153 lines
5.8 KiB
C
153 lines
5.8 KiB
C
/* Subroutine for function pointer canonicalization on PA-RISC with ELF32.
|
|
Copyright (C) 2002-2020 Free Software Foundation, Inc.
|
|
Contributed by John David Anglin (dave.anglin@nrc.ca).
|
|
|
|
This file is part of GCC.
|
|
|
|
GCC is free software; you can redistribute it and/or modify it under
|
|
the terms of the GNU General Public License as published by the Free
|
|
Software Foundation; either version 3, or (at your option) any later
|
|
version.
|
|
|
|
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
|
|
WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
for more details.
|
|
|
|
Under Section 7 of GPL version 3, you are granted additional
|
|
permissions described in the GCC Runtime Library Exception, version
|
|
3.1, as published by the Free Software Foundation.
|
|
|
|
You should have received a copy of the GNU General Public License and
|
|
a copy of the GCC Runtime Library Exception along with this program;
|
|
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
|
|
/* WARNING: The code is this function depends on internal and undocumented
|
|
details of the GNU linker and dynamic loader as implemented for parisc
|
|
linux. */
|
|
|
|
/* This MUST match the defines sysdeps/hppa/dl-machine.h and
|
|
bfd/elf32-hppa.c. */
|
|
#define GOT_FROM_PLT_STUB (4*4)
|
|
|
|
/* List of byte offsets in _dl_runtime_resolve to search for "bl" branches.
|
|
The first "bl" branch instruction found MUST be a call to fixup. See
|
|
the define for TRAMPOLINE_TEMPLATE in sysdeps/hppa/dl-machine.h. If
|
|
the trampoline template is changed, the list must be appropriately
|
|
updated. The offset of -4 allows for a magic branch at the start of
|
|
the template should it be necessary to change the current branch
|
|
position. */
|
|
#define NOFFSETS 2
|
|
static int fixup_branch_offset[NOFFSETS] = { -4, 32 };
|
|
|
|
#define GET_FIELD(X, FROM, TO) \
|
|
((X) >> (31 - (TO)) & ((1 << ((TO) - (FROM) + 1)) - 1))
|
|
#define SIGN_EXTEND(VAL,BITS) \
|
|
((int) ((VAL) >> ((BITS) - 1) ? ((unsigned)(-1) << (BITS)) | (VAL) : (VAL)))
|
|
|
|
struct link_map;
|
|
typedef int (*fptr_t) (void);
|
|
typedef int (*fixup_t) (struct link_map *, unsigned int);
|
|
extern unsigned int _GLOBAL_OFFSET_TABLE_;
|
|
|
|
static inline int
|
|
_dl_read_access_allowed (unsigned int addr)
|
|
{
|
|
int result;
|
|
|
|
asm ("proberi (%1),3,%0" : "=r" (result) : "r" (addr) : );
|
|
|
|
return result;
|
|
}
|
|
|
|
#pragma GCC diagnostic push
|
|
#pragma GCC diagnostic ignored "-Warray-bounds"
|
|
|
|
/* __canonicalize_funcptr_for_compare must be hidden so that it is not
|
|
placed in the dynamic symbol table. Like millicode functions, it
|
|
must be linked into all binaries in order access the got table of
|
|
that binary. However, we don't use the millicode calling convention
|
|
and the routine must be a normal function so that it can be compiled
|
|
as pic code. */
|
|
unsigned int __canonicalize_funcptr_for_compare (fptr_t)
|
|
__attribute__ ((visibility ("hidden")));
|
|
|
|
unsigned int
|
|
__canonicalize_funcptr_for_compare (fptr_t fptr)
|
|
{
|
|
static unsigned int fixup_plabel[2] __attribute__((used));
|
|
fixup_t fixup;
|
|
volatile unsigned int *plabel;
|
|
unsigned int *got, *iptr, reloc_offset;
|
|
int i;
|
|
|
|
/* -1 and page 0 are special. -1 is used in crtend to mark the end of
|
|
a list of function pointers. Also return immediately if the plabel
|
|
bit is not set in the function pointer. In this case, the function
|
|
pointer points directly to the function. */
|
|
if ((int) fptr == -1 || (unsigned int) fptr < 4096 || !((int) fptr & 2))
|
|
return (unsigned int) fptr;
|
|
|
|
/* The function pointer points to a function descriptor (plabel). If
|
|
the plabel hasn't been resolved, the first word of the plabel points
|
|
to the entry of the PLT stub just before the global offset table.
|
|
The second word in the plabel contains the relocation offset for the
|
|
function. */
|
|
plabel = (volatile unsigned int *) ((unsigned int) fptr & ~3);
|
|
if (!_dl_read_access_allowed ((unsigned int)plabel))
|
|
return (unsigned int) fptr;
|
|
|
|
/* Load first word of candidate descriptor. It should be a pointer
|
|
with word alignment and point to memory that can be read. */
|
|
got = (unsigned int *) plabel[0];
|
|
if (((unsigned int) got & 3) != 0
|
|
|| !_dl_read_access_allowed ((unsigned int)got))
|
|
return (unsigned int) fptr;
|
|
|
|
/* We need to load the relocation offset before the function address. */
|
|
reloc_offset = plabel[1];
|
|
__sync_synchronize();
|
|
got = (unsigned int *) (plabel[0] + GOT_FROM_PLT_STUB);
|
|
|
|
/* Return the address of the function if the plabel has been resolved. */
|
|
if (got != &_GLOBAL_OFFSET_TABLE_)
|
|
return plabel[0];
|
|
|
|
/* Find the first "bl" branch in the offset search list. This is a
|
|
call to _dl_fixup or a magic branch to fixup at the beginning of the
|
|
trampoline template. The fixup function does the actual runtime
|
|
resolution of function descriptors. We only look for "bl" branches
|
|
with a 17-bit pc-relative displacement. */
|
|
for (i = 0; i < NOFFSETS; i++)
|
|
{
|
|
iptr = (unsigned int *) (got[-2] + fixup_branch_offset[i]);
|
|
if ((*iptr & 0xfc00e000) == 0xe8000000)
|
|
break;
|
|
}
|
|
|
|
/* This should not happen... */
|
|
if (i == NOFFSETS)
|
|
return ~0;
|
|
|
|
/* Extract the 17-bit displacement from the instruction. */
|
|
iptr += SIGN_EXTEND (GET_FIELD (*iptr, 19, 28) |
|
|
GET_FIELD (*iptr, 29, 29) << 10 |
|
|
GET_FIELD (*iptr, 11, 15) << 11 |
|
|
GET_FIELD (*iptr, 31, 31) << 16, 17);
|
|
|
|
/* Build a plabel for an indirect call to _dl_fixup. */
|
|
fixup_plabel[0] = (unsigned int) iptr + 8; /* address of fixup */
|
|
fixup_plabel[1] = got[-1]; /* ltp for fixup */
|
|
fixup = (fixup_t) ((int) fixup_plabel | 2);
|
|
|
|
/* Call fixup to resolve the function address. got[1] contains the
|
|
link_map pointer and plabel[1] the relocation offset. */
|
|
fixup ((struct link_map *) got[1], reloc_offset);
|
|
|
|
return plabel[0];
|
|
}
|
|
|
|
#pragma GCC diagnostic pop
|