From patchwork Fri May 29 07:26:38 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Herrenschmidt X-Patchwork-Id: 27821 Return-Path: X-Original-To: patchwork-incoming@bilbo.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from ozlabs.org (ozlabs.org [203.10.76.45]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.ozlabs.org", Issuer "CA Cert Signing Authority" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id DC619B7080 for ; Fri, 29 May 2009 17:27:13 +1000 (EST) Received: by ozlabs.org (Postfix) id 4C9DDDE01B; Fri, 29 May 2009 17:26:58 +1000 (EST) Delivered-To: patchwork-incoming@ozlabs.org Received: from ozlabs.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 4913CDDFD2 for ; Fri, 29 May 2009 17:26:58 +1000 (EST) X-Original-To: linuxppc-dev@ozlabs.org Delivered-To: linuxppc-dev@ozlabs.org Received: by ozlabs.org (Postfix, from userid 1030) id 7797ADDF84; Fri, 29 May 2009 17:26:44 +1000 (EST) To: From: Benjamin Herrenschmidt Date: Fri, 29 May 2009 17:26:38 +1000 Subject: [RFC/PATCH] powerpc: Add PTRACE_SINGLEBLOCK support Message-Id: <20090529072644.7797ADDF84@ozlabs.org> Cc: roland@redhat.com X-BeenThere: linuxppc-dev@ozlabs.org X-Mailman-Version: 2.1.11 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@ozlabs.org From: Roland McGrath Reworked by: Benjamin Herrenschmidt This adds block-step support on powerpc, including a PTRACE_SINGLEBLOCK request for ptrace. The BookE implementation is tweaked to fire a single step after a block step in order to mimmic the server behaviour. Signed-off-by: Roland McGrath --- WARNING: There is a difference between the BookE implementations (that use DBCR0:BT) and the "classic" implementations (that use MSR:BE). The former will stop -on- the branch that is about to be taken without actually taking it, while the later will stop on the -target- of the branch. The BookE variant is superior in some ways as it allows to know where you come from on branches. But that also means that the semantics exposed to user space would not be consistent which is BAD (tm). I'm not sure what the right approach is. For now, I've made BookE mimmic server by automatically firing a single step right after the blockstep from the kernel, so the semantics exposed to userspace are identical, but that mean we do lose some information in the BookE case that would have otherwise been available (the branch origin). Now, some server processors do provide it via an SPR, but I don't know if we can retrieve it, because I think it could be clobbered by the act of taking the debug interrupt ... non trivial. Roland, what do you think is the right approach ? This patch ? arch/powerpc/include/asm/ptrace.h | 4 ++++ arch/powerpc/kernel/head_booke.h | 10 +++++----- arch/powerpc/kernel/ptrace.c | 23 +++++++++++++++++++++-- arch/powerpc/kernel/traps.c | 34 ++++++++++++++++++++++++++++++---- 4 files changed, 60 insertions(+), 11 deletions(-) --- linux-work.orig/arch/powerpc/include/asm/ptrace.h 2009-02-05 16:22:24.000000000 +1100 +++ linux-work/arch/powerpc/include/asm/ptrace.h 2009-05-29 14:53:39.000000000 +1000 @@ -135,7 +135,9 @@ do { \ * These are defined as per linux/ptrace.h, which see. */ #define arch_has_single_step() (1) +#define arch_has_block_step() (!cpu_has_feature(CPU_FTR_601)) extern void user_enable_single_step(struct task_struct *); +extern void user_enable_block_step(struct task_struct *); extern void user_disable_single_step(struct task_struct *); #endif /* __ASSEMBLY__ */ @@ -288,4 +290,6 @@ extern void user_disable_single_step(str #define PPC_PTRACE_PEEKUSR_3264 0x91 #define PPC_PTRACE_POKEUSR_3264 0x90 +#define PTRACE_SINGLEBLOCK 0x100 /* resume execution until next branch */ + #endif /* _ASM_POWERPC_PTRACE_H */ Index: linux-work/arch/powerpc/kernel/ptrace.c =================================================================== --- linux-work.orig/arch/powerpc/kernel/ptrace.c 2009-02-05 16:22:25.000000000 +1100 +++ linux-work/arch/powerpc/kernel/ptrace.c 2009-05-29 14:31:15.000000000 +1000 @@ -704,15 +704,34 @@ void user_enable_single_step(struct task if (regs != NULL) { #if defined(CONFIG_40x) || defined(CONFIG_BOOKE) + task->thread.dbcr0 &= ~DBCR0_BT; task->thread.dbcr0 |= DBCR0_IDM | DBCR0_IC; regs->msr |= MSR_DE; #else + regs->msr &= ~MSR_BE; regs->msr |= MSR_SE; #endif } set_tsk_thread_flag(task, TIF_SINGLESTEP); } +void user_enable_block_step(struct task_struct *task) +{ + struct pt_regs *regs = task->thread.regs; + + if (regs != NULL) { +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE) + task->thread.dbcr0 &= ~DBCR0_IC; + task->thread.dbcr0 = DBCR0_IDM | DBCR0_BT; + regs->msr |= MSR_DE; +#else + regs->msr &= ~MSR_SE; + regs->msr |= MSR_BE; +#endif + } + set_tsk_thread_flag(task, TIF_SINGLESTEP); +} + void user_disable_single_step(struct task_struct *task) { struct pt_regs *regs = task->thread.regs; @@ -726,10 +745,10 @@ void user_disable_single_step(struct tas if (regs != NULL) { #if defined(CONFIG_40x) || defined(CONFIG_BOOKE) - task->thread.dbcr0 &= ~(DBCR0_IC | DBCR0_IDM); + task->thread.dbcr0 &= ~(DBCR0_IC | DBCR0_BT | DBCR0_IDM); regs->msr &= ~MSR_DE; #else - regs->msr &= ~MSR_SE; + regs->msr &= ~(MSR_SE | MSR_BE); #endif } clear_tsk_thread_flag(task, TIF_SINGLESTEP); Index: linux-work/arch/powerpc/kernel/head_booke.h =================================================================== --- linux-work.orig/arch/powerpc/kernel/head_booke.h 2009-05-29 14:24:47.000000000 +1000 +++ linux-work/arch/powerpc/kernel/head_booke.h 2009-05-29 14:54:26.000000000 +1000 @@ -256,7 +256,7 @@ label: * off DE in the DSRR1 value and clearing the debug status. \ */ \ mfspr r10,SPRN_DBSR; /* check single-step/branch taken */ \ - andis. r10,r10,DBSR_IC@h; \ + andis. r10,r10,(DBSR_IC|DBSR_BT)@h; \ beq+ 2f; \ \ lis r10,KERNELBASE@h; /* check if exception in vectors */ \ @@ -271,7 +271,7 @@ label: \ /* here it looks like we got an inappropriate debug exception. */ \ 1: rlwinm r9,r9,0,~MSR_DE; /* clear DE in the CDRR1 value */ \ - lis r10,DBSR_IC@h; /* clear the IC event */ \ + lis r10,(DBSR_IC|DBSR_BT)@h; /* clear the IC event */ \ mtspr SPRN_DBSR,r10; \ /* restore state and get out */ \ lwz r10,_CCR(r11); \ @@ -309,7 +309,7 @@ label: * off DE in the CSRR1 value and clearing the debug status. \ */ \ mfspr r10,SPRN_DBSR; /* check single-step/branch taken */ \ - andis. r10,r10,DBSR_IC@h; \ + andis. r10,r10,(DBSR_IC|DBSR_BT)@h; \ beq+ 2f; \ \ lis r10,KERNELBASE@h; /* check if exception in vectors */ \ @@ -317,14 +317,14 @@ label: cmplw r12,r10; \ blt+ 2f; /* addr below exception vectors */ \ \ - lis r10,DebugCrit@h; \ + lis r10,DebugCrit@h; \ ori r10,r10,DebugCrit@l; \ cmplw r12,r10; \ bgt+ 2f; /* addr above exception vectors */ \ \ /* here it looks like we got an inappropriate debug exception. */ \ 1: rlwinm r9,r9,0,~MSR_DE; /* clear DE in the CSRR1 value */ \ - lis r10,DBSR_IC@h; /* clear the IC event */ \ + lis r10,(DBSR_IC|DBSR_BT)@h; /* clear the IC event */ \ mtspr SPRN_DBSR,r10; \ /* restore state and get out */ \ lwz r10,_CCR(r11); \ Index: linux-work/arch/powerpc/kernel/traps.c =================================================================== --- linux-work.orig/arch/powerpc/kernel/traps.c 2009-05-29 14:32:06.000000000 +1000 +++ linux-work/arch/powerpc/kernel/traps.c 2009-05-29 17:02:35.000000000 +1000 @@ -1041,7 +1041,34 @@ void SoftwareEmulation(struct pt_regs *r void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status) { - if (debug_status & DBSR_IC) { /* instruction completion */ + /* Hack alert: On BookE, Branch Taken stops on the branch itself, while + * on server, it stops on the target of the branch. In order to simulate + * the server behaviour, we thus restart right away with a single step + * instead of stopping here when hitting a BT + */ + if (debug_status & DBSR_BT) { + regs->msr &= ~MSR_DE; + + /* Disable BT */ + mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~DBCR0_BT); + /* Clear the BT event */ + mtspr(SPRN_DBSR, DBSR_BT); + + /* Do the single step trick only when coming from userspace */ + if (user_mode(regs)) { + current->thread.dbcr0 &= ~DBCR0_BT; + current->thread.dbcr0 |= DBCR0_IDM | DBCR0_IC; + regs->msr |= MSR_DE; + return; + } + + if (notify_die(DIE_SSTEP, "block_step", regs, 5, + 5, SIGTRAP) == NOTIFY_STOP) { + return; + } + if (debugger_sstep(regs)) + return; + } else if (debug_status & DBSR_IC) { /* Instruction complete */ regs->msr &= ~MSR_DE; /* Disable instruction completion */ @@ -1057,9 +1084,8 @@ void __kprobes DebugException(struct pt_ if (debugger_sstep(regs)) return; - if (user_mode(regs)) { - current->thread.dbcr0 &= ~DBCR0_IC; - } + if (user_mode(regs)) + current->thread.dbcr0 &= ~(DBCR0_IC); _exception(SIGTRAP, regs, TRAP_TRACE, regs->nip); } else if (debug_status & (DBSR_DAC1R | DBSR_DAC1W)) {