From 13d543cd79963133cd26748547552c99df8d23a7 Mon Sep 17 00:00:00 2001 From: Bharat Bhushan Date: Wed, 22 May 2013 09:50:59 +0530 Subject: [PATCH] powerpc: Restore dbcr0 on user space exit On BookE (Branch taken + Single Step) is as same as Branch Taken on BookS and in Linux we simulate BookS behavior for BookE as well. When doing so, in Branch taken handling we want to set DBCR0_IC but we update the current->thread->dbcr0 and not DBCR0. Now on 64bit the current->thread.dbcr0 (and other debug registers) is synchronized ONLY on context switch flow. But after handling Branch taken in debug exception if we return back to user space without context switch then single stepping change (DBCR0_ICMP) does not get written in h/w DBCR0 and Instruction Complete exception does not happen. This fixes using ptrace reliably on BookE-PowerPC lmbench latency test (lat_syscall) Results are (they varies a little on each run) 1) ./lat_syscall /dev/shm/uImage action: Open read write stat fstat null Before: 3.8618 0.2017 0.2851 1.6789 0.2256 0.0856 After: 3.8580 0.2017 0.2851 1.6955 0.2255 0.0856 1) ./lat_syscall -P 2 -N 10 /dev/shm/uImage action: Open read write stat fstat null Before: 4.1388 0.2238 0.3066 1.7106 0.2256 0.0856 After: 4.1413 0.2236 0.3062 1.7107 0.2256 0.0856 [ Slightly modified to avoid extra branch in the fast path on Book3S and fix build on all non-BookE 64-bit -- BenH ] Signed-off-by: Bharat Bhushan Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/asm-offsets.c | 6 +++--- arch/powerpc/kernel/entry_64.S | 30 ++++++++++++++++++++++++++---- 2 files changed, 29 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 6f16ffa..dc684b1 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -105,9 +105,6 @@ int main(void) DEFINE(KSP_VSID, offsetof(struct thread_struct, ksp_vsid)); #else /* CONFIG_PPC64 */ DEFINE(PGDIR, offsetof(struct thread_struct, pgdir)); -#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) - DEFINE(THREAD_DBCR0, offsetof(struct thread_struct, dbcr0)); -#endif #ifdef CONFIG_SPE DEFINE(THREAD_EVR0, offsetof(struct thread_struct, evr[0])); DEFINE(THREAD_ACC, offsetof(struct thread_struct, acc)); @@ -115,6 +112,9 @@ int main(void) DEFINE(THREAD_USED_SPE, offsetof(struct thread_struct, used_spe)); #endif /* CONFIG_SPE */ #endif /* CONFIG_PPC64 */ +#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) + DEFINE(THREAD_DBCR0, offsetof(struct thread_struct, dbcr0)); +#endif #ifdef CONFIG_KVM_BOOK3S_32_HANDLER DEFINE(THREAD_KVM_SVCPU, offsetof(struct thread_struct, kvm_shadow_vcpu)); #endif diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 8741c85..ab15b8d 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -629,21 +629,43 @@ _GLOBAL(ret_from_except_lite) CURRENT_THREAD_INFO(r9, r1) ld r3,_MSR(r1) +#ifdef CONFIG_PPC_BOOK3E + ld r10,PACACURRENT(r13) +#endif /* CONFIG_PPC_BOOK3E */ ld r4,TI_FLAGS(r9) andi. r3,r3,MSR_PR beq resume_kernel +#ifdef CONFIG_PPC_BOOK3E + lwz r3,(THREAD+THREAD_DBCR0)(r10) +#endif /* CONFIG_PPC_BOOK3E */ /* Check current_thread_info()->flags */ andi. r0,r4,_TIF_USER_WORK_MASK +#ifdef CONFIG_PPC_BOOK3E + bne 1f + /* + * Check to see if the dbcr0 register is set up to debug. + * Use the internal debug mode bit to do this. + */ + andis. r0,r3,DBCR0_IDM@h beq restore - - andi. r0,r4,_TIF_NEED_RESCHED - beq 1f + mfmsr r0 + rlwinm r0,r0,0,~MSR_DE /* Clear MSR.DE */ + mtmsr r0 + mtspr SPRN_DBCR0,r3 + li r10, -1 + mtspr SPRN_DBSR,r10 + b restore +#else + beq restore +#endif +1: andi. r0,r4,_TIF_NEED_RESCHED + beq 2f bl .restore_interrupts SCHEDULE_USER b .ret_from_except_lite -1: bl .save_nvgprs +2: bl .save_nvgprs bl .restore_interrupts addi r3,r1,STACK_FRAME_OVERHEAD bl .do_notify_resume -- 2.7.4