[v2,07/15] Breakpoints, don't skip prologue of ifunc resolvers with debug info
Commit Message
In v2:
- The minsym/symbol matching in convert_linespec_to_sals is done
differently. The v1 bsearch method wouldn't work for PPC64, given
function descriptors. convert_linespec_to_sals will be touched
again later in the series, for PPC64.
- Moved declarations of locals closer to uses, because at some point
I managed to reuse 'i' in an inner loop messing the outer loop...
Without this patch, some of the tests added to gdb.base/gnu-ifunc.exp
by a following patch fail like so:
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=0: set-break: before resolving: break gnu_ifunc
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=0: set-break: before resolving: info breakpoints
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=0: set-break: after resolving: break gnu_ifunc
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=0: set-break: after resolving: info breakpoints
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=1: set-break: before resolving: break gnu_ifunc
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=1: set-break: before resolving: info breakpoints
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=1: set-break: after resolving: break gnu_ifunc
FAIL: gdb.base/gnu-ifunc.exp: resolver_attr=0: resolver_debug=1: resolved_debug=1: set-break: after resolving: info breakpoints
All of them trigger iff:
- you have debug info for the ifunc resolver.
- the resolver and the user-visible symbol have the same name.
If you have an ifunc that has a resolver with the same name as the
user visible symbol, debug info for the resolver masks out the ifunc
minsym. When you set a breakpoint by name on the user visible symbol,
GDB finds the DWARF symbol for the resolver, and thinking that it's a
regular function, sets a breakpoint location past its prologue.
Like so, location 1.2, before the ifunc is resolved by the inferior:
(gdb) break gnu_ifunc
Breakpoint 2 at 0x7ffff7bd36ea (2 locations)
(gdb) info breakpoints
Num Type Disp Enb Address What
1 breakpoint keep y <MULTIPLE>
1.1 y 0x00007ffff7bd36ea <gnu_ifunc>
1.2 y 0x00007ffff7bd36f2 in gnu_ifunc at src/gdb/testsuite/gdb.base/gnu-ifunc-lib.c:34
(gdb)
And like so, location 2.2, if you set the breakpoint after the ifunc
is resolved by the inferior (to "final"):
(gdb) break gnu_ifunc
Breakpoint 5 at 0x400757 (2 locations)
(gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y <MULTIPLE>
2.1 y 0x000000000040075a in final at src/gdb/testsuite/gdb.base/gnu-ifunc-resd.c:21
2.2 y 0x00007ffff7bd36f2 in gnu_ifunc at src/gdb/testsuite/gdb.base/gnu-ifunc-lib.c:34
(gdb)
I don't think this is right because when users set a breakpoint at an
ifunc, they don't care about debugging the resolver. Instead what you
should is a single location for the ifunc in the first case, and a
single location of the ifunc target in the second case.
gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>
* linespec.c (struct bound_minimal_symbol_search_key): New.
(convert_linespec_to_sals): Sort minimal symbols earlier. Don't
skip first line if we found a GNU ifunc minimal symbol by name.
(compare_msymbols): Change parameters to work with a destructured
lhs minsym.
(compare_msymbols_for_qsort, compare_msymbols_for_bsearch): New
functions.
---
gdb/linespec.c | 60 +++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 45 insertions(+), 15 deletions(-)
@@ -2308,12 +2308,6 @@ convert_linespec_to_sals (struct linespec_state *state, linespec_p ls)
else if (ls->function_symbols != NULL || ls->minimal_symbols != NULL)
{
/* We have just a bunch of functions and/or methods. */
- int i;
- struct symtab_and_line sal;
- struct symbol *sym;
- bound_minimal_symbol_d *elem;
- struct program_space *pspace;
-
if (ls->function_symbols != NULL)
{
/* Sort symbols so that symbols with the same program space are next
@@ -2322,30 +2316,66 @@ convert_linespec_to_sals (struct linespec_state *state, linespec_p ls)
VEC_length (symbolp, ls->function_symbols),
sizeof (symbolp), compare_symbols);
- for (i = 0; VEC_iterate (symbolp, ls->function_symbols, i, sym); ++i)
+ struct symbol *sym;
+ for (int i = 0; VEC_iterate (symbolp, ls->function_symbols, i, sym); ++i)
{
- pspace = SYMTAB_PSPACE (symbol_symtab (sym));
+ program_space *pspace = SYMTAB_PSPACE (symbol_symtab (sym));
set_current_program_space (pspace);
- if (symbol_to_sal (&sal, state->funfirstline, sym)
- && maybe_add_address (state->addr_set, pspace, sal.pc))
- add_sal_to_sals (state, &sals, &sal,
- SYMBOL_NATURAL_NAME (sym), 0);
+
+ /* Don't skip to the first line of the function if we
+ had found an ifunc minimal symbol for this function,
+ because that means that this function is an ifunc
+ resolver with the same name as the ifunc itself. */
+ bool found_ifunc = false;
+
+ if (state->funfirstline
+ && ls->minimal_symbols != NULL
+ && SYMBOL_CLASS (sym) == LOC_BLOCK)
+ {
+ const CORE_ADDR addr
+ = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
+
+ bound_minimal_symbol_d *elem;
+ for (int m = 0;
+ VEC_iterate (bound_minimal_symbol_d, ls->minimal_symbols,
+ m, elem);
+ ++m)
+ {
+ if (MSYMBOL_TYPE (elem->minsym) == mst_text_gnu_ifunc
+ && BMSYMBOL_VALUE_ADDRESS (*elem) == addr)
+ {
+ found_ifunc = true;
+ break;
+ }
+ }
+ }
+
+ if (!found_ifunc)
+ {
+ symtab_and_line sal;
+ if (symbol_to_sal (&sal, state->funfirstline, sym)
+ && maybe_add_address (state->addr_set, pspace, sal.pc))
+ add_sal_to_sals (state, &sals, &sal,
+ SYMBOL_NATURAL_NAME (sym), 0);
+ }
}
}
if (ls->minimal_symbols != NULL)
{
- /* Sort minimal symbols by program space, too. */
+ /* Sort minimal symbols by program space, too */
qsort (VEC_address (bound_minimal_symbol_d, ls->minimal_symbols),
VEC_length (bound_minimal_symbol_d, ls->minimal_symbols),
sizeof (bound_minimal_symbol_d), compare_msymbols);
- for (i = 0;
+ bound_minimal_symbol_d *elem;
+
+ for (int i = 0;
VEC_iterate (bound_minimal_symbol_d, ls->minimal_symbols,
i, elem);
++i)
{
- pspace = elem->objfile->pspace;
+ program_space *pspace = elem->objfile->pspace;
set_current_program_space (pspace);
minsym_found (state, elem->objfile, elem->minsym, &sals);
}