1/*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
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4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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8 * published by the Free Software Foundation.
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10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
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18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26#ifndef CPU_S390_VM_RELOCINFO_S390_HPP
27#define CPU_S390_VM_RELOCINFO_S390_HPP
28
29//----------------------------
30//  relocInfo layout
31//----------------------------
32
33// This description should be contained in code/relocInfo.hpp
34// but was put here to minimize shared code diffs.
35
36// Relocation information for a nmethod is stored in compressed
37// form in an array of element type short int (16 bits).
38// Each array element constitutes one relocInfo record.
39// The layout of one such record is described here.
40
41// +------------+---+---+------------------------------+
42// |    type    |  fmt  |      offset/offset_unit      |
43// +------------+---+---+------------------------------+
44//
45// |<-- value_width (16) ----------------------------->|
46// |<type_width>|<-- nontype_width (12) -------------->|
47//      (4)
48// |            |<--+-->|<-- offset_width (10) ------->|
49//              /       \
50//             /   (2)   \
51//            /<--format->\
52//            |    width  |
53
54
55// only for type == data_prefix_tag:
56// +------------+---+---+------------------------------+
57// |    type    |   |              data                |
58// +------------+---+---+------------------------------+
59// |     15     |<->|<-- datalen_width (11) ---------->|
60//                |
61//                +--datalen_tag (1)
62
63// relocType
64//   The type field holds a value of relocType (which is
65//   an enum of all possible relocation types). Currently,
66//   there are 16 distinct relocation types, requiring
67//   type_width to be (at least) 4.
68// relocFormat
69//   The format field holds a value of relocFormat (which is
70//   an enum of all possible relocation formats). Currently,
71//   there are 4 distinct relocation formats, requiring
72//   format_width to be (at least) 2.
73// offset
74//   Each relocInfo is related to one specific address in the CodeBlob.
75//   The address always points to the first byte of the target instruction.
76//   It does NOT refer directly to the relocation subfield or embedded constant.
77//   offset contains the distance of this relocInfo from the previous one.
78//   offset is scaled by offset_unit (the platform-specific instruction
79//   alignment requirement) to maximize the encodable distance.
80//   To obtain the absolute address in the CodeBlob the relocInfo is
81//   related to, you have to iterate over all relocInfos from the
82//   beginning, and then use RelocIterator::addr() to get the address.
83
84// relocType == data_prefix_tag
85//   These are relocInfo records containing inline data that belongs to
86//   the next non-data relocInfo record. Usage of that inline data is
87//   specific and private to that relocInfo record.
88//   For details refer to code/relocInfo.hpp
89
90
91  // machine-dependent parts of class relocInfo
92 private:
93  enum {
94    // Instructions are HW (2-byte) aligned on z/Architecture.
95    offset_unit        =  2,
96
97    // Encodes Assembler::disp32_operand vs. Assembler::imm64_operand.
98    // (Assembler::call32_operand is used on call instructions only.)
99    format_width       =  2
100  };
101
102 public:
103
104  enum relocFormat {
105    no_format           = 0,
106    uncompressed_format = 0,  // Relocation is for a regular oop.
107    compressed_format   = 1,  // Relocation is for a narrow (compressed) oop or klass.
108                              // Similar to relocInfo::narrow_oop_in_const.
109    pcrel_addr_format   = 2,  // Relocation is for the target LOCATION of a pc-relative instruction.
110    pcrel_data_format   = 3   // Relocation is for the target data of a pc-relative instruction.
111  };
112
113  // Store the new target address into an oop_Relocation cell, if any.
114  // Return indication if update happened.
115  static bool update_oop_pool(address begin, address end, address newTarget, CodeBlob* cb);
116
117#endif // CPU_S390_VM_RELOCINFO_S390_HPP
118