linux.git/arch/powerpc/kernel/interrupt_64.S, branch v5.14

powerpc/64e: Fix system call illegal mtmsrd instruction

2021-07-06T09:58:54+00:00

BookE does not have mtmsrd, switch to use wrteei to enable MSR[EE].

Fixes: dd152f70bdc1 ("powerpc/64s: system call avoid setting MSR[RI] until we set MSR[EE]")
Reported-by: Christian Zigotzky 
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210706051310.608992-1-npiggin@gmail.com

powerpc/64s: move ret_from_fork etc above __end_soft_masked

2021-06-30T12:21:20+00:00

Code which runs with interrupts enabled should be moved above
__end_soft_masked where possible, because maskable interrupts that hit
below that symbol will need to consult the soft mask table, which is an
extra cost.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-10-npiggin@gmail.com

powerpc/64s/interrupt: clean up interrupt return labels

2021-06-30T12:21:20+00:00

Normal kernel-interrupt exits can get interrupt_return_srr_user_restart
in their backtrace, which is an unusual and notable function, and it is
part of the user-interrupt exit path, which is doubly confusing.

Add non-local labels for both user and kernel interrupt exit cases to
address this and make the user and kernel cases more symmetric. Also get
rid of an unused label.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-9-npiggin@gmail.com

powerpc/64/interrupt: add missing kprobe annotations on interrupt exit symbols

2021-06-30T12:21:20+00:00

If one interrupt exit symbol must not be kprobed, none of them can be,
without more justification for why it's safe. Disallow kprobing on any
of the (non-local) labels in the exit paths.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-8-npiggin@gmail.com

powerpc/64s: add a table of implicit soft-masked addresses

2021-06-30T12:21:20+00:00

Commit 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs
soft-masked") ends up catching too much code, including ret_from_fork,
and parts of interrupt and syscall return that do not expect to be
interrupts to be soft-masked. If an interrupt gets marked pending,
and then the code proceeds out of the implicit soft-masked region it
will fail to deal with the pending interrupt.

Fix this by adding a new table of addresses which explicitly marks
the regions of code that are soft masked. This table is only checked
for interrupts that below __end_soft_masked, so most kernel interrupts
will not have the overhead of the table search.

Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked")
Reported-by: Sachin Sant 
Signed-off-by: Nicholas Piggin 
Tested-by: Sachin Sant 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-5-npiggin@gmail.com

powerpc/64e: remove implicit soft-masking and interrupt exit restart logic

2021-06-30T12:21:20+00:00

The implicit soft-masking to speed up interrupt return was going to be
used by 64e as well, but it has not been extensively tested on that
platform and is not considered ready. It was intended to be disabled
before merge. Disable it for now.

Most of the restart code is common with 64s, so with more correctness
and performance testing this could be re-enabled again by adding the
extra soft-mask checks to interrupt handlers and flipping
exit_must_hard_disable().

Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked")
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-4-npiggin@gmail.com

powerpc/64: use interrupt restart table to speed up return from interrupt

2021-06-24T14:06:56+00:00

Use the restart table facility to return from interrupt or system calls
without disabling MSR[EE] or MSR[RI].

Interrupt return asm is put into the low soft-masked region, to prevent
interrupts being processed here, although they are still taken as masked
interrupts which causes SRRs to be clobbered, and a pending soft-masked
interrupt to require replaying.

The return code uses restart table regions to redirct to a fixup handler
rather than continue with the exit, if such an interrupt happens. In
this case the interrupt return is redirected to a fixup handler which
reloads r1 for the interrupt stack and reloads registers and sets state
up to replay the soft-masked interrupt and try the exit again.

Some types of security exit fallback flushes and barriers are currently
unable to cope with reentrant interrupts, e.g., because they store some
state in the scratch SPR which would be clobbered even by masked
interrupts. For now the interrupts-enabled exits are disabled when these
flushes are used.

Signed-off-by: Nicholas Piggin 
[mpe: Guard unused exit_must_hard_disable() as reported by lkp]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-13-npiggin@gmail.com

powerpc/64: treat low kernel text as irqs soft-masked

2021-06-24T14:06:56+00:00

Treat code below __end_soft_masked as soft-masked for the purpose
of alternate return. 64s already mostly does this for scv entry.

This will be used to exit from interrupts without disabling MSR[EE].

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-12-npiggin@gmail.com

powerpc/64s: system call avoid setting MSR[RI] until we set MSR[EE]

2021-06-24T14:06:56+00:00

This extends the MSR[RI]=0 window a little further into the system
call in order to pair RI and EE enabling with a single mtmsrd.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-8-npiggin@gmail.com

powerpc/64: move interrupt return asm to interrupt_64.S

2021-06-24T14:06:55+00:00

The next patch would like to move interrupt return assembly code to a low
location before general text, so move it into its own file and include via
head_64.S

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-7-npiggin@gmail.com