[ELF] Add --export-dynamic-symbol-list

[MaskRay]

Summary

This is available in GNU ld 2.35 and can be seen as a shortcut for multiple
--export-dynamic-symbol, or a --dynamic-list variant without the symbolic intention.

In the long term, this option probably should be preferred over --dynamic-list.

[MaskRay]

add doc.

Note: -Bsymbolic-non-weak-functions is in release/13.x so I deleted it from the release notes.

[peter.smith]

LGTM.

lld/ELF/Driver.cpp

else
       error(arg->getSpelling() + ": " + toString(pat.takeError()));
   }
 
   // When producing an executable, --dynamic-list specifies non-local defined
   // symbols which are required to be exported. When producing a shared object,
   // symbols not specified by --dynamic-list are non-preemptible.
   config->symbolic =
       config->bsymbolic == BsymbolicKind::All || args.hasArg(OPT_dynamic_list);
-  for (auto *arg : args.filtered(OPT_dynamic_list))
+  for (auto *arg :
+       args.filtered(OPT_dynamic_list, OPT_export_dynamic_symbol_list))
     if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
       readDynamicList(*buffer);
 
   // --export-dynamic-symbol specifies additional --dynamic-list symbols if any
   // other option expresses a symbolic intention: -no-pie, -pie, -Bsymbolic,
   // -Bsymbolic-functions (if STT_FUNC), --dynamic-list.
   for (auto *arg : args.filtered(OPT_export_dynamic_symbol))
     config->dynamicList.push_back(

lld/ELF/Options.td

def discard_locals: F<"discard-locals">,
   HelpText<"Delete temporary local symbols">;
 
 def discard_none: F<"discard-none">,
   HelpText<"Keep all symbols in the symbol table">;
 
 defm dynamic_linker: Eq<"dynamic-linker", "Which dynamic linker to use">;
 
 defm dynamic_list : Eq<"dynamic-list",
-   "Read a list of dynamic symbols. (executable) Put matched non-local defined"
-   "symbols to the dynamic symbol table. (shared object) References to matched"
-   "non-local STV_DEFAULT symbols shouldn't be bound to definitions within the "
-   "shared object. Implies -Bsymbolic but does not set DF_SYMBOLIC">,
+   "Similar to --export-dynamic-symbol-list. When creating a shared object, "
+   "this additionally implies -Bsymbolic but does not set DF_SYMBOLIC">,
    MetaVarName<"<file>">;
 
 def eb: F<"EB">, HelpText<"Select the big-endian format in OUTPUT_FORMAT">;
 def el: F<"EL">, HelpText<"Select the little-endian format in OUTPUT_FORMAT">;
 
 defm eh_frame_hdr: B<"eh-frame-hdr",
     "Request creation of .eh_frame_hdr section and PT_GNU_EH_FRAME segment header",
     "Do not create .eh_frame_hdr section">;

 
 defm export_dynamic_symbol : EEq<"export-dynamic-symbol",
     "(executable) Put matched symbols in the dynamic symbol table. "
     "(shared object) References to matched non-local STV_DEFAULT symbols "
     "shouldn't be bound to definitions within the shared object. "
     "Does not imply -Bsymbolic.">,
     MetaVarName<"glob">;
 
+defm export_dynamic_symbol_list : EEq<"export-dynamic-symbol-list",
+   "Read a list of dynamic symbol patterns. Apply --export-dynamic-symbol on each pattern">,
+    MetaVarName<"file">;
+
 defm fatal_warnings: B<"fatal-warnings",
     "Treat warnings as errors",
     "Do not treat warnings as errors (default)">;
 
 defm filter: Eq<"filter", "Set DT_FILTER field to the specified name">;
 
 defm fini: Eq<"fini", "Specify a finalizer function">, MetaVarName<"<symbol>">;
 

lld/test/ELF/export-dynamic-symbol.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
 
 ## For an executable, --export-dynamic-symbol exports a symbol if it is non-local and defined.
-# RUN: ld.lld -pie --export-dynamic-symbol foo %t.o -o %t
+# RUN: ld.lld -pie --export-dynamic-symbol foo --export-dynamic-symbol qux %t.o -o %t
+# RUN: llvm-nm -D -p %t | FileCheck %s
+# RUN: echo '{ foo; };' > %t1.list
+# RUN: echo '{ foo; qux; };' > %t2.list
+# RUN: ld.lld -pie --export-dynamic-symbol-list=%t2.list %t.o -o %t
 # RUN: llvm-nm -D -p %t | FileCheck %s
 
 ## --export-dynamic exports all non-local defined symbols.
 ## --export-dynamic-symbol is shadowed.
 # RUN: ld.lld -pie --export-dynamic --export-dynamic-symbol foo %t.o -o %t.start
 # RUN: llvm-nm -D -p %t.start | FileCheck --check-prefixes=CHECK,START %s
 
 # CHECK-NOT:  .
 # START:      T _start
 # CHECK:      T foo
+# CHECK:      T qux
 # CHECK-NOT:  .
 
 ## --export-dynamic-symbol does not imply -u: %t1.a(%t1.o) is not fetched.
 ## This is compatible with GNU ld since binutils 2.35 onwards.
 # RUN: echo '.globl foo, bar; foo: bar:' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
 # RUN: rm -f %t1.a && llvm-ar rc %t1.a %t1.o
 # RUN: ld.lld --export-dynamic-symbol bar %t1.a %t.o -o %t.nofetch
 # RUN: llvm-nm %t.nofetch | FileCheck /dev/null --implicit-check-not=bar
 
+## For -shared, if no option expresses a symbolic intention, --export-dynamic-symbol is a no-op.
+# RUN: ld.lld -shared --export-dynamic-symbol foo %t.o -o %t.noop
+# RUN: llvm-objdump -d %t.noop | FileCheck --check-prefix=PLT2 %s
+# RUN: ld.lld -shared --export-dynamic-symbol-list %t2.list %t.o -o %t.noop
+# RUN: llvm-objdump -d %t.noop | FileCheck --check-prefix=PLT2 %s
+
 ## --export-dynamic-symbol can make a symbol preemptible even if it would be otherwise
 ## non-preemptible (due to -Bsymbolic, -Bsymbolic-functions or --dynamic-list).
 # RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol nomatch %t.o -o %t.nopreempt
 # RUN: llvm-objdump -d %t.nopreempt | FileCheck --check-prefix=NOPLT %s
 # RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol foo %t.o -o %t.preempt
-# RUN: llvm-objdump -d %t.preempt | FileCheck --check-prefix=PLT %s
+# RUN: llvm-objdump -d %t.preempt | FileCheck --check-prefix=PLT1 %s
+# RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol-list %t1.list %t.o -o %t.preempt
+# RUN: llvm-objdump -d %t.preempt | FileCheck --check-prefix=PLT1 %s
 
 ## 'nomatch' does not match any symbol. Don't warn.
 # RUN: ld.lld --fatal-warnings -shared -Bsymbolic-functions --export-dynamic-symbol nomatch %t.o -o %t.nopreempt2
 # RUN: llvm-objdump -d %t.nopreempt2 | FileCheck --check-prefix=NOPLT %s
 # RUN: ld.lld -shared -Bsymbolic-functions --export-dynamic-symbol foo %t.o -o %t.preempt2
-# RUN: llvm-objdump -d %t.preempt2 | FileCheck --check-prefix=PLT %s
+# RUN: llvm-objdump -d %t.preempt2 | FileCheck --check-prefix=PLT1 %s
 
 # RUN: echo '{};' > %t.list
 # RUN: ld.lld -shared --dynamic-list %t.list --export-dynamic-symbol foo %t.o -o %t.preempt3
-# RUN: llvm-objdump -d %t.preempt3 | FileCheck --check-prefix=PLT %s
+# RUN: llvm-objdump -d %t.preempt3 | FileCheck --check-prefix=PLT1 %s
 
 ## The option value is a glob.
 # RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol 'f*' %t.o -o - | \
-# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT %s
+# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT1 %s
 # RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol '[f]o[o]' %t.o -o - | \
-# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT %s
+# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT1 %s
 # RUN: ld.lld -shared -Bsymbolic --export-dynamic-symbol 'f?o' %t.o -o - | \
-# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT %s
+# RUN:   llvm-objdump -d - | FileCheck --check-prefix=PLT1 %s
+
+# PLT1:      <foo@plt>
+# PLT1:      <qux>
+
+# PLT2:      <foo@plt>
+# PLT2:      <qux@plt>
 
-# PLT:       <foo@plt>
 # NOPLT-NOT: <foo@plt>
+# NOPLT-NOT: <qux@plt>
 
-.global _start, foo
+.global _start, foo, qux
 .type foo, @function
+.type qux, @function
 _start:
   call foo
+  call qux
 foo:
+qux: