iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arm64: mte: avoid TFSRE0_EL1 related operations unless in async mode

Browse Source 
There is no reason to touch TFSRE0_EL1 nor issue a DSB unless our task
is in asynchronous mode. Since these operations (especially the DSB) may
be expensive on certain microarchitectures, only perform them if
necessary.

Furthermore, stop clearing TFSRE0_EL1 on entry because it will be
cleared on exit and it is not necessary to have any particular value in
TFSRE0_EL1 between entry and exit.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ib353a63e3d0abc2b0b008e96aa2d9692cfc1b815
Link: https://lore.kernel.org/r/20210709023532.2133673-1-pcc@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Peter Collingbourne 2021-07-08 19:35:32 -07:00 committed by Catalin Marinas
parent ff1176468d
commit 42b6b10a54
1 changed files with 19 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
arch/arm64/kernel/entry.S
View File

@ -133,29 +133,37 @@ alternative_cb_end
.endm
/* Check for MTE asynchronous tag check faults */
.macro check_mte_async_tcf, tmp, ti_flags
.macro check_mte_async_tcf, tmp, ti_flags, thread_sctlr
#ifdef CONFIG_ARM64_MTE
.arch_extension lse
alternative_if_not ARM64_MTE
b 1f
alternative_else_nop_endif
/*
* Asynchronous tag check faults are only possible in ASYNC (2) or
* ASYM (3) modes. In each of these modes bit 1 of SCTLR_EL1.TCF0 is
* set, so skip the check if it is unset.
*/
tbz \thread_sctlr, #(SCTLR_EL1_TCF0_SHIFT + 1), 1f
mrs_s \tmp, SYS_TFSRE0_EL1
tbz \tmp, #SYS_TFSR_EL1_TF0_SHIFT, 1f
/* Asynchronous TCF occurred for TTBR0 access, set the TI flag */
mov \tmp, #_TIF_MTE_ASYNC_FAULT
add \ti_flags, tsk, #TSK_TI_FLAGS
stset \tmp, [\ti_flags]
msr_s SYS_TFSRE0_EL1, xzr
1:
#endif
.endm
/* Clear the MTE asynchronous tag check faults */
.macro clear_mte_async_tcf
.macro clear_mte_async_tcf thread_sctlr
#ifdef CONFIG_ARM64_MTE
alternative_if ARM64_MTE
/* See comment in check_mte_async_tcf above. */
tbz \thread_sctlr, #(SCTLR_EL1_TCF0_SHIFT + 1), 1f
dsb ish
msr_s SYS_TFSRE0_EL1, xzr
1:
alternative_else_nop_endif
#endif
.endm
@ -231,8 +239,8 @@ alternative_else_nop_endif
disable_step_tsk x19, x20
/* Check for asynchronous tag check faults in user space */
check_mte_async_tcf x22, x23
apply_ssbd 1, x22, x23
ldr x0, [tsk, THREAD_SCTLR_USER]
check_mte_async_tcf x22, x23, x0
#ifdef CONFIG_ARM64_PTR_AUTH
alternative_if ARM64_HAS_ADDRESS_AUTH
@ -245,7 +253,6 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
* was disabled on kernel exit then we would have left the kernel IA
* installed so there is no need to install it again.
*/
ldr x0, [tsk, THREAD_SCTLR_USER]
tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f
__ptrauth_keys_install_kernel_nosync tsk, x20, x22, x23
b 2f
@ -258,6 +265,8 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
alternative_else_nop_endif
#endif
apply_ssbd 1, x22, x23
mte_set_kernel_gcr x22, x23
scs_load tsk
@ -362,6 +371,10 @@ alternative_else_nop_endif
3:
scs_save tsk
/* Ignore asynchronous tag check faults in the uaccess routines */
ldr x0, [tsk, THREAD_SCTLR_USER]
clear_mte_async_tcf x0
#ifdef CONFIG_ARM64_PTR_AUTH
alternative_if ARM64_HAS_ADDRESS_AUTH
/*
@ -371,7 +384,6 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
*
* No kernel C function calls after this.
*/
ldr x0, [tsk, THREAD_SCTLR_USER]
tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f
__ptrauth_keys_install_user tsk, x0, x1, x2
b 2f
@ -599,8 +611,6 @@ SYM_CODE_START_LOCAL(ret_to_user)
cbnz x2, work_pending
finish_ret_to_user:
user_enter_irqoff
/* Ignore asynchronous tag check faults in the uaccess routines */
clear_mte_async_tcf
enable_step_tsk x19, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
bl stackleak_erase