kernel/arch/powerpc/include/asm/kup.h, branch linux-6.2.y

powerpc/kuap: Remove unused inline function __kuap_assert_locked()

2022-05-04T09:37:46Z

commit 2341964e27b0 ("powerpc/kuap: Remove __kuap_assert_locked()") left behind this one, remove it. Signed-off-by: YueHaibing Acked-by: Christophe Leroy Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220311130017.22936-1-yuehaibing@huawei.com

powerpc: Add KUAP support for BOOKE and 40x

2021-12-09T11:41:19Z

On booke/40x we don't have segments like book3s/32. On booke/40x we don't have access protection groups like 8xx. Use the PID register to provide user access protection. Kernel address space can be accessed with any PID. User address space has to be accessed with the PID of the user. User PID is always not null. Everytime the kernel is entered, set PID register to 0 and restore PID register when returning to user. Everytime kernel needs to access user data, PID is restored for the access. In TLB miss handlers, check the PID and bail out to data storage exception when PID is 0 and accessed address is in user space. Note that also forbids execution of user text by kernel except when user access is unlocked. But this shouldn't be a problem as the kernel is not supposed to ever run user text. This patch prepares the infrastructure but the real activation of KUAP is done by following patches for each processor type one by one. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/5d65576a8e31e9480415785a180c92dd4e72306d.1634627931.git.christophe.leroy@csgroup.eu

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

2021-12-09T11:41:19Z

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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1cbf94e26e6d6e2e028fd687588a7e6622d454a6.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Add kuap_lock()

2021-12-09T11:41:19Z

Add kuap_lock() and call it when entering interrupts from user. It is called kuap_lock() as it is similar to kuap_save_and_lock() without the save. However book3s/32 already have a kuap_lock(). Rename it kuap_lock_addr(). Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/4437e2deb9f6f549f7089d45e9c6f96a7e77905a.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Remove __kuap_assert_locked()

2021-12-09T11:41:18Z

__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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1a60198a25d2ba38a37f1b92bc7d096435df4224.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Check KUAP activation in generic functions

2021-12-09T11:41:18Z

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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/894f110397fcd248e125fb855d1e863e4e633a0d.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuap: Add a generic intermediate layer

2021-12-09T11:41:18Z

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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/eaef143a8dae7288cd34565ffa7b49c16aee1ec3.1634627931.git.christophe.leroy@csgroup.eu

powerpc/kuep: Remove 'nosmep' boot time parameter except for book3s/64

2021-12-09T11:41:18Z

Deactivating KUEP at boot time is unrelevant for PPC32 and BOOK3E/64. Remove it. It allows to refactor setup_kuep() via a __weak function that only PPC64s will overide for now. Signed-off-by: Christophe Leroy [mpe: Fix CONFIG_PPC_BOOKS_64 -> CONFIG_PPC_BOOK3S_64 typo] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/4c36df18b41c988c4512f45d96220486adbe4c99.1634627931.git.christophe.leroy@csgroup.eu

powerpc/32s: Do kuep_lock() and kuep_unlock() in assembly

2021-12-09T11:41:17Z

When interrupt and syscall entries where converted to C, KUEP locking and unlocking was also converted. It improved performance by unrolling the loop, and allowed easily implementing boot time deactivation of KUEP. However, null_syscall selftest shows that KUEP is still heavy (361 cycles with KUEP, 212 cycles without). A way to improve more is to group 'mtsr's together, instead of repeating 'addi' + 'mtsr' several times. In order to do that, more registers need to be available. In C, GCC will always be able to provide the requested number of registers, but at the cost of saving some data on the stack, which is counter performant here. So let's do it in assembly, when we have full control of which register can be used. It also has the advantage of locking earlier and unlocking later and it helps GCC generating less tricky code. The only drawback is to make boot time deactivation less straight forward and require 'hand' instruction patching. Group 'mtsr's by 4. With this change, null_syscall selftest reports 336 cycles. Without the change it was 361 cycles, that's a 7% reduction. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/115cb279e9b9948dfd93a065e047081c59e3a2a6.1634627931.git.christophe.leroy@csgroup.eu

Revert "powerpc: Inline setup_kup()"

2021-12-09T11:41:16Z

This reverts commit 1791ebd131c46539b024c0f2ebf12b6c88a265b9. setup_kup() was inlined to manage conflict between PPC32 marking setup_{kuap/kuep}() __init and PPC64 not marking them __init. But in fact PPC32 has removed the __init mark for all but 8xx in order to properly handle SMP. In order to make setup_kup() grow a bit, revert the commit mentioned above but remove __init for 8xx as well so that we don't have to mark setup_kup() as __ref. Also switch the order so that KUAP is initialised before KUEP because on the 40x, KUEP will depend on the activation of KUAP. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/7691088fd0994ee3c8db6298dc8c00259e3f6a7f.1634627931.git.christophe.leroy@csgroup.eu