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powerpc/64s: Add support for a store forwarding barrier at kernel entry/exit

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On some CPUs we can prevent a vulnerability related to store-to-load
forwarding by preventing store forwarding between privilege domains,
by inserting a barrier in kernel entry and exit paths.

This is known to be the case on at least Power7, Power8 and Power9
powerpc CPUs.

Barriers must be inserted generally before the first load after moving
to a higher privilege, and after the last store before moving to a
lower privilege, HV and PR privilege transitions must be protected.

Barriers are added as patch sections, with all kernel/hypervisor entry
points patched, and the exit points to lower privilge levels patched
similarly to the RFI flush patching.

Firmware advertisement is not implemented yet, so CPU flush types
are hard coded.

Thanks to Michal Suchánek for bug fixes and review.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nicholas Piggin
2018-05-22 09:00:00 +10:00
committed by Linus Torvalds
parent c85061e6e0
commit a048a07d7f
9 changed files with 356 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
arch/powerpc/include/asm/exception-64s.h
View File

@@ -74,6 +74,27 @@
*/
#define EX_R3 EX_DAR
#define STF_ENTRY_BARRIER_SLOT \
STF_ENTRY_BARRIER_FIXUP_SECTION; \
nop; \
nop; \
nop
#define STF_EXIT_BARRIER_SLOT \
STF_EXIT_BARRIER_FIXUP_SECTION; \
nop; \
nop; \
nop; \
nop; \
nop; \
nop
/*
* r10 must be free to use, r13 must be paca
*/
#define INTERRUPT_TO_KERNEL \
STF_ENTRY_BARRIER_SLOT
/*
* Macros for annotating the expected destination of (h)rfid
*
@@ -90,16 +111,19 @@
rfid
#define RFI_TO_USER \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
rfid; \
b rfi_flush_fallback
#define RFI_TO_USER_OR_KERNEL \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
rfid; \
b rfi_flush_fallback
#define RFI_TO_GUEST \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
rfid; \
b rfi_flush_fallback
@@ -108,21 +132,25 @@
hrfid
#define HRFI_TO_USER \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
hrfid; \
b hrfi_flush_fallback
#define HRFI_TO_USER_OR_KERNEL \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
hrfid; \
b hrfi_flush_fallback
#define HRFI_TO_GUEST \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
hrfid; \
b hrfi_flush_fallback
#define HRFI_TO_UNKNOWN \
STF_EXIT_BARRIER_SLOT; \
RFI_FLUSH_SLOT; \
hrfid; \
b hrfi_flush_fallback
@@ -254,6 +282,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
#define __EXCEPTION_PROLOG_1_PRE(area) \
OPT_SAVE_REG_TO_PACA(area+EX_PPR, r9, CPU_FTR_HAS_PPR); \
OPT_SAVE_REG_TO_PACA(area+EX_CFAR, r10, CPU_FTR_CFAR); \
INTERRUPT_TO_KERNEL; \
SAVE_CTR(r10, area); \
mfcr r9;