From: Ard Biesheuvel Date: Sat, 18 Sep 2021 08:44:37 +0000 (+0200) Subject: ARM: smp: Store current pointer in TPIDRURO register if available X-Git-Tag: v6.1-rc5~2761^2^2~2^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=50596b7559bf226bb35ad55855ee979453ec06a1;p=platform%2Fkernel%2Flinux-starfive.git ARM: smp: Store current pointer in TPIDRURO register if available Now that the user space TLS register is assigned on every return to user space, we can use it to keep the 'current' pointer while running in the kernel. This removes the need to access it via thread_info, which is located at the base of the stack, but will be moved out of there in a subsequent patch. Use the __builtin_thread_pointer() helper when available - this will help GCC understand that reloading the value within the same function is not necessary, even when using the per-task stack protector (which also generates accesses via the TLS register). For example, the generated code below loads TPIDRURO only once, and uses it to access both the stack canary and the preempt_count fields. : e92d 41f0 stmdb sp!, {r4, r5, r6, r7, r8, lr} ee1d 4f70 mrc 15, 0, r4, cr13, cr0, {3} 4606 mov r6, r0 b094 sub sp, #80 ; 0x50 f8d4 34e8 ldr.w r3, [r4, #1256] ; 0x4e8 <- stack canary 9313 str r3, [sp, #76] ; 0x4c f8d4 8004 ldr.w r8, [r4, #4] <- preempt count Co-developed-by: Keith Packard Signed-off-by: Keith Packard Signed-off-by: Ard Biesheuvel Reviewed-by: Linus Walleij Tested-by: Amit Daniel Kachhap --- diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index ff3e64a..cd195e6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1157,6 +1157,11 @@ config SMP_ON_UP If you don't know what to do here, say Y. + +config CURRENT_POINTER_IN_TPIDRURO + def_bool y + depends on SMP && CPU_32v6K && !CPU_V6 + config ARM_CPU_TOPOLOGY bool "Support cpu topology definition" depends on SMP && CPU_V7 diff --git a/arch/arm/Makefile b/arch/arm/Makefile index b46e673..1c54015 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -113,6 +113,10 @@ ifeq ($(CONFIG_CC_IS_CLANG),y) CFLAGS_ABI += -meabi gnu endif +ifeq ($(CONFIG_CURRENT_POINTER_IN_TPIDRURO),y) +CFLAGS_ABI += -mtp=cp15 +endif + # Accept old syntax despite ".syntax unified" AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W) diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index e2b1fd5..c1551de 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -199,6 +199,30 @@ .endm .endr + .macro get_current, rd +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + mrc p15, 0, \rd, c13, c0, 3 @ get TPIDRURO register +#else + get_thread_info \rd + ldr \rd, [\rd, #TI_TASK] +#endif + .endm + + .macro set_current, rn +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + mcr p15, 0, \rn, c13, c0, 3 @ set TPIDRURO register +#endif + .endm + + .macro reload_current, t1:req, t2:req +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + adr_l \t1, __entry_task @ get __entry_task base address + mrc p15, 0, \t2, c13, c0, 4 @ get per-CPU offset + ldr \t1, [\t1, \t2] @ load variable + mcr p15, 0, \t1, c13, c0, 3 @ store in TPIDRURO +#endif + .endm + /* * Get current thread_info. */ diff --git a/arch/arm/include/asm/current.h b/arch/arm/include/asm/current.h new file mode 100644 index 0000000..1d472fa --- /dev/null +++ b/arch/arm/include/asm/current.h @@ -0,0 +1,50 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2021 Keith Packard + * Copyright (c) 2021 Google, LLC + */ + +#ifndef _ASM_ARM_CURRENT_H +#define _ASM_ARM_CURRENT_H + +#ifndef __ASSEMBLY__ + +struct task_struct; + +static inline void set_current(struct task_struct *cur) +{ + if (!IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO)) + return; + + /* Set TPIDRURO */ + asm("mcr p15, 0, %0, c13, c0, 3" :: "r"(cur) : "memory"); +} + +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + +static inline struct task_struct *get_current(void) +{ + struct task_struct *cur; + +#if __has_builtin(__builtin_thread_pointer) + /* + * Use the __builtin helper when available - this results in better + * code, especially when using GCC in combination with the per-task + * stack protector, as the compiler will recognize that it needs to + * load the TLS register only once in every function. + */ + cur = __builtin_thread_pointer(); +#else + asm("mrc p15, 0, %0, c13, c0, 3" : "=r"(cur)); +#endif + return cur; +} + +#define current get_current() +#else +#include +#endif /* CONFIG_CURRENT_POINTER_IN_TPIDRURO */ + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_ARM_CURRENT_H */ diff --git a/arch/arm/include/asm/switch_to.h b/arch/arm/include/asm/switch_to.h index 007d8fe..61e4a3c 100644 --- a/arch/arm/include/asm/switch_to.h +++ b/arch/arm/include/asm/switch_to.h @@ -26,6 +26,8 @@ extern struct task_struct *__switch_to(struct task_struct *, struct thread_info #define switch_to(prev,next,last) \ do { \ __complete_pending_tlbi(); \ + if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO)) \ + __this_cpu_write(__entry_task, next); \ last = __switch_to(prev,task_thread_info(prev), task_thread_info(next)); \ } while (0) diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index f0cacc7..76b6fbd5 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -29,6 +29,8 @@ struct task_struct; +DECLARE_PER_CPU(struct task_struct *, __entry_task); + #include struct cpu_context_save { diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 241b73d..7263a45 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -384,6 +384,8 @@ ENDPROC(__fiq_abt) ATRAP( teq r8, r7) ATRAP( mcrne p15, 0, r8, c1, c0, 0) + reload_current r7, r8 + @ @ Clear FP to mark the first stack frame @ @@ -762,6 +764,8 @@ ENTRY(__switch_to) add r7, r7, #TSK_STACK_CANARY & ~IMM12_MASK .endif ldr r7, [r7, #TSK_STACK_CANARY & IMM12_MASK] +#elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) + ldr r7, [r2, #TI_TASK] #endif #ifdef CONFIG_CPU_USE_DOMAINS mcr p15, 0, r6, c3, c0, 0 @ Set domain register @@ -776,6 +780,7 @@ ENTRY(__switch_to) #endif THUMB( mov ip, r4 ) mov r0, r5 + set_current r7 ARM( ldmia r4, {r4 - sl, fp, sp, pc} ) @ Load all regs saved previously THUMB( ldmia ip!, {r4 - sl, fp} ) @ Load all regs saved previously THUMB( ldr sp, [ip], #4 ) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index d9c99db..ac86c34 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -170,6 +170,7 @@ ENTRY(vector_swi) str saved_psr, [sp, #S_PSR] @ Save CPSR str r0, [sp, #S_OLD_R0] @ Save OLD_R0 #endif + reload_current r10, ip zero_fp alignment_trap r10, ip, __cr_alignment asm_trace_hardirqs_on save=0 diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S index 29b2eda..da18e0a 100644 --- a/arch/arm/kernel/head-common.S +++ b/arch/arm/kernel/head-common.S @@ -105,6 +105,11 @@ __mmap_switched: mov r1, #0 bl __memset @ clear .bss +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + adr_l r0, init_task @ get swapper task_struct + set_current r0 +#endif + ldmia r4, {r0, r1, r2, r3} str r9, [r0] @ Save processor ID str r7, [r1] @ Save machine type diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index cd73c21..30428d7 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -36,6 +36,10 @@ #include "signal.h" +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO +DEFINE_PER_CPU(struct task_struct *, __entry_task); +#endif + #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) #include unsigned long __stack_chk_guard __read_mostly; diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 8979d54..97ee6b1 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -409,6 +409,8 @@ asmlinkage void secondary_start_kernel(struct task_struct *task) struct mm_struct *mm = &init_mm; unsigned int cpu; + set_current(task); + secondary_biglittle_init(); /* diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S index e2c743a..d48ba99 100644 --- a/arch/arm/mm/proc-macros.S +++ b/arch/arm/mm/proc-macros.S @@ -30,8 +30,7 @@ * act_mm - get current->active_mm */ .macro act_mm, rd - get_thread_info \rd - ldr \rd, [\rd, #TI_TASK] + get_current \rd .if (TSK_ACTIVE_MM > IMM12_MASK) add \rd, \rd, #TSK_ACTIVE_MM & ~IMM12_MASK .endif