From 6f26aa05c9edffff6a4c2cd71774bc659a5cceec Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 2 Aug 2011 16:16:57 +0100 Subject: [PATCH] ARM: hw_breakpoint: add support for multiple watchpoints ARM debug architecture 7.1 mandates that the DFAR is updated on a watchpoint debug exception to contain the faulting virtual address of the memory access. This allows us to determine which watchpoints have fired and therefore report useful information to userspace. This patch adds support for using the DFAR in the watchpoint handler, which allows us to support multiple watchpoints on CPUs implementing the new debug architecture. Signed-off-by: Will Deacon --- arch/arm/include/asm/hw_breakpoint.h | 1 + arch/arm/kernel/hw_breakpoint.c | 102 +++++++++++++++++---------- 2 files changed, 67 insertions(+), 36 deletions(-) diff --git a/arch/arm/include/asm/hw_breakpoint.h b/arch/arm/include/asm/hw_breakpoint.h index 0ac141a87616..c190bc992f0e 100644 --- a/arch/arm/include/asm/hw_breakpoint.h +++ b/arch/arm/include/asm/hw_breakpoint.h @@ -58,6 +58,7 @@ static inline void decode_ctrl_reg(u32 reg, /* Watchpoints */ #define ARM_BREAKPOINT_LOAD 1 #define ARM_BREAKPOINT_STORE 2 +#define ARM_FSR_ACCESS_MASK (1 << 11) /* Privilege Levels */ #define ARM_BREAKPOINT_PRIV 1 diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 156b8af13571..448143e44b65 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -339,24 +339,10 @@ int arch_install_hw_breakpoint(struct perf_event *bp) val_base = ARM_BASE_BVR; slots = (struct perf_event **)__get_cpu_var(bp_on_reg); max_slots = core_num_brps; - if (info->step_ctrl.enabled) { - /* Override the breakpoint data with the step data. */ - addr = info->trigger & ~0x3; - ctrl = encode_ctrl_reg(info->step_ctrl); - } } else { /* Watchpoint */ - if (info->step_ctrl.enabled) { - /* Install into the reserved breakpoint region. */ - ctrl_base = ARM_BASE_BCR + core_num_brps; - val_base = ARM_BASE_BVR + core_num_brps; - /* Override the watchpoint data with the step data. */ - addr = info->trigger & ~0x3; - ctrl = encode_ctrl_reg(info->step_ctrl); - } else { - ctrl_base = ARM_BASE_WCR; - val_base = ARM_BASE_WVR; - } + ctrl_base = ARM_BASE_WCR; + val_base = ARM_BASE_WVR; slots = (struct perf_event **)__get_cpu_var(wp_on_reg); max_slots = core_num_wrps; } @@ -375,6 +361,17 @@ int arch_install_hw_breakpoint(struct perf_event *bp) goto out; } + /* Override the breakpoint data with the step data. */ + if (info->step_ctrl.enabled) { + addr = info->trigger & ~0x3; + ctrl = encode_ctrl_reg(info->step_ctrl); + if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) { + i = 0; + ctrl_base = ARM_BASE_BCR + core_num_brps; + val_base = ARM_BASE_BVR + core_num_brps; + } + } + /* Setup the address register. */ write_wb_reg(val_base + i, addr); @@ -398,10 +395,7 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp) max_slots = core_num_brps; } else { /* Watchpoint */ - if (info->step_ctrl.enabled) - base = ARM_BASE_BCR + core_num_brps; - else - base = ARM_BASE_WCR; + base = ARM_BASE_WCR; slots = (struct perf_event **)__get_cpu_var(wp_on_reg); max_slots = core_num_wrps; } @@ -419,6 +413,13 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp) if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n")) return; + /* Ensure that we disable the mismatch breakpoint. */ + if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE && + info->step_ctrl.enabled) { + i = 0; + base = ARM_BASE_BCR + core_num_brps; + } + /* Reset the control register. */ write_wb_reg(base + i, 0); } @@ -659,34 +660,62 @@ static void disable_single_step(struct perf_event *bp) arch_install_hw_breakpoint(bp); } -static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs) +static void watchpoint_handler(unsigned long addr, unsigned int fsr, + struct pt_regs *regs) { - int i; + int i, access; + u32 val, ctrl_reg, alignment_mask; struct perf_event *wp, **slots; struct arch_hw_breakpoint *info; + struct arch_hw_breakpoint_ctrl ctrl; slots = (struct perf_event **)__get_cpu_var(wp_on_reg); - /* Without a disassembler, we can only handle 1 watchpoint. */ - BUG_ON(core_num_wrps > 1); - for (i = 0; i < core_num_wrps; ++i) { rcu_read_lock(); wp = slots[i]; - if (wp == NULL) { - rcu_read_unlock(); - continue; + if (wp == NULL) + goto unlock; + + info = counter_arch_bp(wp); + /* + * The DFAR is an unknown value on debug architectures prior + * to 7.1. Since we only allow a single watchpoint on these + * older CPUs, we can set the trigger to the lowest possible + * faulting address. + */ + if (debug_arch < ARM_DEBUG_ARCH_V7_1) { + BUG_ON(i > 0); + info->trigger = wp->attr.bp_addr; + } else { + if (info->ctrl.len == ARM_BREAKPOINT_LEN_8) + alignment_mask = 0x7; + else + alignment_mask = 0x3; + + /* Check if the watchpoint value matches. */ + val = read_wb_reg(ARM_BASE_WVR + i); + if (val != (addr & ~alignment_mask)) + goto unlock; + + /* Possible match, check the byte address select. */ + ctrl_reg = read_wb_reg(ARM_BASE_WCR + i); + decode_ctrl_reg(ctrl_reg, &ctrl); + if (!((1 << (addr & alignment_mask)) & ctrl.len)) + goto unlock; + + /* Check that the access type matches. */ + access = (fsr & ARM_FSR_ACCESS_MASK) ? HW_BREAKPOINT_W : + HW_BREAKPOINT_R; + if (!(access & hw_breakpoint_type(wp))) + goto unlock; + + /* We have a winner. */ + info->trigger = addr; } - /* - * The DFAR is an unknown value. Since we only allow a - * single watchpoint, we can set the trigger to the lowest - * possible faulting address. - */ - info = counter_arch_bp(wp); - info->trigger = wp->attr.bp_addr; pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); perf_bp_event(wp, regs); @@ -698,6 +727,7 @@ static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs) if (!wp->overflow_handler) enable_single_step(wp, instruction_pointer(regs)); +unlock: rcu_read_unlock(); } } @@ -813,7 +843,7 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, case ARM_ENTRY_ASYNC_WATCHPOINT: WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n"); case ARM_ENTRY_SYNC_WATCHPOINT: - watchpoint_handler(addr, regs); + watchpoint_handler(addr, fsr, regs); break; default: ret = 1; /* Unhandled fault. */