linux.git/arch/powerpc/kernel/exceptions-64s.S, branch v6.7

docs: move powerpc under arch

2023-10-10T19:35:55+00:00

and fix all in-tree references.

Architecture-specific documentation is being moved into Documentation/arch/
as a way of cleaning up the top-level documentation directory and making
the docs hierarchy more closely match the source hierarchy.

Signed-off-by: Costa Shulyupin 
Acked-by: Michael Ellerman 
Signed-off-by: Jonathan Corbet 
Link: https://lore.kernel.org/r/20230826165737.2101199-1-costa.shul@redhat.com

powerpc: add CFUNC assembly label annotation

2023-04-20T02:54:24+00:00

This macro is to be used in assembly where C functions are called.
pcrel addressing mode requires branches to functions with a
localentry value of 1 to have either a trailing nop or @notoc.
This macro permits the latter without changing callers.

Signed-off-by: Nicholas Piggin 
[mpe: Add dummy definitions to fix selftests build]
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230408021752.862660-5-npiggin@gmail.com

Merge branch 'topic/objtool' into next

2022-12-08T12:57:47+00:00

Merge the powerpc objtool support, which we were keeping in a topic
branch in case of any merge conflicts.

powerpc/64s: Zeroise gprs on interrupt routine entry on Book3S

2022-12-02T09:46:05+00:00

Zeroise user state in gprs (assign to zero) to reduce the influence of user
registers on speculation within kernel syscall handlers. Clears occur
at the very beginning of the sc and scv 0 interrupt handlers, with
restores occurring following the execution of the syscall handler.

Zeroise GPRS r0, r2-r11, r14-r31, on entry into the kernel for all
other interrupt sources. The remaining gprs are overwritten by
entry macros to interrupt handlers, irrespective of whether or not a
given handler consumes these register values. If an interrupt does not
select the IMSR_R12 IOption, zeroise r12.

Prior to this commit, r14-r31 are restored on a per-interrupt basis at
exit, but now they are always restored on 64bit Book3S. Remove explicit
REST_NVGPRS invocations on 64-bit Book3S. 32-bit systems do not clear
user registers on interrupt, and continue to depend on the return value
of interrupt_exit_user_prepare to determine whether or not to restore
non-volatiles.

The mmap_bench benchmark in selftests should rapidly invoke pagefaults.
See ~0.8% performance regression with this mitigation, but this
indicates the worst-case performance due to heavier-weight interrupt
handlers. This mitigation is able to be enabled/disabled through
CONFIG_INTERRUPT_SANITIZE_REGISTERS.

Reviewed-by: Nicholas Piggin 
Signed-off-by: Rohan McLure 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221201071019.1953023-5-rmclure@linux.ibm.com

powerpc/64s: IOption for MSR stored in r12

2022-12-02T09:46:01+00:00

Interrupt handlers in asm/exceptions-64s.S contain a great deal of common
code produced by the GEN_COMMON macros. Currently, at the exit point of
the macro, r12 will contain the contents of the MSR. A future patch will
cause these macros to zeroise architected registers to avoid potential
speculation influence of user data.

Provide an IOption that signals that r12 must be retained, as the
interrupt handler assumes it to hold the contents of the MSR.

Reviewed-by: Nicholas Piggin 
Signed-off-by: Rohan McLure 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221201071019.1953023-4-rmclure@linux.ibm.com

powerpc: add a definition for the marker offset within the interrupt frame

2022-12-02T06:54:08+00:00

Define a constant rather than open-code the offset for the
"regs" marker.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221127124942.1665522-9-npiggin@gmail.com

powerpc: add definition for pt_regs offset within an interrupt frame

2022-12-02T06:54:08+00:00

This is a common offset that currently uses the overloaded
STACK_FRAME_OVERHEAD constant. It's easier to read and more
flexible to use a specific regs offset for this.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221127124942.1665522-8-npiggin@gmail.com

powerpc: Fix objtool unannotated intra-function call warnings

2022-11-15T09:11:47+00:00

Objtool throws unannotated intra-function call warnings in the following
assembly files:

arch/powerpc/kernel/vector.o: warning: objtool: .text+0x53c: unannotated intra-function call

arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0x60: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0x124: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0x5d4: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0x5dc: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0xcb8: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0xd0c: unannotated intra-function call
arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: objtool: .text+0x1030: unannotated intra-function call

arch/powerpc/kernel/head_64.o: warning: objtool: .text+0x358: unannotated intra-function call
arch/powerpc/kernel/head_64.o: warning: objtool: .text+0x728: unannotated intra-function call
arch/powerpc/kernel/head_64.o: warning: objtool: .text+0x4d94: unannotated intra-function call
arch/powerpc/kernel/head_64.o: warning: objtool: .text+0x4ec4: unannotated intra-function call

arch/powerpc/kvm/book3s_hv_interrupts.o: warning: objtool: .text+0x6c: unannotated intra-function call
arch/powerpc/kernel/misc_64.o: warning: objtool: .text+0x64: unannotated intra-function call

Objtool does not add STT_NOTYPE symbols with size 0 to the rbtree, which
is why find_call_destination() function is not able to find the
destination symbol for 'bl' instruction. For such symbols, objtool is
throwing unannotated intra-function call warnings in assembly files. Fix
these warnings by annotating those symbols with SYM_FUNC_START_LOCAL and
SYM_FUNC_END macros, inorder to set symbol type to STT_FUNC and symbol
size accordingly.

Tested-by: Naveen N. Rao 
Reviewed-by: Naveen N. Rao 
Reviewed-by: Christophe Leroy 
Acked-by: Josh Poimboeuf 
Signed-off-by: Sathvika Vasireddy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221114175754.1131267-4-sv@linux.ibm.com

powerpc/64s/interrupt: Perf NMI should not take normal exit path

2022-10-18T11:46:19+00:00

NMI interrupts should exit with EXCEPTION_RESTORE_REGS not with
interrupt_return_srr, which is what the perf NMI handler currently does.
This breaks if a PMI hits after interrupt_exit_user_prepare_main() has
switched the context tracking to user mode, then the CT_WARN_ON() in
interrupt_exit_kernel_prepare() fires because it returns to kernel with
context set to user.

This could possibly be solved by soft-disabling PMIs in the exit path,
but that reduces our ability to profile that code. The warning could be
removed, but it's potentially useful.

All other NMIs and soft-NMIs return using EXCEPTION_RESTORE_REGS, so
this makes perf interrupts consistent with that and seems like the best
fix.

Signed-off-by: Nicholas Piggin 
[mpe: Squash in fixups from Nick]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221006140413.126443-3-npiggin@gmail.com

powerpc/64s/interrupt: Fix stack frame regs marker

2022-10-05T00:09:22+00:00

The value of the stack frame regs marker that gets saved on the stack in
interrupt entry code does not match the regs marker value, which breaks
stack frame marker matching.

This stray instruction looks to have been introduced in a mismerge.

Fixes: bf75a3258a403 ("powerpc/64s/interrupt: move early boot ILE fixup into a macro")
Signed-off-by: Nicholas Piggin 
[mpe: Mismerge by yours truly -_-]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221004132952.984341-1-npiggin@gmail.com