From cc0967490c1c3824bc5b75718b6ca8a51d9f2617 Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Thu, 28 Jan 2010 17:04:42 -0600 Subject: [PATCH] x86, hw_breakpoints, kgdb: Fix kgdb to use hw_breakpoint API In the 2.6.33 kernel, the hw_breakpoint API is now used for the performance event counters. The hw_breakpoint_handler() now consumes the hw breakpoints that were previously set by kgdb arch specific code. In order for kgdb to work in conjunction with this core API change, kgdb must use some of the low level functions of the hw_breakpoint API to install, uninstall, and deal with hw breakpoint reservations. The kgdb core required a change to call kgdb_disable_hw_debug anytime a slave cpu enters kgdb_wait() in order to keep all the hw breakpoints in sync as well as to prevent hitting a hw breakpoint while kgdb is active. During the architecture specific initialization of kgdb, it will pre-allocate 4 disabled (struct perf event **) structures. Kgdb will use these to manage the capabilities for the 4 hw breakpoint registers, per cpu. Right now the hw_breakpoint API does not have a way to ask how many breakpoints are available, on each CPU so it is possible that the install of a breakpoint might fail when kgdb restores the system to the run state. The intent of this patch is to first get the basic functionality of hw breakpoints working and leave it to the person debugging the kernel to understand what hw breakpoints are in use and what restrictions have been imposed as a result. Breakpoint constraints will be dealt with in a future patch. While atomic, the x86 specific kgdb code will call arch_uninstall_hw_breakpoint() and arch_install_hw_breakpoint() to manage the cpu specific hw breakpoints. The net result of these changes allow kgdb to use the same pool of hw_breakpoints that are used by the perf event API, but neither knows about future reservations for the available hw breakpoint slots. Signed-off-by: Jason Wessel Acked-by: Frederic Weisbecker Cc: kgdb-bugreport@lists.sourceforge.net Cc: K.Prasad Cc: Peter Zijlstra Cc: Alan Stern Cc: torvalds@linux-foundation.org LKML-Reference: <1264719883-7285-2-git-send-email-jason.wessel@windriver.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/kgdb.c | 171 +++++++++++++++++++++++++++-------------- kernel/kgdb.c | 3 + 2 files changed, 117 insertions(+), 57 deletions(-) diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c index dd74fe7273b1..62bea7307eaa 100644 --- a/arch/x86/kernel/kgdb.c +++ b/arch/x86/kernel/kgdb.c @@ -42,6 +42,7 @@ #include #include #include +#include #include #include @@ -204,40 +205,38 @@ void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs) static struct hw_breakpoint { unsigned enabled; - unsigned type; - unsigned len; unsigned long addr; + int len; + int type; + struct perf_event **pev; } breakinfo[4]; static void kgdb_correct_hw_break(void) { - unsigned long dr7; - int correctit = 0; - int breakbit; int breakno; - get_debugreg(dr7, 7); for (breakno = 0; breakno < 4; breakno++) { - breakbit = 2 << (breakno << 1); - if (!(dr7 & breakbit) && breakinfo[breakno].enabled) { - correctit = 1; - dr7 |= breakbit; - dr7 &= ~(0xf0000 << (breakno << 2)); - dr7 |= ((breakinfo[breakno].len << 2) | - breakinfo[breakno].type) << - ((breakno << 2) + 16); - set_debugreg(breakinfo[breakno].addr, breakno); - - } else { - if ((dr7 & breakbit) && !breakinfo[breakno].enabled) { - correctit = 1; - dr7 &= ~breakbit; - dr7 &= ~(0xf0000 << (breakno << 2)); - } - } + struct perf_event *bp; + struct arch_hw_breakpoint *info; + int val; + int cpu = raw_smp_processor_id(); + if (!breakinfo[breakno].enabled) + continue; + bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu); + info = counter_arch_bp(bp); + if (bp->attr.disabled != 1) + continue; + bp->attr.bp_addr = breakinfo[breakno].addr; + bp->attr.bp_len = breakinfo[breakno].len; + bp->attr.bp_type = breakinfo[breakno].type; + info->address = breakinfo[breakno].addr; + info->len = breakinfo[breakno].len; + info->type = breakinfo[breakno].type; + val = arch_install_hw_breakpoint(bp); + if (!val) + bp->attr.disabled = 0; } - if (correctit) - set_debugreg(dr7, 7); + hw_breakpoint_restore(); } static int @@ -259,15 +258,23 @@ kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) static void kgdb_remove_all_hw_break(void) { int i; + int cpu = raw_smp_processor_id(); + struct perf_event *bp; - for (i = 0; i < 4; i++) - memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint)); + for (i = 0; i < 4; i++) { + if (!breakinfo[i].enabled) + continue; + bp = *per_cpu_ptr(breakinfo[i].pev, cpu); + if (bp->attr.disabled == 1) + continue; + arch_uninstall_hw_breakpoint(bp); + bp->attr.disabled = 1; + } } static int kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) { - unsigned type; int i; for (i = 0; i < 4; i++) @@ -278,27 +285,38 @@ kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) switch (bptype) { case BP_HARDWARE_BREAKPOINT: - type = 0; - len = 1; + len = 1; + breakinfo[i].type = X86_BREAKPOINT_EXECUTE; break; case BP_WRITE_WATCHPOINT: - type = 1; + breakinfo[i].type = X86_BREAKPOINT_WRITE; break; case BP_ACCESS_WATCHPOINT: - type = 3; + breakinfo[i].type = X86_BREAKPOINT_RW; break; default: return -1; } - - if (len == 1 || len == 2 || len == 4) - breakinfo[i].len = len - 1; - else + switch (len) { + case 1: + breakinfo[i].len = X86_BREAKPOINT_LEN_1; + break; + case 2: + breakinfo[i].len = X86_BREAKPOINT_LEN_2; + break; + case 4: + breakinfo[i].len = X86_BREAKPOINT_LEN_4; + break; +#ifdef CONFIG_X86_64 + case 8: + breakinfo[i].len = X86_BREAKPOINT_LEN_8; + break; +#endif + default: return -1; - - breakinfo[i].enabled = 1; + } breakinfo[i].addr = addr; - breakinfo[i].type = type; + breakinfo[i].enabled = 1; return 0; } @@ -313,8 +331,21 @@ kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) */ void kgdb_disable_hw_debug(struct pt_regs *regs) { + int i; + int cpu = raw_smp_processor_id(); + struct perf_event *bp; + /* Disable hardware debugging while we are in kgdb: */ set_debugreg(0UL, 7); + for (i = 0; i < 4; i++) { + if (!breakinfo[i].enabled) + continue; + bp = *per_cpu_ptr(breakinfo[i].pev, cpu); + if (bp->attr.disabled == 1) + continue; + arch_uninstall_hw_breakpoint(bp); + bp->attr.disabled = 1; + } } /** @@ -378,7 +409,6 @@ int kgdb_arch_handle_exception(int e_vector, int signo, int err_code, struct pt_regs *linux_regs) { unsigned long addr; - unsigned long dr6; char *ptr; int newPC; @@ -404,20 +434,6 @@ int kgdb_arch_handle_exception(int e_vector, int signo, int err_code, raw_smp_processor_id()); } - get_debugreg(dr6, 6); - if (!(dr6 & 0x4000)) { - int breakno; - - for (breakno = 0; breakno < 4; breakno++) { - if (dr6 & (1 << breakno) && - breakinfo[breakno].type == 0) { - /* Set restore flag: */ - linux_regs->flags |= X86_EFLAGS_RF; - break; - } - } - } - set_debugreg(0UL, 6); kgdb_correct_hw_break(); return 0; @@ -485,8 +501,7 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd) break; case DIE_DEBUG: - if (atomic_read(&kgdb_cpu_doing_single_step) == - raw_smp_processor_id()) { + if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { if (user_mode(regs)) return single_step_cont(regs, args); break; @@ -539,7 +554,42 @@ static struct notifier_block kgdb_notifier = { */ int kgdb_arch_init(void) { - return register_die_notifier(&kgdb_notifier); + int i, cpu; + int ret; + struct perf_event_attr attr; + struct perf_event **pevent; + + ret = register_die_notifier(&kgdb_notifier); + if (ret != 0) + return ret; + /* + * Pre-allocate the hw breakpoint structions in the non-atomic + * portion of kgdb because this operation requires mutexs to + * complete. + */ + attr.bp_addr = (unsigned long)kgdb_arch_init; + attr.type = PERF_TYPE_BREAKPOINT; + attr.bp_len = HW_BREAKPOINT_LEN_1; + attr.bp_type = HW_BREAKPOINT_W; + attr.disabled = 1; + for (i = 0; i < 4; i++) { + breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL); + if (IS_ERR(breakinfo[i].pev)) { + printk(KERN_ERR "kgdb: Could not allocate hw breakpoints\n"); + breakinfo[i].pev = NULL; + kgdb_arch_exit(); + return -1; + } + for_each_online_cpu(cpu) { + pevent = per_cpu_ptr(breakinfo[i].pev, cpu); + pevent[0]->hw.sample_period = 1; + if (pevent[0]->destroy != NULL) { + pevent[0]->destroy = NULL; + release_bp_slot(*pevent); + } + } + } + return ret; } /** @@ -550,6 +600,13 @@ int kgdb_arch_init(void) */ void kgdb_arch_exit(void) { + int i; + for (i = 0; i < 4; i++) { + if (breakinfo[i].pev) { + unregister_wide_hw_breakpoint(breakinfo[i].pev); + breakinfo[i].pev = NULL; + } + } unregister_die_notifier(&kgdb_notifier); } diff --git a/kernel/kgdb.c b/kernel/kgdb.c index 2eb517e23514..c7ade62e4ef0 100644 --- a/kernel/kgdb.c +++ b/kernel/kgdb.c @@ -583,6 +583,9 @@ static void kgdb_wait(struct pt_regs *regs) smp_wmb(); atomic_set(&cpu_in_kgdb[cpu], 1); + /* Disable any cpu specific hw breakpoints */ + kgdb_disable_hw_debug(regs); + /* Wait till primary CPU is done with debugging */ while (atomic_read(&passive_cpu_wait[cpu])) cpu_relax(); -- 2.20.1