Add a new library for collecting stack traces.

Supports collecting the stack trace of the current thread,
another thread in the same process, or a thread in a
different process (using ptrace).

Change-Id: Ica2594e4436edde4ceb7bcc3d78e6c31a7902cbf

1 files changed, 204 insertions, 0 deletions

diff --git a/libcorkscrew/symbol_table.c b/libcorkscrew/symbol_table.c
new file mode 100644
index 000000000..8257c7737
--- /dev/null
+++ b/libcorkscrew/symbol_table.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "Corkscrew"
+//#define LOG_NDEBUG 0
+
+#include <corkscrew/symbol_table.h>
+
+#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/exec_elf.h>
+#include <cutils/log.h>
+
+// Compare function for qsort
+static int qcompar(const void *a, const void *b) {
+    const symbol_t* asym = (const symbol_t*)a;
+    const symbol_t* bsym = (const symbol_t*)b;
+    if (asym->start > bsym->start) return 1;
+    if (asym->start < bsym->start) return -1;
+    return 0;
+}
+
+// Compare function for bsearch
+static int bcompar(const void *key, const void *element) {
+    uintptr_t addr = *(const uintptr_t*)key;
+    const symbol_t* symbol = (const symbol_t*)element;
+    if (addr < symbol->start) return -1;
+    if (addr >= symbol->end) return 1;
+    return 0;
+}
+
+symbol_table_t* load_symbol_table(const char *filename) {
+    symbol_table_t* table = NULL;
+
+    int fd = open(filename, O_RDONLY);
+    if (fd < 0) {
+        goto out;
+    }
+
+    struct stat sb;
+    if (fstat(fd, &sb)) {
+        goto out_close;
+    }
+
+    size_t length = sb.st_size;
+    char* base = mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, 0);
+    if (base == MAP_FAILED) {
+        goto out_close;
+    }
+
+    // Parse the file header
+    Elf32_Ehdr *hdr = (Elf32_Ehdr*)base;
+    if (!IS_ELF(*hdr)) {
+        goto out_close;
+    }
+    Elf32_Shdr *shdr = (Elf32_Shdr*)(base + hdr->e_shoff);
+
+    // Search for the dynamic symbols section
+    int sym_idx = -1;
+    int dynsym_idx = -1;
+    for (Elf32_Half i = 0; i < hdr->e_shnum; i++) {
+        if (shdr[i].sh_type == SHT_SYMTAB) {
+            sym_idx = i;
+        }
+        if (shdr[i].sh_type == SHT_DYNSYM) {
+            dynsym_idx = i;
+        }
+    }
+    if (dynsym_idx == -1 && sym_idx == -1) {
+        goto out_unmap;
+    }
+
+    table = malloc(sizeof(symbol_table_t));
+    if(!table) {
+        goto out_unmap;
+    }
+    table->num_symbols = 0;
+
+    Elf32_Sym *dynsyms = NULL;
+    int dynnumsyms = 0;
+    char *dynstr = NULL;
+    if (dynsym_idx != -1) {
+        dynsyms = (Elf32_Sym*)(base + shdr[dynsym_idx].sh_offset);
+        dynnumsyms = shdr[dynsym_idx].sh_size / shdr[dynsym_idx].sh_entsize;
+        int dynstr_idx = shdr[dynsym_idx].sh_link;
+        dynstr = base + shdr[dynstr_idx].sh_offset;
+    }
+
+    Elf32_Sym *syms = NULL;
+    int numsyms = 0;
+    char *str = NULL;
+    if (sym_idx != -1) {
+        syms = (Elf32_Sym*)(base + shdr[sym_idx].sh_offset);
+        numsyms = shdr[sym_idx].sh_size / shdr[sym_idx].sh_entsize;
+        int str_idx = shdr[sym_idx].sh_link;
+        str = base + shdr[str_idx].sh_offset;
+    }
+
+    int dynsymbol_count = 0;
+    if (dynsym_idx != -1) {
+        // Iterate through the dynamic symbol table, and count how many symbols
+        // are actually defined
+        for (int i = 0; i < dynnumsyms; i++) {
+            if (dynsyms[i].st_shndx != SHN_UNDEF) {
+                dynsymbol_count++;
+            }
+        }
+    }
+
+    size_t symbol_count = 0;
+    if (sym_idx != -1) {
+        // Iterate through the symbol table, and count how many symbols
+        // are actually defined
+        for (int i = 0; i < numsyms; i++) {
+            if (syms[i].st_shndx != SHN_UNDEF
+                    && str[syms[i].st_name]
+                    && syms[i].st_value
+                    && syms[i].st_size) {
+                symbol_count++;
+            }
+        }
+    }
+
+    // Now, create an entry in our symbol table structure for each symbol...
+    table->num_symbols += symbol_count + dynsymbol_count;
+    table->symbols = malloc(table->num_symbols * sizeof(symbol_t));
+    if (!table->symbols) {
+        free(table);
+        table = NULL;
+        goto out_unmap;
+    }
+
+    size_t symbol_index = 0;
+    if (dynsym_idx != -1) {
+        // ...and populate them
+        for (int i = 0; i < dynnumsyms; i++) {
+            if (dynsyms[i].st_shndx != SHN_UNDEF) {
+                table->symbols[symbol_index].name = strdup(dynstr + dynsyms[i].st_name);
+                table->symbols[symbol_index].start = dynsyms[i].st_value;
+                table->symbols[symbol_index].end = dynsyms[i].st_value + dynsyms[i].st_size;
+                symbol_index += 1;
+            }
+        }
+    }
+
+    if (sym_idx != -1) {
+        // ...and populate them
+        for (int i = 0; i < numsyms; i++) {
+            if (syms[i].st_shndx != SHN_UNDEF
+                    && str[syms[i].st_name]
+                    && syms[i].st_value
+                    && syms[i].st_size) {
+                table->symbols[symbol_index].name = strdup(str + syms[i].st_name);
+                table->symbols[symbol_index].start = syms[i].st_value;
+                table->symbols[symbol_index].end = syms[i].st_value + syms[i].st_size;
+                symbol_index += 1;
+            }
+        }
+    }
+
+    // Sort the symbol table entries, so they can be bsearched later
+    qsort(table->symbols, table->num_symbols, sizeof(symbol_t), qcompar);
+
+out_unmap:
+    munmap(base, length);
+
+out_close:
+    close(fd);
+
+out:
+    return table;
+}
+
+void free_symbol_table(symbol_table_t* table) {
+    if (table) {
+        for (size_t i = 0; i < table->num_symbols; i++) {
+            free(table->symbols[i].name);
+        }
+        free(table->symbols);
+        free(table);
+    }
+}
+
+const symbol_t* find_symbol(const symbol_table_t* table, uintptr_t addr) {
+    if (!table) return NULL;
+    return (const symbol_t*)bsearch(&addr, table->symbols, table->num_symbols,
+            sizeof(symbol_t), bcompar);
+}