powerpc/kuap: KUAP enabling/disabling functions must be __always_inline

Objtool reports following warnings:

arch/powerpc/kernel/signal_32.o: warning: objtool:
__prevent_user_access.constprop.0+0x4 (.text+0x4):
redundant UACCESS disable

arch/powerpc/kernel/signal_32.o: warning: objtool: user_access_begin+0x2c
(.text+0x4c): return with UACCESS enabled

arch/powerpc/kernel/signal_32.o: warning: objtool: handle_rt_signal32+0x188
(.text+0x360): call to __prevent_user_access.constprop.0() with UACCESS enabled

arch/powerpc/kernel/signal_32.o: warning: objtool: handle_signal32+0x150
(.text+0x4d4): call to __prevent_user_access.constprop.0() with UACCESS enabled

This is due to some KUAP enabling/disabling functions being outline
allthough they are marked inline. Use __always_inline instead.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/ca5e50ddbec3867db5146ebddbc9a1dc0e443bc8.1689091022.git.christophe.leroy@csgroup.eu

powerpc/kuap: Use MMU_FTR_KUAP on all and refactor disabling kuap

All but book3s/64 use a static branch key for disabling kuap.
book3s/64 uses an mmu feature.

Refactor all targets to use MMU_FTR_KUAP like book3s/64.

For PPC32 that implies updating mmu features fixups once KUAP
has been initialised.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/6b3d7c977bad73378ea368bc6818e9c94ea95ab0.1689091022.git.christophe.leroy@csgroup.eu

powerpc/kuap: MMU_FTR_BOOK3S_KUAP becomes MMU_FTR_KUAP

In order to reuse MMU_FTR_BOOK3S_KUAP for other targets than BOOK3S,
rename it MMU_FTR_KUAP.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/c8b6f7b8cd0eeaace96879ed0e0a157faa619451.1689091022.git.christophe.leroy@csgroup.eu

powerpc/kuap: Avoid useless jump_label on empty function

Disassembly of interrupt_enter_prepare() shows a pointless nop
before the mftb

c000abf0 <interrupt_enter_prepare>:
c000abf0: 81 23 00 84 lwz r9,132(r3)
c000abf4: 71 29 40 00 andi. r9,r9,16384
c000abf8: 41 82 00 28 beq- c000ac20 <interrupt_enter_prepare+0x30>
c000abfc: ===> 60 00 00 00 nop <====
c000ac00: 7d 0c 42 e6 mftb r8
c000ac04: 80 e2 00 08 lwz r7,8(r2)
c000ac08: 81 22 00 28 lwz r9,40(r2)
c000ac0c: 91 02 00 24 stw r8,36(r2)
c000ac10: 7d 29 38 50 subf r9,r9,r7
c000ac14: 7d 29 42 14 add r9,r9,r8
c000ac18: 91 22 00 08 stw r9,8(r2)
c000ac1c: 4e 80 00 20 blr
c000ac20: 60 00 00 00 nop
c000ac24: 7d 5a c2 a6 mfmd_ap r10
c000ac28: 3d 20 de 00 lis r9,-8704
c000ac2c: 91 43 00 b0 stw r10,176(r3)
c000ac30: 7d 3a c3 a6 mtspr 794,r9
c000ac34: 4e 80 00 20 blr

That comes from the call to kuap_loc(), allthough __kuap_lock() is an
empty function on the 8xx.

To avoid that, only perform kuap_is_disabled() check when there is
something to do with __kuap_lock().

Do the same with __kuap_save_and_lock() and
__kuap_get_and_assert_locked().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/a854d25bea375d4ba6ca9c2617f9edbba397100a.1689091022.git.christophe.leroy@csgroup.eu

powerpc/book3s: Add missing <linux/sched.h> include

The functions here use struct task_struct fields, so need to import
the full definition from <linux/sched.h>. The <asm/current.h> header
that defines current only forward declares struct task_struct.

Failing to include this <linux/sched.h> header leads to a compilation
error when a translation unit does not also include <linux/sched.h>
indirectly.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230616034846.311705-2-bgray@linux.ibm.com

powerpc/64: Force inlining of prevent_user_access() and set_kuap()

A ppc64_defconfig build exhibits about 10 copied of
prevent_user_access(). It also have one copy of set_kuap().

c000000000017340 <.prevent_user_access.constprop.0>:
c00000000001a038: 4b ff d3 09 bl c000000000017340 <.prevent_user_access.constprop.0>
c00000000001aabc: 4b ff c8 85 bl c000000000017340 <.prevent_user_access.constprop.0>
c00000000001ab38: 4b ff c8 09 bl c000000000017340 <.prevent_user_access.constprop.0>
c00000000001ade0: 4b ff c5 61 bl c000000000017340 <.prevent_user_access.constprop.0>
c000000000039b90 <.prevent_user_access.constprop.0>:
c00000000003ac08: 4b ff ef 89 bl c000000000039b90 <.prevent_user_access.constprop.0>
c00000000003b9d0: 4b ff e1 c1 bl c000000000039b90 <.prevent_user_access.constprop.0>
c00000000003ba54: 4b ff e1 3d bl c000000000039b90 <.prevent_user_access.constprop.0>
c00000000003bbfc: 4b ff df 95 bl c000000000039b90 <.prevent_user_access.constprop.0>
c00000000015dde0 <.prevent_user_access.constprop.0>:
c0000000001612c0: 4b ff cb 21 bl c00000000015dde0 <.prevent_user_access.constprop.0>
c000000000161b54: 4b ff c2 8d bl c00000000015dde0 <.prevent_user_access.constprop.0>
c000000000188cf0 <.prevent_user_access.constprop.0>:
c00000000018d658: 4b ff b6 99 bl c000000000188cf0 <.prevent_user_access.constprop.0>
c00000000030fe20 <.prevent_user_access.constprop.0>:
c0000000003123d4: 4b ff da 4d bl c00000000030fe20 <.prevent_user_access.constprop.0>
c000000000313970: 4b ff c4 b1 bl c00000000030fe20 <.prevent_user_access.constprop.0>
c0000000005e6bd0 <.prevent_user_access.constprop.0>:
c0000000005e7d8c: 4b ff ee 45 bl c0000000005e6bd0 <.prevent_user_access.constprop.0>
c0000000007bcae0 <.prevent_user_access.constprop.0>:
c0000000007bda10: 4b ff f0 d1 bl c0000000007bcae0 <.prevent_user_access.constprop.0>
c0000000007bda54: 4b ff f0 8d bl c0000000007bcae0 <.prevent_user_access.constprop.0>
c0000000007bdd28: 4b ff ed b9 bl c0000000007bcae0 <.prevent_user_access.constprop.0>
c0000000007c0390: 4b ff c7 51 bl c0000000007bcae0 <.prevent_user_access.constprop.0>
c00000000094e4f0 <.prevent_user_access.constprop.0>:
c000000000950e40: 4b ff d6 b1 bl c00000000094e4f0 <.prevent_user_access.constprop.0>
c00000000097d2d0 <.prevent_user_access.constprop.0>:
c0000000009813fc: 4b ff be d5 bl c00000000097d2d0 <.prevent_user_access.constprop.0>
c000000000acd540 <.prevent_user_access.constprop.0>:
c000000000ad1d60: 4b ff b7 e1 bl c000000000acd540 <.prevent_user_access.constprop.0>
c000000000e5d680 <.prevent_user_access.constprop.0>:
c000000000e64b60: 4b ff 8b 21 bl c000000000e5d680 <.prevent_user_access.constprop.0>
c000000000e64b6c: 4b ff 8b 15 bl c000000000e5d680 <.prevent_user_access.constprop.0>
c000000000e64c38: 4b ff 8a 49 bl c000000000e5d680 <.prevent_user_access.constprop.0>

When building signal_64.c with -Winline the following messages appear:

./arch/powerpc/include/asm/book3s/64/kup.h:331:20: error: inlining failed in call to 'set_kuap': call is unlikely and code size would grow [-Werror=inline]
./arch/powerpc/include/asm/book3s/64/kup.h:401:20: error: inlining failed in call to 'prevent_user_access.constprop': call is unlikely and code size would grow [-Werror=inline]

Those functions are used on hot pathes and have been
expected to be inlined at all time.

Force them inline.

This patch reduces the kernel text size by 700 bytes, confirming
that not inlining those functions is not worth it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/eff9b2b211957fa2e8707e46f31674097fd563a3.1644588972.git.christophe.leroy@csgroup.eu

powerpc/kuap: Prepare for supporting KUAP on BOOK3E/64

Also call kuap_lock() and kuap_save_and_lock() from
interrupt functions with CONFIG_PPC64.

For book3s/64 we keep them empty as it is done in assembly.

Also do the locked assert when switching task unless it is
book3s/64.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1cbf94e26e6d6e2e028fd687588a7e6622d454a6.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Remove __kuap_assert_locked()

__kuap_assert_locked() is redundant with
__kuap_get_and_assert_locked().

Move the verification of CONFIG_PPC_KUAP_DEBUG in kuap_assert_locked()
and make it call __kuap_get_and_assert_locked() directly.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1a60198a25d2ba38a37f1b92bc7d096435df4224.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Check KUAP activation in generic functions

Today, every platform checks that KUAP is not de-activated
before doing the real job.

Move the verification out of platform specific functions.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/894f110397fcd248e125fb855d1e863e4e633a0d.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Add a generic intermediate layer

Make the following functions generic to all platforms.
- bad_kuap_fault()
- kuap_assert_locked()
- kuap_save_and_lock() (PPC32 only)
- kuap_kernel_restore()
- kuap_get_and_assert_locked()

And for all platforms except book3s/64
- allow_user_access()
- prevent_user_access()
- prevent_user_access_return()
- restore_user_access()

Prepend __ in front of the name of platform specific ones.

For now the generic just calls the platform specific, but
next patch will move redundant parts of specific functions
into the generic one.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/eaef143a8dae7288cd34565ffa7b49c16aee1ec3.1634627931.git.christophe.leroy@csgroup.eu

powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto

Using asm goto in __WARN_FLAGS() and WARN_ON() allows more
flexibility to GCC.

For that add an entry to the exception table so that
program_check_exception() knowns where to resume execution
after a WARNING.

Here are two exemples. The first one is done on PPC32 (which
benefits from the previous patch), the second is on PPC64.

unsigned long test(struct pt_regs *regs)
{
int ret;

WARN_ON(regs->msr & MSR_PR);

return regs->gpr[3];
}

unsigned long test9w(unsigned long a, unsigned long b)
{
if (WARN_ON(!b))
return 0;
return a / b;
}

Before the patch:

000003a8 <test>:
3a8: 81 23 00 84 lwz r9,132(r3)
3ac: 71 29 40 00 andi. r9,r9,16384
3b0: 40 82 00 0c bne 3bc <test+0x14>
3b4: 80 63 00 0c lwz r3,12(r3)
3b8: 4e 80 00 20 blr

3bc: 0f e0 00 00 twui r0,0
3c0: 80 63 00 0c lwz r3,12(r3)
3c4: 4e 80 00 20 blr

0000000000000bf0 <.test9w>:
bf0: 7c 89 00 74 cntlzd r9,r4
bf4: 79 29 d1 82 rldicl r9,r9,58,6
bf8: 0b 09 00 00 tdnei r9,0
bfc: 2c 24 00 00 cmpdi r4,0
c00: 41 82 00 0c beq c0c <.test9w+0x1c>
c04: 7c 63 23 92 divdu r3,r3,r4
c08: 4e 80 00 20 blr

c0c: 38 60 00 00 li r3,0
c10: 4e 80 00 20 blr

After the patch:

000003a8 <test>:
3a8: 81 23 00 84 lwz r9,132(r3)
3ac: 71 29 40 00 andi. r9,r9,16384
3b0: 40 82 00 0c bne 3bc <test+0x14>
3b4: 80 63 00 0c lwz r3,12(r3)
3b8: 4e 80 00 20 blr

3bc: 0f e0 00 00 twui r0,0

0000000000000c50 <.test9w>:
c50: 7c 89 00 74 cntlzd r9,r4
c54: 79 29 d1 82 rldicl r9,r9,58,6
c58: 0b 09 00 00 tdnei r9,0
c5c: 7c 63 23 92 divdu r3,r3,r4
c60: 4e 80 00 20 blr

c70: 38 60 00 00 li r3,0
c74: 4e 80 00 20 blr

In the first exemple, we see GCC doesn't need to duplicate what
happens after the trap.

In the second exemple, we see that GCC doesn't need to emit a test
and a branch in the likely path in addition to the trap.

We've got some WARN_ON() in .softirqentry.text section so it needs
to be added in the OTHER_TEXT_SECTIONS in modpost.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/389962b1b702e3c78d169e59bcfac56282889173.1618331882.git.christophe.leroy@csgroup.eu

powerpc/kuap: Remove to/from/size parameters of prevent_user_access()

prevent_user_access() doesn't use anymore to/from/size parameters.

Remove them.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b7113662fd2c26e4c33e9d705de324bd3860822e.1622708530.git.christophe.leroy@csgroup.eu

powerpc/64s: Make kuap_check_amr() and kuap_get_and_check_amr() generic

In preparation of porting powerpc32 to C syscall entry/exit,
rename kuap_check_amr() and kuap_get_and_check_amr() as
kuap_assert_locked() and kuap_get_and_assert_locked(), and move in the
generic asm/kup.h the stub for when CONFIG_PPC_KUAP is not selected.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f82614d9b17b83abd739aa18fc08811815d0c2e3.1615552867.git.christophe.leroy@csgroup.eu

powerpc/64s/kuap: Use mmu_has_feature()

In commit 8150a153c013 ("powerpc/64s: Use early_mmu_has_feature() in
set_kuap()") we switched the KUAP code to use early_mmu_has_feature(),
to avoid a bug where we called set_kuap() before feature patching had
been done, leading to recursion and crashes.

That path, which called probe_kernel_read() from printk(), has since
been removed, see commit 2ac5a3bf7042 ("vsprintf: Do not break early
boot with probing addresses").

Additionally probe_kernel_read() no longer invokes any KUAP routines,
since commit fe557319aa06 ("maccess: rename probe_kernel_{read,write}
to copy_{from,to}_kernel_nofault") and c33165253492 ("powerpc: use
non-set_fs based maccess routines").

So it should now be safe to use mmu_has_feature() in the KUAP
routines, because we shouldn't invoke them prior to feature patching.

This is essentially a revert of commit 8150a153c013 ("powerpc/64s: Use
early_mmu_has_feature() in set_kuap()"), but we've since added a
second usage of early_mmu_has_feature() in get_kuap(), so we convert
that to use mmu_has_feature() as well.

Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Depends-on: c33165253492 ("powerpc: use non-set_fs based maccess routines").
Link: https://lore.kernel.org/r/20201217005306.895685-1-mpe@ellerman.id.au

powerpc/kuap: Allow kernel thread to access userspace after kthread_use_mm

This fix the bad fault reported by KUAP when io_wqe_worker access userspace.

Bug: Read fault blocked by KUAP!
WARNING: CPU: 1 PID: 101841 at arch/powerpc/mm/fault.c:229 __do_page_fault+0x6b4/0xcd0
NIP [c00000000009e7e4] __do_page_fault+0x6b4/0xcd0
LR [c00000000009e7e0] __do_page_fault+0x6b0/0xcd0
..........
Call Trace:
[c000000016367330] [c00000000009e7e0] __do_page_fault+0x6b0/0xcd0 (unreliable)
[c0000000163673e0] [c00000000009ee3c] do_page_fault+0x3c/0x120
[c000000016367430] [c00000000000c848] handle_page_fault+0x10/0x2c
--- interrupt: 300 at iov_iter_fault_in_readable+0x148/0x6f0
..........
NIP [c0000000008e8228] iov_iter_fault_in_readable+0x148/0x6f0
LR [c0000000008e834c] iov_iter_fault_in_readable+0x26c/0x6f0
interrupt: 300
[c0000000163677e0] [c0000000007154a0] iomap_write_actor+0xc0/0x280
[c000000016367880] [c00000000070fc94] iomap_apply+0x1c4/0x780
[c000000016367990] [c000000000710330] iomap_file_buffered_write+0xa0/0x120
[c0000000163679e0] [c00800000040791c] xfs_file_buffered_aio_write+0x314/0x5e0 [xfs]
[c000000016367a90] [c0000000006d74bc] io_write+0x10c/0x460
[c000000016367bb0] [c0000000006d80e4] io_issue_sqe+0x8d4/0x1200
[c000000016367c70] [c0000000006d8ad0] io_wq_submit_work+0xc0/0x250
[c000000016367cb0] [c0000000006e2578] io_worker_handle_work+0x498/0x800
[c000000016367d40] [c0000000006e2cdc] io_wqe_worker+0x3fc/0x4f0
[c000000016367da0] [c0000000001cb0a4] kthread+0x1c4/0x1d0
[c000000016367e10] [c00000000000dbf0] ret_from_kernel_thread+0x5c/0x6c

The kernel consider thread AMR value for kernel thread to be
AMR_KUAP_BLOCKED. Hence access to userspace is denied. This
of course not correct and we should allow userspace access after
kthread_use_mm(). To be precise, kthread_use_mm() should inherit the
AMR value of the operating address space. But, the AMR value is
thread-specific and we inherit the address space and not thread
access restrictions. Because of this ignore AMR value when accessing
userspace via kernel thread.

current_thread_amr/iamr() are updated, because we use them in the
below stack.
....
[ 530.710838] CPU: 13 PID: 5587 Comm: io_wqe_worker-0 Tainted: G D 5.11.0-rc6+ #3
....

NIP [c0000000000aa0c8] pkey_access_permitted+0x28/0x90
LR [c0000000004b9278] gup_pte_range+0x188/0x420
--- interrupt: 700
[c00000001c4ef3f0] [0000000000000000] 0x0 (unreliable)
[c00000001c4ef490] [c0000000004bd39c] gup_pgd_range+0x3ac/0xa20
[c00000001c4ef5a0] [c0000000004bdd44] internal_get_user_pages_fast+0x334/0x410
[c00000001c4ef620] [c000000000852028] iov_iter_get_pages+0xf8/0x5c0
[c00000001c4ef6a0] [c0000000007da44c] bio_iov_iter_get_pages+0xec/0x700
[c00000001c4ef770] [c0000000006a325c] iomap_dio_bio_actor+0x2ac/0x4f0
[c00000001c4ef810] [c00000000069cd94] iomap_apply+0x2b4/0x740
[c00000001c4ef920] [c0000000006a38b8] __iomap_dio_rw+0x238/0x5c0
[c00000001c4ef9d0] [c0000000006a3c60] iomap_dio_rw+0x20/0x80
[c00000001c4ef9f0] [c008000001927a30] xfs_file_dio_aio_write+0x1f8/0x650 [xfs]
[c00000001c4efa60] [c0080000019284dc] xfs_file_write_iter+0xc4/0x130 [xfs]
[c00000001c4efa90] [c000000000669984] io_write+0x104/0x4b0
[c00000001c4efbb0] [c00000000066cea4] io_issue_sqe+0x3d4/0xf50
[c00000001c4efc60] [c000000000670200] io_wq_submit_work+0xb0/0x2f0
[c00000001c4efcb0] [c000000000674268] io_worker_handle_work+0x248/0x4a0
[c00000001c4efd30] [c0000000006746e8] io_wqe_worker+0x228/0x2a0
[c00000001c4efda0] [c00000000019d994] kthread+0x1b4/0x1c0

Fixes: 48a8ab4eeb82 ("powerpc/book3s64/pkeys: Don't update SPRN_AMR when in kernel mode.")
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210206025634.521979-1-aneesh.kumar@linux.ibm.com

powerpc/mm: Move the WARN() out of bad_kuap_fault()

In order to prepare the removal of calls to
search_exception_tables() on the fast path, move the
WARN() out of bad_kuap_fault().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/9501311014bd6507e04b27a0c3035186ccf65cd5.1607491748.git.christophe.leroy@csgroup.eu

powerpc/book3s64/kuap: Improve error reporting with KUAP

This partially reverts commit eb232b162446 ("powerpc/book3s64/kuap: Improve
error reporting with KUAP") and update the fault handler to print

[ 55.022514] Kernel attempted to access user page (7e6725b70000) - exploit attempt? (uid: 0)
[ 55.022528] BUG: Unable to handle kernel data access on read at 0x7e6725b70000
[ 55.022533] Faulting instruction address: 0xc000000000e8b9bc
[ 55.022540] Oops: Kernel access of bad area, sig: 11 [#1]
....

when the kernel access userspace address without unlocking AMR.

bad_kuap_fault() is added as part of commit 5e5be3aed230 ("powerpc/mm: Detect
bad KUAP faults") to catch userspace access incorrectly blocked by AMR. Hence
retain the full stack dump there even with hash translation. Also, add a comment
explaining the difference between hash and radix.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201208031539.84878-1-aneesh.kumar@linux.ibm.com

powerpc/book3s64/pkeys: Optimize KUAP and KUEP feature disabled case

If FTR_BOOK3S_KUAP is disabled, kernel will continue to run with the same AMR
value with which it was entered. Hence there is a high chance that
we can return without restoring the AMR value. This also helps the case
when applications are not using the pkey feature. In this case, different
applications will have the same AMR values and hence we can avoid restoring
AMR in this case too.

Also avoid isync() if not really needed.

Do the same for IAMR.

null-syscall benchmark results:

With smap/smep disabled:
Without patch:
957.95 ns 2778.17 cycles
With patch:
858.38 ns 2489.30 cycles

With smap/smep enabled:
Without patch:
1017.26 ns 2950.36 cycles
With patch:
1021.51 ns 2962.44 cycles

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-23-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuep: Use Key 3 to implement KUEP with hash translation.

Radix use IAMR Key 0 and hash translation use IAMR key 3.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-19-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuap: Use Key 3 to implement KUAP with hash translation.

Radix use AMR Key 0 and hash translation use AMR key 3.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-18-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuap: Improve error reporting with KUAP

With hash translation use DSISR_KEYFAULT to identify a wrong access.
With Radix we look at the AMR value and type of fault.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-17-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuap: Restrict access to userspace based on userspace AMR

If an application has configured address protection such that read/write is
denied using pkey even the kernel should receive a FAULT on accessing the same.

This patch use user AMR value stored in pt_regs.amr to achieve the same.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-16-aneesh.kumar@linux.ibm.com

powerpc/book3s64/pkeys: Don't update SPRN_AMR when in kernel mode.

Now that kernel correctly store/restore userspace AMR/IAMR values, avoid
manipulating AMR and IAMR from the kernel on behalf of userspace.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-15-aneesh.kumar@linux.ibm.com

powerpc/book3s64/pkeys: Store/restore userspace AMR/IAMR correctly on entry and exit from kernel

This prepare kernel to operate with a different value than userspace AMR/IAMR.
For this, AMR/IAMR need to be saved and restored on entry and return from the
kernel.

With KUAP we modify kernel AMR when accessing user address from the kernel
via copy_to/from_user interfaces. We don't need to modify IAMR value in
similar fashion.

If MMU_FTR_PKEY is enabled we need to save AMR/IAMR in pt_regs on entering
kernel from userspace. If not we can assume that AMR/IAMR is not modified
from userspace.

We need to save AMR if we have MMU_FTR_BOOK3S_KUAP feature enabled and we are
interrupted within kernel. This is required so that if we get interrupted
within copy_to/from_user we continue with the right AMR value.

If we hae MMU_FTR_BOOK3S_KUEP enabled we need to restore IAMR on
return to userspace beause kernel will be running with a different
IAMR value.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-11-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuap: Rename MMU_FTR_RADIX_KUAP and MMU_FTR_KUEP

This is in preparation to adding support for kuap with hash translation.
In preparation for that rename/move kuap related functions to
non radix names. Also move the feature bit closer to MMU_FTR_KUEP.

MMU_FTR_KUEP is renamed to MMU_FTR_BOOK3S_KUEP to indicate the feature
is only relevant to BOOK3S_64

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-8-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuep: Move KUEP related function outside radix

The next set of patches adds support for kuep with hash translation.
In preparation for that rename/move kuap related functions to
non radix names.

Also set MMU_FTR_KUEP and add the missing isync().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-7-aneesh.kumar@linux.ibm.com

powerpc/book3s64/kuap: Move KUAP related function outside radix

The next set of patches adds support for kuap with hash translation.
In preparation for that rename/move kuap related functions to
non radix names.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-6-aneesh.kumar@linux.ibm.com