LoongArch: Make protected function symbols local for -shared

On LoongArch there is no reason to treat STV_PROTECTED STT_FUNC symbols
as preemptible.  See the comment above LARCH_REF_LOCAL for detailed
explanation.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>

diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index bcb144357ff34830f17c4846e32c61f250edc315..fa8ed1feb29aa789cee3381c6fa4b1ddaca619c0 100644 (file)
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -181,6 +181,44 @@ struct loongarch_elf_link_hash_table
     } \
     while (0)
 
+/* TL;DR always use it in this file instead when you want to type
+   SYMBOL_REFERENCES_LOCAL.
+
+   It's like SYMBOL_REFERENCES_LOCAL, but it returns true for local
+   protected functions.  It happens to be same as SYMBOL_CALLS_LOCAL but
+   let's not reuse SYMBOL_CALLS_LOCAL or "CALLS" may puzzle people.
+
+   We do generate a PLT entry when someone attempts to la.pcrel an external
+   function.  But we never really implemented "R_LARCH_COPY", thus we've
+   never supported la.pcrel an external symbol unless the loaded address is
+   only used for locating a function to be called.  Thus the PLT entry is
+   a normal PLT entry, not intended to be a so-called "canonical PLT entry"
+   on the ports supporting copy relocation.  So attempting to la.pcrel an
+   external function will just break pointer equality, even it's a
+   STV_DEFAULT function:
+
+   $ cat t.c
+   #include <assert.h>
+   void check(void *p) {assert(p == check);}
+   $ cat main.c
+   extern void check(void *);
+   int main(void) { check(check); }
+   $ cc t.c -fPIC -shared -o t.so
+   $ cc main.c -mdirect-extern-access t.so -Wl,-rpath=. -fpie -pie
+   $ ./a.out
+   a.out: t.c:2: check: Assertion `p == check' failed.
+   Aborted
+
+   Thus handling STV_PROTECTED function specially just fixes nothing:
+   adding -fvisibility=protected compiling t.c will not magically fix
+   the inequality.  The only possible and correct fix is not to use
+   -mdirect-extern-access.
+
+   So we should remove this special handling, because it's only an
+   unsuccessful workaround for invalid code and it's penalizing valid
+   code.  */
+#define LARCH_REF_LOCAL(info, h) \
+  (_bfd_elf_symbol_refs_local_p ((h), (info), true))
 
 /* Generate a PLT header.  */
 
@@ -712,7 +750,7 @@ loongarch_tls_transition_without_check (struct bfd_link_info *info,
                                        struct elf_link_hash_entry *h)
 {
   bool local_exec = bfd_link_executable (info)
-                   && SYMBOL_REFERENCES_LOCAL (info, h);
+                   && LARCH_REF_LOCAL (info, h);
 
   switch (r_type)
     {
@@ -1221,7 +1259,7 @@ loongarch_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
     {
       if (h->plt.refcount <= 0
          || (h->type != STT_GNU_IFUNC
-             && (SYMBOL_REFERENCES_LOCAL (info, h)
+             && (LARCH_REF_LOCAL (info, h)
                  || (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
                      && h->root.type == bfd_link_hash_undefweak))))
        {
@@ -1739,14 +1777,14 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h,
      here if it is defined and referenced in a non-shared object.  */
   if (h->type == STT_GNU_IFUNC && h->def_regular)
     {
-      if (ref_local && SYMBOL_REFERENCES_LOCAL (info, h))
+      if (ref_local && LARCH_REF_LOCAL (info, h))
        return local_allocate_ifunc_dyn_relocs (info, h,
                                                &h->dyn_relocs,
                                                PLT_ENTRY_SIZE,
                                                PLT_HEADER_SIZE,
                                                GOT_ENTRY_SIZE,
                                                false);
-      else if (!ref_local && !SYMBOL_REFERENCES_LOCAL (info, h))
+      else if (!ref_local && !LARCH_REF_LOCAL (info, h))
        return _bfd_elf_allocate_ifunc_dyn_relocs (info, h,
                                                   &h->dyn_relocs,
                                                   PLT_ENTRY_SIZE,
@@ -1774,7 +1812,6 @@ elfNN_allocate_ifunc_dynrelocs_ref_global (struct elf_link_hash_entry *h,
                                         false);
 }
 
-
 /* Allocate space in .plt, .got and associated reloc sections for
    ifunc dynamic relocs.  */
 
@@ -2687,7 +2724,6 @@ tlsoff (struct bfd_link_info *info, bfd_vma addr)
   return addr - elf_hash_table (info)->tls_sec->vma;
 }
 
-
 static int
 loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                                bfd *input_bfd, asection *input_section,
@@ -2813,7 +2849,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
            {
              defined_local = !unresolved_reloc && !ignored;
              resolved_local =
-               defined_local && SYMBOL_REFERENCES_LOCAL (info, h);
+               defined_local && LARCH_REF_LOCAL (info, h);
              resolved_dynly = !resolved_local;
              resolved_to_const = !resolved_local && !resolved_dynly;
            }
@@ -2902,7 +2938,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                      outrel.r_addend = 0;
                    }
 
-                 if (SYMBOL_REFERENCES_LOCAL (info, h))
+                 if (LARCH_REF_LOCAL (info, h))
                    {
 
                      if (htab->elf.splt != NULL)
@@ -3252,7 +3288,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                  if (!WILL_CALL_FINISH_DYNAMIC_SYMBOL (is_dyn,
                                                        bfd_link_pic (info), h)
                      && ((bfd_link_pic (info)
-                          && SYMBOL_REFERENCES_LOCAL (info, h))))
+                          && LARCH_REF_LOCAL (info, h))))
                    {
                      /* This is actually a static link, or it is a
                         -Bsymbolic link and the symbol is defined
@@ -3397,7 +3433,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                asection *srel = htab->elf.srelgot;
                bfd_vma tls_block_off = 0;
 
-               if (SYMBOL_REFERENCES_LOCAL (info, h))
+               if (LARCH_REF_LOCAL (info, h))
                  {
                    BFD_ASSERT (elf_hash_table (info)->tls_sec);
                    tls_block_off = relocation
@@ -3408,7 +3444,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                  {
                    rela.r_offset = sec_addr (got) + got_off;
                    rela.r_addend = 0;
-                   if (SYMBOL_REFERENCES_LOCAL (info, h))
+                   if (LARCH_REF_LOCAL (info, h))
                      {
                        /* Local sym, used in exec, set module id 1.  */
                        if (bfd_link_executable (info))
@@ -3441,7 +3477,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                if (tls_type & GOT_TLS_IE)
                  {
                    rela.r_offset = sec_addr (got) + got_off + ie_off;
-                   if (SYMBOL_REFERENCES_LOCAL (info, h))
+                   if (LARCH_REF_LOCAL (info, h))
                      {
                        /* Local sym, used in exec, set module id 1.  */
                        if (!bfd_link_executable (info))
@@ -3643,7 +3679,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
                                                            bfd_link_pic (info),
                                                            h)
                          && bfd_link_pic (info)
-                         && SYMBOL_REFERENCES_LOCAL (info, h))
+                         && LARCH_REF_LOCAL (info, h))
                        {
                          Elf_Internal_Rela rela;
                          rela.r_offset = sec_addr (got) + got_off;
@@ -4184,7 +4220,7 @@ loongarch_tls_perform_trans (bfd *abfd, asection *sec,
 {
   unsigned long insn;
   bool local_exec = bfd_link_executable (info)
-                     && SYMBOL_REFERENCES_LOCAL (info, h);
+                     && LARCH_REF_LOCAL (info, h);
   bfd_byte *contents = elf_section_data (sec)->this_hdr.contents;
   unsigned long r_type = ELFNN_R_TYPE (rel->r_info);
   unsigned long r_symndx = ELFNN_R_SYM (rel->r_info);
@@ -4896,7 +4932,7 @@ loongarch_elf_relax_section (bfd *abfd, asection *sec,
          else
            continue;
 
-         if (h && SYMBOL_REFERENCES_LOCAL (info, h))
+         if (h && LARCH_REF_LOCAL (info, h))
            local_got = true;
          symtype = h->type;
        }
@@ -5033,12 +5069,12 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
       if (htab->elf.splt)
        {
          BFD_ASSERT ((h->type == STT_GNU_IFUNC
-                      && SYMBOL_REFERENCES_LOCAL (info, h))
+                      && LARCH_REF_LOCAL (info, h))
                      || h->dynindx != -1);
 
          plt = htab->elf.splt;
          gotplt = htab->elf.sgotplt;
-         if (h->type == STT_GNU_IFUNC && SYMBOL_REFERENCES_LOCAL (info, h))
+         if (h->type == STT_GNU_IFUNC && LARCH_REF_LOCAL (info, h))
            relplt = htab->elf.srelgot;
          else
            relplt = htab->elf.srelplt;
@@ -5049,7 +5085,7 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
       else /* if (htab->elf.iplt) */
        {
          BFD_ASSERT (h->type == STT_GNU_IFUNC
-                     && SYMBOL_REFERENCES_LOCAL (info, h));
+                     && LARCH_REF_LOCAL (info, h));
 
          plt = htab->elf.iplt;
          gotplt = htab->elf.igotplt;
@@ -5137,7 +5173,7 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
              if (htab->elf.splt == NULL)
                srela = htab->elf.irelplt;
 
-             if (SYMBOL_REFERENCES_LOCAL (info, h))
+             if (LARCH_REF_LOCAL (info, h))
                {
                  asection *sec = h->root.u.def.section;
                  rela.r_info = ELFNN_R_INFO (0, R_LARCH_IRELATIVE);
@@ -5174,7 +5210,7 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
              return true;
            }
        }
-      else if (bfd_link_pic (info) && SYMBOL_REFERENCES_LOCAL (info, h))
+      else if (bfd_link_pic (info) && LARCH_REF_LOCAL (info, h))
        {
          asection *sec = h->root.u.def.section;
          rela.r_info = ELFNN_R_INFO (0, R_LARCH_RELATIVE);

diff --git a/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
index cb592874b1eee4e520122cea9af8cb5c25169430..968e7564b49cbd55b7125599ab15c6f7dbef40e9 100644 (file)
--- a/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
+++ b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
@@ -8,6 +8,7 @@
 .* R_LARCH_IRELATIVE .*
 .* R_LARCH_IRELATIVE .*
 .* R_LARCH_IRELATIVE .*
+.* R_LARCH_IRELATIVE .*
 #...
 .*'\.rela\.plt'.*
 #...
@@ -16,4 +17,3 @@
 .* R_LARCH_JUMP_SLOT .*
 .* R_LARCH_JUMP_SLOT .*
 .* R_LARCH_JUMP_SLOT .*
-.* R_LARCH_JUMP_SLOT .*

diff --git a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
index 6cff117e29b2f1033a0ed8f3dafcc3df63ae15b8..9a668fb7164ecdd1ea91f5183e86b9f06b8c7053 100644 (file)
--- a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
+++ b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
@@ -134,6 +134,7 @@ if [istarget "loongarch64-*-*"] {
     run_dump_test "reloc_abs_with_shared"
     run_dump_test "r_larch_32_elf64"
     run_dump_test "ifunc-reloc"
+    run_dump_test "protected-func"
   }
 
   if [check_pie_support] {

diff --git a/ld/testsuite/ld-loongarch-elf/protected-func.d b/ld/testsuite/ld-loongarch-elf/protected-func.d
new file mode 100644 (file)
index 0000000..501c7cb
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/protected-func.d
@@ -0,0 +1,6 @@
+#ld: -shared
+#readelf: -Wr
+
+#...
+.* R_LARCH_RELATIVE .*
+.* R_LARCH_RELATIVE .*

diff --git a/ld/testsuite/ld-loongarch-elf/protected-func.s b/ld/testsuite/ld-loongarch-elf/protected-func.s
new file mode 100644 (file)
index 0000000..8f28f92
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/protected-func.s
@@ -0,0 +1,17 @@
+# protected function should be non-preemptible and relocated with
+# R_LARCH_RELATIVE in shared library, for both GOT and pointer data
+
+.globl x
+.protected x
+.type x, @function
+x:
+  ret
+
+.globl _start
+_start:
+  la.got $a0, x
+  ret
+
+.data
+p:
+  .quad x