From mboxrd@z Thu Jan 1 00:00:00 1970 From: zsm@chromium.org (Zubin Mithra) Date: Mon, 18 Jun 2018 08:30:50 -0700 Subject: [RFC v2 1/4] arm: Store address of thread_info in sp^ In-Reply-To: <20180618153053.186224-1-zsm@chromium.org> References: <20180618153053.186224-1-zsm@chromium.org> Message-ID: <20180618153053.186224-2-zsm@chromium.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org There is a need to store thread_info in a register so that subsequent patches can move thread_info into task_struct. This would also facilitate having separate IRQ stacks. Banked register sp is an unused scratch register in EL1 context. We can utilize this register for stashing the current thread_info. The macro save_ti_sp_usr is used to stash the address of thread_info into sp^. The macro get_thread_info is modified to retrieve thread_info from sp^. Additionally, upon context switch, sp^ is set to current's thread_info by using set_sp_usr. Signed-off-by: Zubin Mithra --- arch/arm/include/asm/assembler.h | 27 ++++++++++++++++++++++----- arch/arm/include/asm/switch_to.h | 11 +++++++++++ arch/arm/include/asm/thread_info.h | 14 ++++++++++++-- arch/arm/kernel/entry-armv.S | 5 ++++- arch/arm/kernel/entry-common.S | 2 ++ arch/arm/kernel/head-common.S | 2 ++ arch/arm/kernel/head.S | 1 + 7 files changed, 54 insertions(+), 8 deletions(-) diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index 0cd4dccbae78..be18a364f590 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -205,11 +205,28 @@ /* * Get current thread_info. */ - .macro get_thread_info, rd - ARM( mov \rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT ) - THUMB( mov \rd, sp ) - THUMB( lsr \rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT ) - mov \rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT + .macro get_thread_info, rd + sub sp, #4 + stm sp, {sp}^ + pop {\rd} + .endm + + .macro save_ti_sp_usr, tmp, restore=0 + .if \restore + push {\tmp} + .endif + + ARM( mov \tmp, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT ) + THUMB( mov \tmp, sp ) + THUMB( lsr \tmp, \tmp, #THREAD_SIZE_ORDER + PAGE_SHIFT ) + mov \tmp, \tmp, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT + push {\tmp} + ldm sp, {sp}^ + add sp, 4 + + .if \restore + pop {\tmp} + .endif .endm /* diff --git a/arch/arm/include/asm/switch_to.h b/arch/arm/include/asm/switch_to.h index d3e937dcee4d..5b4572f78cf4 100644 --- a/arch/arm/include/asm/switch_to.h +++ b/arch/arm/include/asm/switch_to.h @@ -16,6 +16,16 @@ #define __complete_pending_tlbi() #endif +static inline void set_sp_usr(unsigned long ti) +{ + asm volatile( + "push {%0}\n" + "ldm sp, {sp}^\n" + "add sp, #4\n" + :: "r"(ti) + ); +} + /* * switch_to(prev, next) should switch from task `prev' to `next' * `prev' will never be the same as `next'. schedule() itself @@ -27,6 +37,7 @@ extern struct task_struct *__switch_to(struct task_struct *, struct thread_info do { \ __complete_pending_tlbi(); \ last = __switch_to(prev,task_thread_info(prev), task_thread_info(next)); \ + set_sp_usr(current_stack_pointer & ~(THREAD_SIZE - 1)); \ } while (0) #endif /* __ASM_ARM_SWITCH_TO_H */ diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index e71cc35de163..4a351e0aba0e 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -80,6 +80,7 @@ struct thread_info { */ register unsigned long current_stack_pointer asm ("sp"); + /* * how to get the thread information struct from C */ @@ -87,8 +88,17 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__; static inline struct thread_info *current_thread_info(void) { - return (struct thread_info *) - (current_stack_pointer & ~(THREAD_SIZE - 1)); + unsigned long ti; + + asm volatile( + "sub sp, #4\n" + "stm sp, {sp}^\n" + "ldr %0, [sp]\n" + "add sp, #4\n" + : "=r" (ti) + ); + + return (struct thread_info *)ti; } #define thread_saved_pc(tsk) \ diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 179a9f6bd1e3..af79f9053530 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -181,7 +181,8 @@ ENDPROC(__und_invalid) @ stmia r7, {r2 - r6} - get_thread_info tsk + save_ti_sp_usr tsk restore=0 + ldr r0, [tsk, #TI_ADDR_LIMIT] mov r1, #TASK_SIZE str r1, [tsk, #TI_ADDR_LIMIT] @@ -411,6 +412,8 @@ ENDPROC(__fiq_abt) uaccess_disable ip .endif + save_ti_sp_usr tsk restore=0 + @ Enable the alignment trap while in kernel mode ATRAP( teq r8, r7) ATRAP( mcrne p15, 0, r8, c1, c0, 0) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 106a1466518d..0dbeaccebf62 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -149,6 +149,7 @@ ENDPROC(ret_to_user) * This is how we return from a fork. */ ENTRY(ret_from_fork) + save_ti_sp_usr tsk bl schedule_tail cmp r5, #0 movne r0, r4 @@ -185,6 +186,7 @@ ENTRY(vector_swi) asm_trace_hardirqs_on save=0 enable_irq_notrace ct_user_exit save=0 + save_ti_sp_usr tsk /* * Get the system call number. diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S index 6e0375e7db05..84e649144a32 100644 --- a/arch/arm/kernel/head-common.S +++ b/arch/arm/kernel/head-common.S @@ -109,6 +109,8 @@ __mmap_switched: mov r1, #0 bl memset @ clear .bss + save_ti_sp_usr r9 + ldmia r4, {r0, r1, r2, r3} str r9, [r0] @ Save processor ID str r7, [r1] @ Save machine type diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index 6b1148cafffd..66bba1b27d2c 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -418,6 +418,7 @@ ENDPROC(secondary_startup_arm) ENTRY(__secondary_switched) ldr sp, [r7, #12] @ get secondary_data.stack mov fp, #0 + save_ti_sp_usr r0 b secondary_start_kernel ENDPROC(__secondary_switched) -- 2.18.0.rc1.244.gcf134e6275-goog