[Bug ld/23169] New: IFUNC pointer should be allowed in executable

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=23169

            Bug ID: 23169
           Summary: IFUNC pointer should be allowed in executable
           Product: binutils
           Version: 2.31 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---

address@hidden ifunc-exec]$ cat main.c 
extern int (*func_p) (void);
extern int func (void);
extern void foo (void);


void
bar (void)
{
  if (func_p != &func || func_p () != 0xbadbeef)
    __builtin_abort ();
}

int
main ()
{
  func_p = &func;
  foo ();
  bar ();
  return 0;
}
address@hidden ifunc-exec]$ cat func.c 
static int
ifunc (void)
{
  return 0xbadbeef;
}

void func(void) __attribute__((ifunc("resolve_func")));

static void *
resolve_func (void)
{
  return ifunc;
}
address@hidden ifunc-exec]$ cat foo.c 
int (*func_p) (void);
extern int func (void);

void
foo (void)
{
  if (func_p != &func || func_p () != 0xbadbeef)
    __builtin_abort ();
}
address@hidden ifunc-exec]$ make
gcc -g   -c -o main.o main.c
gcc -g   -c -o func.o func.c
gcc -g -fPIC   -c -o foo.o foo.c
gcc -shared -o libfoo.so foo.o
gcc -o x main.o func.o libfoo.so -Wl,-R,.
/usr/local/bin/ld: dynamic STT_GNU_IFUNC symbol `func' with pointer equality in
`func.o' can not be used when making an executable; recompile with -fPIE and
relink with -pie
collect2: error: ld returned 1 exit status
make: *** [Makefile:17: x] Error 1
address@hidden ifunc-exec]$

If STT_GNU_IFUNC symbol is defined in executable, backend should change
it to the normal function and set its address to its PLT entry which should
be resolved by R_*_IRELATIVE at run-time.  All external references should
be resolved to its PLT in executable.

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