
   // largest section seen in the overlay.
@@ -891,8 +922,22 @@ OutputDesc *ScriptParser::readOverlaySectionDescription() {
   while (!errorCount() && !consume("}")) {
     uint64_t withFlags = 0;
     uint64_t withoutFlags = 0;
-    if (consume("INPUT_SECTION_FLAGS"))
+    StringRef tok = next();
+    // nanoMIPS change begin
+    if (tok == ";") {
+      continue;
+    } else if (SymbolAssignment *assign = readAssignment(tok)) {
+      osd->osec.commands.push_back(assign);
+      continue;
+    } else if (ByteCommand *data = readByteCommand(tok)) {
+      osd->osec.commands.push_back(data);
+      continue;
+    }
+    if (tok == "INPUT_SECTION_FLAGS") {
       std::tie(withFlags, withoutFlags) = readInputSectionFlags();
+      tok = next();
+    }
+
     osd->osec.commands.push_back(
         readInputSectionRules(next(), withFlags, withoutFlags));
   }

lld/ELF/Writer.cpp

@@ -2391,9 +2391,21 @@ SmallVector<PhdrEntry *, 0> Writer<ELFT>::createPhdrs(Partition &part) {
     uint64_t newFlags = computeFlags(sec->getPhdrFlags());
     bool sameLMARegion =
         load && !sec->lmaExpr && sec->lmaRegion == load->firstSec->lmaRegion;
+    // FIXME: Added specifics for EM_NANOMIPS, as parsing OVERLAY in linker
+    // script is different for this architecture. New load program header is
+    // needed so OVERLAY sections can have same virtual addresses but different
+    // load addresses
+    // FIXME: Also nanoMIPS, added a case where when output section alignment is
+    // not the same as the first section's in the load program header, then a
+    // new load program header is created, as this can result in lmas
+    // overlapping
     if (!(load && newFlags == flags && sec != relroEnd &&
           sec->memRegion == load->firstSec->memRegion &&
-          (sameLMARegion || load->lastSec == Out::programHeaders))) {
+          (sameLMARegion || load->lastSec == Out::programHeaders)) ||
+        (config->emachine == EM_NANOMIPS &&
+         (sec->inOverlay || sec->type == SHT_NOBITS ||
+          load->firstSec->type == SHT_NOBITS ||
+          sec->addralign != load->firstSec->addralign))) {
       load = addHdr(PT_LOAD, newFlags);
       flags = newFlags;
     }
@@ -2571,7 +2583,10 @@ static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {
   // If two sections share the same PT_LOAD the file offset is calculated
   // using this formula: Off2 = Off1 + (VA2 - VA1).
   OutputSection *first = os->ptLoad->firstSec;
-  return first->offset + os->addr - first->addr;
+  uint64_t result = first->offset + os->addr - first->addr;
+  if (config->emachine == EM_NANOMIPS && os->inOverlay)
+    result = first->offset + os->getLMA() - first->getLMA();
+  return result;
 }
 
 template <class ELFT> void Writer<ELFT>::assignFileOffsetsBinary() {
@@ -2721,6 +2736,10 @@ static void checkOverlap(StringRef name, std::vector<SectionOffset> &sections,
     if (isVirtualAddr && a.sec->inOverlay && b.sec->inOverlay)
       continue;
 
+    if (config->emachine == EM_NANOMIPS &&
+        (a.sec->type == SHT_NOBITS || b.sec->type == SHT_NOBITS))
+      continue;
+
     errorOrWarn("section " + a.sec->name + " " + name +
                 " range overlaps with " + b.sec->name + "\n>>> " + a.sec->name +
                 " range is " + rangeToString(a.offset, a.sec->size) + "\n>>> " +

lld/test/ELF/Inputs/nanomips-align-outsec.ld

@@ -0,0 +1,19 @@
+MEMORY {
+    SEG1 : ORIGIN = 0x1000, LENGTH = 0x1000
+    SEG2 : ORIGIN = 0x2000, LENGTH = 0x1000
+}
+
+SECTIONS {
+
+    .text : {
+        *(.text)
+    } > SEG1 AT> SEG1
+
+    .first ORIGIN(SEG2) + SIZEOF(.text) : ALIGN(0x20) {
+        *(.first)
+    } > SEG2 AT> SEG1
+
+    .second : ALIGN(0x40) {
+        *(.second)
+    } > SEG2 AT> SEG1
+}

lld/test/ELF/Inputs/nanomips-dot-adjust.ld

@@ -0,0 +1,16 @@
+MEMORY {
+    SEG1 : ORIGIN = 0x1000, LENGTH = 0x1000
+}
+
+SECTIONS {
+
+    .text : {
+        *(.text)
+    } > SEG1 AT> SEG1
+
+    . = ALIGN(0x100);
+
+    .first . : {
+        *(.first)
+    } > SEG1 AT> SEG1
+}

lld/test/ELF/Inputs/nanomips-nobits-section.ld

@@ -0,0 +1,37 @@
+MEMORY {
+    SEG1 : ORIGIN = 0x1000, LENGTH = 0x1000
+    SEG2 : ORIGIN = 0x2000, LENGTH = 0x1000
+}
+
+SECTIONS {
+
+    .text : {
+        *(.text)
+    } > SEG1 AT> SEG1
+
+    .first (NOLOAD) : {
+        *(.first)
+    } > SEG2 AT> SEG1
+
+    .second : {
+        *(.second)
+    } > SEG2 AT> SEG1
+
+    .third (NOLOAD) : {
+        *(.third)
+    } > SEG2 AT> SEG1
+
+    .nanoMIPS.abiflags : {
+        *(.nanoMIPS.abiflags)
+    } > SEG2 AT> SEG1
+
+
+
+    .bss : {
+        *(.bss)
+    } > SEG2 AT> SEG1
+
+    .data : {
+        *(.data)
+    } > SEG2 AT> SEG1
+}

lld/test/ELF/nanomips-align-outsec.s

@@ -0,0 +1,47 @@
+# REQUIRES: nanomips
+
+
+# RUN: llvm-mc -filetype=obj -triple nanomips-elf -mcpu=i7200 %s -o %t.o
+# RUN: ld.lld -T %S/Inputs/nanomips-align-outsec.ld %t.o -o %t
+# RUN: llvm-objdump -h --triple=nanomips-elf --mcpu=i7200 %t | FileCheck %s
+# RUN: llvm-objdump -p --triple=nanomips-elf --mcpu=i7200 %t | FileCheck %s --check-prefix=CHECK-PHDR
+
+# CHECK: .first 00000004 00002020 00001020
+# CHECK-NEXT: .second 00000004 00002040 00001040
+
+
+# CHECK-PHDR: 0x00002020 vaddr 0x00002020 paddr 0x00001020
+# CHECK-PHDR:  0x00002040 vaddr 0x00002040 paddr 0x00001040
+
+    .section .text, "ax", @progbits
+    .align 1
+    .globl _start
+    .ent _start
+
+_start:
+    addiu $a1, $a2, 1
+
+    .end _start
+    .size _start, .-_start
+
+    .section .first, "ax", @progbits
+    .align 1
+    .globl first_fun
+    .ent first_fun
+
+first_fun:
+    addiu $a1, $a2, 2
+
+    .end first_fun
+    .size first_fun, .-first_fun
+
+    .section .second, "ax", @progbits
+    .align 1
+    .globl second_fun
+    .ent second_fun
+
+second_fun:
+    beqic $a1, 2, second_fun
+
+    .end second_fun
+    .size second_fun, .-second_fun

lld/test/ELF/nanomips-dot-adjust.s

@@ -0,0 +1,31 @@
+# REQUIRES: nanomips
+
+
+# RUN: llvm-mc -filetype=obj -triple nanomips-elf -mcpu=i7200 %s -o %t.o
+# RUN: ld.lld -T %S/Inputs/nanomips-dot-adjust.ld %t.o -o %t
+# RUN: llvm-objdump -h --triple=nanomips-elf --mcpu=i7200 %t | FileCheck %s
+
+# CHECK: .text {{[0-9a-fA-F]*}} 00001000
+# CHECK-NEXT: .first {{[0-9a-fA-F]*}} 00001100
+
+    .section .text, "ax", @progbits
+    .align 1
+    .globl _start
+    .ent _start
+
+_start:
+    addiu $a1, $a2, 1
+
+    .end _start
+    .size _start, .-_start
+
+    .section .first, "ax", @progbits
+    .align 1
+    .globl first_fun
+    .ent first_fun
+
+first_fun:
+    addiu $a1, $a2, 2
+
+    .end first_fun
+    .size first_fun, .-first_fun