From c384ca3c6a49197c3f752b64871379cb673d52b9 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Wed, 8 Apr 2020 21:45:21 -0700 Subject: [PATCH] [ELF] For relative paths in INPUT() and GROUP(), search the directory of the current linker script before searching other paths For a relative path in INPUT() or GROUP(), this patch changes the search order by adding the directory of the current linker script. The new search order (consistent with GNU ld >= 2.35 regarding the new test `test/ELF/input-relative.s`): 1. the directory of the current linker script (GNU ld from Binutils 2.35 onwards; https://sourceware.org/bugzilla/show_bug.cgi?id=25806) 2. the current working directory 3. library paths (-L) This behavior makes it convenient to replace a .so or .a with a linker script with additional input. For example, glibc ``` % cat /usr/lib/x86_64-linux-gnu/libm.a /* GNU ld script */ OUTPUT_FORMAT(elf64-x86-64) GROUP ( /usr/lib/x86_64-linux-gnu/libm-2.29.a /usr/lib/x86_64-linux-gnu/libmvec.a ) ``` could be simplified as `GROUP(libm-2.29.a libmvec.a)`. Another example is to make libc++.a a linker script: ``` INPUT(libc++.a.1 libc++abi.a) ``` Note, -l is not affected. Reviewed By: psmith Differential Revision: https://reviews.llvm.org/D77779 --- lld/ELF/ScriptLexer.h | 5 ++- lld/ELF/ScriptParser.cpp | 30 ++++++++++++--- lld/test/ELF/linkerscript/input-relative.s | 44 ++++++++++++++++++++++ 3 files changed, 71 insertions(+), 8 deletions(-) create mode 100644 lld/test/ELF/linkerscript/input-relative.s diff --git a/lld/ELF/ScriptLexer.h b/lld/ELF/ScriptLexer.h index 98e4cac95a73..306d428e98fe 100644 --- a/lld/ELF/ScriptLexer.h +++ b/lld/ELF/ScriptLexer.h @@ -40,13 +40,14 @@ public: bool inExpr = false; size_t pos = 0; +protected: + MemoryBufferRef getCurrentMB(); + private: void maybeSplitExpr(); StringRef getLine(); size_t getLineNumber(); size_t getColumnNumber(); - - MemoryBufferRef getCurrentMB(); }; } // namespace elf diff --git a/lld/ELF/ScriptParser.cpp b/lld/ELF/ScriptParser.cpp index b487f31f9cae..95de8d88f821 100644 --- a/lld/ELF/ScriptParser.cpp +++ b/lld/ELF/ScriptParser.cpp @@ -290,22 +290,40 @@ void ScriptParser::addFile(StringRef s) { } if (s.startswith("/")) { + // Case 1: s is an absolute path. Just open it. driver->addFile(s, /*withLOption=*/false); } else if (s.startswith("=")) { + // Case 2: relative to the sysroot. if (config->sysroot.empty()) driver->addFile(s.substr(1), /*withLOption=*/false); else driver->addFile(saver.save(config->sysroot + "/" + s.substr(1)), /*withLOption=*/false); } else if (s.startswith("-l")) { + // Case 3: search in the list of library paths. driver->addLibrary(s.substr(2)); - } else if (sys::fs::exists(s)) { - driver->addFile(s, /*withLOption=*/false); } else { - if (Optional path = findFromSearchPaths(s)) - driver->addFile(saver.save(*path), /*withLOption=*/true); - else - setError("unable to find " + s); + // Case 4: s is a relative path. Search in the directory of the script file. + std::string filename = std::string(getCurrentMB().getBufferIdentifier()); + StringRef directory = sys::path::parent_path(filename); + if (!directory.empty()) { + SmallString<0> path(directory); + sys::path::append(path, s); + if (sys::fs::exists(path)) { + driver->addFile(path, /*withLOption=*/false); + return; + } + } + // Then search in the current working directory. + if (sys::fs::exists(s)) { + driver->addFile(s, /*withLOption=*/false); + } else { + // Finally, search in the list of library paths. + if (Optional path = findFromSearchPaths(s)) + driver->addFile(saver.save(*path), /*withLOption=*/true); + else + setError("unable to find " + s); + } } } diff --git a/lld/test/ELF/linkerscript/input-relative.s b/lld/test/ELF/linkerscript/input-relative.s new file mode 100644 index 000000000000..771684c7c4f8 --- /dev/null +++ b/lld/test/ELF/linkerscript/input-relative.s @@ -0,0 +1,44 @@ +# REQUIRES: x86 +## For a relative pathname in INPUT() or GROUP(), the parent directory of +## the current linker script has priority over current working directory and -L. + +# RUN: rm -rf %t.dir && mkdir %t.dir && cd %t.dir + +# RUN: mkdir dir +# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o a.o +# RUN: echo '.globl b, cwd; b: cwd:' | llvm-mc -filetype=obj -triple=x86_64 - -o b.o +# RUN: echo '.globl b, dir; b: dir:' | llvm-mc -filetype=obj -triple=x86_64 - -o dir/b.o +# RUN: llvm-ar rc libb.a b.o +# RUN: llvm-ar rc dir/libb.a dir/b.o + +## A relative pathname is relative to the parent directory of the current linker script. +## The directory has priority over current working directory and -L. +# RUN: echo 'INPUT(libb.a)' > dir/relative.lds +# RUN: ld.lld -L. a.o dir/relative.lds -o - | llvm-nm - | FileCheck --check-prefix=DIR %s +## GROUP() uses the same search order. +# RUN: echo 'GROUP(libb.a)' > dir/relative1.lds +# RUN: ld.lld -L. a.o dir/relative1.lds -o - | llvm-nm - | FileCheck --check-prefix=DIR %s + +# DIR: T dir + +## -l does not use the special rule. +# RUN: echo 'INPUT(-lb)' > dir/cwd.lds +# RUN: ld.lld -L. a.o dir/cwd.lds -o - | llvm-nm - | FileCheck --check-prefix=CWD %s +# RUN: echo 'GROUP(-lb)' > dir/cwd1.lds +# RUN: ld.lld -L. a.o dir/cwd1.lds -o - | llvm-nm - | FileCheck --check-prefix=CWD %s + +# CWD: T cwd + +## The rules does not apply to an absolute path. +# RUN: echo 'INPUT(/libb.a)' > dir/absolute.lds +# RUN: not ld.lld a.o dir/absolute.lds -o /dev/null + +## If the parent directory of the current linker script does not contain the file, +## fall back to the current working directory. +# RUN: cp libb.a libc.a +# RUN: echo 'INPUT(libc.a)' > dir/fallback.lds +# RUN: ld.lld a.o dir/fallback.lds -o /dev/null + +.globl _start +_start: + call b