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* dwarf2read.c: Whitespace fixes for DWP file format documentation,

Browse source 
and fix header docs.
This commit is contained in:
Doug Evans 2013-06-06 23:51:09 +00:00
parent 48e65d55bb
commit d2415c6cf4
2 changed files with 47 additions and 37 deletions
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5
gdb/ChangeLog
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@ -1,3 +1,8 @@
2013-06-06 Doug Evans <dje@google.com>
* dwarf2read.c: Whitespace fixes for DWP file format documentation,
and fix header docs.
2013-06-05 Doug Evans <dje@google.com>
Keith Seitz <keiths@redhat.com>

79
gdb/dwarf2read.c
View file

@ -8867,62 +8867,67 @@ create_dwo_cu (struct dwo_file *dwo_file)
/* DWP file .debug_{cu,tu}_index section format:
[ref: http://gcc.gnu.org/wiki/DebugFissionDWP]
DWP Version 1:
Both index sections have the same format, and serve to map a 64-bit
signature to a set of section numbers. Each section begins with a header,
followed by a hash table of 64-bit signatures, a parallel table of 32-bit
indexes, and a pool of 32-bit section numbers. The index sections will be
aligned at 8-byte boundaries in the file.
The index section header contains two unsigned 32-bit values (using the
byte order of the application binary):
The index section header consists of:
N, the number of compilation units or type units in the index
M, the number of slots in the hash table
V, 32 bit version number
-, 32 bits unused
N, 32 bit number of compilation units or type units in the index
M, 32 bit number of slots in the hash table
(We assume that N and M will not exceed 2^32 - 1.)
Numbers are recorded using the byte order of the application binary.
The size of the hash table, M, must be 2^k such that 2^k > 3*N/2.
We assume that N and M will not exceed 2^32 - 1.
The hash table begins at offset 8 in the section, and consists of an array
of M 64-bit slots. Each slot contains a 64-bit signature (using the byte
order of the application binary). Unused slots in the hash table are 0.
(We rely on the extreme unlikeliness of a signature being exactly 0.)
The size of the hash table, M, must be 2^k such that 2^k > 3*N/2.
The parallel table begins immediately after the hash table
(at offset 8 + 8 * M from the beginning of the section), and consists of an
array of 32-bit indexes (using the byte order of the application binary),
corresponding 1-1 with slots in the hash table. Each entry in the parallel
table contains a 32-bit index into the pool of section numbers. For unused
hash table slots, the corresponding entry in the parallel table will be 0.
The hash table begins at offset 16 in the section, and consists of an array
of M 64-bit slots. Each slot contains a 64-bit signature (using the byte
order of the application binary). Unused slots in the hash table are 0.
(We rely on the extreme unlikeliness of a signature being exactly 0.)
Given a 64-bit compilation unit signature or a type signature S, an entry
in the hash table is located as follows:
The parallel table begins immediately after the hash table
(at offset 16 + 8 * M from the beginning of the section), and consists of an
array of 32-bit indexes (using the byte order of the application binary),
corresponding 1-1 with slots in the hash table. Each entry in the parallel
table contains a 32-bit index into the pool of section numbers. For unused
hash table slots, the corresponding entry in the parallel table will be 0.
1) Calculate a primary hash H = S & MASK(k), where MASK(k) is a mask with
the low-order k bits all set to 1.
Given a 64-bit compilation unit signature or a type signature S, an entry
in the hash table is located as follows:
2) Calculate a secondary hash H' = (((S >> 32) & MASK(k)) | 1).
1) Calculate a primary hash H = S & MASK(k), where MASK(k) is a mask with
the low-order k bits all set to 1.
3) If the hash table entry at index H matches the signature, use that
entry. If the hash table entry at index H is unused (all zeroes),
terminate the search: the signature is not present in the table.
2) Calculate a secondary hash H' = (((S >> 32) & MASK(k)) | 1).
4) Let H = (H + H') modulo M. Repeat at Step 3.
3) If the hash table entry at index H matches the signature, use that
entry. If the hash table entry at index H is unused (all zeroes),
terminate the search: the signature is not present in the table.
Because M > N and H' and M are relatively prime, the search is guaranteed
to stop at an unused slot or find the match.
4) Let H = (H + H') modulo M. Repeat at Step 3.
The pool of section numbers begins immediately following the hash table
(at offset 8 + 12 * M from the beginning of the section). The pool of
section numbers consists of an array of 32-bit words (using the byte order
of the application binary). Each item in the array is indexed starting
from 0. The hash table entry provides the index of the first section
number in the set. Additional section numbers in the set follow, and the
set is terminated by a 0 entry (section number 0 is not used in ELF).
Because M > N and H' and M are relatively prime, the search is guaranteed
to stop at an unused slot or find the match.
In each set of section numbers, the .debug_info.dwo or .debug_types.dwo
section must be the first entry in the set, and the .debug_abbrev.dwo must
be the second entry. Other members of the set may follow in any order. */
The pool of section numbers begins immediately following the hash table
(at offset 16 + 12 * M from the beginning of the section). The pool of
section numbers consists of an array of 32-bit words (using the byte order
of the application binary). Each item in the array is indexed starting
from 0. The hash table entry provides the index of the first section
number in the set. Additional section numbers in the set follow, and the
set is terminated by a 0 entry (section number 0 is not used in ELF).
In each set of section numbers, the .debug_info.dwo or .debug_types.dwo
section must be the first entry in the set, and the .debug_abbrev.dwo must
be the second entry. Other members of the set may follow in any order. */
/* Create a hash table to map DWO IDs to their CU/TU entry in
.debug_{info,types}.dwo in DWP_FILE.