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Ard Biesheuvel 07415be140 x86/decompressor: Don't rely on upper 32 bits of GPRs being preserved
[ Upstream commit 264b82fdb4989cf6a44a2bcd0c6ea05e8026b2ac ]

The 4-to-5 level mode switch trampoline disables long mode and paging in
order to be able to flick the LA57 bit. According to section 3.4.1.1 of
the x86 architecture manual [0], 64-bit GPRs might not retain the upper
32 bits of their contents across such a mode switch.

Given that RBP, RBX and RSI are live at this point, preserve them on the
stack, along with the return address that might be above 4G as well.

[0] Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1: Basic Architecture

  "Because the upper 32 bits of 64-bit general-purpose registers are
   undefined in 32-bit modes, the upper 32 bits of any general-purpose
   register are not preserved when switching from 64-bit mode to a 32-bit
   mode (to protected mode or compatibility mode). Software must not
   depend on these bits to maintain a value after a 64-bit to 32-bit
   mode switch."

Fixes: 194a9749c7 ("x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-2-ardb@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-09-23 10:59:41 +02:00
arch x86/decompressor: Don't rely on upper 32 bits of GPRs being preserved 2023-09-23 10:59:41 +02:00
block block/partition: fix signedness issue for Amiga partitions 2023-07-27 08:37:29 +02:00
certs
crypto KEYS: asymmetric: Copy sig and digest in public_key_verify_signature() 2023-06-21 15:44:08 +02:00
Documentation Documentation/sysctl: document page_lock_unfairness 2023-08-30 16:27:27 +02:00
drivers OPP: Fix passing 0 to PTR_ERR in _opp_attach_genpd() 2023-09-23 10:59:40 +02:00
fs fs: Fix error checking for d_hash_and_lookup() 2023-09-23 10:59:40 +02:00
include new helper: lookup_positive_unlocked() 2023-09-23 10:59:40 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:56:36 +02:00
ipc
kernel modules: only allow symbol_get of EXPORT_SYMBOL_GPL modules 2023-09-23 10:59:36 +02:00
lib radix tree: remove unused variable 2023-08-30 16:27:26 +02:00
LICENSES
mm tmpfs: verify {g,u}id mount options correctly 2023-09-23 10:59:40 +02:00
net net: Avoid address overwrite in kernel_connect 2023-09-23 10:59:39 +02:00
samples samples/bpf: Fix buffer overflow in tcp_basertt 2023-07-27 08:37:07 +02:00
scripts modpost: fix off by one in is_executable_section() 2023-07-27 08:37:18 +02:00
security security: keys: perform capable check only on privileged operations 2023-09-23 10:59:39 +02:00
sound ALSA: seq: oss: Fix racy open/close of MIDI devices 2023-09-23 10:59:39 +02:00
tools selftests: mirror_gre_changes: Tighten up the TTL test match 2023-08-30 16:27:16 +02:00
usr
virt KVM: Destroy target device if coalesced MMIO unregistration fails 2023-03-11 16:44:01 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-30 16:27:12 +02:00
Makefile Linux 5.4.256 2023-09-02 09:19:19 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.