Hi, Tao
On Wed, Jul 9, 2025 at 1:42 PM <devel-requ...@lists.crash-utility.osci.io>
wrote:
> Date: Tue, 8 Jul 2025 13:26:38 +1200
> From: Tao Liu <l...@redhat.com>
> Subject: [Crash-utility] [PATCH] Fix a regression for eppic extension
> on gdb-16.2
> To: devel@lists.crash-utility.osci.io
> Cc: Tao Liu <l...@redhat.com>
> Message-ID: <20250708012638.97698-1-l...@redhat.com>
> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>
> There is a regression found when testing eppic extension on gdb-16.2
> crash:
>
> crash> cgroup
> /root/.eppic/cgroup.c : line 99 : Error: undefined variable
> 'cgroup_roots'
>
> The root cause is when doing gdb upgrading, the replacement of
> gdb_get_datatype() is incorrect:
>
> The original gdb-10.2 version:
>
> long value = SYMBOL_VALUE(expr->elts[2].symbol);
>
> The incorrect gdb-16.2 replacement:
>
> long value = value_as_long(expr->evaluate());
>
> According to gdb/tracepoint.c, the correct gdb-16.2 replacement should be:
>
> symbol *sym;
> expr::var_value_operation *vvop
> = (gdb::checked_static_cast<expr::var_value_operation *>
> (exp->op.get ()));
> sym = vvop->get_symbol ();
> long value = sym->value_longest ();
>
> Otherwise, the value_as_long() will throw an exception when trying to
> convert a struct into long, such as "cgroup_roots". The reason why this
> issue only observed on crash extensions, is the faulty code block
> triggered with "req->tcb", which is a callback for gdb_interface(), and
> the callback is used by eppic extension, but the normal crash internal
> calls
> hardly use it.
>
> After:
> crash> cgroup
> 0:/user.slice/user-1000.slice/session-2.scope
>
> Signed-off-by: Tao Liu <l...@redhat.com>
> ---
> gdb-16.2.patch | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/gdb-16.2.patch b/gdb-16.2.patch
> index 151e4e2..eb620f7 100644
> --- a/gdb-16.2.patch
> +++ b/gdb-16.2.patch
>
Can you help to add the gdb-16.2/gdb/symtab.c to gdb-16.2.patch, and it
looks like this:
# to all subsequent patch applications.
tar xvzmf gdb-16.2.tar.gz \
- gdb-16.2/gdb/symfile.c
+ gdb-16.2/gdb/symfile.c \
+ gdb-16.2/gdb/symtab.c
exit 0
In addition, also please add a prefix "gdb: " to patch title, E.g:
gdb: Fix a regression for eppic extension on gdb-16.2
Other changes are fine to me. So: Ack(with the above change)
Thanks
Lianbo
> @@ -1952,3 +1952,32 @@ exit 0
> }
>
> /* Remember the bfd indexes for the .text, .data, .bss and
> +--- gdb-16.2/gdb/symtab.c.orig
> ++++ gdb-16.2/gdb/symtab.c
> +@@ -7690,7 +7690,11 @@
> + console("expr->first_opcode(): OP_VAR_VALUE\n");
> + type = expr->evaluate_type()->type();
> + if (req->tcb) {
> +- long value = value_as_long(expr->evaluate());
> ++ expr::var_value_operation *vvop
> ++ =
> (gdb::checked_static_cast<expr::var_value_operation *>
> ++ (expr->op.get ()));
> ++ sym = vvop->get_symbol ();
> ++ long value = sym->value_longest ();
> + /* callback with symbol value */
> + req->typecode = TYPE_CODE(type);
> + req->tcb(EOP_VALUE, req, &value, 0, 0, 0);
> +@@ -7701,8 +7705,12 @@
> + req->length = type->length();
> + }
> + if (TYPE_CODE(type) == TYPE_CODE_ENUM) {
> ++ expr::var_value_operation *vvop
> ++ =
> (gdb::checked_static_cast<expr::var_value_operation *>
> ++ (expr->op.get ()));
> ++ sym = vvop->get_symbol ();
> + req->typecode = TYPE_CODE(type);
> +- req->value =
> value_as_long(expr->evaluate());
> ++ req->value = sym->value_longest ();
> + req->tagname = (char
> *)TYPE_TAG_NAME(type);
> + if (!req->tagname) {
> + val = expr->evaluate_type();
> --
> 2.47.0
>
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