Tables: Fix invalid pointer accesses in AcpiTbParseRootTable().

This commit of back porting Linux XSDT validation mechanism has introduced
a regreession:
  Commit: 4e917154c46af024a011ac90ca2f7782ae0a97da
  Subject: Add validation of the XSDT root table if present.
There is a pointer still accessed after unmapping.

This patch fixes this issue.  Lv Zheng.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=73911
Buglink: https://bugs.archlinux.org/task/39811
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reported-and-tested-by: Bruce Chiarelli <mano155@gmail.com>
Reported-and-tested-by: Spyros Stathopoulos <spystath@gmail.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
acpidump: Add support to force using RSDT.

This patch adds "-x" and "-x -x" options to disable XSDT for acpidump.

The single "-x" can be used to stop using XSDT, RSDT will be forced to find
static tables, note that XSDT will still be dumped. The double "-x" can
stop dumping XSDT, which is useful when the XSDT address reported by RSDP
is pointing to an invalid address.

It is reported there are platforms having broken XSDT shipped, acpidump
will stop working while accessing such XSDT. This patch adds new option so
that users can force acpidump to dump tables listed in the RSDT. Lv Zheng.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=73911
Buglink: https://bugs.archlinux.org/task/39811
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reported-and-tested-by: Bruce Chiarelli <mano155@gmail.com>
Reported-and-tested-by: Spyros Stathopoulos <spystath@gmail.com>
Tables: Skip NULL entries in RSDT and XSDT.

It is reported that there are buggy BIOSes in the world: AMI uses a XSDT
compiler for early BIOSes, this compiler will generate XSDT with a NULL
entry.  The affected BIOS versions are "AMI BIOS F2-F4".

Original solution on Linux is to use an alternative heathy root table
instead of the ill one.  This commit is:
  Commit: 4e917154c46af024a011ac90ca2f7782ae0a97da
  Subject: Add validation of the XSDT root table if present.
But according to the bug report, the XSDT in fact is not broken, we should
just add NULL entry sanity check before installing a table address from
XSDT.

This patch adds code to skip NULL entries that can be found in RSDT or
XSDT. Lv Zheng.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=73911
Buglink: https://bugs.archlinux.org/task/39811
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reported-and-tested-by: Bruce Chiarelli <mano155@gmail.com>
Reported-and-tested-by: Spyros Stathopoulos <spystath@gmail.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Tables: Remove XSDT validation logic.

With the NULL entry sanity check implemented, the XSDT validation is
useless because:
1. If XSDT contains NULL entries, it can be bypassed by the new sanity
   check mechanism;
2. If RSDP contains a bad XSDT address, invoking XSDT validation will still
   lead to kernel crash.

This patch deletes XSDT validation logics. Lv Zheng.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=73911
Buglink: https://bugs.archlinux.org/task/39811
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reported-and-tested-by: Bruce Chiarelli <mano155@gmail.com>
Reported-and-tested-by: Spyros Stathopoulos <spystath@gmail.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>