[Crash-utility] Re: [PATCH] Fix a regression for eppic extension on gdb-16.2

Hi, Tao On Wed, Jul 9, 2025 at 1:42 PM <devel-request(a)lists.crash-utility.osci.io&gt; wrote: > > Date: Tue, 8 Jul 2025 13:26:38 +1200 > From: Tao Liu <ltao(a)redhat.com&gt; > Subject: [Crash-utility] [PATCH] Fix a regression for eppic extension > on gdb-16.2 > To: devel(a)lists.crash-utility.osci.io > Cc: Tao Liu <ltao(a)redhat.com&gt; > Message-ID: <20250708012638.97698-1-ltao(a)redhat.com&gt; > 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 <ltao(a)redhat.com&gt; > --- > 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