[PATCH] D70468: [ELF] Error if -Ttext-segment is specified

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, peter.smith, ruiu.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

In GNU ld, -Ttext sets the address of the .text section and -Ttext-segment sets the address of the text segment (RX).

gold only supports the -Ttext-segment semantic and treats -Ttext as an alias for -Ttext-segment.

lld only supports the -Ttext semantic and treats -Ttext-segment as an
alias for -Ttext.  The text segment will be assigned to an address less
than the specified -Ttext-segment value.

This patch drops the -Ttext-segment alias.

The text segment is traditionally the first segment. Users who specify
-Ttext-segment may actually want to specify --image-base, the lld way to
express this. Unfortunately currently this is supported by GNU ld's
COFF port but not by its ELF port. gold does not support this option.

rL289827 <https://reviews.llvm.org/rL289827> introduced the alias for linking qemu's non-pie user mode
binaries. As explained previously, this actually assigns the text
segment to an address less than 0x60000000. I feel that a better fix is
on the qemu side:
https://lists.nongnu.org/archive/html/qemu-devel/2019-11/msg02480.html


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70468

Files:
  lld/ELF/Driver.cpp
  lld/ELF/Options.td
  lld/test/ELF/sectionstart.s


Index: lld/test/ELF/sectionstart.s
===================================================================
--- lld/test/ELF/sectionstart.s
+++ lld/test/ELF/sectionstart.s
@@ -20,12 +20,6 @@
 # RUN: ld.lld %t.o -Ttext=0x100000 -Tdata=0x110000 -Tbss=0x200000 -o %t4
 # RUN: llvm-objdump -section-headers %t4 | FileCheck %s
 
-## Check Ttext-segment X and Ttext-segment=X forms.
-# RUN: ld.lld %t.o -Ttext-segment=0x100000 -Tdata=0x110000 -Tbss=0x200000 -o %t4
-# RUN: llvm-objdump -section-headers %t4 | FileCheck %s
-# RUN: ld.lld %t.o -Ttext-segment 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
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -59,6 +59,8 @@
 
 defm Ttext: Eq<"Ttext", "Same as --section-start with .text as the sectionname">;
 
+def Ttext_segment: Separate<["-", "--"], "Ttext-segment">, HelpText<"unsupported">;
+
 defm allow_multiple_definition: B<"allow-multiple-definition",
     "Allow multiple definitions",
     "Do not allow multiple definitions (default)">;
@@ -462,9 +464,8 @@
 def: Flag<["-"], "s">, Alias<strip_all>, HelpText<"Alias for --strip-all">;
 def: Flag<["-"], "S">, Alias<strip_debug>, HelpText<"Alias for --strip-debug">;
 def: Flag<["-"], "t">, Alias<trace>, HelpText<"Alias for --trace">;
+def: Joined<["-", "--"], "Ttext-segment=">, Alias<Ttext_segment>;
 def: JoinedOrSeparate<["-"], "y">, Alias<trace_symbol>, HelpText<"Alias for --trace-symbol">;
-def: Separate<["-", "--"], "Ttext-segment">, Alias<Ttext>, HelpText<"Alias for --Ttext">;
-def: Joined<["-", "--"], "Ttext-segment=">, Alias<Ttext>, HelpText<"Alias for --Ttext">;
 def: JoinedOrSeparate<["-"], "u">, Alias<undefined>, HelpText<"Alias for --undefined">;
 def: Flag<["-"], "V">, Alias<version>, HelpText<"Alias for --version">;
 
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -1012,6 +1012,12 @@
   if (config->splitStackAdjustSize < 0)
     error("--split-stack-adjust-size: size must be >= 0");
 
+  // The text segment is traditionally the first segment. Suggest --image-base
+  // as a likely alternative.
+  if (args.hasArg(OPT_Ttext_segment))
+    error("-Ttext-segment is not supported. Use --image-base if you "
+          "intend to set the base address");
+
   // Parse ELF{32,64}{LE,BE} and CPU type.
   if (auto *arg = args.getLastArg(OPT_m)) {
     StringRef s = arg->getValue();


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D70468.230154.patch
Type: text/x-patch
Size: 2714 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20191119/e5621f30/attachment.bin>