leb128.c revision 5aefb6555731130ca4fd295960123d71f2d21fe8
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include <stdio.h>
#include <dwarf.h>
/*
* Little Endian Base 128 (LEB128) numbers.
* ----------------------------------------
*
* LEB128 is a scheme for encoding integers densely that exploits the
* assumption that most integers are small in magnitude. (This encoding
* is equally suitable whether the target machine architecture represents
* data in big-endian or little- endian
*
* Unsigned LEB128 numbers are encoded as follows: start at the low order
* end of an unsigned integer and chop it into 7-bit chunks. Place each
* chunk into the low order 7 bits of a byte. Typically, several of the
* high order bytes will be zero; discard them. Emit the remaining bytes in
* a stream, starting with the low order byte; set the high order bit on
* each byte except the last emitted byte. The high bit of zero on the last
* byte indicates to the decoder that it has encountered the last byte.
* The integer zero is a special case, consisting of a single zero byte.
*
* Signed, 2s complement LEB128 numbers are encoded in a similar except
* that the criterion for discarding high order bytes is not whether they
* are zero, but whether they consist entirely of sign extension bits.
* Consider the 32-bit integer -2. The three high level bytes of the number
* are sign extension, thus LEB128 would represent it as a single byte
* containing the low order 7 bits, with the high order bit cleared to
* indicate the end of the byte stream.
*
* Note that there is nothing within the LEB128 representation that
* indicates whether an encoded number is signed or unsigned. The decoder
* must know what type of number to expect.
*
* DWARF Exception Header Encoding
* -------------------------------
*
* The DWARF Exception Header Encoding is used to describe the type of data
* used in the .eh_frame_hdr section. The upper 4 bits indicate how the
* value is to be applied. The lower 4 bits indicate the format of the data.
*
* DWARF Exception Header value format
*
* Name Value Meaning
* DW_EH_PE_omit 0xff No value is present.
* DW_EH_PE_absptr 0x00 Value is a void*
* DW_EH_PE_uleb128 0x01 Unsigned value is encoded using the
* Little Endian Base 128 (LEB128)
* DW_EH_PE_udata2 0x02 A 2 bytes unsigned value.
* DW_EH_PE_udata4 0x03 A 4 bytes unsigned value.
* DW_EH_PE_udata8 0x04 An 8 bytes unsigned value.
* DW_EH_PE_signed 0x08 bit on for all signed encodings
* DW_EH_PE_sleb128 0x09 Signed value is encoded using the
* Little Endian Base 128 (LEB128)
* DW_EH_PE_sdata2 0x0A A 2 bytes signed value.
* DW_EH_PE_sdata4 0x0B A 4 bytes signed value.
* DW_EH_PE_sdata8 0x0C An 8 bytes signed value.
*
* DWARF Exception Header application
*
* Name Value Meaning
* DW_EH_PE_absptr 0x00 Value is used with no modification.
* DW_EH_PE_pcrel 0x10 Value is reletive to the location of itself
* DW_EH_PE_textrel 0x20
* DW_EH_PE_datarel 0x30 Value is reletive to the beginning of the
* eh_frame_hdr segment ( segment type
* PT_GNU_EH_FRAME )
* DW_EH_PE_funcrel 0x40
* DW_EH_PE_aligned 0x50 value is an aligned void*
* DW_EH_PE_indirect 0x80 bit to signal indirection after relocation
* DW_EH_PE_omit 0xff No value is present.
*
*/
{
int more = 1;
int shift = 0;
int val;
while (more) {
/*
* Pull off lower 7 bits
*/
/*
* Add prepend value to head of number.
*/
/*
* Increment shift & dot pointer
*/
shift += 7;
dot++;
/*
* Check to see if hi bit is set - if not, this
* is the last byte.
*/
}
return (res);
}
{
int more = 1;
int shift = 0;
int val;
while (more) {
/*
* Pull off lower 7 bits
*/
/*
* Add prepend value to head of number.
*/
/*
* Increment shift & dot pointer
*/
shift += 7;
dot++;
/*
* Check to see if hi bit is set - if not, this
* is the last byte.
*/
}
/*
* Make sure value is properly sign extended.
*/
return (res);
}
{
lsb = 1;
else
lsb = 0;
wordsize = 8;
else
wordsize = 4;
switch (ehe_flags & 0x0f) {
case DW_EH_PE_omit:
return (0);
case DW_EH_PE_absptr:
break;
case DW_EH_PE_udata8:
case DW_EH_PE_sdata8:
fsize = 8;
break;
case DW_EH_PE_udata4:
case DW_EH_PE_sdata4:
fsize = 4;
break;
case DW_EH_PE_udata2:
case DW_EH_PE_sdata2:
fsize = 2;
break;
case DW_EH_PE_uleb128:
case DW_EH_PE_sleb128:
default:
return (0);
}
if (lsb) {
/*
* Extract unaligned LSB formated data
*/
result = 0;
}
} else {
/*
* Extract unaligned MSB formated data
*/
result = 0;
}
}
/*
* perform sign extension
*/
if ((ehe_flags & DW_EH_PE_signed) &&
}
/*
* If pcrel and we have a value (ie: we've been
* relocated), then adjust the value.
*/
}
return (result);
}