Re: [Crash-utility] [PATCH] In verify_version() don't require specific syment type values for linux_banner symbol to get it's address

Date: Tue, 12 Sep 2023 18:11:33 -0600 From: David Mair <dmair(a)suse.com&gt; To: crash-utility(a)redhat.com Subject: [Crash-utility] [PATCH] In verify_version() don't require specific syment type values for linux_banner symbol to get it's address Message-ID: <55b4eb1f-8cdc-eca4-e370-1eed12133681(a)suse.com&gt; Content-Type: text/plain; charset=UTF-8; format=flowed verify_version() in kernel.c gets a struct syment for linux_banner using symbol_search() and uses the value member of the result as the address of linux_banner in some cases based on the type member's value in the same struct syment. A small number of coredumps with an unhandled type ('B' or 'b') for linux_banner result in the address of linux_banner being loaded from the actual linux_banner data. This fails because the first ulong of the linux_banner ASCII text is treated as a dumped kernel address and attempting to access that in the core fails. Based on a suggestion from Kazu, continue to get the struct syment for linux_banner using symbol_search(). Also use get_symbol_type() for linux_banner and use the result of that to decide where to get the linux_banner address from, disregarding the syment type member. If get_symbol_type() reports a TYPE_CODE_ARRAY (and by default with a warning) use the syment value member as the linux_banner address. If get_symbol_type() reports a TYPE_CODE_PTR read the address of linux_banner using get_symbol_data(). The else block doesn't strictly require braced content for a single switch statement but braces are included to match style of locally similar cases. Signed-off-by: David Mair <dmair(a)suse.com&gt; --- diff --git a/kernel.c b/kernel.c index 988206b..6dcf414 100644 --- a/kernel.c +++ b/kernel.c @@ -1076,13 +1076,21 @@ verify_version(void) if (!(sp = symbol_search("linux_banner"))) error(FATAL, "linux_banner symbol does not exist?\n"); - else if ((sp->type == 'R') || (sp->type == 'r') || - (THIS_KERNEL_VERSION >= LINUX(2,6,11) && (sp->type == 'D' || sp->type == 'd')) || - (machine_type("ARM") && sp->type == 'T') || - (machine_type("ARM64"))) - linux_banner = symbol_value("linux_banner"); - else - get_symbol_data("linux_banner", sizeof(ulong), &linux_banner); + else { + switch (get_symbol_type("linux_banner", NULL, NULL)) + { + case TYPE_CODE_ARRAY: + linux_banner = sp->value; + break; + case TYPE_CODE_PTR: + get_symbol_data("linux_banner", sizeof(ulong), &linux_banner); + break; + default: + error(WARNING, "linux_banner is unknown type\n"); + linux_banner = sp->value; + break; + } + }

if (!IS_KVADDR(linux_banner)) error(WARNING, "invalid linux_banner pointer: %lx\n",