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powerpc/64s: fix scv entry fallback flush vs interrupt

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commit 08685be7761d69914f08c3d6211c543a385a5b9c upstream.

The L1D flush fallback functions are not recoverable vs interrupts,
yet the scv entry flush runs with MSR[EE]=1. This can result in a
timer (soft-NMI) or MCE or SRESET interrupt hitting here and overwriting
the EXRFI save area, which ends up corrupting userspace registers for
scv return.

Fix this by disabling RI and EE for the scv entry fallback flush.

Fixes: f79643787e ("powerpc/64s: flush L1D on kernel entry")
Cc: stable@vger.kernel.org # 5.9+ which also have flush L1D patch backport
Reported-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210111062408.287092-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicholas Piggin
2021-01-11 16:24:08 +10:00
committed by Greg Kroah-Hartman
parent 1bac5333d4
commit 062dea906b
6 changed files with 71 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/kernel/entry_64.S
View File

@@ -75,7 +75,7 @@ BEGIN_FTR_SECTION
bne .Ltabort_syscall
END_FTR_SECTION_IFSET(CPU_FTR_TM)
#endif
INTERRUPT_TO_KERNEL
SCV_INTERRUPT_TO_KERNEL
mr r10,r1
ld r1,PACAKSAVE(r13)
std r10,0(r1)

19
arch/powerpc/kernel/exceptions-64s.S
View File

@@ -2993,6 +2993,25 @@ TRAMP_REAL_BEGIN(entry_flush_fallback)
ld r11,PACA_EXRFI+EX_R11(r13)
blr
/*
* The SCV entry flush happens with interrupts enabled, so it must disable
* to prevent EXRFI being clobbered by NMIs (e.g., soft_nmi_common). r10
* (containing LR) does not need to be preserved here because scv entry
* puts 0 in the pt_regs, CTR can be clobbered for the same reason.
*/
TRAMP_REAL_BEGIN(scv_entry_flush_fallback)
li r10,0
mtmsrd r10,1
lbz r10,PACAIRQHAPPENED(r13)
ori r10,r10,PACA_IRQ_HARD_DIS
stb r10,PACAIRQHAPPENED(r13)
std r11,PACA_EXRFI+EX_R11(r13)
L1D_DISPLACEMENT_FLUSH
ld r11,PACA_EXRFI+EX_R11(r13)
li r10,MSR_RI
mtmsrd r10,1
blr
TRAMP_REAL_BEGIN(rfi_flush_fallback)
SET_SCRATCH0(r13);
GET_PACA(r13);

7
arch/powerpc/kernel/vmlinux.lds.S
View File

@@ -145,6 +145,13 @@ SECTIONS
__stop___entry_flush_fixup = .;
}
. = ALIGN(8);
__scv_entry_flush_fixup : AT(ADDR(__scv_entry_flush_fixup) - LOAD_OFFSET) {
__start___scv_entry_flush_fixup = .;
*(__scv_entry_flush_fixup)
__stop___scv_entry_flush_fixup = .;
}
. = ALIGN(8);
__stf_exit_barrier_fixup : AT(ADDR(__stf_exit_barrier_fixup) - LOAD_OFFSET) {
__start___stf_exit_barrier_fixup = .;