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arm64: enable ptrauth earlier 

When the kernel is compiled with pointer auth instructions, the boot CPU
needs to start using address auth very early, so change the cpucap to
account for this.

Pointer auth must be enabled before we call C functions, because it is
not possible to enter a function with pointer auth disabled and exit it
with pointer auth enabled. Note, mismatches between architected and
IMPDEF algorithms will still be caught by the cpufeature framework (the
separate *_ARCH and *_IMP_DEF cpucaps).

Note the change in behavior: if the boot CPU has address auth and a
late CPU does not, then the late CPU is parked by the cpufeature
framework. This is possible as kernel will only have NOP space intructions
for PAC so such mismatched late cpu will silently ignore those
instructions in C functions. Also, if the boot CPU does not have address
auth and the late CPU has then the late cpu will still boot but with
ptrauth feature disabled.

Leave generic authentication as a "system scope" cpucap for now, since
initially the kernel will only use address authentication.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-worked ptrauth setup logic, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Kristina Martsenko 2020-03-13 14:34:55 +05:30 committed by Catalin Marinas
parent deeaac5175
commit 6982934e19
4 changed files with 49 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/arm64/Kconfig
View File

@ -1515,6 +1515,12 @@ config ARM64_PTR_AUTH
be enabled. However, KVM guest also require VHE mode and hence
CONFIG_ARM64_VHE=y option to use this feature.
If the feature is present on the boot CPU but not on a late CPU, then
the late CPU will be parked. Also, if the boot CPU does not have
address auth and the late CPU has then the late CPU will still boot
but with the feature disabled. On such a system, this option should
not be selected.
endmenu
menu "ARMv8.5 architectural features"

9
arch/arm64/include/asm/cpufeature.h
View File

@ -291,6 +291,15 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE \
(ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PANIC_ON_CONFLICT)
/*
* CPU feature used early in the boot based on the boot CPU. It is safe for a
* late CPU to have this feature even though the boot CPU hasn't enabled it,
* although the feature will not be used by Linux in this case. If the boot CPU
* has enabled this feature already, then every late CPU must have it.
*/
#define ARM64_CPUCAP_BOOT_CPU_FEATURE \
(ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
struct arm64_cpu_capabilities {
const char *desc;
u16 capability;

13
arch/arm64/kernel/cpufeature.c
View File

@ -1318,12 +1318,6 @@ static void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused)
#endif /* CONFIG_ARM64_RAS_EXTN */
#ifdef CONFIG_ARM64_PTR_AUTH
static void cpu_enable_address_auth(struct arm64_cpu_capabilities const *cap)
{
sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
SCTLR_ELx_ENDA | SCTLR_ELx_ENDB);
}
static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
int __unused)
{
@ -1627,7 +1621,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
{
.desc = "Address authentication (architected algorithm)",
.capability = ARM64_HAS_ADDRESS_AUTH_ARCH,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
.sys_reg = SYS_ID_AA64ISAR1_EL1,
.sign = FTR_UNSIGNED,
.field_pos = ID_AA64ISAR1_APA_SHIFT,
@ -1637,7 +1631,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
{
.desc = "Address authentication (IMP DEF algorithm)",
.capability = ARM64_HAS_ADDRESS_AUTH_IMP_DEF,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
.sys_reg = SYS_ID_AA64ISAR1_EL1,
.sign = FTR_UNSIGNED,
.field_pos = ID_AA64ISAR1_API_SHIFT,
@ -1646,9 +1640,8 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
},
{
.capability = ARM64_HAS_ADDRESS_AUTH,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
.matches = has_address_auth,
.cpu_enable = cpu_enable_address_auth,
},
{
.desc = "Generic authentication (architected algorithm)",

31
arch/arm64/mm/proc.S
View File

@ -16,6 +16,7 @@
#include <asm/pgtable-hwdef.h>
#include <asm/cpufeature.h>
#include <asm/alternative.h>
#include <asm/smp.h>
#ifdef CONFIG_ARM64_64K_PAGES
#define TCR_TG_FLAGS TCR_TG0_64K | TCR_TG1_64K
@ -468,9 +469,39 @@ SYM_FUNC_START(__cpu_setup)
1:
#endif /* CONFIG_ARM64_HW_AFDBM */
msr tcr_el1, x10
mov x1, x0
/*
* Prepare SCTLR
*/
mov_q x0, SCTLR_EL1_SET
#ifdef CONFIG_ARM64_PTR_AUTH
/* No ptrauth setup for run time cpus */
cmp x1, #ARM64_CPU_RUNTIME
b.eq 3f
/* Check if the CPU supports ptrauth */
mrs x2, id_aa64isar1_el1
ubfx x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8
cbz x2, 3f
msr_s SYS_APIAKEYLO_EL1, xzr
msr_s SYS_APIAKEYHI_EL1, xzr
/* Just enable ptrauth for primary cpu */
cmp x1, #ARM64_CPU_BOOT_PRIMARY
b.eq 2f
/* if !system_supports_address_auth() then skip enable */
alternative_if_not ARM64_HAS_ADDRESS_AUTH
b 3f
alternative_else_nop_endif
2: /* Enable ptrauth instructions */
ldr x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
SCTLR_ELx_ENDA | SCTLR_ELx_ENDB
orr x0, x0, x2
3:
#endif
ret // return to head.S
SYM_FUNC_END(__cpu_setup)