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[ELF] Error if -Ttext-segment is specified

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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.
With -z separate-code, the behavior of GNU ld -Ttext-segment is weird (see https://sourceware.org/bugzilla/show_bug.cgi?id=25207)

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

Reviewed By: grimar, ruiu

Differential Revision: https://reviews.llvm.org/D70468
This commit is contained in:
Fangrui Song
2019-11-19 14:16:04 -08:00
committed by Fangrui Song
parent 30ccee71ca
commit 4dc2fb123d
4 changed files with 19 additions and 8 deletions
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8
lld/ELF/Driver.cpp
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@@ -1012,6 +1012,14 @@ static void readConfigs(opt::InputArgList &args) {
if (config->splitStackAdjustSize < 0)
error("--split-stack-adjust-size: size must be >= 0");
// The text segment is traditionally the first segment, whose address equals
// the base address. However, lld places the R PT_LOAD first. -Ttext-segment
// is an old-fashioned option that does not play well with lld's layout.
// 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();

5
lld/ELF/Options.td
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@@ -59,6 +59,8 @@ defm Tdata: Eq<"Tdata", "Same as --section-start with .data as the sectionname">
defm Ttext: Eq<"Ttext", "Same as --section-start with .text as the sectionname">;
def Ttext_segment: Separate<["-", "--"], "Ttext-segment">;
defm allow_multiple_definition: B<"allow-multiple-definition",
"Allow multiple definitions",
"Do not allow multiple definitions (default)">;
@@ -462,9 +464,8 @@ def: Flag<["-"], "(">, Alias<start_group>, HelpText<"Alias for --start-group">;
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">;

6
lld/test/ELF/sectionstart.s
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@@ -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

8
lld/test/ELF/ttext-segment.s Normal file
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@@ -0,0 +1,8 @@
# REQUIRES: x86
## Check that we emit an error for -Ttext-segment.
# RUN: llvm-mc -filetype=obj -triple=x86_64 /dev/null -o %t.o
# RUN: not ld.lld %t.o -Ttext-segment=0x100000 -o /dev/null 2>&1 | FileCheck %s
# RUN: not ld.lld %t.o -Ttext-segment 0x100000 -o /dev/null 2>&1 | FileCheck %s
# CHECK: error: -Ttext-segment is not supported. Use --image-base if you intend to set the base address