1 files changed, 178 insertions, 0 deletions
diff --git a/debuggerd/symbol_table.c b/debuggerd/symbol_table.c
new file mode 100644
index 0000000..150c058
--- /dev/null
+++ b/debuggerd/symbol_table.c
@@ -0,0 +1,178 @@
+#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include "symbol_table.h"
+
+#include <linux/elf.h>
+
+// Compare func for qsort
+static int qcompar(const void *a, const void *b)
+{
+    return ((struct symbol*)a)->addr - ((struct symbol*)b)->addr;
+}
+
+// Compare func for bsearch
+static int bcompar(const void *addr, const void *element)
+{
+    struct symbol *symbol = (struct symbol*)element;
+
+    if((unsigned int)addr < symbol->addr) {
+        return -1;
+    }
+
+    if((unsigned int)addr - symbol->addr >= symbol->size) {
+        return 1;
+    }
+
+    return 0;
+}
+
+/*
+ *  Create a symbol table from a given file
+ *
+ *  Parameters:
+ *      filename - Filename to process
+ *
+ *  Returns:
+ *      A newly-allocated SymbolTable structure, or NULL if error.
+ *      Free symbol table with symbol_table_free()
+ */
+struct symbol_table *symbol_table_create(const char *filename)
+{
+    struct symbol_table *table = NULL;
+
+    // Open the file, and map it into memory
+    struct stat sb;
+    int length;
+    char *base;
+
+    int fd = open(filename, O_RDONLY);
+
+    if(fd < 0) {
+        goto out;
+    }
+
+    fstat(fd, &sb);
+    length = sb.st_size;
+
+    base = mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, 0);
+
+    if(!base) {
+        goto out_close;
+    }
+
+    // Parse the file header
+    Elf32_Ehdr *hdr = (Elf32_Ehdr*)base;
+    Elf32_Shdr *shdr = (Elf32_Shdr*)(base + hdr->e_shoff);
+
+    // Search for the dynamic symbols section
+    int dynsym_idx = -1;
+    int i;
+
+    for(i = 0; i < hdr->e_shnum; i++) {
+        if(shdr[i].sh_type == SHT_DYNSYM ) {
+            dynsym_idx = i;
+        }
+    }
+
+    if(dynsym_idx == -1) {
+        goto out_unmap;
+    }
+
+    Elf32_Sym *dynsyms = (Elf32_Sym*)(base + shdr[dynsym_idx].sh_offset);
+    int numsyms = shdr[dynsym_idx].sh_size / shdr[dynsym_idx].sh_entsize;
+
+    table = malloc(sizeof(struct symbol_table));
+    if(!table) {
+        goto out_unmap;
+    }
+    table->num_symbols = 0;
+
+    // Iterate through the dynamic symbol table, and count how many symbols
+    // are actually defined
+    for(i = 0; i < numsyms; i++) {
+        if(dynsyms[i].st_shndx != SHN_UNDEF) {
+            table->num_symbols++;
+        }
+    }
+
+    int dynstr_idx = shdr[dynsym_idx].sh_link;
+    char *dynstr = base + shdr[dynstr_idx].sh_offset;
+
+    // Now, create an entry in our symbol table structure for each symbol...
+    table->symbols = malloc(table->num_symbols * sizeof(struct symbol));
+    if(!table->symbols) {
+        free(table);
+        table = NULL;
+        goto out_unmap;
+    }
+
+    // ...and populate them
+    int j = 0;
+    for(i = 0; i < numsyms; i++) {
+        if(dynsyms[i].st_shndx != SHN_UNDEF) {
+            table->symbols[j].name = strdup(dynstr + dynsyms[i].st_name);
+            table->symbols[j].addr = dynsyms[i].st_value;
+            table->symbols[j].size = dynsyms[i].st_size;
+            j++;
+        }
+    }
+
+    // Sort the symbol table entries, so they can be bsearched later
+    qsort(table->symbols, table->num_symbols, sizeof(struct symbol), qcompar);
+
+out_unmap:
+    munmap(base, length);
+
+out_close:
+    close(fd);
+
+out:
+    return table;
+}
+
+/*
+ * Free a symbol table
+ *
+ * Parameters:
+ *     table - Table to free
+ */
+void symbol_table_free(struct symbol_table *table)
+{
+    int i;
+
+    if(!table) {
+        return;
+    }
+
+    for(i=0; i<table->num_symbols; i++) {
+        free(table->symbols[i].name);
+    }
+
+    free(table->symbols);
+    free(table);
+}
+
+/*
+ * Search for an address in the symbol table
+ *
+ * Parameters:
+ *      table - Table to search in
+ *      addr - Address to search for.
+ *
+ * Returns:
+ *      A pointer to the Symbol structure corresponding to the
+ *      symbol which contains this address, or NULL if no symbol
+ *      contains it.
+ */
+const struct symbol *symbol_table_lookup(struct symbol_table *table, unsigned int addr)
+{
+    if(!table) {
+        return NULL;
+    }
+
+    return bsearch((void*)addr, table->symbols, table->num_symbols, sizeof(struct symbol), bcompar);
+}