diff options
Diffstat (limited to '')
-rw-r--r-- | arch/arm/kernel/hw_breakpoint.c | 159 |
1 files changed, 123 insertions, 36 deletions
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 02ca7adf5375..054e9199f30d 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -547,7 +547,7 @@ static int arch_build_bp_info(struct perf_event *bp, if ((hw->ctrl.type != ARM_BREAKPOINT_EXECUTE) && max_watchpoint_len >= 8) break; - /* Else, fall through */ + fallthrough; default: return -EINVAL; } @@ -612,12 +612,12 @@ int hw_breakpoint_arch_parse(struct perf_event *bp, /* Allow halfword watchpoints and breakpoints. */ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2) break; - /* Else, fall through */ + fallthrough; case 3: /* Allow single byte watchpoint. */ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) break; - /* Else, fall through */ + fallthrough; default: ret = -EINVAL; goto out; @@ -683,26 +683,68 @@ static void disable_single_step(struct perf_event *bp) arch_install_hw_breakpoint(bp); } +/* + * Arm32 hardware does not always report a watchpoint hit address that matches + * one of the watchpoints set. It can also report an address "near" the + * watchpoint if a single instruction access both watched and unwatched + * addresses. There is no straight-forward way, short of disassembling the + * offending instruction, to map that address back to the watchpoint. This + * function computes the distance of the memory access from the watchpoint as a + * heuristic for the likelyhood that a given access triggered the watchpoint. + * + * See this same function in the arm64 platform code, which has the same + * problem. + * + * The function returns the distance of the address from the bytes watched by + * the watchpoint. In case of an exact match, it returns 0. + */ +static u32 get_distance_from_watchpoint(unsigned long addr, u32 val, + struct arch_hw_breakpoint_ctrl *ctrl) +{ + u32 wp_low, wp_high; + u32 lens, lene; + + lens = __ffs(ctrl->len); + lene = __fls(ctrl->len); + + wp_low = val + lens; + wp_high = val + lene; + if (addr < wp_low) + return wp_low - addr; + else if (addr > wp_high) + return addr - wp_high; + else + return 0; +} + +static int watchpoint_fault_on_uaccess(struct pt_regs *regs, + struct arch_hw_breakpoint *info) +{ + return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER; +} + static void watchpoint_handler(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { - int i, access; - u32 val, ctrl_reg, alignment_mask; + int i, access, closest_match = 0; + u32 min_dist = -1, dist; + u32 val, ctrl_reg; struct perf_event *wp, **slots; struct arch_hw_breakpoint *info; struct arch_hw_breakpoint_ctrl ctrl; slots = this_cpu_ptr(wp_on_reg); + /* + * Find all watchpoints that match the reported address. If no exact + * match is found. Attribute the hit to the closest watchpoint. + */ + rcu_read_lock(); for (i = 0; i < core_num_wrps; ++i) { - rcu_read_lock(); - wp = slots[i]; - if (wp == NULL) - goto unlock; + continue; - 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 @@ -711,50 +753,69 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr, */ if (debug_arch < ARM_DEBUG_ARCH_V7_1) { BUG_ON(i > 0); + info = counter_arch_bp(wp); 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. */ if (debug_exception_updates_fsr()) { access = (fsr & ARM_FSR_ACCESS_MASK) ? HW_BREAKPOINT_W : HW_BREAKPOINT_R; if (!(access & hw_breakpoint_type(wp))) - goto unlock; + continue; + } + + val = read_wb_reg(ARM_BASE_WVR + i); + ctrl_reg = read_wb_reg(ARM_BASE_WCR + i); + decode_ctrl_reg(ctrl_reg, &ctrl); + dist = get_distance_from_watchpoint(addr, val, &ctrl); + if (dist < min_dist) { + min_dist = dist; + closest_match = i; } + /* Is this an exact match? */ + if (dist != 0) + continue; /* We have a winner. */ + info = counter_arch_bp(wp); info->trigger = addr; } pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); + + /* + * If we triggered a user watchpoint from a uaccess routine, + * then handle the stepping ourselves since userspace really + * can't help us with this. + */ + if (watchpoint_fault_on_uaccess(regs, info)) + goto step; + perf_bp_event(wp, regs); /* - * If no overflow handler is present, insert a temporary - * mismatch breakpoint so we can single-step over the - * watchpoint trigger. + * Defer stepping to the overflow handler if one is installed. + * Otherwise, insert a temporary mismatch breakpoint so that + * we can single-step over the watchpoint trigger. */ + if (!is_default_overflow_handler(wp)) + continue; +step: + enable_single_step(wp, instruction_pointer(regs)); + } + + if (min_dist > 0 && min_dist != -1) { + /* No exact match found. */ + wp = slots[closest_match]; + info = counter_arch_bp(wp); + info->trigger = addr; + pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); + perf_bp_event(wp, regs); if (is_default_overflow_handler(wp)) enable_single_step(wp, instruction_pointer(regs)); - -unlock: - rcu_read_unlock(); } + + rcu_read_unlock(); } static void watchpoint_single_step_handler(unsigned long pc) @@ -825,7 +886,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs) info->trigger = addr; pr_debug("breakpoint fired: address = 0x%x\n", addr); perf_bp_event(bp, regs); - if (!bp->overflow_handler) + if (is_default_overflow_handler(bp)) enable_single_step(bp, addr); goto unlock; } @@ -867,7 +928,7 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, break; case ARM_ENTRY_ASYNC_WATCHPOINT: WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n"); - /* Fall through */ + fallthrough; case ARM_ENTRY_SYNC_WATCHPOINT: watchpoint_handler(addr, fsr, regs); break; @@ -880,6 +941,23 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, return ret; } +#ifdef CONFIG_ARM_ERRATA_764319 +static int oslsr_fault; + +static int debug_oslsr_trap(struct pt_regs *regs, unsigned int instr) +{ + oslsr_fault = 1; + instruction_pointer(regs) += 4; + return 0; +} + +static struct undef_hook debug_oslsr_hook = { + .instr_mask = 0xffffffff, + .instr_val = 0xee115e91, + .fn = debug_oslsr_trap, +}; +#endif + /* * One-time initialisation. */ @@ -913,10 +991,19 @@ static bool core_has_os_save_restore(void) case ARM_DEBUG_ARCH_V7_1: return true; case ARM_DEBUG_ARCH_V7_ECP14: +#ifdef CONFIG_ARM_ERRATA_764319 + oslsr_fault = 0; + register_undef_hook(&debug_oslsr_hook); ARM_DBG_READ(c1, c1, 4, oslsr); + unregister_undef_hook(&debug_oslsr_hook); + if (oslsr_fault) + return false; +#else + ARM_DBG_READ(c1, c1, 4, oslsr); +#endif if (oslsr & ARM_OSLSR_OSLM0) return true; - /* Else, fall through */ + fallthrough; default: return false; } |