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Re: [Patch bfd/mach-o] some tweaks to bfd_mach_o_canonicalize_one_reloc
On Feb 23, 2012, at 3:29 PM, Iain Sandoe wrote:
>
> On 23 Feb 2012, at 09:11, Tristan Gingold wrote:
>>> ... or a set of macros to do the same.
>> Yes, a set of macros should do it.
>
> well, doing it completely in macros was looking unwieldy ..
> so I've made two small routines and macro-ized the values (and shifted all this to external.h).
>
> .. I've done the output side too - but I don't have enough of the PPC port working to test that (output) much.
> .. for [BE] input it's OK and the x86 port has unchanged test results [in & out].
>
> so, how about this?
Yes, looks good. One minor nit, see below.
I think the usual name in BFD for encode/decode is swap in/swap out. Feel free to rename.
Ok for commit,
thank you for the work.
Tristan
> Iain
>
> BFD:
>
> * mach-o.c (bfd_mach_o_decode_non_scattered_reloc): New.
> (bfd_mach_o_canonicalize_one_reloc): Swap non-scattered reloc
> bit-fields when target and host differ in endian-ness. When
> PAIRs are non-scattered find the 'symbol' from the preceding
> reloc. Add FIXME re. reloc symbols on section boundaries.
> (bfd_mach_o_encode_non_scattered_reloc): New.
> (bfd_mach_o_write_relocs): Use bfd_mach_o_encode_non_scattered_reloc.
>
> include/mach-o:
>
> * external.h: Add comments about relocations fields. Add macros
> for non-scattered relocations. Move scattered relocation macros to here.
> * reloc.h: Remove macros related to external representation of reloc fields.
>
> Index: bfd/mach-o.c
> ===================================================================
> RCS file: /cvs/src/src/bfd/mach-o.c,v
> retrieving revision 1.101
> diff -u -p -r1.101 mach-o.c
> --- bfd/mach-o.c 10 Feb 2012 11:24:44 -0000 1.101
> +++ bfd/mach-o.c 23 Feb 2012 14:14:34 -0000
> @@ -975,6 +975,35 @@ bfd_mach_o_get_reloc_upper_bound (bfd *a
> return (asect->reloc_count + 1) * sizeof (arelent *);
> }
>
> +/* In addition to the need to byte-swap the symbol number, the bit positions
> + of the fields in the relocation information vary per target endian-ness. */
> +
> +static void
> +bfd_mach_o_decode_non_scattered_reloc (bfd *abfd, bfd_mach_o_reloc_info *rel,
> + unsigned char *fields)
> +{
> + unsigned char info = fields[3];
> +
> + if (bfd_big_endian (abfd))
> + {
> + rel->r_value = (fields[0] << 16) | (fields[1] << 8) | fields[2];
> + rel->r_type = (info >> BFD_MACH_O_BE_TYPE_SHIFT) & BFD_MACH_O_TYPE_MASK;
> + rel->r_pcrel = (info & BFD_MACH_O_BE_PCREL) ? 1 : 0;
> + rel->r_length = (info >> BFD_MACH_O_BE_LENGTH_SHIFT)
> + & BFD_MACH_O_LENGTH_MASK;
> + rel->r_extern = (info & BFD_MACH_O_BE_EXTERN) ? 1 : 0;
> + }
> + else
> + {
> + rel->r_value = (fields[2] << 16) | (fields[1] << 8) | fields[0];
> + rel->r_type = (info >> BFD_MACH_O_LE_TYPE_SHIFT) & BFD_MACH_O_TYPE_MASK;
> + rel->r_pcrel = (info & BFD_MACH_O_LE_PCREL) ? 1 : 0;
> + rel->r_length = (info >> BFD_MACH_O_LE_LENGTH_SHIFT)
> + & BFD_MACH_O_LENGTH_MASK;
> + rel->r_extern = (info & BFD_MACH_O_LE_EXTERN) ? 1 : 0;
> + }
> +}
> +
> static int
> bfd_mach_o_canonicalize_one_reloc (bfd *abfd,
> struct mach_o_reloc_info_external *raw,
> @@ -984,20 +1013,28 @@ bfd_mach_o_canonicalize_one_reloc (bfd *
> bfd_mach_o_backend_data *bed = bfd_mach_o_get_backend_data (abfd);
> bfd_mach_o_reloc_info reloc;
> bfd_vma addr;
> - bfd_vma symnum;
> asymbol **sym;
>
> addr = bfd_get_32 (abfd, raw->r_address);
> - symnum = bfd_get_32 (abfd, raw->r_symbolnum);
> + res->sym_ptr_ptr = NULL;
> + res->addend = 0;
>
> if (addr & BFD_MACH_O_SR_SCATTERED)
> {
> unsigned int j;
> + bfd_vma symnum = bfd_get_32 (abfd, raw->r_symbolnum);
>
> - /* Scattered relocation.
> - Extract section and offset from r_value. */
> - res->sym_ptr_ptr = NULL;
> - res->addend = 0;
> + /* Scattered relocation, can't be extern. */
> + reloc.r_scattered = 1;
> + reloc.r_extern = 0;
> +
> + /* Extract section and offset from r_value (symnum). */
> + reloc.r_value = symnum;
> + /* FIXME: This breaks when a symbol in a reloc exactly follows the
> + end of the data for the section (e.g. in a calculation of section
> + data length). At present, the symbol will end up associated with
> + the following section or, if it falls within alignment padding, as
> + null - which will assert later. */
> for (j = 0; j < mdata->nsects; j++)
> {
> bfd_mach_o_section *sect = mdata->sections[j];
> @@ -1008,42 +1045,62 @@ bfd_mach_o_canonicalize_one_reloc (bfd *
> break;
> }
> }
> - res->address = BFD_MACH_O_GET_SR_ADDRESS (addr);
> +
> + /* Extract the info and address fields from r_address. */
> reloc.r_type = BFD_MACH_O_GET_SR_TYPE (addr);
> reloc.r_length = BFD_MACH_O_GET_SR_LENGTH (addr);
> reloc.r_pcrel = addr & BFD_MACH_O_SR_PCREL;
> - reloc.r_scattered = 1;
> + reloc.r_address = BFD_MACH_O_GET_SR_TYPE (addr);
> + res->address = BFD_MACH_O_GET_SR_ADDRESS (addr);
> }
> else
> {
> - unsigned int num = BFD_MACH_O_GET_R_SYMBOLNUM (symnum);
> - res->addend = 0;
> - res->address = addr;
> - if (symnum & BFD_MACH_O_R_EXTERN)
> - {
> + unsigned int num;
> +
> + /* Non-scattered relocation. */
> + reloc.r_scattered = 0;
> +
> + /* The value and info fields have to be extracted dependent on target
> + endian-ness. */
> + bfd_mach_o_decode_non_scattered_reloc (abfd, &reloc, raw->r_symbolnum);
> + num = reloc.r_value;
> +
> + if (reloc.r_extern)
> sym = syms + num;
> - reloc.r_extern = 1;
> - }
> - else
> + else if (reloc.r_scattered
> + || (reloc.r_type != BFD_MACH_O_GENERIC_RELOC_PAIR))
> {
> BFD_ASSERT (num != 0);
> BFD_ASSERT (num <= mdata->nsects);
> sym = mdata->sections[num - 1]->bfdsection->symbol_ptr_ptr;
> /* For a symbol defined in section S, the addend (stored in the
> binary) contains the address of the section. To comply with
> - bfd conventio, substract the section address.
> + bfd convention, subtract the section address.
> Use the address from the header, so that the user can modify
> the vma of the section. */
> res->addend = -mdata->sections[num - 1]->addr;
> - reloc.r_extern = 0;
> + }
> + else /* ... The 'symnum' in a non-scattered PAIR will be 0x00ffffff. */
> + {
> + /* Pairs for PPC LO/HI/HA are not scattered, but contain the offset
> + in the lower 16bits of the address value. So we have to find the
> + 'symbol' from the preceding reloc. We do this even thoough the
> + section symbol is probably not needed here, because NULL symbol
> + values cause an assert in generic BFD code. */
> + sym = (res-1)->sym_ptr_ptr;
res - 1.
> }
> res->sym_ptr_ptr = sym;
> - reloc.r_type = BFD_MACH_O_GET_R_TYPE (symnum);
> - reloc.r_length = BFD_MACH_O_GET_R_LENGTH (symnum);
> - reloc.r_pcrel = (symnum & BFD_MACH_O_R_PCREL) ? 1 : 0;
> - reloc.r_scattered = 0;
> +
> + /* The 'address' is just r_address.
> + ??? maybe this should be masked with 0xffffff for safety. */
> + res->address = addr;
> + reloc.r_address = addr;
> }
>
> + /* We have set up a reloc with all the information present, so the swapper can
> + modify address, value and addend fields, if necessary, to convey information
> + in the generic BFD reloc that is mach-o specific. */
> +
> if (!(*bed->_bfd_mach_o_swap_reloc_in)(res, &reloc))
> return -1;
> return 0;
> @@ -1182,6 +1239,41 @@ bfd_mach_o_canonicalize_dynamic_reloc (b
> return i;
> }
>
> +/* In addition to the need to byte-swap the symbol number, the bit positions
> + of the fields in the relocation information vary per target endian-ness. */
> +
> +static void
> +bfd_mach_o_encode_non_scattered_reloc (bfd *abfd, unsigned char *fields,
> + bfd_mach_o_reloc_info *rel)
> +{
> + unsigned char info = 0;
> +
> + BFD_ASSERT (rel->r_type <= 15);
> + BFD_ASSERT (rel->r_length <= 3);
> +
> + if (bfd_big_endian (abfd))
> + {
> + fields[0] = (rel->r_value >> 16) & 0xff;
> + fields[1] = (rel->r_value >> 8) & 0xff;
> + fields[2] = rel->r_value & 0xff;
> + info |= rel->r_type << BFD_MACH_O_BE_TYPE_SHIFT;
> + info |= rel->r_pcrel ? BFD_MACH_O_BE_PCREL : 0;
> + info |= rel->r_length << BFD_MACH_O_BE_LENGTH_SHIFT;
> + info |= rel->r_extern ? BFD_MACH_O_BE_EXTERN : 0;
> + }
> + else
> + {
> + fields[2] = (rel->r_value >> 16) & 0xff;
> + fields[1] = (rel->r_value >> 8) & 0xff;
> + fields[0] = rel->r_value & 0xff;
> + info |= rel->r_type << BFD_MACH_O_LE_TYPE_SHIFT;
> + info |= rel->r_pcrel ? BFD_MACH_O_LE_PCREL : 0;
> + info |= rel->r_length << BFD_MACH_O_LE_LENGTH_SHIFT;
> + info |= rel->r_extern ? BFD_MACH_O_LE_EXTERN : 0;
> + }
> + fields[3] = info;
> +}
> +
> static bfd_boolean
> bfd_mach_o_write_relocs (bfd *abfd, bfd_mach_o_section *section)
> {
> @@ -1228,15 +1320,8 @@ bfd_mach_o_write_relocs (bfd *abfd, bfd_
> }
> else
> {
> - unsigned long v;
> -
> bfd_put_32 (abfd, pinfo->r_address, raw.r_address);
> - v = BFD_MACH_O_SET_R_SYMBOLNUM (pinfo->r_value)
> - | (pinfo->r_pcrel ? BFD_MACH_O_R_PCREL : 0)
> - | BFD_MACH_O_SET_R_LENGTH (pinfo->r_length)
> - | (pinfo->r_extern ? BFD_MACH_O_R_EXTERN : 0)
> - | BFD_MACH_O_SET_R_TYPE (pinfo->r_type);
> - bfd_put_32 (abfd, v, raw.r_symbolnum);
> + bfd_mach_o_encode_non_scattered_reloc (abfd, raw.r_symbolnum, pinfo);
> }
>
> if (bfd_bwrite (&raw, BFD_MACH_O_RELENT_SIZE, abfd)
> Index: include/mach-o/external.h
> ===================================================================
> RCS file: /cvs/src/src/include/mach-o/external.h,v
> retrieving revision 1.4
> diff -u -p -r1.4 external.h
> --- include/mach-o/external.h 4 Jan 2012 10:37:36 -0000 1.4
> +++ include/mach-o/external.h 23 Feb 2012 14:14:34 -0000
> @@ -116,6 +116,45 @@ struct mach_o_reloc_info_external
> };
> #define BFD_MACH_O_RELENT_SIZE 8
>
> +/* Relocations are based on 'address' being a section offset and an assumption
> + that sections are never more than 2^24-1 bytes in size. Relocation data
> + also carry information on type/size/PC-relative/extern and whether scattered
> + or not [stored in the MSB of the r_address]. */
> +
> +#define BFD_MACH_O_SR_SCATTERED 0x80000000
> +
> +/* For a non-scattered reloc, the relocation info is found in r_symbolnum.
> + Bytes 1 to 3 contain the symbol number (0xffffff, in a non-scattered PAIR).
> + Byte 4 contains the relocation info - but with differing bit-positions
> + dependent on target endian-ness - as below. */
> +
> +#define BFD_MACH_O_LE_PCREL 0x01
> +#define BFD_MACH_O_LE_LENGTH_SHIFT 1
> +#define BFD_MACH_O_LE_EXTERN 0x08
> +#define BFD_MACH_O_LE_TYPE_SHIFT 4
> +
> +#define BFD_MACH_O_BE_PCREL 0x80
> +#define BFD_MACH_O_BE_LENGTH_SHIFT 6
> +#define BFD_MACH_O_BE_EXTERN 0x10
> +#define BFD_MACH_O_BE_TYPE_SHIFT 0
> +
> +/* The field sizes are the same for both BE and LE. */
> +#define BFD_MACH_O_LENGTH_MASK 0x03
> +#define BFD_MACH_O_TYPE_MASK 0x0f
> +
> +/* For a scattered reloc entry the info is contained in r_address. There
> + is no need to discriminate on target endian-ness, since the design was
> + arranged to produce the same layout on both. Scattered relocations are
> + only used for local items, therefore there is no 'extern' field. */
> +
> +#define BFD_MACH_O_SR_PCREL 0x40000000
> +#define BFD_MACH_O_GET_SR_LENGTH(s) (((s) >> 28) & 0x3)
> +#define BFD_MACH_O_GET_SR_TYPE(s) (((s) >> 24) & 0x0f)
> +#define BFD_MACH_O_GET_SR_ADDRESS(s) ((s) & 0x00ffffff)
> +#define BFD_MACH_O_SET_SR_LENGTH(l) (((l) & 0x3) << 28)
> +#define BFD_MACH_O_SET_SR_TYPE(t) (((t) & 0xf) << 24)
> +#define BFD_MACH_O_SET_SR_ADDRESS(s) ((s) & 0x00ffffff)
> +
> struct mach_o_symtab_command_external
> {
> unsigned char symoff[4]; /* File offset of the symbol table. */
> Index: include/mach-o/reloc.h
> ===================================================================
> RCS file: /cvs/src/src/include/mach-o/reloc.h,v
> retrieving revision 1.1
> diff -u -p -r1.1 reloc.h
> --- include/mach-o/reloc.h 8 Aug 2011 08:59:33 -0000 1.1
> +++ include/mach-o/reloc.h 23 Feb 2012 14:14:34 -0000
> @@ -1,5 +1,5 @@
> /* Mach-O support for BFD.
> - Copyright 2011
> + Copyright 2011, 2012
> Free Software Foundation, Inc.
>
> This file is part of BFD, the Binary File Descriptor library.
> @@ -22,26 +22,6 @@
> #ifndef _MACH_O_RELOC_H
> #define _MACH_O_RELOC_H
>
> -/* Fields for a normal (non-scattered) entry. */
> -#define BFD_MACH_O_R_PCREL 0x01000000
> -#define BFD_MACH_O_GET_R_LENGTH(s) (((s) >> 25) & 0x3)
> -#define BFD_MACH_O_R_EXTERN 0x08000000
> -#define BFD_MACH_O_GET_R_TYPE(s) (((s) >> 28) & 0x0f)
> -#define BFD_MACH_O_GET_R_SYMBOLNUM(s) ((s) & 0x00ffffff)
> -#define BFD_MACH_O_SET_R_LENGTH(l) (((l) & 0x3) << 25)
> -#define BFD_MACH_O_SET_R_TYPE(t) (((t) & 0xf) << 28)
> -#define BFD_MACH_O_SET_R_SYMBOLNUM(s) ((s) & 0x00ffffff)
> -
> -/* Fields for a scattered entry. */
> -#define BFD_MACH_O_SR_SCATTERED 0x80000000
> -#define BFD_MACH_O_SR_PCREL 0x40000000
> -#define BFD_MACH_O_GET_SR_LENGTH(s) (((s) >> 28) & 0x3)
> -#define BFD_MACH_O_GET_SR_TYPE(s) (((s) >> 24) & 0x0f)
> -#define BFD_MACH_O_GET_SR_ADDRESS(s) ((s) & 0x00ffffff)
> -#define BFD_MACH_O_SET_SR_LENGTH(l) (((l) & 0x3) << 28)
> -#define BFD_MACH_O_SET_SR_TYPE(t) (((t) & 0xf) << 24)
> -#define BFD_MACH_O_SET_SR_ADDRESS(s) ((s) & 0x00ffffff)
> -
> /* Generic relocation types (used by i386). */
> #define BFD_MACH_O_GENERIC_RELOC_VANILLA 0
> #define BFD_MACH_O_GENERIC_RELOC_PAIR 1
>