In v2:
- find_gnu_ifunc is now based on name search. Need exposed by
PP64 (see later patches in the series).
- Added iterate_over_minimal_symbols function_view overload for
that, and made it possible to stop the search if the callback says
so.
If the GNU ifunc resolver has the same name as the user visible
symbol, and the resolver has debug info, then the DWARF info for the
resolver masks the ifunc minsym. In that scenario, if you try calling
the ifunc from GDB, you call the resolver instead. With the
gnu-ifunc.exp testcase added in a following patch, you'd see:
(gdb) p gnu_ifunc (3)
$1 = (int (*)(int)) 0x400753 <final>
(gdb) FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=0: p gnu_ifunc (3)
^^^^^^^^^^^^^^^^
That is, we called the ifunc resolver manually, which returned a
pointer to the ifunc target function ("final"). The "final" symbol is
the function that GDB should have called automatically,
~~~~~~~~~~~~
int
final (int arg)
{
return arg + 1;
}
~~~~~~~~~
which is what happens if you don't have debug info for the resolver:
(gdb) p gnu_ifunc (3)
$1 = 4
(gdb) PASS: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=0: resolved_debug=1: p gnu_ifunc (3)
^^^^^^^^^^^^^^^^
or if the resolver's symbol has a different name from the ifunc (as is
the case with modern uses of ifunc via __attribute__ ifunc, such as
glibc uses):
(gdb) p gnu_ifunc (3)
$1 = 4
(gdb) PASS: gdb.base/gnu-ifunc.exp: resolver_attr=1: resolver_debug=1: resolved_debug=0: p gnu_ifunc (3)
^^^^^^^^^^^^^^^
in which case after this patch, you can still call the resolver
directly if you want:
(gdb) p gnu_ifunc_resolver (3)
$1 = (int (*)(int)) 0x400753 <final>
gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>
* c-exp.y (variable production): Prefer ifunc minsyms over
regular function symbols.
* symtab.c (find_gnu_ifunc): New function.
* minsyms.h (lookup_msym_prefer): New enum.
(lookup_minimal_symbol_by_pc_section): Replace 'want_trampoline'
parameter by a lookup_msym_prefer parameter.
* symtab.h (find_gnu_ifunc): New declaration.
---
gdb/c-exp.y | 20 ++++++++++++++++----
gdb/linespec.c | 7 ++++---
gdb/minsyms.c | 30 +++++++++++++++++++++++-------
gdb/minsyms.h | 13 +++++++++++--
gdb/symtab.c | 32 ++++++++++++++++++++++++++++++++
gdb/symtab.h | 3 +++
6 files changed, 89 insertions(+), 16 deletions(-)
@@ -1041,10 +1041,22 @@ variable: name_not_typename
if (symbol_read_needs_frame (sym.symbol))
innermost_block.update (sym);
- write_exp_elt_opcode (pstate, OP_VAR_VALUE);
- write_exp_elt_block (pstate, sym.block);
- write_exp_elt_sym (pstate, sym.symbol);
- write_exp_elt_opcode (pstate, OP_VAR_VALUE);
+ /* If we found a function, see if it's
+ an ifunc resolver that has the same
+ address as the ifunc symbol itself.
+ If so, prefer the ifunc symbol. */
+
+ bound_minimal_symbol resolver
+ = find_gnu_ifunc (sym.symbol);
+ if (resolver.minsym != NULL)
+ write_exp_msymbol (pstate, resolver);
+ else
+ {
+ write_exp_elt_opcode (pstate, OP_VAR_VALUE);
+ write_exp_elt_block (pstate, sym.block);
+ write_exp_elt_sym (pstate, sym.symbol);
+ write_exp_elt_opcode (pstate, OP_VAR_VALUE);
+ }
}
else if ($1.is_a_field_of_this)
{
@@ -4431,7 +4431,7 @@ compare_msyms (const void *a, const void *b)
/* Callback for iterate_over_minimal_symbols that adds the symbol to
the result. */
-static void
+static bool
add_minsym (struct minimal_symbol *minsym, void *d)
{
struct collect_minsyms *info = (struct collect_minsyms *) d;
@@ -4446,16 +4446,17 @@ add_minsym (struct minimal_symbol *minsym, void *d)
symtab_and_line sal = find_pc_sect_line (func_addr, NULL, 0);
if (info->symtab != sal.symtab)
- return;
+ return false;
}
}
/* Exclude data symbols when looking for breakpoint locations. */
if (!info->list_mode && !msymbol_is_function (info->objfile, minsym))
- return;
+ return false;
bound_minimal_symbol_d mo = {minsym, info->objfile};
VEC_safe_push (bound_minimal_symbol_d, info->msyms, &mo);
+ return false;
}
/* Search for minimal symbols called NAME. If SEARCH_PSPACE
@@ -469,11 +469,10 @@ linkage_name_str (const lookup_name_info &lookup_name)
/* See minsyms.h. */
void
-iterate_over_minimal_symbols (struct objfile *objf,
- const lookup_name_info &lookup_name,
- void (*callback) (struct minimal_symbol *,
- void *),
- void *user_data)
+iterate_over_minimal_symbols
+ (struct objfile *objf,
+ const lookup_name_info &lookup_name,
+ gdb::function_view<bool (minimal_symbol *)> callback)
{
/* The first pass is over the ordinary hash table. */
@@ -490,7 +489,8 @@ iterate_over_minimal_symbols (struct objfile *objf,
iter = iter->hash_next)
{
if (mangled_cmp (MSYMBOL_LINKAGE_NAME (iter), name) == 0)
- (*callback) (iter, user_data);
+ if (callback (iter))
+ return;
}
}
@@ -509,12 +509,28 @@ iterate_over_minimal_symbols (struct objfile *objf,
iter != NULL;
iter = iter->demangled_hash_next)
if (name_match (MSYMBOL_SEARCH_NAME (iter), lookup_name, NULL))
- (*callback) (iter, user_data);
+ if (callback (iter))
+ return;
}
}
/* See minsyms.h. */
+void
+iterate_over_minimal_symbols (struct objfile *objf,
+ const lookup_name_info &lookup_name,
+ bool (*callback) (struct minimal_symbol *,
+ void *),
+ void *user_data)
+{
+ iterate_over_minimal_symbols (objf, lookup_name, [&] (minimal_symbol *iter)
+ {
+ return callback (iter, user_data);
+ });
+}
+
+/* See minsyms.h. */
+
struct bound_minimal_symbol
lookup_minimal_symbol_text (const char *name, struct objfile *objf)
{
@@ -20,6 +20,8 @@
#ifndef MINSYMS_H
#define MINSYMS_H
+#include "common/function-view.h"
+
struct type;
/* Several lookup functions return both a minimal symbol and the
@@ -266,14 +268,21 @@ struct bound_minimal_symbol lookup_minimal_symbol_by_pc (CORE_ADDR);
should that need to be done.
For each matching symbol, CALLBACK is called with the symbol and
- USER_DATA as arguments. */
+ USER_DATA as arguments. If CALLBACK returns true, the search
+ stops. */
void iterate_over_minimal_symbols (struct objfile *objf,
const lookup_name_info &name,
- void (*callback) (struct minimal_symbol *,
+ bool (*callback) (struct minimal_symbol *,
void *),
void *user_data);
+/* Same, but use a gdb::function_view as callback type. */
+void iterate_over_minimal_symbols
+ (struct objfile *objf,
+ const lookup_name_info &name,
+ gdb::function_view<bool (minimal_symbol *)> callback);
+
/* Compute the upper bound of MINSYM. The upper bound is the last
address thought to be part of the symbol. If the symbol has a
size, it is used. Otherwise use the lesser of the next minimal
@@ -4945,6 +4945,38 @@ symbol_is_function_or_method (minimal_symbol *msymbol)
}
}
+/* See symtab.h. */
+
+bound_minimal_symbol
+find_gnu_ifunc (const symbol *sym)
+{
+ if (SYMBOL_CLASS (sym) != LOC_BLOCK)
+ return {};
+
+ lookup_name_info lookup_name (SYMBOL_SEARCH_NAME (sym),
+ symbol_name_match_type::SEARCH_NAME);
+ struct objfile *objfile = symbol_objfile (sym);
+
+ CORE_ADDR address = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
+ minimal_symbol *ifunc = NULL;
+
+ iterate_over_minimal_symbols (objfile, lookup_name,
+ [&] (minimal_symbol *minsym)
+ {
+ if (MSYMBOL_TYPE (minsym) == mst_text_gnu_ifunc
+ && MSYMBOL_VALUE_ADDRESS (objfile, minsym) == address)
+ {
+ ifunc = minsym;
+ return true;
+ }
+ return false;
+ });
+
+ if (ifunc != NULL)
+ return {ifunc, objfile};
+ return {};
+}
+
/* Add matching symbols from SYMTAB to the current completion list. */
static void
@@ -1681,6 +1681,9 @@ extern int find_pc_partial_function (CORE_ADDR, const char **, CORE_ADDR *,
extern struct type *find_gnu_ifunc_target_type (CORE_ADDR resolver_funaddr);
+/* Find the GNU ifunc minimal symbol that matches SYM. */
+extern bound_minimal_symbol find_gnu_ifunc (const symbol *sym);
+
extern void clear_pc_function_cache (void);
/* Expand symtab containing PC, SECTION if not already expanded. */