RISC-V: Go PLT for CALL/JUMP/RVC_JUMP if `h->plt.offset' isn't -1

I got an request about the undefined behaviors, considering the following case,

$ cat test.c
void main ()
{
  foo();
}
$ cat lib.h
void foo(void);
$ riscv64-unknown-linux-gnu-gcc test.c
riscv64-unknown-linux-gnu/bin/ld: /tmp/ccRO8fJl.o: in function `main':
test.c:(.text+0x8): undefined reference to `foo'
collect2: error: ld returned 1 exit status
$ riscv64-unknown-linux-gnu-gcc test.c -Wl,--unresolved-symbols=ignore-in-object-files
$ qemu-riscv64 a.out
Segmentation fault (core dumped)

Testing with x86 and aarch64, they won't get the segfault since they go plt
for the undefined foo symbol.  So, after applying this patch, I can get the
following too,

$ qemu-riscv64 a.out
a.out: symbol lookup error: a.out: undefined symbol: foo

The change of this patch should only affect the call behavior, which refer
to an undefined (weak) symbol, when building an dynamic executable.  I think
the pic/pie behavior won't be affected as usual.

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 57ced95fdb38a8b2868c0a2952b51c4cc821426a..bca3a585f5617912efca4ce9186101baafae45b6 100644 (file)
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -2263,6 +2263,7 @@ riscv_elf_relocate_section (bfd *output_bfd,
       reloc_howto_type *howto = riscv_elf_rtype_to_howto (input_bfd, r_type);
       const char *msg = NULL;
       bool resolved_to_zero;
+      bool via_plt = false;
 
       if (howto == NULL)
        continue;
@@ -2565,6 +2566,12 @@ riscv_elf_relocate_section (bfd *output_bfd,
       resolved_to_zero = (h != NULL
                          && UNDEFWEAK_NO_DYNAMIC_RELOC (info, h));
 
+      /* Refer to the PLT entry.  This check has to match the check in
+        _bfd_riscv_relax_section.  */
+      via_plt = (htab->elf.splt != NULL
+                && h != NULL
+                && h->plt.offset != MINUS_ONE);
+
       switch (r_type)
        {
        case R_RISCV_NONE:
@@ -2776,8 +2783,7 @@ riscv_elf_relocate_section (bfd *output_bfd,
        case R_RISCV_CALL_PLT:
          /* Handle a call to an undefined weak function.  This won't be
             relaxed, so we have to handle it here.  */
-         if (h != NULL && h->root.type == bfd_link_hash_undefweak
-             && (!bfd_link_pic (info) || h->plt.offset == MINUS_ONE))
+         if (h->root.type == bfd_link_hash_undefweak && !via_plt)
            {
              /* We can use x0 as the base register.  */
              bfd_vma insn = bfd_getl32 (contents + rel->r_offset + 4);
@@ -2791,42 +2797,40 @@ riscv_elf_relocate_section (bfd *output_bfd,
 
        case R_RISCV_JAL:
        case R_RISCV_RVC_JUMP:
-         if (bfd_link_pic (info) && h != NULL)
+         if (via_plt)
            {
-             if (h->plt.offset != MINUS_ONE)
-               {
-                 /* Refer to the PLT entry.  This check has to match the
-                    check in _bfd_riscv_relax_section.  */
-                 relocation = sec_addr (htab->elf.splt) + h->plt.offset;
-                 unresolved_reloc = false;
-               }
-             else if (!SYMBOL_REFERENCES_LOCAL (info, h)
-                      && (input_section->flags & SEC_ALLOC) != 0
-                      && (input_section->flags & SEC_READONLY) != 0
-                      && ELF_ST_VISIBILITY (h->other) == STV_DEFAULT)
-               {
-                 /* PR 28509, when generating the shared object, these
-                    referenced symbols may bind externally, which means
-                    they will be exported to the dynamic symbol table,
-                    and are preemptible by default.  These symbols cannot
-                    be referenced by the non-pic relocations, like
-                    R_RISCV_JAL and R_RISCV_RVC_JUMP relocations.
-
-                    However, consider that linker may relax the R_RISCV_CALL
-                    relocations to R_RISCV_JAL or R_RISCV_RVC_JUMP, if
-                    these relocations are relocated to the plt entries,
-                    then we won't report error for them.
-
-                    Perhaps we also need the similar checks for the
-                    R_RISCV_BRANCH and R_RISCV_RVC_BRANCH relocations.  */
-                 msg = bfd_asprintf (_("%%X%%P: relocation %s against `%s'"
-                                       " which may bind externally"
-                                       " can not be used"
-                                       " when making a shared object;"
-                                       " recompile with -fPIC\n"),
-                                     howto->name, h->root.root.string);
-                 r = bfd_reloc_notsupported;
-               }
+             relocation = sec_addr (htab->elf.splt) + h->plt.offset;
+             unresolved_reloc = false;
+           }
+         else if (bfd_link_pic (info)
+                  && h != NULL
+                  && h->plt.offset == MINUS_ONE
+                  && !SYMBOL_REFERENCES_LOCAL (info, h)
+                  && (input_section->flags & SEC_ALLOC) != 0
+                  && (input_section->flags & SEC_READONLY) != 0
+                  && ELF_ST_VISIBILITY (h->other) == STV_DEFAULT)
+           {
+             /* PR 28509, when generating the shared object, these
+                referenced symbols may bind externally, which means
+                they will be exported to the dynamic symbol table,
+                and are preemptible by default.  These symbols cannot
+                be referenced by the non-pic relocations, like
+                R_RISCV_JAL and R_RISCV_RVC_JUMP relocations.
+
+                However, consider that linker may relax the R_RISCV_CALL
+                relocations to R_RISCV_JAL or R_RISCV_RVC_JUMP, if
+                these relocations are relocated to the plt entries,
+                then we won't report error for them.
+
+                Perhaps we also need the similar checks for the
+                R_RISCV_BRANCH and R_RISCV_RVC_BRANCH relocations.  */
+             msg = bfd_asprintf (_("%%X%%P: relocation %s against `%s'"
+                                   " which may bind externally"
+                                   " can not be used"
+                                   " when making a shared object;"
+                                   " recompile with -fPIC\n"),
+                                 howto->name, h->root.root.string);
+             r = bfd_reloc_notsupported;
            }
          break;
 
@@ -5365,9 +5369,9 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
              undefined_weak = true;
            }
 
-         /* This line has to match the check in riscv_elf_relocate_section
-            in the R_RISCV_CALL[_PLT] case.  */
-         if (bfd_link_pic (info) && h->plt.offset != MINUS_ONE)
+         /* This line has to match the via_pltcheck in
+            riscv_elf_relocate_section in the R_RISCV_CALL[_PLT] case.  */
+         if (h->plt.offset != MINUS_ONE)
            {
              sym_sec = htab->elf.splt;
              symval = h->plt.offset;