kernel/linux.git/arch/powerpc/include/asm/kup.h, branch v6.7

powerpc/kuap: Use ASM feature fixups instead of static branches

2023-08-02T12:22:18+00:00

To avoid a useless nop on top of every uaccess enable/disable and make life easier for objtool, replace static branches by ASM feature fixups that will nop KUAP enabling instructions out in the unlikely case KUAP is disabled at boottime. Leave it as is on book3s/64 for now, it will be handled later when objtool is activated on PPC64. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/671948788024fd890ec4ed175bc332dab8664ea5.1689091022.git.christophe.leroy@csgroup.eu

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

2023-08-02T12:22:18+00:00

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 Signed-off-by: Michael Ellerman Link: https://msgid.link/ca5e50ddbec3867db5146ebddbc9a1dc0e443bc8.1689091022.git.christophe.leroy@csgroup.eu

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

2023-08-02T12:22:18+00:00

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 Signed-off-by: Michael Ellerman Link: https://msgid.link/6b3d7c977bad73378ea368bc6818e9c94ea95ab0.1689091022.git.christophe.leroy@csgroup.eu

powerpc/kuap: Avoid useless jump_label on empty function

2023-08-02T12:22:17+00:00

Disassembly of interrupt_enter_prepare() shows a pointless nop before the mftb c000abf0 : 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 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 Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://msgid.link/a854d25bea375d4ba6ca9c2617f9edbba397100a.1689091022.git.christophe.leroy@csgroup.eu

powerpc/kuap: Remove unused inline function __kuap_assert_locked()

2022-05-04T09:37:46+00:00

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

2021-12-09T11:41:19+00:00

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

2021-12-09T11:41:19+00:00

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()

2021-12-09T11:41:19+00:00

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()

2021-12-09T11:41:18+00:00

__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

2021-12-09T11:41:18+00:00

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