Author: Fangrui Song Date: 2021-01-19T21:23:57-08:00 New Revision: f96ff3c0f8ebd941b3f6b345164c3d858b781484
URL: https://github.com/llvm/llvm-project/commit/f96ff3c0f8ebd941b3f6b345164c3d858b781484 DIFF: https://github.com/llvm/llvm-project/commit/f96ff3c0f8ebd941b3f6b345164c3d858b781484.diff LOG: [ELF] --wrap: Produce a dynamic symbol for undefined __wrap_ ``` // a.s jmp fcntl // b.s .globl fcntl fcntl: ret ``` `ld.lld -shared --wrap=fcntl a.o b.o` has an `R_X86_64_JUMP_SLOT` referencing the index 0 undefined symbol, which will cause a glibc `symbol lookup error` at runtime. This is because `__wrap_fcntl` is not in .dynsym We use an approximation `!wrap->isUndefined()`, which doesn't set `isUsedInRegularObj` of `__wrap_fcntl` when `fcntl` is referenced and `__wrap_fcntl` is undefined. Fix this by using `sym->referenced`. Added: Modified: lld/ELF/Driver.cpp lld/ELF/Symbols.h lld/test/ELF/wrap-shlib-undefined.s Removed: ################################################################################ diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp index e1395a568ea2..de613b5c9d19 100644 --- a/lld/ELF/Driver.cpp +++ b/lld/ELF/Driver.cpp @@ -1922,7 +1922,7 @@ static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) { // Tell LTO not to eliminate these symbols. sym->isUsedInRegularObj = true; - if (!wrap->isUndefined()) + if (sym->referenced) wrap->isUsedInRegularObj = true; } return v; diff --git a/lld/ELF/Symbols.h b/lld/ELF/Symbols.h index bb87ac75f9c6..38c20d55bb08 100644 --- a/lld/ELF/Symbols.h +++ b/lld/ELF/Symbols.h @@ -132,9 +132,11 @@ class Symbol { // doesn't know the final contents of the symbol. uint8_t canInline : 1; - // Used by Undefined and SharedSymbol to track if there has been at least one - // undefined reference to the symbol. The binding may change to STB_WEAK if - // the first undefined reference from a non-shared object is weak. + // Used to track if there has been at least one undefined reference to the + // symbol. For Undefined and SharedSymbol, the binding may change to STB_WEAK + // if the first undefined reference from a non-shared object is weak. + // + // This is also used to retain __wrap_foo when foo is referenced. uint8_t referenced : 1; // True if this symbol is specified by --trace-symbol option. diff --git a/lld/test/ELF/wrap-shlib-undefined.s b/lld/test/ELF/wrap-shlib-undefined.s index acc9fd8b943e..f46ebe36b779 100644 --- a/lld/test/ELF/wrap-shlib-undefined.s +++ b/lld/test/ELF/wrap-shlib-undefined.s @@ -8,11 +8,12 @@ # RUN: llvm-mc -filetype=obj -triple=x86_64 %t/wrap.s -o %t/wrap.o # RUN: ld.lld -shared --soname=fixed %t/wrap.o -o %t/wrap.so +## foo is defined, then referenced in another object file. # RUN: ld.lld -shared %t/main.o %t/call-foo.o --wrap foo -o %t1.so # RUN: llvm-readelf -r %t1.so | FileCheck %s --check-prefix=CHECK1 # CHECK1: R_X86_64_JUMP_SLOT 0000000000000000 bar + 0 -# CHECK1-NEXT: R_X86_64_JUMP_SLOT 0{{$}} +# CHECK1-NEXT: R_X86_64_JUMP_SLOT 0000000000000000 __wrap_foo + 0 ## --no-allow-shlib-undefined errors because __real_foo is not defined. # RUN: not ld.lld %t/main.o %t/bar.so -o /dev/null 2>&1 | FileCheck --check-prefix=ERR %s @@ -32,9 +33,10 @@ ## __wrap_bar is undefined. # RUN: ld.lld -shared %t.o --wrap=bar -o %t3.so # RUN: llvm-readelf -r --dyn-syms %t3.so | FileCheck %s --check-prefix=CHECK3 -# CHECK3: R_X86_64_JUMP_SLOT 0{{$}} -# CHECK3: Symbol table '.dynsym' contains 3 entries: +# CHECK3: R_X86_64_JUMP_SLOT 0000000000000000 __wrap_bar + 0 +# CHECK3: Symbol table '.dynsym' contains 4 entries: # CHECK3: NOTYPE LOCAL DEFAULT UND +# CHECK3-NEXT: NOTYPE GLOBAL DEFAULT UND __wrap_bar # CHECK3-NEXT: NOTYPE GLOBAL DEFAULT 6 _start # CHECK3-NEXT: NOTYPE GLOBAL DEFAULT 6 foo _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
