From: Andrew Burgess <aburgess@redhat.com>
To: Tom Tromey <tom@tromey.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH] gdb: add gdbarch_stack_grows_down function
Date: Fri, 10 May 2024 09:54:32 +0100 [thread overview]
Message-ID: <87bk5erqrb.fsf@redhat.com> (raw)
In-Reply-To: <874jb63h5s.fsf@tromey.com>
Tom Tromey <tom@tromey.com> writes:
>>>>>> "Andrew" == Andrew Burgess <aburgess@redhat.com> writes:
>
> Andrew> I propose adding a new function `gdbarch_stack_grows_down`. This is
> Andrew> not going to be a gdbarch method that can be overridden, instead, this
> Andrew> will just call the gdbarch_inner_than function. We already have some
> Andrew> gdbarch methods like this, checkout arch-utils.c for examples.
>
> This makes sense to me.
>
> Andrew> + /* The current assumption is that stacks either grow down, or they grow
> Andrew> + up, so one of these checks should be true. */
> Andrew> + gdb_assert (gdbarch_inner_than (arch, 1, 2)
> Andrew> + || gdbarch_inner_than (arch, 2, 1));
>
> I wonder if this would be better as a new all-arch self-test in
> gdbarch-selftests.c.
Great idea. How about the update below?
Thanks,
Andrew
---
commit aedb3394b8c59c1bce7ca48b5d1a5805071eea34
Author: Andrew Burgess <aburgess@redhat.com>
Date: Sun May 5 11:00:04 2024 +0100
gdb: add gdbarch_stack_grows_down function
In another patch I'm working on I needed to ask: does the stack grow
down, or grow up?
Looking around I found in infcall.c some code where we needed to ask
the same question, what we do there is ask:
gdbarch_inner_than (gdbarch, 1, 2)
which should do the job. However, I don't particularly like copying
this, it feels like we're asking something slightly different that
just happens to align with the question we're actually asking.
I propose adding a new function `gdbarch_stack_grows_down`. This is
not going to be a gdbarch method that can be overridden, instead, this
will just call the gdbarch_inner_than function. We already have some
gdbarch methods like this, checkout arch-utils.c for examples.
I think it's now clearer what we're actually doing.
A new self-test ensures that all architectures have a stack that
either grows down, or grows up.
There should be no user visible changes after this commit.
diff --git a/gdb/gdbarch-selftests.c b/gdb/gdbarch-selftests.c
index 0dc0c500654..707012bcd0d 100644
--- a/gdb/gdbarch-selftests.c
+++ b/gdb/gdbarch-selftests.c
@@ -164,6 +164,20 @@ register_name_test (struct gdbarch *gdbarch)
}
}
+/* Test gdbarch_stack_grows_down. Stacks must either grow down or up. */
+
+static void
+check_stack_growth (struct gdbarch *gdbarch)
+{
+ /* We don't call gdbarch_stack_grows_down here, instead we're testing the
+ implementation by calling gdbarch_inner_than. GDB assumes that stacks
+ either grow down or up (see uses of gdbarch_stack_grows_down), so one of
+ these needs to be true. */
+ bool stack_grows = (gdbarch_inner_than (gdbarch, 1, 2)
+ || gdbarch_inner_than (gdbarch, 2, 1));
+ SELF_CHECK (stack_grows);
+}
+
} // namespace selftests
void _initialize_gdbarch_selftests ();
@@ -175,4 +189,7 @@ _initialize_gdbarch_selftests ()
selftests::register_test_foreach_arch ("register_name",
selftests::register_name_test);
+
+ selftests::register_test_foreach_arch ("stack_growth",
+ selftests::check_stack_growth);
}
diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index 77d3406779f..5175ef79e5b 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -370,4 +370,12 @@ gdbarch_num_cooked_regs (gdbarch *arch)
return gdbarch_num_regs (arch) + gdbarch_num_pseudo_regs (arch);
}
+/* Return true if stacks for ARCH grow down, otherwise return true. */
+
+static inline bool
+gdbarch_stack_grows_down (gdbarch *arch)
+{
+ return gdbarch_inner_than (arch, 1, 2);
+}
+
#endif
diff --git a/gdb/infcall.c b/gdb/infcall.c
index 23d5652dd21..edac9a74179 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -947,7 +947,7 @@ reserve_stack_space (const type *values_type, CORE_ADDR &sp)
struct gdbarch *gdbarch = get_frame_arch (frame);
CORE_ADDR addr = 0;
- if (gdbarch_inner_than (gdbarch, 1, 2))
+ if (gdbarch_stack_grows_down (gdbarch))
{
/* Stack grows downward. Align STRUCT_ADDR and SP after
making space. */
@@ -1128,7 +1128,7 @@ call_function_by_hand_dummy (struct value *function,
address. AMD64 called that region the "red zone". Skip at
least the "red zone" size before allocating any space on
the stack. */
- if (gdbarch_inner_than (gdbarch, 1, 2))
+ if (gdbarch_stack_grows_down (gdbarch))
sp -= gdbarch_frame_red_zone_size (gdbarch);
else
sp += gdbarch_frame_red_zone_size (gdbarch);
@@ -1156,11 +1156,9 @@ call_function_by_hand_dummy (struct value *function,
to pay :-). */
if (sp == old_sp)
{
- if (gdbarch_inner_than (gdbarch, 1, 2))
- /* Stack grows down. */
+ if (gdbarch_stack_grows_down (gdbarch))
sp = gdbarch_frame_align (gdbarch, old_sp - 1);
else
- /* Stack grows up. */
sp = gdbarch_frame_align (gdbarch, old_sp + 1);
}
/* SP may have underflown address zero here from OLD_SP. Memory access
@@ -1193,7 +1191,7 @@ call_function_by_hand_dummy (struct value *function,
{
CORE_ADDR lastval_addr = lastval->address ();
- if (gdbarch_inner_than (gdbarch, 1, 2))
+ if (gdbarch_stack_grows_down (gdbarch))
{
gdb_assert (sp >= lastval_addr);
sp = lastval_addr;
next prev parent reply other threads:[~2024-05-10 8:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-09 14:59 Andrew Burgess
2024-05-09 19:43 ` Tom Tromey
2024-05-10 8:54 ` Andrew Burgess [this message]
2024-05-10 9:43 ` Tom Tromey
2024-05-10 13:31 ` Andrew Burgess
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