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Revision 595d153dd1022392083ac93a1550382cbee127e0 authored by Michael Ellerman on 26 May 2020, 06:18:08 UTC, committed by Michael Ellerman on 26 May 2020, 07:32:37 UTC 
powerpc/64s: Fix restore of NV GPRs after facility unavailable exception
 
Commit 702f09805222 ("powerpc/64s/exception: Remove lite interrupt
return") changed the interrupt return path to not restore non-volatile
registers by default, and explicitly restore them in paths where it is
required.

But it missed that the facility unavailable exception can sometimes
modify user registers, ie. when it does emulation of move from DSCR.

This is seen as a failure of the dscr_sysfs_thread_test:
  test: dscr_sysfs_thread_test
  [cpu 0] User DSCR should be 1 but is 0
  failure: dscr_sysfs_thread_test

So restore non-volatile GPRs after facility unavailable exceptions.

Currently the hypervisor facility unavailable exception is also wired
up to call facility_unavailable_exception().

In practice we should never take a hypervisor facility unavailable
exception for the DSCR. On older bare metal systems we set HFSCR_DSCR
unconditionally in __init_HFSCR, or on newer systems it should be
enabled via the "data-stream-control-register" device tree CPU
feature.

Even if it's not, since commit f3c99f97a3cd ("KVM: PPC: Book3S HV:
Don't access HFSCR, LPIDR or LPCR when running nested"), the KVM code
has unconditionally set HFSCR_DSCR when running guests.

So we should only get a hypervisor facility unavailable for the DSCR
if skiboot has disabled the "data-stream-control-register" feature,
and we are somehow in guest context but not via KVM.

Given all that, it should be unnecessary to add a restore of
non-volatile GPRs after the hypervisor facility exception, because we
never expect to hit that path. But equally we may as well add the
restore, because we never expect to hit that path, and if we ever did,
at least we would correctly restore the registers to their post
emulation state.

In future we can split the non-HV and HV facility unavailable handling
so that there is no emulation in the HV handler, and then remove the
restore for the HV case.

Fixes: 702f09805222 ("powerpc/64s/exception: Remove lite interrupt return")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200526061808.2472279-1-mpe@ellerman.id.au
1 parent 8659a0e
Raw File
headers_install.sh 
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0

if [ $# -ne 2 ]
then
	echo "Usage: headers_install.sh INFILE OUTFILE"
	echo
	echo "Prepares kernel header files for use by user space, by removing"
	echo "all compiler.h definitions and #includes, removing any"
	echo "#ifdef __KERNEL__ sections, and putting __underscores__ around"
	echo "asm/inline/volatile keywords."
	echo
	echo "INFILE: header file to operate on"
	echo "OUTFILE: output file which the processed header is writen to"

	exit 1
fi

# Grab arguments
INFILE=$1
OUTFILE=$2
TMPFILE=$OUTFILE.tmp

trap 'rm -f $OUTFILE $TMPFILE' EXIT

# SPDX-License-Identifier with GPL variants must have "WITH Linux-syscall-note"
if [ -n "$(sed -n -e "/SPDX-License-Identifier:.*GPL-/{/WITH Linux-syscall-note/!p}" $INFILE)" ]; then
	echo "error: $INFILE: missing \"WITH Linux-syscall-note\" for SPDX-License-Identifier" >&2
	exit 1
fi

sed -E -e '
	s/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g
	s/__attribute_const__([[:space:]]|$)/\1/g
	s@^#include <linux/compiler(|_types).h>@@
	s/(^|[^a-zA-Z0-9])__packed([^a-zA-Z0-9_]|$)/\1__attribute__((packed))\2/g
	s/(^|[[:space:](])(inline|asm|volatile)([[:space:](]|$)/\1__\2__\3/g
	s@#(ifndef|define|endif[[:space:]]*/[*])[[:space:]]*_UAPI@#\1 @
' $INFILE > $TMPFILE || exit 1

scripts/unifdef -U__KERNEL__ -D__EXPORTED_HEADERS__ $TMPFILE > $OUTFILE
[ $? -gt 1 ] && exit 1

# Remove /* ... */ style comments, and find CONFIG_ references in code
configs=$(sed -e '
:comment
	s:/\*[^*][^*]*:/*:
	s:/\*\*\**\([^/]\):/*\1:
	t comment
	s:/\*\*/: :
	t comment
	/\/\*/! b check
	N
	b comment
:print
	P
	D
:check
	s:^\(CONFIG_[[:alnum:]_]*\):\1\n:
	t print
	s:^[[:alnum:]_][[:alnum:]_]*::
	s:^[^[:alnum:]_][^[:alnum:]_]*::
	t check
	d
' $OUTFILE)

# The entries in the following list are not warned.
# Please do not add a new entry. This list is only for existing ones.
# The list will be reduced gradually, and deleted eventually. (hopefully)
#
# The format is <file-name>:<CONFIG-option> in each line.
config_leak_ignores="
arch/alpha/include/uapi/asm/setup.h:CONFIG_ALPHA_LEGACY_START_ADDRESS
arch/arc/include/uapi/asm/page.h:CONFIG_ARC_PAGE_SIZE_16K
arch/arc/include/uapi/asm/page.h:CONFIG_ARC_PAGE_SIZE_4K
arch/arc/include/uapi/asm/swab.h:CONFIG_ARC_HAS_SWAPE
arch/arm/include/uapi/asm/ptrace.h:CONFIG_CPU_ENDIAN_BE8
arch/hexagon/include/uapi/asm/ptrace.h:CONFIG_HEXAGON_ARCH_VERSION
arch/hexagon/include/uapi/asm/user.h:CONFIG_HEXAGON_ARCH_VERSION
arch/ia64/include/uapi/asm/cmpxchg.h:CONFIG_IA64_DEBUG_CMPXCHG
arch/m68k/include/uapi/asm/ptrace.h:CONFIG_COLDFIRE
arch/nios2/include/uapi/asm/swab.h:CONFIG_NIOS2_CI_SWAB_NO
arch/nios2/include/uapi/asm/swab.h:CONFIG_NIOS2_CI_SWAB_SUPPORT
arch/sh/include/uapi/asm/ptrace.h:CONFIG_CPU_SH5
arch/sh/include/uapi/asm/sigcontext.h:CONFIG_CPU_SH5
arch/sh/include/uapi/asm/stat.h:CONFIG_CPU_SH5
arch/x86/include/uapi/asm/auxvec.h:CONFIG_IA32_EMULATION
arch/x86/include/uapi/asm/auxvec.h:CONFIG_X86_64
arch/x86/include/uapi/asm/mman.h:CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
include/uapi/asm-generic/fcntl.h:CONFIG_64BIT
include/uapi/linux/atmdev.h:CONFIG_COMPAT
include/uapi/linux/elfcore.h:CONFIG_BINFMT_ELF_FDPIC
include/uapi/linux/eventpoll.h:CONFIG_PM_SLEEP
include/uapi/linux/hw_breakpoint.h:CONFIG_HAVE_MIXED_BREAKPOINTS_REGS
include/uapi/linux/pktcdvd.h:CONFIG_CDROM_PKTCDVD_WCACHE
include/uapi/linux/raw.h:CONFIG_MAX_RAW_DEVS
"

for c in $configs
do
	warn=1

	for ignore in $config_leak_ignores
	do
		if echo "$INFILE:$c" | grep -q "$ignore$"; then
			warn=
			break
		fi
	done

	if [ "$warn" = 1 ]; then
		echo "warning: $INFILE: leak $c to user-space" >&2
	fi
done

rm -f $TMPFILE
trap - EXIT
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