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powerpc/kuap: Wire-up KUAP on 40x

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This adds KUAP support to 40x. This is done by checking
the content of SPRN_PID at the time user pgtable is loaded.

40x doesn't have KUEP, but KUAP implies KUEP because when the
PID doesn't match the page's PID, the page cannot be read nor
executed.

So KUEP is now automatically selected when KUAP is selected and
disabled when KUAP is disabled.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/aaefa91897ddc42ac11019dc0e1d1a525bd08e90.1634627931.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-10-19 09:29:30 +02:00 committed by Michael Ellerman
parent f6fad4fb55
commit fcf9bb6d32
3 changed files with 15 additions and 2 deletions
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8
arch/powerpc/kernel/head_40x.S
View file

@ -298,6 +298,10 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
3:
mfspr r11,SPRN_SPRG_THREAD
lwz r11,PGDIR(r11)
#ifdef CONFIG_PPC_KUAP
rlwinm. r9, r9, 0, 0xff
beq 5f /* Kuap fault */
#endif
4:
tophys(r11, r11)
rlwimi r11, r10, 12, 20, 29 /* Create L1 (pgdir/pmd) address */
@ -378,6 +382,10 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
3:
mfspr r11,SPRN_SPRG_THREAD
lwz r11,PGDIR(r11)
#ifdef CONFIG_PPC_KUAP
rlwinm. r9, r9, 0, 0xff
beq 5f /* Kuap fault */
#endif
4:
tophys(r11, r11)
rlwimi r11, r10, 12, 20, 29 /* Create L1 (pgdir/pmd) address */

2
arch/powerpc/mm/nohash/kup.c
View file

@ -19,6 +19,8 @@ EXPORT_SYMBOL(disable_kuap_key);
void setup_kuap(bool disabled)
{
if (disabled) {
if (IS_ENABLED(CONFIG_40x))
disable_kuep = true;
if (smp_processor_id() == boot_cpuid)
static_branch_enable(&disable_kuap_key);
return;

7
arch/powerpc/platforms/Kconfig.cputype
View file

@ -54,6 +54,9 @@ config 40x
select PPC_UDBG_16550
select 4xx_SOC
select HAVE_PCI
select PPC_HAVE_KUAP
select PPC_HAVE_KUEP
select PPC_KUEP if PPC_KUAP
config 44x
bool "AMCC 44x, 46x or 47x"
@ -425,9 +428,9 @@ config PPC_HAVE_KUEP
bool
config PPC_KUEP
bool "Kernel Userspace Execution Prevention"
bool "Kernel Userspace Execution Prevention" if !40x
depends on PPC_HAVE_KUEP
default y
default y if !40x
help
Enable support for Kernel Userspace Execution Prevention (KUEP)