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Diffstat (limited to 'arch/arm64/kernel/hw_breakpoint.c')
-rw-r--r--arch/arm64/kernel/hw_breakpoint.c155
1 files changed, 116 insertions, 39 deletions
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index 948b73148d56..0296e7924240 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -317,9 +317,21 @@ static int get_hbp_len(u8 hbp_len)
case ARM_BREAKPOINT_LEN_2:
len_in_bytes = 2;
break;
+ case ARM_BREAKPOINT_LEN_3:
+ len_in_bytes = 3;
+ break;
case ARM_BREAKPOINT_LEN_4:
len_in_bytes = 4;
break;
+ case ARM_BREAKPOINT_LEN_5:
+ len_in_bytes = 5;
+ break;
+ case ARM_BREAKPOINT_LEN_6:
+ len_in_bytes = 6;
+ break;
+ case ARM_BREAKPOINT_LEN_7:
+ len_in_bytes = 7;
+ break;
case ARM_BREAKPOINT_LEN_8:
len_in_bytes = 8;
break;
@@ -349,7 +361,7 @@ int arch_check_bp_in_kernelspace(struct perf_event *bp)
* to generic breakpoint descriptions.
*/
int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
- int *gen_len, int *gen_type)
+ int *gen_len, int *gen_type, int *offset)
{
/* Type */
switch (ctrl.type) {
@@ -369,17 +381,33 @@ int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
return -EINVAL;
}
+ if (!ctrl.len)
+ return -EINVAL;
+ *offset = __ffs(ctrl.len);
+
/* Len */
- switch (ctrl.len) {
+ switch (ctrl.len >> *offset) {
case ARM_BREAKPOINT_LEN_1:
*gen_len = HW_BREAKPOINT_LEN_1;
break;
case ARM_BREAKPOINT_LEN_2:
*gen_len = HW_BREAKPOINT_LEN_2;
break;
+ case ARM_BREAKPOINT_LEN_3:
+ *gen_len = HW_BREAKPOINT_LEN_3;
+ break;
case ARM_BREAKPOINT_LEN_4:
*gen_len = HW_BREAKPOINT_LEN_4;
break;
+ case ARM_BREAKPOINT_LEN_5:
+ *gen_len = HW_BREAKPOINT_LEN_5;
+ break;
+ case ARM_BREAKPOINT_LEN_6:
+ *gen_len = HW_BREAKPOINT_LEN_6;
+ break;
+ case ARM_BREAKPOINT_LEN_7:
+ *gen_len = HW_BREAKPOINT_LEN_7;
+ break;
case ARM_BREAKPOINT_LEN_8:
*gen_len = HW_BREAKPOINT_LEN_8;
break;
@@ -423,9 +451,21 @@ static int arch_build_bp_info(struct perf_event *bp)
case HW_BREAKPOINT_LEN_2:
info->ctrl.len = ARM_BREAKPOINT_LEN_2;
break;
+ case HW_BREAKPOINT_LEN_3:
+ info->ctrl.len = ARM_BREAKPOINT_LEN_3;
+ break;
case HW_BREAKPOINT_LEN_4:
info->ctrl.len = ARM_BREAKPOINT_LEN_4;
break;
+ case HW_BREAKPOINT_LEN_5:
+ info->ctrl.len = ARM_BREAKPOINT_LEN_5;
+ break;
+ case HW_BREAKPOINT_LEN_6:
+ info->ctrl.len = ARM_BREAKPOINT_LEN_6;
+ break;
+ case HW_BREAKPOINT_LEN_7:
+ info->ctrl.len = ARM_BREAKPOINT_LEN_7;
+ break;
case HW_BREAKPOINT_LEN_8:
info->ctrl.len = ARM_BREAKPOINT_LEN_8;
break;
@@ -517,18 +557,17 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
default:
return -EINVAL;
}
-
- info->address &= ~alignment_mask;
- info->ctrl.len <<= offset;
} else {
if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE)
alignment_mask = 0x3;
else
alignment_mask = 0x7;
- if (info->address & alignment_mask)
- return -EINVAL;
+ offset = info->address & alignment_mask;
}
+ info->address &= ~alignment_mask;
+ info->ctrl.len <<= offset;
+
/*
* Disallow per-task kernel breakpoints since these would
* complicate the stepping code.
@@ -661,12 +700,47 @@ unlock:
}
NOKPROBE_SYMBOL(breakpoint_handler);
+/*
+ * Arm64 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 Section D2.10.5 "Determining the memory location that caused a Watchpoint
+ * exception" of ARMv8 Architecture Reference Manual for details.
+ *
+ * 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 u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
+ struct arch_hw_breakpoint_ctrl *ctrl)
+{
+ u64 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_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
- int i, step = 0, *kernel_step, access;
+ int i, step = 0, *kernel_step, access, closest_match = 0;
+ u64 min_dist = -1, dist;
u32 ctrl_reg;
- u64 val, alignment_mask;
+ u64 val;
struct perf_event *wp, **slots;
struct debug_info *debug_info;
struct arch_hw_breakpoint *info;
@@ -675,35 +749,15 @@ static int watchpoint_handler(unsigned long addr, unsigned int esr,
slots = this_cpu_ptr(wp_on_reg);
debug_info = &current->thread.debug;
+ /*
+ * 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;
-
- info = counter_arch_bp(wp);
- /* AArch32 watchpoints are either 4 or 8 bytes aligned. */
- if (is_compat_task()) {
- if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
- alignment_mask = 0x7;
- else
- alignment_mask = 0x3;
- } else {
- alignment_mask = 0x7;
- }
-
- /* Check if the watchpoint value matches. */
- val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
- if (val != (addr & ~alignment_mask))
- goto unlock;
-
- /* Possible match, check the byte address select to confirm. */
- ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i);
- decode_ctrl_reg(ctrl_reg, &ctrl);
- if (!((1 << (addr & alignment_mask)) & ctrl.len))
- goto unlock;
+ continue;
/*
* Check that the access type matches.
@@ -712,18 +766,41 @@ static int watchpoint_handler(unsigned long addr, unsigned int esr,
access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W :
HW_BREAKPOINT_R;
if (!(access & hw_breakpoint_type(wp)))
- goto unlock;
+ continue;
+ /* Check if the watchpoint value and byte select match. */
+ val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
+ ctrl_reg = read_wb_reg(AARCH64_DBG_REG_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;
+
+ info = counter_arch_bp(wp);
info->trigger = addr;
perf_bp_event(wp, regs);
/* Do we need to handle the stepping? */
if (is_default_overflow_handler(wp))
step = 1;
+ }
+ if (min_dist > 0 && min_dist != -1) {
+ /* No exact match found. */
+ wp = slots[closest_match];
+ info = counter_arch_bp(wp);
+ info->trigger = addr;
+ perf_bp_event(wp, regs);
-unlock:
- rcu_read_unlock();
+ /* Do we need to handle the stepping? */
+ if (is_default_overflow_handler(wp))
+ step = 1;
}
+ rcu_read_unlock();
if (!step)
return 0;
@@ -924,7 +1001,7 @@ static int __init arch_hw_breakpoint_init(void)
* debugger will leave the world in a nice state for us.
*/
ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
- "CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING",
+ "perf/arm64/hw_breakpoint:starting",
hw_breakpoint_reset, NULL);
if (ret)
pr_err("failed to register CPU hotplug notifier: %d\n", ret);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.