| // -*- mode: C++ -*- |
| |
| // Copyright (c) 2010, Google Inc. |
| // All rights reserved. |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com> |
| |
| // test-assembler.h: interface to class for building complex binary streams. |
| |
| // To test the Breakpad symbol dumper and processor thoroughly, for |
| // all combinations of host system and minidump processor |
| // architecture, we need to be able to easily generate complex test |
| // data like debugging information and minidump files. |
| // |
| // For example, if we want our unit tests to provide full code |
| // coverage for stack walking, it may be difficult to persuade the |
| // compiler to generate every possible sort of stack walking |
| // information that we want to support; there are probably DWARF CFI |
| // opcodes that GCC never emits. Similarly, if we want to test our |
| // error handling, we will need to generate damaged minidumps or |
| // debugging information that (we hope) the client or compiler will |
| // never produce on its own. |
| // |
| // google_breakpad::TestAssembler provides a predictable and |
| // (relatively) simple way to generate complex formatted data streams |
| // like minidumps and CFI. Furthermore, because TestAssembler is |
| // portable, developers without access to (say) Visual Studio or a |
| // SPARC assembler can still work on test data for those targets. |
| |
| #ifndef PROCESSOR_TEST_ASSEMBLER_H_ |
| #define PROCESSOR_TEST_ASSEMBLER_H_ |
| |
| #include <list> |
| #include <vector> |
| #include <string> |
| |
| #include "google_breakpad/common/breakpad_types.h" |
| |
| namespace google_breakpad { |
| |
| using std::list; |
| using std::string; |
| using std::vector; |
| |
| namespace TestAssembler { |
| |
| // A Label represents a value not yet known that we need to store in a |
| // section. As long as all the labels a section refers to are defined |
| // by the time we retrieve its contents as bytes, we can use undefined |
| // labels freely in that section's construction. |
| // |
| // A label can be in one of three states: |
| // - undefined, |
| // - defined as the sum of some other label and a constant, or |
| // - a constant. |
| // |
| // A label's value never changes, but it can accumulate constraints. |
| // Adding labels and integers is permitted, and yields a label. |
| // Subtracting a constant from a label is permitted, and also yields a |
| // label. Subtracting two labels that have some relationship to each |
| // other is permitted, and yields a constant. |
| // |
| // For example: |
| // |
| // Label a; // a's value is undefined |
| // Label b; // b's value is undefined |
| // { |
| // Label c = a + 4; // okay, even though a's value is unknown |
| // b = c + 4; // also okay; b is now a+8 |
| // } |
| // Label d = b - 2; // okay; d == a+6, even though c is gone |
| // d.Value(); // error: d's value is not yet known |
| // d - a; // is 6, even though their values are not known |
| // a = 12; // now b == 20, and d == 18 |
| // d.Value(); // 18: no longer an error |
| // b.Value(); // 20 |
| // d = 10; // error: d is already defined. |
| // |
| // Label objects' lifetimes are unconstrained: notice that, in the |
| // above example, even though a and b are only related through c, and |
| // c goes out of scope, the assignment to a sets b's value as well. In |
| // particular, it's not necessary to ensure that a Label lives beyond |
| // Sections that refer to it. |
| class Label { |
| public: |
| Label(); // An undefined label. |
| Label(u_int64_t value); // A label with a fixed value |
| Label(const Label &value); // A label equal to another. |
| ~Label(); |
| |
| // Return this label's value; it must be known. |
| // |
| // Providing this as a cast operator is nifty, but the conversions |
| // happen in unexpected places. In particular, ISO C++ says that |
| // Label + size_t becomes ambigious, because it can't decide whether |
| // to convert the Label to a u_int64_t and then to a size_t, or use |
| // the overloaded operator that returns a new label, even though the |
| // former could fail if the label is not yet defined and the latter won't. |
| u_int64_t Value() const; |
| |
| Label &operator=(u_int64_t value); |
| Label &operator=(const Label &value); |
| Label operator+(u_int64_t addend) const; |
| Label operator-(u_int64_t subtrahend) const; |
| u_int64_t operator-(const Label &subtrahend) const; |
| |
| // We could also provide == and != that work on undefined, but |
| // related, labels. |
| |
| // Return true if this label's value is known. If VALUE_P is given, |
| // set *VALUE_P to the known value if returning true. |
| bool IsKnownConstant(u_int64_t *value_p = NULL) const; |
| |
| // Return true if the offset from LABEL to this label is known. If |
| // OFFSET_P is given, set *OFFSET_P to the offset when returning true. |
| // |
| // You can think of l.KnownOffsetFrom(m, &d) as being like 'd = l-m', |
| // except that it also returns a value indicating whether the |
| // subtraction is possible given what we currently know of l and m. |
| // It can be possible even if we don't know l and m's values. For |
| // example: |
| // |
| // Label l, m; |
| // m = l + 10; |
| // l.IsKnownConstant(); // false |
| // m.IsKnownConstant(); // false |
| // u_int64_t d; |
| // l.IsKnownOffsetFrom(m, &d); // true, and sets d to -10. |
| // l-m // -10 |
| // m-l // 10 |
| // m.Value() // error: m's value is not known |
| bool IsKnownOffsetFrom(const Label &label, u_int64_t *offset_p = NULL) const; |
| |
| private: |
| // A label's value, or if that is not yet known, how the value is |
| // related to other labels' values. A binding may be: |
| // - a known constant, |
| // - constrained to be equal to some other binding plus a constant, or |
| // - unconstrained, and free to take on any value. |
| // |
| // Many labels may point to a single binding, and each binding may |
| // refer to another, so bindings and labels form trees whose leaves |
| // are labels, whose interior nodes (and roots) are bindings, and |
| // where links point from children to parents. Bindings are |
| // reference counted, allowing labels to be lightweight, copyable, |
| // assignable, placed in containers, and so on. |
| class Binding { |
| public: |
| Binding(); |
| Binding(u_int64_t addend); |
| ~Binding(); |
| |
| // Increment our reference count. |
| void Acquire() { reference_count_++; }; |
| // Decrement our reference count, and return true if it is zero. |
| bool Release() { return --reference_count_ == 0; } |
| |
| // Set this binding to be equal to BINDING + ADDEND. If BINDING is |
| // NULL, then set this binding to the known constant ADDEND. |
| // Update every binding on this binding's chain to point directly |
| // to BINDING, or to be a constant, with addends adjusted |
| // appropriately. |
| void Set(Binding *binding, u_int64_t value); |
| |
| // Return what we know about the value of this binding. |
| // - If this binding's value is a known constant, set BASE to |
| // NULL, and set ADDEND to its value. |
| // - If this binding is not a known constant but related to other |
| // bindings, set BASE to the binding at the end of the relation |
| // chain (which will always be unconstrained), and set ADDEND to the |
| // value to add to that binding's value to get this binding's |
| // value. |
| // - If this binding is unconstrained, set BASE to this, and leave |
| // ADDEND unchanged. |
| void Get(Binding **base, u_int64_t *addend); |
| |
| private: |
| // There are three cases: |
| // |
| // - A binding representing a known constant value has base_ NULL, |
| // and addend_ equal to the value. |
| // |
| // - A binding representing a completely unconstrained value has |
| // base_ pointing to this; addend_ is unused. |
| // |
| // - A binding whose value is related to some other binding's |
| // value has base_ pointing to that other binding, and addend_ |
| // set to the amount to add to that binding's value to get this |
| // binding's value. We only represent relationships of the form |
| // x = y+c. |
| // |
| // Thus, the bind_ links form a chain terminating in either a |
| // known constant value or a completely unconstrained value. Most |
| // operations on bindings do path compression: they change every |
| // binding on the chain to point directly to the final value, |
| // adjusting addends as appropriate. |
| Binding *base_; |
| u_int64_t addend_; |
| |
| // The number of Labels and Bindings pointing to this binding. |
| // (When a binding points to itself, indicating a completely |
| // unconstrained binding, that doesn't count as a reference.) |
| int reference_count_; |
| }; |
| |
| // This label's value. |
| Binding *value_; |
| }; |
| |
| inline Label operator+(u_int64_t a, const Label &l) { return l + a; } |
| // Note that int-Label isn't defined, as negating a Label is not an |
| // operation we support. |
| |
| // Conventions for representing larger numbers as sequences of bytes. |
| enum Endianness { |
| kBigEndian, // Big-endian: the most significant byte comes first. |
| kLittleEndian, // Little-endian: the least significant byte comes first. |
| kUnsetEndian, // used internally |
| }; |
| |
| // A section is a sequence of bytes, constructed by appending bytes |
| // to the end. Sections have a convenient and flexible set of member |
| // functions for appending data in various formats: big-endian and |
| // little-endian signed and unsigned values of different sizes; |
| // LEB128 and ULEB128 values (see below), and raw blocks of bytes. |
| // |
| // If you need to append a value to a section that is not convenient |
| // to compute immediately, you can create a label, append the |
| // label's value to the section, and then set the label's value |
| // later, when it's convenient to do so. Once a label's value is |
| // known, the section class takes care of updating all previously |
| // appended references to it. |
| // |
| // Once all the labels to which a section refers have had their |
| // values determined, you can get a copy of the section's contents |
| // as a string. |
| // |
| // Note that there is no specified "start of section" label. This is |
| // because there are typically several different meanings for "the |
| // start of a section": the offset of the section within an object |
| // file, the address in memory at which the section's content appear, |
| // and so on. It's up to the code that uses the Section class to |
| // keep track of these explicitly, as they depend on the application. |
| class Section { |
| public: |
| Section(Endianness endianness = kUnsetEndian) |
| : endianness_(endianness) { }; |
| ~Section() { }; |
| |
| // Set the default endianness of this section to ENDIANNESS. This |
| // sets the behavior of the D<N> appending functions. If the |
| // assembler's default endianness was set, this is the |
| void set_endianness(Endianness endianness) { |
| endianness_ = endianness; |
| } |
| |
| // Return the default endianness of this section. |
| Endianness endianness() const { return endianness_; } |
| |
| // Append the SIZE bytes at DATA or the contents of STRING to the |
| // end of this section. Return a reference to this section. |
| Section &Append(const u_int8_t *data, size_t size) { |
| contents_.append(reinterpret_cast<const char *>(data), size); |
| return *this; |
| }; |
| Section &Append(const string &data) { |
| contents_.append(data); |
| return *this; |
| }; |
| |
| // Append SIZE copies of BYTE to the end of this section. Return a |
| // reference to this section. |
| Section &Append(size_t size, u_int8_t byte) { |
| contents_.append(size, (char) byte); |
| return *this; |
| } |
| |
| // Append NUMBER to this section. ENDIANNESS is the endianness to |
| // use to write the number. SIZE is the length of the number in |
| // bytes. Return a reference to this section. |
| Section &Append(Endianness endianness, size_t size, u_int64_t number); |
| Section &Append(Endianness endianness, size_t size, const Label &label); |
| |
| // Append SECTION to the end of this section. The labels SECTION |
| // refers to need not be defined yet. |
| // |
| // Note that this has no effect on any Labels' values, or on |
| // SECTION. If placing SECTION within 'this' provides new |
| // constraints on existing labels' values, then it's up to the |
| // caller to fiddle with those labels as needed. |
| Section &Append(const Section §ion); |
| |
| // Append the contents of DATA as a series of bytes terminated by |
| // a NULL character. |
| Section &AppendCString(const string &data) { |
| Append(data); |
| contents_ += '\0'; |
| return *this; |
| } |
| |
| // Append VALUE or LABEL to this section, with the given bit width and |
| // endianness. Return a reference to this section. |
| // |
| // The names of these functions have the form <ENDIANNESS><BITWIDTH>: |
| // <ENDIANNESS> is either 'L' (little-endian, least significant byte first), |
| // 'B' (big-endian, most significant byte first), or |
| // 'D' (default, the section's default endianness) |
| // <BITWIDTH> is 8, 16, 32, or 64. |
| // |
| // Since endianness doesn't matter for a single byte, all the |
| // <BITWIDTH>=8 functions are equivalent. |
| // |
| // These can be used to write both signed and unsigned values, as |
| // the compiler will properly sign-extend a signed value before |
| // passing it to the function, at which point the function's |
| // behavior is the same either way. |
| Section &L8(u_int8_t value) { contents_ += value; return *this; } |
| Section &B8(u_int8_t value) { contents_ += value; return *this; } |
| Section &D8(u_int8_t value) { contents_ += value; return *this; } |
| Section &L16(u_int16_t), &L32(u_int32_t), &L64(u_int64_t), |
| &B16(u_int16_t), &B32(u_int32_t), &B64(u_int64_t), |
| &D16(u_int16_t), &D32(u_int32_t), &D64(u_int64_t); |
| Section &L8(const Label &label), &L16(const Label &label), |
| &L32(const Label &label), &L64(const Label &label), |
| &B8(const Label &label), &B16(const Label &label), |
| &B32(const Label &label), &B64(const Label &label), |
| &D8(const Label &label), &D16(const Label &label), |
| &D32(const Label &label), &D64(const Label &label); |
| |
| // Append VALUE in a signed LEB128 (Little-Endian Base 128) form. |
| // |
| // The signed LEB128 representation of an integer N is a variable |
| // number of bytes: |
| // |
| // - If N is between -0x40 and 0x3f, then its signed LEB128 |
| // representation is a single byte whose value is N. |
| // |
| // - Otherwise, its signed LEB128 representation is (N & 0x7f) | |
| // 0x80, followed by the signed LEB128 representation of N / 128, |
| // rounded towards negative infinity. |
| // |
| // In other words, we break VALUE into groups of seven bits, put |
| // them in little-endian order, and then write them as eight-bit |
| // bytes with the high bit on all but the last. |
| // |
| // Note that VALUE cannot be a Label (we would have to implement |
| // relaxation). |
| Section &LEB128(long long value); |
| |
| // Append VALUE in unsigned LEB128 (Little-Endian Base 128) form. |
| // |
| // The unsigned LEB128 representation of an integer N is a variable |
| // number of bytes: |
| // |
| // - If N is between 0 and 0x7f, then its unsigned LEB128 |
| // representation is a single byte whose value is N. |
| // |
| // - Otherwise, its unsigned LEB128 representation is (N & 0x7f) | |
| // 0x80, followed by the unsigned LEB128 representation of N / |
| // 128, rounded towards negative infinity. |
| // |
| // Note that VALUE cannot be a Label (we would have to implement |
| // relaxation). |
| Section &ULEB128(u_int64_t value); |
| |
| // Jump to the next location aligned on an ALIGNMENT-byte boundary, |
| // relative to the start of the section. Fill the gap with PAD_BYTE. |
| // ALIGNMENT must be a power of two. Return a reference to this |
| // section. |
| Section &Align(size_t alignment, u_int8_t pad_byte = 0); |
| |
| // Clear the contents of this section. |
| void Clear(); |
| |
| // Return the current size of the section. |
| size_t Size() const { return contents_.size(); } |
| |
| // Return a label representing the start of the section. |
| // |
| // It is up to the user whether this label represents the section's |
| // position in an object file, the section's address in memory, or |
| // what have you; some applications may need both, in which case |
| // this simple-minded interface won't be enough. This class only |
| // provides a single start label, for use with the Here and Mark |
| // member functions. |
| // |
| // Ideally, we'd provide this in a subclass that actually knows more |
| // about the application at hand and can provide an appropriate |
| // collection of start labels. But then the appending member |
| // functions like Append and D32 would return a reference to the |
| // base class, not the derived class, and the chaining won't work. |
| // Since the only value here is in pretty notation, that's a fatal |
| // flaw. |
| Label start() const { return start_; } |
| |
| // Return a label representing the point at which the next Appended |
| // item will appear in the section, relative to start(). |
| Label Here() const { return start_ + Size(); } |
| |
| // Set *LABEL to Here, and return a reference to this section. |
| Section &Mark(Label *label) { *label = Here(); return *this; } |
| |
| // If there are no undefined label references left in this |
| // section, set CONTENTS to the contents of this section, as a |
| // string, and clear this section. Return true on success, or false |
| // if there were still undefined labels. |
| bool GetContents(string *contents); |
| |
| private: |
| // Used internally. A reference to a label's value. |
| struct Reference { |
| Reference(size_t set_offset, Endianness set_endianness, size_t set_size, |
| const Label &set_label) |
| : offset(set_offset), endianness(set_endianness), size(set_size), |
| label(set_label) { } |
| |
| // The offset of the reference within the section. |
| size_t offset; |
| |
| // The endianness of the reference. |
| Endianness endianness; |
| |
| // The size of the reference. |
| size_t size; |
| |
| // The label to which this is a reference. |
| Label label; |
| }; |
| |
| // The default endianness of this section. |
| Endianness endianness_; |
| |
| // The contents of the section. |
| string contents_; |
| |
| // References to labels within those contents. |
| vector<Reference> references_; |
| |
| // A label referring to the beginning of the section. |
| Label start_; |
| }; |
| |
| } // namespace TestAssembler |
| } // namespace google_breakpad |
| |
| #endif // PROCESSOR_TEST_ASSEMBLER_H_ |