Provide source code info for Symbol

For function symbols, provide the source code file,
line number, and column.

Signed-off-by: Paul Zuchowski <[email protected]>

_drgn.pyi

@@ -1529,6 +1529,14 @@ class Symbol:
     kind: SymbolKind
     """Kind of entity represented by this symbol."""
 
+    def source(self, long) -> Tuple[str, int, int]:
+        """
+        Get the source code location of this function at the given offset.
+
+        :return: Location as a ``(filename, line, column)`` triple.
+        :raises LookupError: if the source code location is not available
+        """
+
 class SymbolBinding(enum.Enum):
     """
     A ``SymbolBinding`` describes the linkage behavior and visibility of a

libdrgn/debug_info.c

@@ -303,6 +303,25 @@ static int drgn_dwfl_module_removed(Dwfl_Module *dwfl_module, void *userdatap,
 	return DWARF_CB_OK;
 }
 
+struct drgn_debug_info_module *
+drgn_debug_info_module_byaddress(struct drgn_debug_info *dbinfo, uint64_t addr)
+{
+
+	for (struct drgn_debug_info_module_table_iterator it =
+             drgn_debug_info_module_table_first(&dbinfo->modules); it.entry; ) {
+                struct drgn_debug_info_module *module = *it.entry;
+                do {
+			struct drgn_debug_info_module *next = module->next;
+			if (!next)
+				it = drgn_debug_info_module_table_next(it);
+			if (addr >= module->start && addr <= module->end)
+				return module;
+			module = next;
+                } while (module);
+	}
+	return NULL;
+}
+
 static void drgn_debug_info_free_modules(struct drgn_debug_info *dbinfo,
 					 bool finish_indexing, bool free_all)
 {

libdrgn/debug_info.h

@@ -171,6 +171,10 @@ drgn_debug_info_buffer_init(struct drgn_debug_info_buffer *buffer,
 	buffer->scn = scn;
 }
 
+struct drgn_debug_info_module *
+drgn_debug_info_module_byaddress(struct drgn_debug_info *dbinfo, uint64_t addr);
+
+
 DEFINE_HASH_TABLE_TYPE(drgn_debug_info_module_table,
 		       struct drgn_debug_info_module *)
 

libdrgn/drgn.h.in

@@ -2675,6 +2675,15 @@ void drgn_symbol_destroy(struct drgn_symbol *sym);
  */
 void drgn_symbols_destroy(struct drgn_symbol **syms, size_t count);
 
+/** Get the source code file, line, and column of a @ref drgn_symbol */
+struct drgn_error *drgn_symbol_source(struct drgn_symbol *sym,
+			              struct drgn_program *prog,
+				      unsigned long offset,
+				      size_t size,
+				      char *src_file_ret,
+				      int *line_num_ret,
+				      int *line_col_ret);
+
 /**
  * Get the name of a @ref drgn_symbol.
  *

libdrgn/python/symbol.c

@@ -36,6 +36,27 @@ static PyObject *Symbol_richcompare(Symbol *self, PyObject *other, int op)
 	Py_RETURN_BOOL(ret);
 }
 
+#define MAXPATHLEN 256
+
+static PyObject *Symbol_source(Symbol *self, PyObject *arg)
+{
+	char source[MAXPATHLEN];
+	Program *prgm = ((Symbol *)self)->prog;
+	struct drgn_program *p = &prgm->prog;
+	int ln_num = 0;
+	int ln_col = 0;
+	unsigned long offset = PyLong_AsLong(arg);
+
+	struct drgn_error *err;
+	err = drgn_symbol_source(((Symbol *)self)->sym, p,
+				 offset, sizeof(source),
+				 source, &ln_num, &ln_col);
+	if (err)
+		return set_drgn_error(err);
+
+	return Py_BuildValue("sii", source, ln_num, ln_col);
+}
+
 static PyObject *Symbol_get_name(Symbol *self, void *arg)
 {
 	return PyUnicode_FromString(drgn_symbol_name(self->sym));
@@ -93,6 +114,12 @@ static PyObject *Symbol_repr(Symbol *self)
 
 }
 
+static PyMethodDef Symbol_methods[] = {
+	{"source", (PyCFunction)Symbol_source, METH_O, 
+	 drgn_Symbol_source_DOC},
+	{},
+};
+
 static PyGetSetDef Symbol_getset[] = {
 	{"name", (getter)Symbol_get_name, NULL, drgn_Symbol_name_DOC},
 	{"address", (getter)Symbol_get_address, NULL, drgn_Symbol_address_DOC},
@@ -111,5 +138,6 @@ PyTypeObject Symbol_type = {
 	.tp_flags = Py_TPFLAGS_DEFAULT,
 	.tp_doc = drgn_Symbol_DOC,
 	.tp_richcompare = (richcmpfunc)Symbol_richcompare,
+	.tp_methods = Symbol_methods,
 	.tp_getset = Symbol_getset,
 };

libdrgn/symbol.c

@@ -4,8 +4,14 @@
 #include <elf.h>
 #include <stdlib.h>
 #include <string.h>
+#include <dwarf.h>
+#include <elfutils/libdw.h>
+#include <elfutils/libdwfl.h>
 
+#include "debug_info.h"
 #include "drgn.h"
+#include "error.h"
+#include "program.h"
 #include "symbol.h"
 #include "util.h"
 
@@ -40,6 +46,44 @@ void drgn_symbol_from_elf(const char *name, uint64_t address,
 		ret->kind = DRGN_SYMBOL_KIND_UNKNOWN;
 }
 
+LIBDRGN_PUBLIC struct drgn_error *
+drgn_symbol_source(struct drgn_symbol *sym,
+	           struct drgn_program *prog,
+	           unsigned long offset,
+	           size_t size,
+	           char *src_file_ret,
+	           int *line_num_ret,
+	           int *line_col_ret)
+{
+	if (sym->kind != DRGN_SYMBOL_KIND_FUNC)
+		return drgn_error_create(DRGN_ERROR_LOOKUP,
+					 "symbol is not a function");
+
+	unsigned long sym_address = sym->address + offset;
+	struct drgn_debug_info_module *dim;
+	dim = drgn_debug_info_module_byaddress(prog->dbinfo, sym_address);
+	if (dim == NULL)
+		return drgn_error_create(DRGN_ERROR_LOOKUP,
+                                         "could not locate module from function address");
+
+
+	Dwfl_Line *line = dwfl_module_getsrc(dim->dwfl_module, sym_address);
+	if (line == NULL)
+		return drgn_error_create(DRGN_ERROR_LOOKUP,
+                                         "could not obtain source code information");
+
+	const char *src;
+	int lineno, linecol;
+	if ((src = dwfl_lineinfo(line, &sym_address, &lineno, &linecol,
+				 NULL, NULL)) != NULL) {
+		strncpy(src_file_ret, src, size);
+		*line_num_ret = lineno;
+		*line_col_ret = linecol;
+	}
+
+	return NULL;
+}
+
 LIBDRGN_PUBLIC const char *drgn_symbol_name(struct drgn_symbol *sym)
 {
 	return sym->name;