[Patch bfd/mach-o] some tweaks to bfd_mach_o_canonicalize_one_reloc
Iain Sandoe
developer@sandoe-acoustics.co.uk
Thu Feb 23 14:30:00 GMT 2012
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?
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->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
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