diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2021-11-24 14:08:11 +0100 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2021-12-06 12:49:17 +0100 |
| commit | 9c46929e7989efacc1dd0a1dd662a839897ea2b6 (patch) | |
| tree | e55a231cce8f02eea3be6e7b19627c58bccdee52 /arch/arm/kernel/entry-armv.S | |
| parent | c2755910373bb5dfb9aa68ba2924036686815c9e (diff) | |
ARM: implement THREAD_INFO_IN_TASK for uniprocessor systems
On UP systems, only a single task can be 'current' at the same time,
which means we can use a global variable to track it. This means we can
also enable THREAD_INFO_IN_TASK for those systems, as in that case,
thread_info is accessed via current rather than the other way around,
removing the need to store thread_info at the base of the task stack.
This, in turn, permits us to enable IRQ stacks and vmap'ed stacks on UP
systems as well.
To partially mitigate the performance overhead of this arrangement, use
a ADD/ADD/LDR sequence with the appropriate PC-relative group
relocations to load the value of current when needed. This means that
accessing current will still only require a single load as before,
avoiding the need for a literal to carry the address of the global
variable in each function. However, accessing thread_info will now
require this load as well.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
Diffstat (limited to 'arch/arm/kernel/entry-armv.S')
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 43d917f0d9a9..b58bda51e4b8 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -807,12 +807,13 @@ ENTRY(__switch_to) switch_tls r1, r4, r5, r3, r7 #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) && \ !defined(CONFIG_STACKPROTECTOR_PER_TASK) - ldr r9, [r2, #TI_TASK] ldr r8, =__stack_chk_guard .if (TSK_STACK_CANARY > IMM12_MASK) - add r9, r9, #TSK_STACK_CANARY & ~IMM12_MASK - .endif + add r9, r2, #TSK_STACK_CANARY & ~IMM12_MASK ldr r9, [r9, #TSK_STACK_CANARY & IMM12_MASK] + .else + ldr r9, [r2, #TSK_STACK_CANARY & IMM12_MASK] + .endif #endif mov r7, r2 @ Preserve 'next' #ifdef CONFIG_CPU_USE_DOMAINS @@ -829,7 +830,7 @@ ENTRY(__switch_to) #endif mov r0, r5 #if !defined(CONFIG_THUMB2_KERNEL) && !defined(CONFIG_VMAP_STACK) - set_current r7 + set_current r7, r8 ldmia r4, {r4 - sl, fp, sp, pc} @ Load all regs saved previously #else mov r1, r7 @@ -851,7 +852,7 @@ ENTRY(__switch_to) @ switches us to another stack, with few other side effects. In order @ to prevent this distinction from causing any inconsistencies, let's @ keep the 'set_current' call as close as we can to the update of SP. - set_current r1 + set_current r1, r2 mov sp, ip ret lr #endif |