Gustavo noticed that 'new' can be left uninitialized if 'bios_start'
happens to be less or equal to 'entry->addr + entry->size'.

Initialize the variable at the begin of the iteration to the current value
of 'bios_start'.

Fixes: 0a46fff2f910 ("x86/boot/compressed/64: Fix boot on machines with broken E820 table")
Reported-by: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190826133326.7cxb4vbmiawffv2r@box

BIOS on Samsung 500C Chromebook reports very rudimentary E820 table that
consists of 2 entries:

  BIOS-e820: [mem 0x0000000000000000-0x0000000000000fff] usable
  BIOS-e820: [mem 0x00000000fffff000-0x00000000ffffffff] reserved

It breaks logic in find_trampoline_placement(): bios_start lands on the
end of the first 4k page and trampoline start gets placed below 0.

Detect underflow and don't touch bios_start for such cases. It makes
kernel ignore E820 table on machines that doesn't have two usable pages
below BIOS_START_MAX.

Fixes: 1b3a62643660 ("x86/boot/compressed/64: Validate trampoline placement against E820")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=203463
Link: https://lkml.kernel.org/r/20190813131654.24378-1-kirill.shutemov@linux.intel.com

Implementing memcpy and memset in terms of __builtin_memcpy and
__builtin_memset is problematic.

GCC at -O2 will replace calls to the builtins with calls to memcpy and
memset (but will generate an inline implementation at -Os).  Clang will
replace the builtins with these calls regardless of optimization level.
$ llvm-objdump -dr arch/x86/purgatory/string.o | tail

0000000000000339 memcpy:
     339: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax
                000000000000033b:  R_X86_64_64  memcpy
     343: ff e0                         jmpq    *%rax

0000000000000345 memset:
     345: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax
                0000000000000347:  R_X86_64_64  memset
     34f: ff e0

Such code results in infinite recursion at runtime. This is observed
when doing kexec.

Instead, reuse an implementation from arch/x86/boot/compressed/string.c.
This requires to implement a stub function for warn(). Also, Clang may
lower memcmp's that compare against 0 to bcmp's, so add a small definition,
too. See also: commit 5f074f3e192f ("lib/string.c: implement a basic bcmp")

Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality")
Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Debugged-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Debugged-by: Manoj Gupta <manojgupta@google.com>
Suggested-by: Alistair Delva <adelva@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Cc: stable@vger.kernel.org
Link: https://bugs.chromium.org/p/chromium/issues/detail?id=984056
Link: https://lkml.kernel.org/r/20190807221539.94583-1-ndesaulniers@google.com

Kernel build warns:
 'sanitize_boot_params' defined but not used [-Wunused-function]

at below files:
  arch/x86/boot/compressed/cmdline.c
  arch/x86/boot/compressed/error.c
  arch/x86/boot/compressed/early_serial_console.c
  arch/x86/boot/compressed/acpi.c

That's becausethey each include misc.h which includes a definition of
sanitize_boot_params() via bootparam_utils.h.

Remove the inclusion from misc.h and have the c file including
bootparam_utils.h directly.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1563283092-1189-1-git-send-email-zhenzhong.duan@oracle.com

Fix gcc warning:

arch/x86/boot/compressed/pgtable_64.c: In function 'find_trampoline_placement':
arch/x86/boot/compressed/pgtable_64.c:43:16: warning: unused variable 'trampoline_start' [-Wunused-variable]
  unsigned long trampoline_start;
               ^

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/1563283040-31101-1-git-send-email-zhenzhong.duan@oracle.com

Fix gcc warnings:

arch/x86/boot/compressed/eboot.c: In function 'make_boot_params':
arch/x86/boot/compressed/eboot.c:394:6: warning: unused variable 'i' [-Wunused-variable]
  int i;
      ^
arch/x86/boot/compressed/eboot.c:393:6: warning: unused variable 's1' [-Wunused-variable]
  u8 *s1;
      ^
arch/x86/boot/compressed/eboot.c:392:7: warning: unused variable 's2' [-Wunused-variable]
  u16 *s2;
       ^
arch/x86/boot/compressed/eboot.c:387:8: warning: unused variable 'options' [-Wunused-variable]
  void *options, *handle;
        ^
arch/x86/boot/compressed/eboot.c: In function 'add_e820ext':
arch/x86/boot/compressed/eboot.c:498:16: warning: unused variable 'size' [-Wunused-variable]
  unsigned long size;
                ^
arch/x86/boot/compressed/eboot.c:497:15: warning: unused variable 'status' [-Wunused-variable]
  efi_status_t status;
               ^
arch/x86/boot/compressed/eboot.c: In function 'exit_boot_func':
arch/x86/boot/compressed/eboot.c:681:15: warning: unused variable 'status' [-Wunused-variable]
  efi_status_t status;
               ^
arch/x86/boot/compressed/eboot.c:680:8: warning: unused variable 'nr_desc' [-Wunused-variable]
  __u32 nr_desc;
        ^
arch/x86/boot/compressed/eboot.c: In function 'efi_main':
arch/x86/boot/compressed/eboot.c:750:22: warning: unused variable 'image' [-Wunused-variable]
  efi_loaded_image_t *image;
                      ^

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1563282957-26898-1-git-send-email-zhenzhong.duan@oracle.com

Pull Documentation updates from Jonathan Corbet:
 "It's been a relatively busy cycle for docs:

   - A fair pile of RST conversions, many from Mauro. These create more
     than the usual number of simple but annoying merge conflicts with
     other trees, unfortunately. He has a lot more of these waiting on
     the wings that, I think, will go to you directly later on.

   - A new document on how to use merges and rebases in kernel repos,
     and one on Spectre vulnerabilities.

   - Various improvements to the build system, including automatic
     markup of function() references because some people, for reasons I
     will never understand, were of the opinion that
     :c:func:``function()`` is unattractive and not fun to type.

   - We now recommend using sphinx 1.7, but still support back to 1.4.

   - Lots of smaller improvements, warning fixes, typo fixes, etc"

* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
  docs: automarkup.py: ignore exceptions when seeking for xrefs
  docs: Move binderfs to admin-guide
  Disable Sphinx SmartyPants in HTML output
  doc: RCU callback locks need only _bh, not necessarily _irq
  docs: format kernel-parameters -- as code
  Doc : doc-guide : Fix a typo
  platform: x86: get rid of a non-existent document
  Add the RCU docs to the core-api manual
  Documentation: RCU: Add TOC tree hooks
  Documentation: RCU: Rename txt files to rst
  Documentation: RCU: Convert RCU UP systems to reST
  Documentation: RCU: Convert RCU linked list to reST
  Documentation: RCU: Convert RCU basic concepts to reST
  docs: filesystems: Remove uneeded .rst extension on toctables
  scripts/sphinx-pre-install: fix out-of-tree build
  docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
  Documentation: PGP: update for newer HW devices
  Documentation: Add section about CPU vulnerabilities for Spectre
  Documentation: platform: Delete x86-laptop-drivers.txt
  docs: Note that :c:func: should no longer be used
  ...

Pull x86 boot updates from Thomas Gleixner:
 "Assorted updates to kexec/kdump:

   - Proper kexec support for 4/5-level paging and jumping from a
     5-level to a 4-level paging kernel.

   - Make the EFI support for kexec/kdump more robust

   - Enforce that the GDT is properly aligned instead of getting the
     alignment by chance"

* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/kdump/64: Restrict kdump kernel reservation to <64TB
  x86/kexec/64: Prevent kexec from 5-level paging to a 4-level only kernel
  x86/boot: Add xloadflags bits to check for 5-level paging support
  x86/boot: Make the GDT 8-byte aligned
  x86/kexec: Add the ACPI NVS region to the ident map
  x86/boot: Call get_rsdp_addr() after console_init()
  Revert "x86/boot: Disable RSDP parsing temporarily"
  x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernels
  x86/kexec: Add the EFI system tables and ACPI tables to the ident map

The current kernel supports 5-level paging mode, and supports dynamically
choosing the paging mode during bootup depending on the kernel image,
hardware and kernel parameter settings. This flexibility brings several
issues to kexec/kdump:

1) Dynamic switching between paging modes requires support in the target
   kernel. This means kexec from a 5-level paging kernel into a kernel
   which does not support mode switching is not possible. So the loader
   needs to be able to analyze the supported paging modes of the kexec
   target kernel.

2) If running on a 5-level paging kernel and the kexec target kernel is a
   4-level paging kernel, the target immage cannot be loaded above the 64TB
   address space limit. But the kexec loader searches for a load area from
   top to bottom which would eventually put the target kernel above 64TB
   when the machine has large enough RAM size. So the loader needs to be
   able to analyze the paging mode of the target kernel to load it at a
   suitable spot in the address space.

Solution:

Add two bits XLF_5LEVEL and XLF_5LEVEL_ENABLED:

 - Bit XLF_5LEVEL indicates whether 5-level paging mode switching support
   is available. (Issue #1)

 - Bit XLF_5LEVEL_ENABLED indicates whether the kernel was compiled with
   full 5-level paging support (CONFIG_X86_5LEVEL=y). (Issue #2)

The loader will use these bits to verify whether the target kernel is
suitable to be kexec'ed to from a 5-level paging kernel and to determine
the constraints of the target kernel load address.

The flags will be used by the kernel kexec subsystem and the userspace
kexec tools.

[ tglx: Massaged changelog ]

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: bp@alien8.de
Cc: hpa@zytor.com
Cc: dyoung@redhat.com
Link: https://lkml.kernel.org/r/20190524073810.24298-2-bhe@redhat.com

The segment descriptors are loaded with an implicitly LOCK-ed instruction,
which could trigger the split lock #AC exception if the variable is not
properly aligned and crosses a cache line.

Align the GDT properly so the descriptors are all 8 byte aligned.

Signed-off-by: Xiaoyao Li <xiaoyao.li@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lkml.kernel.org/r/20190627045525.105266-1-xiaoyao.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>