[ELF] - Implemented --section-start, -Ttext, -Tdata, -Tbss options.

[grimar]

Summary

This is PR30269,

These options defined as:

--section-start=sectionname=org
Locate a section in the output file at the absolute address given by org. You may use this option as many times as necessary to locate multiple sections in the command line. org must be a single hexadecimal integer; for compatibility with other linkers, you may omit the leading `0x' usually associated with hexadecimal values. Note: there should be no white space between sectionname, the equals sign (“<=>”), and org.

-Tbss=org
-Tdata=org
-Ttext=org
Same as --section-start, with .bss, .data or .text as the sectionname.

[ruiu]

ELF/Config.h

67 ↗

(On Diff #70529)

This is not a list but a map.

ELF/Driver.cpp

375 ↗

(On Diff #70529)

read -> parse to be consistent with parseEmulation.

380 ↗

(On Diff #70529)

-Ttext: " + S);

384–385 ↗

(On Diff #70529)

Remove llvm::.

393–398 ↗

(On Diff #70529)

if (auto *Arg = Args.getLastArg(...))
  Ret[...] = readSectionAddress(Arg->getValue());

[grimar]

• Addressed review comments.

ELF/Config.h

67 ↗

(On Diff #70529)

Done.

ELF/Driver.cpp

375 ↗

(On Diff #70529)

Done.

380 ↗

(On Diff #70529)

Done. I did not do this initially because it does not catch everything. Ex:

--section-start ABCDF

ABCDF does not contain '=', and S will be empty, resulting message " ... -Ttext: ".
Was not sure if that worth to add initial expression as argument or do something for that case.

384–385 ↗

(On Diff #70529)

Done.

393–398 ↗

(On Diff #70529)

Done.

[ruiu]

ELF/Driver.cpp

380 ↗

(On Diff #70659)

Please do whatever to make it user friendly.

[grimar]

• Reworked error reporting.

ELF/Driver.cpp

380 ↗

(On Diff #70659)

Well if I would be user, I would be happy to see a detailed message and not the common, so to make it more user friendly I would probably suggest to split reporting.
That also helps to keep code a bit more clean because --section-start as handled a bit differently from other 3 options.
Updated the patch, what do you think ?

[ruiu]

ELF/Driver.cpp

382 ↗

(On Diff #70961)

So I think you want to pass opt::Arg *Arg as the second argument, and

387 ↗

(On Diff #70961)

do

error("invalid argument: " + stringize(Arg));

403–405 ↗

(On Diff #70961)

This doesn't look very beautiful.

[grimar]

• addressed review comments.

ELF/Driver.cpp

387 ↗

(On Diff #70961)

I did not know about stringnize(). Thank you for hint.

403–405 ↗

(On Diff #70961)

Fixed. What personally I do not like here is a way how clang-format works.
In modern time I do not like to see code formatted to the 1/3 of my screen width at left. That is how the result looks for me now though.

[grimar]

ELF/Driver.cpp

403–405 ↗

(On Diff #71153)

I find what clang-format do is ugly sometimes. And what it did for previous revision of this was ugly, but I was unable to change that. That is what I meant.

[ruiu]

LGTM with a nit.

ELF/Options.td

170–181 ↗

(On Diff #71153)

Move the new definitions before allow_multiple_definition. They are sorted in ASCIIbetical order.

lld/trunk/ELF/Config.h

 
 // This struct contains the global configuration for the linker.
 // Most fields are direct mapping from the command line options
 // and such fields have the same name as the corresponding options.
 // Most fields are initialized by the driver.
 struct Configuration {
   Symbol *EntrySym = nullptr;
   InputFile *FirstElf = nullptr;
+  llvm::StringMap<uint64_t> SectionStartMap;
   llvm::StringRef DynamicLinker;
   llvm::StringRef Entry;
   llvm::StringRef Emulation;
   llvm::StringRef Fini;
   llvm::StringRef Init;
   llvm::StringRef LtoAAPipeline;
   llvm::StringRef LtoNewPmPasses;
   llvm::StringRef OutputFile;

lld/trunk/ELF/Driver.cpp

static StripPolicy getStripOption(opt::InputArgList &Args) {
   if (auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug)) {
     if (Arg->getOption().getID() == OPT_strip_all)
       return StripPolicy::All;
     return StripPolicy::Debug;
   }
   return StripPolicy::None;
 }
 
+static uint64_t parseSectionAddress(StringRef S, opt::Arg *Arg) {
+  uint64_t VA = 0;
+  if (S.startswith("0x"))
+    S = S.drop_front(2);
+  if (S.getAsInteger(16, VA))
+    error("invalid argument: " + stringize(Arg));
+  return VA;
+}
+
+static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
+  StringMap<uint64_t> Ret;
+  for (auto *Arg : Args.filtered(OPT_section_start)) {
+    StringRef Name;
+    StringRef Addr;
+    std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
+    Ret[Name] = parseSectionAddress(Addr, Arg);
+  }
+
+  if (auto *Arg = Args.getLastArg(OPT_Ttext))
+    Ret[".text"] = parseSectionAddress(Arg->getValue(), Arg);
+  if (auto *Arg = Args.getLastArg(OPT_Tdata))
+    Ret[".data"] = parseSectionAddress(Arg->getValue(), Arg);
+  if (auto *Arg = Args.getLastArg(OPT_Tbss))
+    Ret[".bss"] = parseSectionAddress(Arg->getValue(), Arg);
+  return Ret;
+}
+
 // Initializes Config members by the command line options.
 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   for (auto *Arg : Args.filtered(OPT_L))
     Config->SearchPaths.push_back(Arg->getValue());
 
   std::vector<StringRef> RPaths;
   for (auto *Arg : Args.filtered(OPT_rpath))
     RPaths.push_back(Arg->getValue());
   if (!RPaths.empty())
     Config->RPath = llvm::join(RPaths.begin(), RPaths.end(), ":");
 
+  Config->SectionStartMap = getSectionStartMap(Args);
+
   if (auto *Arg = Args.getLastArg(OPT_m)) {
     // Parse ELF{32,64}{LE,BE} and CPU type.
     StringRef S = Arg->getValue();
     std::tie(Config->EKind, Config->EMachine) = parseEmulation(S);
     Config->Emulation = S;
   }
 
   Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);

lld/trunk/ELF/Options.td

 
 def build_id_eq: J<"build-id=">, HelpText<"Generate build ID note">;
 
 def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
   HelpText<"Add a directory to the library search path">;
 
 def O: Joined<["-"], "O">, HelpText<"Optimize output file size">;
 
+def Tbss: J<"Tbss=">, HelpText<"Same as --section-start with .bss as the sectionname">;
+
+def Tdata: J<"Tdata=">, HelpText<"Same as --section-start with .data as the sectionname">;
+
+def Ttext: J<"Ttext=">, HelpText<"Same as --section-start with .text as the sectionname">;
+
 def allow_multiple_definition: F<"allow-multiple-definition">,
   HelpText<"Allow multiple definitions">;
 
 def as_needed: F<"as-needed">,
   HelpText<"Only set DT_NEEDED for shared libraries if used">;
 
 def disable_new_dtags: F<"disable-new-dtags">,
   HelpText<"Disable new dynamic tags">;
def reproduce: S<"reproduce">,
   HelpText<"Dump linker invocation and input files for debugging">;
 
 def rpath: S<"rpath">, HelpText<"Add a DT_RUNPATH to the output">;
 
 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
 def script: S<"script">, HelpText<"Read linker script">;
 
+def section_start: S<"section-start">, MetaVarName<"<address>">,
+  HelpText<"Set address of section">;
+
 def shared: F<"shared">, HelpText<"Build a shared object">;
 
 def soname: J<"soname=">, HelpText<"Set DT_SONAME">;
 
 def start_lib: F<"start-lib">,
   HelpText<"Start a grouping of objects that should be treated as if they were together in an archive">;
 
 def strip_all: F<"strip-all">, HelpText<"Strip all symbols">;

lld/trunk/ELF/Writer.cpp

VA +=
         Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
 
   uintX_t ThreadBssOffset = 0;
   for (OutputSectionBase<ELFT> *Sec : OutputSections) {
     uintX_t Alignment = Sec->getAlignment();
     if (Sec->PageAlign)
       Alignment = std::max<uintX_t>(Alignment, Target->PageSize);
 
+    auto I = Config->SectionStartMap.find(Sec->getName());
+    if (I != Config->SectionStartMap.end())
+      VA = I->second;
+
     // We only assign VAs to allocated sections.
     if (needsPtLoad(Sec)) {
       VA = alignTo(VA, Alignment);
       Sec->setVA(VA);
       VA += Sec->getSize();
     } else if (Sec->getFlags() & SHF_TLS && Sec->getType() == SHT_NOBITS) {
       uintX_t TVA = VA + ThreadBssOffset;
       TVA = alignTo(TVA, Alignment);

lld/trunk/test/ELF/sectionstart.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld %t.o --section-start .text=0x100000 \
+# RUN:   --section-start .data=0x110000 --section-start .bss=0x200000 -o %t
+# RUN: llvm-objdump -section-headers %t | FileCheck %s
+
+# CHECK:      Sections:
+# CHECK-NEXT:  Idx Name          Size      Address          Type
+# CHECK-NEXT:    0               00000000 0000000000000000
+# CHECK-NEXT:    1 .text         00000001 0000000000100000 TEXT DATA
+# CHECK-NEXT:    2 .data         00000004 0000000000110000 DATA
+# CHECK-NEXT:    3 .bss          00000004 0000000000200000 BSS
+
+## The same, but dropped "0x" prefix.
+# RUN: ld.lld %t.o --section-start .text=100000 \
+# RUN:   --section-start .data=110000 --section-start .bss=0x200000 -o %t1
+# RUN: llvm-objdump -section-headers %t1 | FileCheck %s
+
+## Use -Ttext, -Tdata, -Tbss as replacement for --section-start:
+# RUN: ld.lld %t.o -Ttext=0x100000 -Tdata=0x110000 -Tbss=0x200000 -o %t4
+# RUN: llvm-objdump -section-headers %t4 | FileCheck %s
+
+## The same, but dropped "0x" prefix.
+# RUN: ld.lld %t.o -Ttext=100000 -Tdata=110000 -Tbss=200000 -o %t5
+# RUN: llvm-objdump -section-headers %t5 | FileCheck %s
+
+## Errors:
+# RUN: not ld.lld %t.o --section-start .text100000 -o %t2 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR1 %s
+# ERR1: invalid argument: --section-start .text100000
+
+# RUN: not ld.lld %t.o --section-start .text=1Q0000 -o %t3 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR2 %s
+# ERR2: invalid argument: --section-start .text=1Q0000
+
+# RUN: not ld.lld %t.o -Ttext=1w0000 -o %t6 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR3 %s
+# ERR3: invalid argument: -Ttext=1w0000
+
+# RUN: not ld.lld %t.o -Tbss=1w0000 -o %t6 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR4 %s
+# ERR4: invalid argument: -Tbss=1w0000
+
+# RUN: not ld.lld %t.o -Tdata=1w0000 -o %t6 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR5 %s
+# ERR5: invalid argument: -Tdata=1w0000
+
+.text
+.globl _start
+_start:
+ nop
+
+.data
+.long 0
+
+.bss
+.zero 4