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Diffstat (limited to 'libgcc/config/pa/fptr.c')
| -rw-r--r-- | libgcc/config/pa/fptr.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/libgcc/config/pa/fptr.c b/libgcc/config/pa/fptr.c new file mode 100644 index 00000000000..320d18267c8 --- /dev/null +++ b/libgcc/config/pa/fptr.c @@ -0,0 +1,131 @@ +/* Subroutine for function pointer canonicalization on PA-RISC with ELF32. + Copyright 2002, 2003, 2004, 2007, 2009 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] = { 32, -4 }; + +#define GET_FIELD(X, FROM, TO) \ + ((X) >> (31 - (TO)) & ((1 << ((TO) - (FROM) + 1)) - 1)) +#define SIGN_EXTEND(VAL,BITS) \ + ((int) ((VAL) >> ((BITS) - 1) ? (-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_; + +/* __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]; + static fixup_t fixup; + unsigned int *plabel, *got; + + /* -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 = (unsigned int *) ((unsigned int) fptr & ~3); + 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]; + + /* Initialize our plabel for calling fixup if we haven't done so already. + This code needs to be thread safe but we don't have to be too careful + as the result is invariant. */ + if (!fixup) + { + int i; + unsigned int *iptr; + + /* Find the first "bl" branch in the offset search list. This is a + call to 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 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 | 3); + } + + /* 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], plabel[1]); + + return plabel[0]; +} |