History log of /openbmc/linux/Documentation/admin-guide/hw-vuln/srso.rst (Results 1 – 24 of 24)
Revision (<<< Hide revision tags) (Show revision tags >>>) Date Author Comments
Revision tags: v6.6.67, v6.6.66, v6.6.65, v6.6.64, v6.6.63, v6.6.62, v6.6.61, v6.6.60, v6.6.59, v6.6.58, v6.6.57, v6.6.56, v6.6.55, v6.6.54, v6.6.53, v6.6.52, v6.6.51, v6.6.50, v6.6.49, v6.6.48, v6.6.47, v6.6.46, v6.6.45, v6.6.44, v6.6.43, v6.6.42, v6.6.41, v6.6.40, v6.6.39, v6.6.38, v6.6.37, v6.6.36, v6.6.35, v6.6.34, v6.6.33, v6.6.32, v6.6.31, v6.6.30, v6.6.29, v6.6.28, v6.6.27, v6.6.26, v6.6.25, v6.6.24, v6.6.23, v6.6.16, v6.6.15, v6.6.14, v6.6.13, v6.6.12, v6.6.11, v6.6.10, v6.6.9, v6.6.8
# b97d6790 13-Dec-2023 Joel Stanley <joel@jms.id.au>

Merge tag 'v6.6.6' into dev-6.6

This is the 6.6.6 stable release

Signed-off-by: Joel Stanley <joel@jms.id.au>


Revision tags: v6.6.7, v6.6.6, v6.6.5, v6.6.4, v6.6.3, v6.6.2, v6.5.11, v6.6.1, v6.5.10, v6.6, v6.5.9, v6.5.8, v6.5.7, v6.5.6, v6.5.5, v6.5.4, v6.5.3, v6.5.2
# 0a958abf 05-Sep-2023 Josh Poimboeuf <jpoimboe@kernel.org>

x86/srso: Fix vulnerability reporting for missing microcode

[ Upstream commit dc6306ad5b0dda040baf1fde3cfd458e6abfc4da ]

The SRSO default safe-ret mitigation is reported as "mitigated" even if
micr

x86/srso: Fix vulnerability reporting for missing microcode

[ Upstream commit dc6306ad5b0dda040baf1fde3cfd458e6abfc4da ]

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated. That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...


# c900529f 12-Sep-2023 Thomas Zimmermann <tzimmermann@suse.de>

Merge drm/drm-fixes into drm-misc-fixes

Forwarding to v6.6-rc1.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>


Revision tags: v6.1.51, v6.5.1, v6.1.50
# 692f5510 28-Aug-2023 Takashi Iwai <tiwai@suse.de>

Merge tag 'asoc-v6.6' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v6.6

The rest of the updates for v6.6, some of the highlights include:

- A

Merge tag 'asoc-v6.6' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v6.6

The rest of the updates for v6.6, some of the highlights include:

- A big API cleanup from Morimoto-san, rationalising the places we put
functions.
- Lots of work on the SOF framework, AMD and Intel drivers, including a
lot of cleanup and new device support.
- Standardisation of the presentation of jacks from drivers.
- Provision of some generic sound card DT properties.
- Conversion oof more drivers to the maple tree register cache.
- New drivers for AMD Van Gogh, AWInic AW88261, Cirrus Logic cs42l43,
various Intel platforms, Mediatek MT7986, RealTek RT1017 and StarFive
JH7110.

show more ...


Revision tags: v6.5, v6.1.49, v6.1.48
# 57ce6427 24-Aug-2023 Jakub Kicinski <kuba@kernel.org>

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Cross-merge networking fixes after downstream PR.

Conflicts:

include/net/inet_sock.h
f866fbc842de ("ipv4: fix data-races around ine

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Cross-merge networking fixes after downstream PR.

Conflicts:

include/net/inet_sock.h
f866fbc842de ("ipv4: fix data-races around inet->inet_id")
c274af224269 ("inet: introduce inet->inet_flags")
https://lore.kernel.org/all/679ddff6-db6e-4ff6-b177-574e90d0103d@tessares.net/

Adjacent changes:

drivers/net/bonding/bond_alb.c
e74216b8def3 ("bonding: fix macvlan over alb bond support")
f11e5bd159b0 ("bonding: support balance-alb with openvswitch")

drivers/net/ethernet/broadcom/bgmac.c
d6499f0b7c7c ("net: bgmac: Return PTR_ERR() for fixed_phy_register()")
23a14488ea58 ("net: bgmac: Fix return value check for fixed_phy_register()")

drivers/net/ethernet/broadcom/genet/bcmmii.c
32bbe64a1386 ("net: bcmgenet: Fix return value check for fixed_phy_register()")
acf50d1adbf4 ("net: bcmgenet: Return PTR_ERR() for fixed_phy_register()")

net/sctp/socket.c
f866fbc842de ("ipv4: fix data-races around inet->inet_id")
b09bde5c3554 ("inet: move inet->mc_loop to inet->inet_frags")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...


# fdebffeb 23-Aug-2023 Dave Airlie <airlied@redhat.com>

BackMerge tag 'v6.5-rc7' into drm-next

Linux 6.5-rc7

This is needed for the CI stuff and the msm pull has fixes in it.

Signed-off-by: Dave Airlie <airlied@redhat.com>


# 0bbe0649 22-Aug-2023 Mark Brown <broonie@kernel.org>

Add cs42l43 PC focused SoundWire CODEC

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

This patch chain adds support for the Cirrus Logic cs42l43 PC focused
SoundWire CODEC. The c

Add cs42l43 PC focused SoundWire CODEC

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

This patch chain adds support for the Cirrus Logic cs42l43 PC focused
SoundWire CODEC. The chain is currently based of Lee's for-mfd-next
branch.

This series is mostly just a resend keeping pace with the kernel under
it, except for a minor fixup in the ASoC stuff.

Thanks,
Charles

Charles Keepax (4):
dt-bindings: mfd: cirrus,cs42l43: Add initial DT binding
mfd: cs42l43: Add support for cs42l43 core driver
pinctrl: cs42l43: Add support for the cs42l43
ASoC: cs42l43: Add support for the cs42l43

Lucas Tanure (2):
soundwire: bus: Allow SoundWire peripherals to register IRQ handlers
spi: cs42l43: Add SPI controller support

.../bindings/sound/cirrus,cs42l43.yaml | 313 +++
MAINTAINERS | 4 +
drivers/mfd/Kconfig | 23 +
drivers/mfd/Makefile | 3 +
drivers/mfd/cs42l43-i2c.c | 98 +
drivers/mfd/cs42l43-sdw.c | 239 ++
drivers/mfd/cs42l43.c | 1188 +++++++++
drivers/mfd/cs42l43.h | 28 +
drivers/pinctrl/cirrus/Kconfig | 11 +
drivers/pinctrl/cirrus/Makefile | 2 +
drivers/pinctrl/cirrus/pinctrl-cs42l43.c | 609 +++++
drivers/soundwire/bus.c | 32 +
drivers/soundwire/bus_type.c | 12 +
drivers/spi/Kconfig | 7 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-cs42l43.c | 284 ++
include/linux/mfd/cs42l43-regs.h | 1184 +++++++++
include/linux/mfd/cs42l43.h | 102 +
include/linux/soundwire/sdw.h | 9 +
include/sound/cs42l43.h | 17 +
sound/soc/codecs/Kconfig | 16 +
sound/soc/codecs/Makefile | 4 +
sound/soc/codecs/cs42l43-jack.c | 946 +++++++
sound/soc/codecs/cs42l43-sdw.c | 74 +
sound/soc/codecs/cs42l43.c | 2278 +++++++++++++++++
sound/soc/codecs/cs42l43.h | 131 +
26 files changed, 7615 insertions(+)
create mode 100644 Documentation/devicetree/bindings/sound/cirrus,cs42l43.yaml
create mode 100644 drivers/mfd/cs42l43-i2c.c
create mode 100644 drivers/mfd/cs42l43-sdw.c
create mode 100644 drivers/mfd/cs42l43.c
create mode 100644 drivers/mfd/cs42l43.h
create mode 100644 drivers/pinctrl/cirrus/pinctrl-cs42l43.c
create mode 100644 drivers/spi/spi-cs42l43.c
create mode 100644 include/linux/mfd/cs42l43-regs.h
create mode 100644 include/linux/mfd/cs42l43.h
create mode 100644 include/sound/cs42l43.h
create mode 100644 sound/soc/codecs/cs42l43-jack.c
create mode 100644 sound/soc/codecs/cs42l43-sdw.c
create mode 100644 sound/soc/codecs/cs42l43.c
create mode 100644 sound/soc/codecs/cs42l43.h

--
2.30.2

show more ...


# a3dd14c0 21-Aug-2023 Georgi Djakov <djakov@kernel.org>

Merge tag 'v6.5-rc6' into icc-next

The fixes that got merged into v6.5-rc6 are needed here.

Signed-off-by: Georgi Djakov <djakov@kernel.org>


# 642073c3 20-Aug-2023 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge commit b320441c04c9 ("Merge tag 'tty-6.5-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty") into tty-next

We need the serial-core fixes in here as well.

Signed-off-by: Greg Kr

Merge commit b320441c04c9 ("Merge tag 'tty-6.5-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty") into tty-next

We need the serial-core fixes in here as well.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...


# bf98bae3 19-Aug-2023 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'x86_urgent_for_v6.5_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Borislav Petkov:
"Extraordinary embargoed times call for extraordinary measures. Tha

Merge tag 'x86_urgent_for_v6.5_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Borislav Petkov:
"Extraordinary embargoed times call for extraordinary measures. That's
why this week's x86/urgent branch is larger than usual, containing all
the known fallout fixes after the SRSO mitigation got merged.

I know, it is a bit late in the game but everyone who has reported a
bug stemming from the SRSO pile, has tested that branch and has
confirmed that it fixes their bug.

Also, I've run it on every possible hardware I have and it is looking
good. It is running on this very machine while I'm typing, for 2 days
now without an issue. Famous last words...

- Use LEA ...%rsp instead of ADD %rsp in the Zen1/2 SRSO return
sequence as latter clobbers flags which interferes with fastop
emulation in KVM, leading to guests freezing during boot

- A fix for the DIV(0) quotient data leak on Zen1 to clear the
divider buffers at the right time

- Disable the SRSO mitigation on unaffected configurations as it got
enabled there unnecessarily

- Change .text section name to fix CONFIG_LTO_CLANG builds

- Improve the optprobe indirect jmp check so that certain
configurations can still be able to use optprobes at all

- A serious and good scrubbing of the untraining routines by PeterZ:
- Add proper speculation stopping traps so that objtool is happy
- Adjust objtool to handle the new thunks
- Make the thunk pointer assignable to the different untraining
sequences at runtime, thus avoiding the alternative at the
return thunk. It simplifies the code a bit too.
- Add a entry_untrain_ret() main entry point which selects the
respective untraining sequence
- Rename things so that they're more clear
- Fix stack validation with FRAME_POINTER=y builds

- Fix static call patching to handle when a JMP to the return thunk
is the last insn on the very last module memory page

- Add more documentation about what each untraining routine does and
why"

* tag 'x86_urgent_for_v6.5_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/srso: Correct the mitigation status when SMT is disabled
x86/static_call: Fix __static_call_fixup()
objtool/x86: Fixup frame-pointer vs rethunk
x86/srso: Explain the untraining sequences a bit more
x86/cpu/kvm: Provide UNTRAIN_RET_VM
x86/cpu: Cleanup the untrain mess
x86/cpu: Rename srso_(.*)_alias to srso_alias_\1
x86/cpu: Rename original retbleed methods
x86/cpu: Clean up SRSO return thunk mess
x86/alternative: Make custom return thunk unconditional
objtool/x86: Fix SRSO mess
x86/cpu: Fix up srso_safe_ret() and __x86_return_thunk()
x86/cpu: Fix __x86_return_thunk symbol type
x86/retpoline,kprobes: Skip optprobe check for indirect jumps with retpolines and IBT
x86/retpoline,kprobes: Fix position of thunk sections with CONFIG_LTO_CLANG
x86/srso: Disable the mitigation on unaffected configurations
x86/CPU/AMD: Fix the DIV(0) initial fix attempt
x86/retpoline: Don't clobber RFLAGS during srso_safe_ret()

show more ...


# ab472430 18-Aug-2023 Mark Brown <broonie@kernel.org>

Add cs42l43 PC focused SoundWire CODEC

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

This patch chain adds support for the Cirrus Logic cs42l43 PC focused
SoundWire CODEC.


Revision tags: v6.1.46
# 42be649d 14-Aug-2023 Peter Zijlstra <peterz@infradead.org>

x86/cpu: Rename srso_(.*)_alias to srso_alias_\1

For a more consistent namespace.

[ bp: Fixup names in the doc too. ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by:

x86/cpu: Rename srso_(.*)_alias to srso_alias_\1

For a more consistent namespace.

[ bp: Fixup names in the doc too. ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.976236447@infradead.org

show more ...


# 9e6b3986 16-Aug-2023 Mark Brown <broonie@kernel.org>

regulator: Get Synquacer testing working

Merge up v6.5-rc6 which has a fix that gets Synquacer netbooting so we
can include it in our testing.


# a35762dd 15-Aug-2023 Jason Gunthorpe <jgg@nvidia.com>

Merge tag 'v6.5-rc6' into iommufd for-next

Required for following patches.

Resolve merge conflict by using the hunk from the for-next branch and
shifting the iommufd_object_deref_user() into iommuf

Merge tag 'v6.5-rc6' into iommufd for-next

Required for following patches.

Resolve merge conflict by using the hunk from the for-next branch and
shifting the iommufd_object_deref_user() into iommufd_hw_pagetable_put()

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

show more ...


# bbb9e06d 14-Aug-2023 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge 6.5-rc6 into usb-next

We need the USB and Thunderbolt fixes in here to build on.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# e75850b4 13-Aug-2023 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge 6.5-rc6 into char-misc-next

We need the char/misc fixes in here as well to build on top of.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# 272b86ba 12-Aug-2023 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'x86_bugs_for_v6.5_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 mitigation fixes from Borislav Petkov:
"The first set of fallout fixes after the embargo madness.

Merge tag 'x86_bugs_for_v6.5_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 mitigation fixes from Borislav Petkov:
"The first set of fallout fixes after the embargo madness. There will
be another set next week too.

- A first series of cleanups/unifications and documentation
improvements to the SRSO and GDS mitigations code which got
postponed to after the embargo date

- Fix the SRSO aliasing addresses assertion so that the LLVM linker
can parse it too"

* tag 'x86_bugs_for_v6.5_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
driver core: cpu: Fix the fallback cpu_show_gds() name
x86: Move gds_ucode_mitigated() declaration to header
x86/speculation: Add cpu_show_gds() prototype
driver core: cpu: Make cpu_show_not_affected() static
x86/srso: Fix build breakage with the LLVM linker
Documentation/srso: Document IBPB aspect and fix formatting
driver core: cpu: Unify redundant silly stubs
Documentation/hw-vuln: Unify filename specification in index

show more ...


Revision tags: v6.1.45
# 35f563d6 10-Aug-2023 Jakub Kicinski <kuba@kernel.org>

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Merge net again, after pulling in x86/bugs fixes to clang
linking errors.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>


# 9ebbb29d 10-Aug-2023 Jakub Kicinski <kuba@kernel.org>

Merge branch 'x86/bugs' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Cross merge x86 fixes to fix clang linking errors:

ld.lld: error: ./arch/x86/kernel/vmlinux.lds:221: at least one si

Merge branch 'x86/bugs' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Cross merge x86 fixes to fix clang linking errors:

ld.lld: error: ./arch/x86/kernel/vmlinux.lds:221: at least one side of the expression must be absolute

These will hopefully be downstream by the time we ship
the next batch of fixes.

* 'x86/bugs' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86: Move gds_ucode_mitigated() declaration to header
x86/speculation: Add cpu_show_gds() prototype
driver core: cpu: Make cpu_show_not_affected() static
x86/srso: Fix build breakage with the LLVM linker
Documentation/srso: Document IBPB aspect and fix formatting
driver core: cpu: Unify redundant silly stubs
Documentation/hw-vuln: Unify filename specification in index

Link: https://lore.kernel.org/all/CAHk-=wj_b+FGTnevQSBAtCWuhCk=0oQ_THvthBW2hzqpOTLFmg@mail.gmail.com/
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...


# 4d016ae4 10-Aug-2023 Jakub Kicinski <kuba@kernel.org>

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Cross-merge networking fixes after downstream PR.

No conflicts.

Adjacent changes:

drivers/net/ethernet/intel/igc/igc_main.c
06b412

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Cross-merge networking fixes after downstream PR.

No conflicts.

Adjacent changes:

drivers/net/ethernet/intel/igc/igc_main.c
06b412589eef ("igc: Add lock to safeguard global Qbv variables")
d3750076d464 ("igc: Add TransmissionOverrun counter")

drivers/net/ethernet/microsoft/mana/mana_en.c
a7dfeda6fdec ("net: mana: Fix MANA VF unload when hardware is unresponsive")
a9ca9f9ceff3 ("page_pool: split types and declarations from page_pool.h")
92272ec4107e ("eth: add missing xdp.h includes in drivers")

net/mptcp/protocol.h
511b90e39250 ("mptcp: fix disconnect vs accept race")
b8dc6d6ce931 ("mptcp: fix rcv buffer auto-tuning")

tools/testing/selftests/net/mptcp/mptcp_join.sh
c8c101ae390a ("selftests: mptcp: join: fix 'implicit EP' test")
03668c65d153 ("selftests: mptcp: join: rework detailed report")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...


# 55b29050 10-Aug-2023 Arnaldo Carvalho de Melo <acme@redhat.com>

Merge remote-tracking branch 'torvalds/master' into perf-tools-next

To pick up some more fixes that went upstream via the perf-tools fixes
branch.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redh

Merge remote-tracking branch 'torvalds/master' into perf-tools-next

To pick up some more fixes that went upstream via the perf-tools fixes
branch.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

show more ...


Revision tags: v6.1.44, v6.1.43
# 09f9f37c 02-Aug-2023 Borislav Petkov (AMD) <bp@alien8.de>

Documentation/srso: Document IBPB aspect and fix formatting

Add a note about the dependency of the User->User mitigation on the
previous Spectre v2 IBPB selection.

Make the layout moar pretty.

Sig

Documentation/srso: Document IBPB aspect and fix formatting

Add a note about the dependency of the User->User mitigation on the
previous Spectre v2 IBPB selection.

Make the layout moar pretty.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230809102700.29449-4-bp@alien8.de

show more ...


# 138bcddb 07-Aug-2023 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'x86_bugs_srso' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86/srso fixes from Borislav Petkov:
"Add a mitigation for the speculative RAS (Return Address Stack)
overf

Merge tag 'x86_bugs_srso' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86/srso fixes from Borislav Petkov:
"Add a mitigation for the speculative RAS (Return Address Stack)
overflow vulnerability on AMD processors.

In short, this is yet another issue where userspace poisons a
microarchitectural structure which can then be used to leak privileged
information through a side channel"

* tag 'x86_bugs_srso' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/srso: Tie SBPB bit setting to microcode patch detection
x86/srso: Add a forgotten NOENDBR annotation
x86/srso: Fix return thunks in generated code
x86/srso: Add IBPB on VMEXIT
x86/srso: Add IBPB
x86/srso: Add SRSO_NO support
x86/srso: Add IBPB_BRTYPE support
x86/srso: Add a Speculative RAS Overflow mitigation
x86/bugs: Increase the x86 bugs vector size to two u32s

show more ...


Revision tags: v6.1.42, v6.1.41, v6.1.40, v6.1.39, v6.1.38, v6.1.37, v6.1.36
# fb3bd914 28-Jun-2023 Borislav Petkov (AMD) <bp@alien8.de>

x86/srso: Add a Speculative RAS Overflow mitigation

Add a mitigation for the speculative return address stack overflow
vulnerability found on AMD processors.

The mitigation works by ensuring all RE

x86/srso: Add a Speculative RAS Overflow mitigation

Add a mitigation for the speculative return address stack overflow
vulnerability found on AMD processors.

The mitigation works by ensuring all RET instructions speculate to
a controlled location, similar to how speculation is controlled in the
retpoline sequence. To accomplish this, the __x86_return_thunk forces
the CPU to mispredict every function return using a 'safe return'
sequence.

To ensure the safety of this mitigation, the kernel must ensure that the
safe return sequence is itself free from attacker interference. In Zen3
and Zen4, this is accomplished by creating a BTB alias between the
untraining function srso_untrain_ret_alias() and the safe return
function srso_safe_ret_alias() which results in evicting a potentially
poisoned BTB entry and using that safe one for all function returns.

In older Zen1 and Zen2, this is accomplished using a reinterpretation
technique similar to Retbleed one: srso_untrain_ret() and
srso_safe_ret().

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>

show more ...