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250 lines
7.1 KiB
Go
250 lines
7.1 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dwarf
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import (
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"sort"
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)
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// pcToFuncEntries maps PC ranges to function entries.
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//
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// Each element contains a *Entry for a function and its corresponding start PC.
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// If we know the address one past the last instruction of a function, and it is
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// not equal to the start address of the next function, we mark that with
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// another element containing that address and a nil entry. The elements are
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// sorted by PC. Among elements with the same PC, those with non-nil *Entry
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// are put earlier.
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type pcToFuncEntries []pcToFuncEntry
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type pcToFuncEntry struct {
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pc uint64
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entry *Entry
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}
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func (p pcToFuncEntries) Len() int { return len(p) }
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func (p pcToFuncEntries) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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func (p pcToFuncEntries) Less(i, j int) bool {
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if p[i].pc != p[j].pc {
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return p[i].pc < p[j].pc
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}
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return p[i].entry != nil && p[j].entry == nil
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}
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// nameCache maps each symbol name to a linked list of the entries with that name.
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type nameCache map[string]*nameCacheEntry
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type nameCacheEntry struct {
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entry *Entry
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link *nameCacheEntry
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}
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// pcToLineEntries maps PCs to line numbers.
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//
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// It is a slice of (PC, line, file number) triples, sorted by PC. The file
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// number is an index into the source files slice.
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// If (PC1, line1, file1) and (PC2, line2, file2) are two consecutive elements,
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// then the span of addresses [PC1, PC2) belongs to (line1, file1). If an
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// element's file number is zero, it only marks the end of a span.
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//
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// TODO: could save memory by changing pcToLineEntries and lineToPCEntries to use
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// interval trees containing references into .debug_line.
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type pcToLineEntries []pcToLineEntry
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type pcToLineEntry struct {
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pc uint64
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line uint64
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file uint64
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}
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func (p pcToLineEntries) Len() int { return len(p) }
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func (p pcToLineEntries) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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func (p pcToLineEntries) Less(i, j int) bool {
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if p[i].pc != p[j].pc {
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return p[i].pc < p[j].pc
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}
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return p[i].file > p[j].file
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}
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// byFileLine is used temporarily while building lineToPCEntries.
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type byFileLine []pcToLineEntry
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func (b byFileLine) Len() int { return len(b) }
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func (b byFileLine) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
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func (b byFileLine) Less(i, j int) bool {
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if b[i].file != b[j].file {
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return b[i].file < b[j].file
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}
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return b[i].line < b[j].line
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}
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// lineToPCEntries maps line numbers to breakpoint addresses.
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//
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// The slice contains, for each source file in Data, a slice of (line, PC)
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// pairs, sorted by line. Note that there may be more than one PC for a line.
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type lineToPCEntries [][]lineToPCEntry
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type lineToPCEntry struct {
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line uint64
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pc uint64
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}
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func (d *Data) buildLineToPCCache(pclfs pcToLineEntries) {
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// TODO: only include lines where is_stmt is true
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sort.Sort(byFileLine(pclfs))
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// Make a slice of (line, PC) pairs for each (non-zero) file.
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var (
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c = make(lineToPCEntries, len(d.sourceFiles))
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curSlice []lineToPCEntry
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)
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for i, pclf := range pclfs {
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if pclf.file == 0 {
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// This entry indicated the end of an instruction sequence, not a breakpoint.
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continue
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}
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curSlice = append(curSlice, lineToPCEntry{line: pclf.line, pc: pclf.pc})
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if i+1 == len(pclfs) || pclf.file != pclfs[i+1].file {
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// curSlice now contains all of the entries for pclf.file.
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if pclf.file > 0 && pclf.file < uint64(len(c)) {
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c[pclf.file] = curSlice
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}
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curSlice = nil
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}
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}
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d.lineToPCEntries = c
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}
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func (d *Data) buildPCToLineCache(cache pcToLineEntries) {
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// Sort cache by PC (in increasing order), then by file number (in decreasing order).
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sort.Sort(cache)
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// Build a copy without redundant entries.
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var out pcToLineEntries
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for i, pclf := range cache {
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if i > 0 && pclf.pc == cache[i-1].pc {
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// This entry is for the same PC as the previous entry.
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continue
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}
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if i > 0 && pclf.file == cache[i-1].file && pclf.line == cache[i-1].line {
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// This entry is for the same file and line as the previous entry.
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continue
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}
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out = append(out, pclf)
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}
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d.pcToLineEntries = out
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}
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// buildLineCaches constructs d.sourceFiles, d.lineToPCEntries, d.pcToLineEntries.
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func (d *Data) buildLineCaches() {
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if len(d.line) == 0 {
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return
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}
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var m lineMachine
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// Assume the address_size in the first unit applies to the whole program.
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// TODO: we could handle executables containing code for multiple address
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// sizes using DW_AT_stmt_list attributes.
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if len(d.unit) == 0 {
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return
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}
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buf := makeBuf(d, &d.unit[0], "line", 0, d.line)
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if err := m.parseHeader(&buf); err != nil {
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return
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}
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for _, f := range m.header.file {
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d.sourceFiles = append(d.sourceFiles, f.name)
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}
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var cache pcToLineEntries
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fn := func(m *lineMachine) bool {
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if m.endSequence {
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cache = append(cache, pcToLineEntry{
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pc: m.address,
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line: 0,
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file: 0,
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})
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} else {
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cache = append(cache, pcToLineEntry{
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pc: m.address,
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line: m.line,
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file: m.file,
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})
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}
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return true
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}
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m.evalCompilationUnit(&buf, fn)
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d.buildLineToPCCache(cache)
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d.buildPCToLineCache(cache)
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}
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// buildInfoCaches initializes nameCache and pcToFuncEntries by walking the
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// top-level entries under each compile unit. It swallows any errors in parsing.
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func (d *Data) buildInfoCaches() {
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// TODO: record errors somewhere?
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d.nameCache = make(map[string]*nameCacheEntry)
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var pcToFuncEntries pcToFuncEntries
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r := d.Reader()
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loop:
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for {
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entry, err := r.Next()
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if entry == nil || err != nil {
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break loop
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}
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if entry.Tag != TagCompileUnit /* DW_TAG_compile_unit */ {
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r.SkipChildren()
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continue
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}
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for {
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entry, err := r.Next()
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if entry == nil || err != nil {
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break loop
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}
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if entry.Tag == 0 {
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// End of children of current compile unit.
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break
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}
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r.SkipChildren()
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// Update name-to-entry cache.
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if name, ok := entry.Val(AttrName).(string); ok {
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d.nameCache[name] = &nameCacheEntry{entry: entry, link: d.nameCache[name]}
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}
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// If this entry is a function, update PC-to-containing-function cache.
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if entry.Tag != TagSubprogram /* DW_TAG_subprogram */ {
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continue
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}
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// DW_AT_low_pc, if present, is the address of the first instruction of
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// the function.
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lowpc, ok := entry.Val(AttrLowpc).(uint64)
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if !ok {
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continue
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}
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pcToFuncEntries = append(pcToFuncEntries, pcToFuncEntry{lowpc, entry})
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// DW_AT_high_pc, if present (TODO: and of class address) is the address
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// one past the last instruction of the function.
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highpc, ok := entry.Val(AttrHighpc).(uint64)
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if !ok {
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continue
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}
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pcToFuncEntries = append(pcToFuncEntries, pcToFuncEntry{highpc, nil})
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}
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}
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// Sort elements by PC. If there are multiple elements with the same PC,
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// those with non-nil *Entry are placed earlier.
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sort.Sort(pcToFuncEntries)
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// Copy only the first element for each PC to out.
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n := 0
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for i, ce := range pcToFuncEntries {
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if i == 0 || ce.pc != pcToFuncEntries[i-1].pc {
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n++
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}
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}
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out := make([]pcToFuncEntry, 0, n)
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for i, ce := range pcToFuncEntries {
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if i == 0 || ce.pc != pcToFuncEntries[i-1].pc {
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out = append(out, ce)
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}
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}
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d.pcToFuncEntries = out
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}
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