[RFC PATCH] LoongArch: Add hardware breakpoints/watchpoints support

From: qing zhang
Date: Tue Dec 13 2022 - 04:13:55 EST

From: Qing Zhang <zhangqing@xxxxxxxxxxx>

Use perf framework to manage hardware instruction and data breakpoints.
LoongArch defines hardware watchpoint functions for instruction fetch
and load/store operations, after the software configures hardware watchpoints
for instruction fetch and load/store operations. The processor hardware will
monitor the access address of the instruction fetch and load/store operation,
and will trigger the exception of the watchpoint when it meets the conditions
set by the watchpoint.

The hardware monitoring points for instruction fetching and load/store operations
each have a register for the overall configuration of all monitoring points,
a register for recording the status of all monitoring points, and four registers
required for configuration of each watchpoint individually.

Watchpoint related control status register chapters:
https://github.com/loongson/LoongArch-Documentation/releases/download/2022.08.12/
LoongArch-Vol1-v1.02-CN.pdf

Initial version has the following limitations:
- userspace debug is not yet enabled: work on ptrace/gdb is in progress
- no support for virtualization

Despite missing userspace debug, initial implementation can be tested: e.g.
see samples/hw_breakpoint and register_wide_hw_breakpoint.

TODO:
- Add Kernel tools that use hardware breakpoints: Kgdb, Ptrace
- Add hardware breakpoints/watchpoints for gdb

Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 12571eedc488..69199812fe74 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -99,6 +99,7 @@ config LOONGARCH
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GENERIC_VDSO
+ select HAVE_HW_BREAKPOINT if PERF_EVENTS
select HAVE_IOREMAP_PROT
select HAVE_IRQ_EXIT_ON_IRQ_STACK
select HAVE_IRQ_TIME_ACCOUNTING
diff --git a/arch/loongarch/include/asm/hw_breakpoint.h b/arch/loongarch/include/asm/hw_breakpoint.h
new file mode 100644
index 000000000000..a57caf117960
--- /dev/null
+++ b/arch/loongarch/include/asm/hw_breakpoint.h
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#ifndef __ASM_HW_BREAKPOINT_H
+#define __ASM_HW_BREAKPOINT_H
+
+#include <asm/loongarch.h>
+
+#ifdef __KERNEL__
+
+/* Breakpoint */
+#define LOONGARCH_BREAKPOINT_EXECUTE (0 << 0)
+
+/* Watchpoints */
+#define LOONGARCH_BREAKPOINT_LOAD (1 << 0)
+#define LOONGARCH_BREAKPOINT_STORE (1 << 1)
+
+struct arch_hw_breakpoint_ctrl {
+ u32 __reserved : 28,
+ type : 2,
+ len : 2;
+};
+
+struct arch_hw_breakpoint {
+ u64 address;
+ u64 mask;
+ struct arch_hw_breakpoint_ctrl ctrl;
+};
+
+/* Lengths */
+#define LOONGARCH_BREAKPOINT_LEN_1 0b11
+#define LOONGARCH_BREAKPOINT_LEN_2 0b10
+#define LOONGARCH_BREAKPOINT_LEN_4 0b01
+#define LOONGARCH_BREAKPOINT_LEN_8 0b00
+
+/*
+ * Limits.
+ * Changing these will require modifications to the register accessors.
+ */
+#define LOONGARCH_MAX_BRP 8
+#define LOONGARCH_MAX_WRP 8
+
+/* Virtual debug register bases. */
+#define CSR_CFG_ADDR 0
+#define CSR_CFG_MASK (CSR_CFG_ADDR + LOONGARCH_MAX_BRP)
+#define CSR_CFG_CTRL (CSR_CFG_MASK + LOONGARCH_MAX_BRP)
+#define CSR_CFG_ASID (CSR_CFG_CTRL + LOONGARCH_MAX_WRP)
+
+/* Debug register names. */
+#define LOONGARCH_CSR_NAME_ADDR ADDR
+#define LOONGARCH_CSR_NAME_MASK MASK
+#define LOONGARCH_CSR_NAME_CTRL CTRL
+#define LOONGARCH_CSR_NAME_ASID ASID
+
+/* Accessor macros for the debug registers. */
+#define LOONGARCH_CSR_READ(N, REG, T, VAL) \
+do { \
+ if (T == 0) \
+ VAL = csr_read64(LOONGARCH_CSR_##IB##N##REG); \
+ else \
+ VAL = csr_read64(LOONGARCH_CSR_##DB##N##REG); \
+} while (0)
+
+#define LOONGARCH_CSR_WRITE(N, REG, T, VAL) \
+do { \
+ if (T == 0) \
+ csr_write64(VAL, LOONGARCH_CSR_##IB##N##REG); \
+ else \
+ csr_write64(VAL, LOONGARCH_CSR_##DB##N##REG); \
+} while (0)
+
+static inline u32 encode_ctrl_reg(struct arch_hw_breakpoint_ctrl ctrl)
+{
+ u32 val = (ctrl.len << 2) | ctrl.type;
+
+ return val;
+}
+
+static inline void decode_ctrl_reg(u32 reg, struct arch_hw_breakpoint_ctrl *ctrl)
+{
+ ctrl->type = reg & 0x3;
+ reg >>= 2;
+ ctrl->len = reg & 0x3;
+}
+
+struct task_struct;
+struct notifier_block;
+struct perf_event_attr;
+struct perf_event;
+
+extern int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
+ int *gen_len, int *gen_type, int *offset);
+extern int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw);
+extern int hw_breakpoint_arch_parse(struct perf_event *bp,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw);
+extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+ unsigned long val, void *data);
+
+extern int arch_install_hw_breakpoint(struct perf_event *bp);
+extern void arch_uninstall_hw_breakpoint(struct perf_event *bp);
+extern void hw_breakpoint_pmu_read(struct perf_event *bp);
+extern int hw_breakpoint_slots(int type);
+
+int breakpoint_handler(struct pt_regs *regs);
+int watchpoint_handler(struct pt_regs *regs);
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+extern void hw_breakpoint_thread_switch(struct task_struct *next);
+extern void ptrace_hw_copy_thread(struct task_struct *task);
+#else
+static inline void hw_breakpoint_thread_switch(struct task_struct *next)
+{
+}
+static inline void ptrace_hw_copy_thread(struct task_struct *task)
+{
+}
+#endif
+
+/* Determine number of BRP registers available. */
+static inline int get_num_brps(void)
+{
+ unsigned int ibcn;
+
+ ibcn = csr_read64(LOONGARCH_CSR_FWPC) & 0x3f;
+ return ibcn;
+}
+
+/* Determine number of WRP registers available. */
+static inline int get_num_wrps(void)
+{
+ unsigned int dbcn;
+
+ dbcn = csr_read64(LOONGARCH_CSR_MWPC) & 0x3f;
+ return dbcn;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __ASM_BREAKPOINT_H */
diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index 7f8d57a61c8b..e9aed583a064 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -970,42 +970,42 @@ static __always_inline void iocsr_write64(u64 val, u32 reg)

#define LOONGARCH_CSR_DB0ADDR 0x310 /* data breakpoint 0 address */
#define LOONGARCH_CSR_DB0MASK 0x311 /* data breakpoint 0 mask */
-#define LOONGARCH_CSR_DB0CTL 0x312 /* data breakpoint 0 control */
+#define LOONGARCH_CSR_DB0CTRL 0x312 /* data breakpoint 0 control */
#define LOONGARCH_CSR_DB0ASID 0x313 /* data breakpoint 0 asid */

#define LOONGARCH_CSR_DB1ADDR 0x318 /* data breakpoint 1 address */
#define LOONGARCH_CSR_DB1MASK 0x319 /* data breakpoint 1 mask */
-#define LOONGARCH_CSR_DB1CTL 0x31a /* data breakpoint 1 control */
+#define LOONGARCH_CSR_DB1CTRL 0x31a /* data breakpoint 1 control */
#define LOONGARCH_CSR_DB1ASID 0x31b /* data breakpoint 1 asid */

#define LOONGARCH_CSR_DB2ADDR 0x320 /* data breakpoint 2 address */
#define LOONGARCH_CSR_DB2MASK 0x321 /* data breakpoint 2 mask */
-#define LOONGARCH_CSR_DB2CTL 0x322 /* data breakpoint 2 control */
+#define LOONGARCH_CSR_DB2CTRL 0x322 /* data breakpoint 2 control */
#define LOONGARCH_CSR_DB2ASID 0x323 /* data breakpoint 2 asid */

#define LOONGARCH_CSR_DB3ADDR 0x328 /* data breakpoint 3 address */
#define LOONGARCH_CSR_DB3MASK 0x329 /* data breakpoint 3 mask */
-#define LOONGARCH_CSR_DB3CTL 0x32a /* data breakpoint 3 control */
+#define LOONGARCH_CSR_DB3CTRL 0x32a /* data breakpoint 3 control */
#define LOONGARCH_CSR_DB3ASID 0x32b /* data breakpoint 3 asid */

#define LOONGARCH_CSR_DB4ADDR 0x330 /* data breakpoint 4 address */
#define LOONGARCH_CSR_DB4MASK 0x331 /* data breakpoint 4 maks */
-#define LOONGARCH_CSR_DB4CTL 0x332 /* data breakpoint 4 control */
+#define LOONGARCH_CSR_DB4CTRL 0x332 /* data breakpoint 4 control */
#define LOONGARCH_CSR_DB4ASID 0x333 /* data breakpoint 4 asid */

#define LOONGARCH_CSR_DB5ADDR 0x338 /* data breakpoint 5 address */
#define LOONGARCH_CSR_DB5MASK 0x339 /* data breakpoint 5 mask */
-#define LOONGARCH_CSR_DB5CTL 0x33a /* data breakpoint 5 control */
+#define LOONGARCH_CSR_DB5CTRL 0x33a /* data breakpoint 5 control */
#define LOONGARCH_CSR_DB5ASID 0x33b /* data breakpoint 5 asid */

#define LOONGARCH_CSR_DB6ADDR 0x340 /* data breakpoint 6 address */
#define LOONGARCH_CSR_DB6MASK 0x341 /* data breakpoint 6 mask */
-#define LOONGARCH_CSR_DB6CTL 0x342 /* data breakpoint 6 control */
+#define LOONGARCH_CSR_DB6CTRL 0x342 /* data breakpoint 6 control */
#define LOONGARCH_CSR_DB6ASID 0x343 /* data breakpoint 6 asid */

#define LOONGARCH_CSR_DB7ADDR 0x348 /* data breakpoint 7 address */
#define LOONGARCH_CSR_DB7MASK 0x349 /* data breakpoint 7 mask */
-#define LOONGARCH_CSR_DB7CTL 0x34a /* data breakpoint 7 control */
+#define LOONGARCH_CSR_DB7CTRL 0x34a /* data breakpoint 7 control */
#define LOONGARCH_CSR_DB7ASID 0x34b /* data breakpoint 7 asid */

#define LOONGARCH_CSR_FWPC 0x380 /* instruction breakpoint config */
@@ -1013,42 +1013,42 @@ static __always_inline void iocsr_write64(u64 val, u32 reg)

#define LOONGARCH_CSR_IB0ADDR 0x390 /* inst breakpoint 0 address */
#define LOONGARCH_CSR_IB0MASK 0x391 /* inst breakpoint 0 mask */
-#define LOONGARCH_CSR_IB0CTL 0x392 /* inst breakpoint 0 control */
+#define LOONGARCH_CSR_IB0CTRL 0x392 /* inst breakpoint 0 control */
#define LOONGARCH_CSR_IB0ASID 0x393 /* inst breakpoint 0 asid */

#define LOONGARCH_CSR_IB1ADDR 0x398 /* inst breakpoint 1 address */
#define LOONGARCH_CSR_IB1MASK 0x399 /* inst breakpoint 1 mask */
-#define LOONGARCH_CSR_IB1CTL 0x39a /* inst breakpoint 1 control */
+#define LOONGARCH_CSR_IB1CTRL 0x39a /* inst breakpoint 1 control */
#define LOONGARCH_CSR_IB1ASID 0x39b /* inst breakpoint 1 asid */

#define LOONGARCH_CSR_IB2ADDR 0x3a0 /* inst breakpoint 2 address */
#define LOONGARCH_CSR_IB2MASK 0x3a1 /* inst breakpoint 2 mask */
-#define LOONGARCH_CSR_IB2CTL 0x3a2 /* inst breakpoint 2 control */
+#define LOONGARCH_CSR_IB2CTRL 0x3a2 /* inst breakpoint 2 control */
#define LOONGARCH_CSR_IB2ASID 0x3a3 /* inst breakpoint 2 asid */

#define LOONGARCH_CSR_IB3ADDR 0x3a8 /* inst breakpoint 3 address */
#define LOONGARCH_CSR_IB3MASK 0x3a9 /* breakpoint 3 mask */
-#define LOONGARCH_CSR_IB3CTL 0x3aa /* inst breakpoint 3 control */
+#define LOONGARCH_CSR_IB3CTRL 0x3aa /* inst breakpoint 3 control */
#define LOONGARCH_CSR_IB3ASID 0x3ab /* inst breakpoint 3 asid */

#define LOONGARCH_CSR_IB4ADDR 0x3b0 /* inst breakpoint 4 address */
#define LOONGARCH_CSR_IB4MASK 0x3b1 /* inst breakpoint 4 mask */
-#define LOONGARCH_CSR_IB4CTL 0x3b2 /* inst breakpoint 4 control */
+#define LOONGARCH_CSR_IB4CTRL 0x3b2 /* inst breakpoint 4 control */
#define LOONGARCH_CSR_IB4ASID 0x3b3 /* inst breakpoint 4 asid */

#define LOONGARCH_CSR_IB5ADDR 0x3b8 /* inst breakpoint 5 address */
#define LOONGARCH_CSR_IB5MASK 0x3b9 /* inst breakpoint 5 mask */
-#define LOONGARCH_CSR_IB5CTL 0x3ba /* inst breakpoint 5 control */
+#define LOONGARCH_CSR_IB5CTRL 0x3ba /* inst breakpoint 5 control */
#define LOONGARCH_CSR_IB5ASID 0x3bb /* inst breakpoint 5 asid */

#define LOONGARCH_CSR_IB6ADDR 0x3c0 /* inst breakpoint 6 address */
#define LOONGARCH_CSR_IB6MASK 0x3c1 /* inst breakpoint 6 mask */
-#define LOONGARCH_CSR_IB6CTL 0x3c2 /* inst breakpoint 6 control */
+#define LOONGARCH_CSR_IB6CTRL 0x3c2 /* inst breakpoint 6 control */
#define LOONGARCH_CSR_IB6ASID 0x3c3 /* inst breakpoint 6 asid */

#define LOONGARCH_CSR_IB7ADDR 0x3c8 /* inst breakpoint 7 address */
#define LOONGARCH_CSR_IB7MASK 0x3c9 /* inst breakpoint 7 mask */
-#define LOONGARCH_CSR_IB7CTL 0x3ca /* inst breakpoint 7 control */
+#define LOONGARCH_CSR_IB7CTRL 0x3ca /* inst breakpoint 7 control */
#define LOONGARCH_CSR_IB7ASID 0x3cb /* inst breakpoint 7 asid */

#define LOONGARCH_CSR_DEBUG 0x500 /* debug config */
diff --git a/arch/loongarch/include/asm/processor.h b/arch/loongarch/include/asm/processor.h
index 7184f1dc61f2..f6ee920122d6 100644
--- a/arch/loongarch/include/asm/processor.h
+++ b/arch/loongarch/include/asm/processor.h
@@ -11,6 +11,7 @@

#include <asm/cpu.h>
#include <asm/cpu-info.h>
+#include <asm/hw_breakpoint.h>
#include <asm/loongarch.h>
#include <asm/vdso/processor.h>
#include <uapi/asm/ptrace.h>
@@ -131,6 +132,9 @@ struct thread_struct {
* they are conditionally copied at fork().
*/
struct loongarch_fpu fpu FPU_ALIGN;
+ /* Hardware breakpoints pinned to this task. */
+ struct perf_event *hbp_break[LOONGARCH_MAX_BRP];
+ struct perf_event *hbp_watch[LOONGARCH_MAX_WRP];
};

#define thread_saved_ra(tsk) (tsk->thread.sched_ra)
@@ -172,6 +176,8 @@ struct thread_struct {
.fcc = 0, \
.fpr = {{{0,},},}, \
}, \
+ .hbp_break = {0}, \
+ .hbp_watch = {0}, \
}

struct task_struct;
@@ -184,10 +190,6 @@ extern unsigned long boot_option_idle_override;
*/
extern void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp);

-static inline void flush_thread(void)
-{
-}
-
unsigned long __get_wchan(struct task_struct *p);

#define __KSTK_TOS(tsk) ((unsigned long)task_stack_page(tsk) + \
diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h
index 43a5ab162d38..24e3094bebab 100644
--- a/arch/loongarch/include/asm/switch_to.h
+++ b/arch/loongarch/include/asm/switch_to.h
@@ -34,6 +34,7 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
#define switch_to(prev, next, last) \
do { \
lose_fpu_inatomic(1, prev); \
+ hw_breakpoint_thread_switch(next); \
(last) = __switch_to(prev, next, task_thread_info(next), \
__builtin_return_address(0), __builtin_frame_address(0)); \
} while (0)
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 7ca65195f7f8..b3aca7f2296e 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o

obj-$(CONFIG_PERF_EVENTS) += perf_event.o perf_regs.o
+obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o

obj-$(CONFIG_KPROBES) += kprobes.o kprobes_trampoline.o

diff --git a/arch/loongarch/kernel/hw_breakpoint.c b/arch/loongarch/kernel/hw_breakpoint.c
new file mode 100644
index 000000000000..16f38ceec321
--- /dev/null
+++ b/arch/loongarch/kernel/hw_breakpoint.c
@@ -0,0 +1,461 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#define pr_fmt(fmt) "hw-breakpoint: " fmt
+
+#include <linux/hw_breakpoint.h>
+#include <linux/kprobes.h>
+#include <linux/perf_event.h>
+
+#include <asm/hw_breakpoint.h>
+
+/* Breakpoint currently in use for each BRP. */
+static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[LOONGARCH_MAX_BRP]);
+
+/* Watchpoint currently in use for each WRP. */
+static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[LOONGARCH_MAX_WRP]);
+
+/* Number of BRP/WRP registers on this CPU. */
+static int core_num_brps;
+static int core_num_wrps;
+
+int hw_breakpoint_slots(int type)
+{
+ /*
+ * We can be called early, so don't rely on
+ * our static variables being initialised.
+ */
+ switch (type) {
+ case TYPE_INST:
+ return get_num_brps();
+ case TYPE_DATA:
+ return get_num_wrps();
+ default:
+ pr_warn("unknown slot type: %d\n", type);
+ return 0;
+ }
+}
+
+#define READ_WB_REG_CASE(OFF, N, REG, T, VAL) \
+ case (OFF + N): \
+ LOONGARCH_CSR_READ(N, REG, T, VAL); \
+ break
+
+#define WRITE_WB_REG_CASE(OFF, N, REG, T, VAL) \
+ case (OFF + N): \
+ LOONGARCH_CSR_WRITE(N, REG, T, VAL); \
+ break
+
+#define GEN_READ_WB_REG_CASES(OFF, REG, T, VAL) \
+ READ_WB_REG_CASE(OFF, 0, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 1, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 2, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 3, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 4, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 5, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 6, REG, T, VAL); \
+ READ_WB_REG_CASE(OFF, 7, REG, T, VAL);
+
+#define GEN_WRITE_WB_REG_CASES(OFF, REG, T, VAL) \
+ WRITE_WB_REG_CASE(OFF, 0, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 1, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 2, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 3, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 4, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 5, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 6, REG, T, VAL); \
+ WRITE_WB_REG_CASE(OFF, 7, REG, T, VAL);
+
+static u64 read_wb_reg(int reg, int n, int t)
+{
+ u64 val = 0;
+
+ switch (reg + n) {
+ GEN_READ_WB_REG_CASES(CSR_CFG_ADDR, ADDR, t, val);
+ GEN_READ_WB_REG_CASES(CSR_CFG_MASK, MASK, t, val);
+ GEN_READ_WB_REG_CASES(CSR_CFG_CTRL, CTRL, t, val);
+ GEN_READ_WB_REG_CASES(CSR_CFG_ASID, ASID, t, val);
+ default:
+ pr_warn("attempt to read from unknown breakpoint register %d\n", n);
+ }
+
+ return val;
+}
+NOKPROBE_SYMBOL(read_wb_reg);
+
+static void write_wb_reg(int reg, int n, int t, u64 val)
+{
+ switch (reg + n) {
+ GEN_WRITE_WB_REG_CASES(CSR_CFG_ADDR, ADDR, t, val);
+ GEN_WRITE_WB_REG_CASES(CSR_CFG_MASK, MASK, t, val);
+ GEN_WRITE_WB_REG_CASES(CSR_CFG_CTRL, CTRL, t, val);
+ GEN_WRITE_WB_REG_CASES(CSR_CFG_ASID, ASID, t, val);
+ default:
+ pr_warn("attempt to write to unknown breakpoint register %d\n", n);
+ }
+}
+NOKPROBE_SYMBOL(write_wb_reg);
+
+enum hw_breakpoint_ops {
+ HW_BREAKPOINT_INSTALL,
+ HW_BREAKPOINT_UNINSTALL,
+};
+
+/**
+ * hw_breakpoint_slot_setup - Find and setup a perf slot according to
+ * operations
+ *
+ * @slots: pointer to array of slots
+ * @max_slots: max number of slots
+ * @bp: perf_event to setup
+ * @ops: operation to be carried out on the slot
+ *
+ * Return:
+ * slot index on success
+ * -ENOSPC if no slot is available/matches
+ * -EINVAL on wrong operations parameter
+ */
+static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots,
+ struct perf_event *bp,
+ enum hw_breakpoint_ops ops)
+{
+ int i;
+ struct perf_event **slot;
+
+ for (i = 0; i < max_slots; ++i) {
+ slot = &slots[i];
+ switch (ops) {
+ case HW_BREAKPOINT_INSTALL:
+ if (!*slot) {
+ *slot = bp;
+ return i;
+ }
+ break;
+ case HW_BREAKPOINT_UNINSTALL:
+ if (*slot == bp) {
+ *slot = NULL;
+ return i;
+ }
+ break;
+ default:
+ pr_warn_once("Unhandled hw breakpoint ops %d\n", ops);
+ return -EINVAL;
+ }
+ }
+ return -ENOSPC;
+}
+
+/*
+ * Unregister breakpoints from this task and reset the pointers in
+ * the thread_struct.
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+}
+
+void ptrace_hw_copy_thread(struct task_struct *tsk)
+{
+ memset(&tsk->thread.hbp_break, 0, sizeof(tsk->thread.hbp_break));
+ memset(&tsk->thread.hbp_watch, 0, sizeof(tsk->thread.hbp_watch));
+}
+
+static int hw_breakpoint_control(struct perf_event *bp,
+ enum hw_breakpoint_ops ops)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ struct perf_event **slots;
+ int i, max_slots, enable;
+ u32 ctrl;
+ struct pt_regs *regs = task_pt_regs(current);
+
+ if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
+ /* Breakpoint */
+ slots = this_cpu_ptr(bp_on_reg);
+ max_slots = core_num_brps;
+ } else {
+ /* Watchpoint */
+ slots = this_cpu_ptr(wp_on_reg);
+ max_slots = core_num_wrps;
+ }
+
+ i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops);
+
+ if (WARN_ONCE(i < 0, "Can't find any breakpoint slot"))
+ return i;
+
+ switch (ops) {
+ case HW_BREAKPOINT_INSTALL:
+ /* Set the FWPnCFG/MWPnCFG 1~3 register. */
+ write_wb_reg(CSR_CFG_ADDR, i, 0, info->address);
+ write_wb_reg(CSR_CFG_ADDR, i, 1, info->address);
+ if (info->mask) {
+ write_wb_reg(CSR_CFG_MASK, i, 0, info->mask);
+ write_wb_reg(CSR_CFG_MASK, i, 1, info->mask);
+ }
+ write_wb_reg(CSR_CFG_ASID, i, 0, 0);
+ write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+ ctrl = encode_ctrl_reg(info->ctrl);
+ if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE)
+ write_wb_reg(CSR_CFG_CTRL, i, 0, ctrl | 0x1e);
+ else
+ write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl | 0x1e | 1 << 8 | 1 << 9);
+
+ enable = csr_read64(LOONGARCH_CSR_CRMD);
+ csr_write64(1 << 9 | enable, LOONGARCH_CSR_CRMD);
+ break;
+ case HW_BREAKPOINT_UNINSTALL:
+ /* Reset the FWPnCFG/MWPnCFG 1~3 register. */
+ write_wb_reg(CSR_CFG_ADDR, i, 0, 0);
+ write_wb_reg(CSR_CFG_ADDR, i, 1, 0);
+ write_wb_reg(CSR_CFG_MASK, i, 0, 0);
+ write_wb_reg(CSR_CFG_MASK, i, 1, 0);
+ write_wb_reg(CSR_CFG_CTRL, i, 0, 0);
+ write_wb_reg(CSR_CFG_CTRL, i, 1, 0);
+ write_wb_reg(CSR_CFG_ASID, i, 0, 0);
+ write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+ break;
+ }
+
+ return 0;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+ return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
+}
+
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+ hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
+}
+
+static int get_hbp_len(u8 hbp_len)
+{
+ unsigned int len_in_bytes = 0;
+
+ switch (hbp_len) {
+ case LOONGARCH_BREAKPOINT_LEN_1:
+ len_in_bytes = 1;
+ break;
+ case LOONGARCH_BREAKPOINT_LEN_2:
+ len_in_bytes = 2;
+ break;
+ case LOONGARCH_BREAKPOINT_LEN_4:
+ len_in_bytes = 4;
+ break;
+ case LOONGARCH_BREAKPOINT_LEN_8:
+ len_in_bytes = 8;
+ break;
+ }
+
+ return len_in_bytes;
+}
+
+/*
+ * Check whether bp virtual address is in kernel space.
+ */
+int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
+{
+ unsigned int len;
+ unsigned long va;
+
+ va = hw->address;
+ len = get_hbp_len(hw->ctrl.len);
+
+ return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+}
+
+/*
+ * Construct an arch_hw_breakpoint from a perf_event.
+ */
+static int arch_build_bp_info(struct perf_event *bp,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw)
+{
+ /* Type */
+ switch (attr->bp_type) {
+ case HW_BREAKPOINT_X:
+ hw->ctrl.type = LOONGARCH_BREAKPOINT_EXECUTE;
+ break;
+ case HW_BREAKPOINT_R:
+ hw->ctrl.type = LOONGARCH_BREAKPOINT_LOAD;
+ break;
+ case HW_BREAKPOINT_W:
+ hw->ctrl.type = LOONGARCH_BREAKPOINT_STORE;
+ break;
+ case HW_BREAKPOINT_RW:
+ hw->ctrl.type = LOONGARCH_BREAKPOINT_LOAD | LOONGARCH_BREAKPOINT_STORE;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ switch (attr->bp_len) {
+ case HW_BREAKPOINT_LEN_1:
+ hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_1;
+ break;
+ case HW_BREAKPOINT_LEN_2:
+ hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_2;
+ break;
+ case HW_BREAKPOINT_LEN_4:
+ hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_4;
+ break;
+ case HW_BREAKPOINT_LEN_8:
+ hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_8;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Address */
+ hw->address = attr->bp_addr;
+
+ return 0;
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings.
+ */
+int hw_breakpoint_arch_parse(struct perf_event *bp,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw)
+{
+ int ret;
+ u64 alignment_mask, offset;
+
+ /* Build the arch_hw_breakpoint. */
+ ret = arch_build_bp_info(bp, attr, hw);
+ if (ret)
+ return ret;
+
+ if (hw->ctrl.type != LOONGARCH_BREAKPOINT_EXECUTE)
+ alignment_mask = 0x7;
+ offset = hw->address & alignment_mask;
+
+ hw->address &= ~alignment_mask;
+ hw->ctrl.len <<= offset;
+
+ return 0;
+}
+
+#define PRMD_WE (1UL<<3) /*prmd watch enable, restore to crmd when eret*/
+static void update_bp_registers(struct pt_regs *regs, int enable)
+{
+ int i, max_slots;
+ u32 ctrl;
+ struct perf_event **slots;
+
+ if (csr_read64(LOONGARCH_CSR_FWPS) & 0xff) {
+ slots = this_cpu_ptr(bp_on_reg);
+ max_slots = core_num_brps;
+
+ } else if (csr_read64(LOONGARCH_CSR_MWPS) & 0xff) {
+ slots = this_cpu_ptr(wp_on_reg);
+ max_slots = core_num_wrps;
+ } else {
+ return;
+ }
+
+ for (i = 0; i < max_slots; ++i) {
+ if (!slots[i])
+ continue;
+
+ ctrl = read_wb_reg(CSR_CFG_CTRL, i, 1);
+ if (enable) {
+ ctrl = read_wb_reg(CSR_CFG_CTRL, i, 1);
+ ctrl |= 0x1 << 8;
+ ctrl |= 0x1 << 9;
+ write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl);
+ regs->csr_prmd |= PRMD_WE;
+ } else {
+ ctrl = read_wb_reg(CSR_CFG_CTRL, i, 1);
+ ctrl &= ~0x1 << 8;
+ ctrl &= ~0x1 << 9;
+ write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl);
+ regs->csr_prmd &= ~PRMD_WE;
+ }
+ }
+}
+NOKPROBE_SYMBOL(update_bp_registers);
+
+/*
+ * Debug exception handlers.
+ */
+int breakpoint_handler(struct pt_regs *regs)
+{
+ int i;
+ u64 addr;
+ struct perf_event *bp, **slots;
+
+ slots = this_cpu_ptr(bp_on_reg);
+
+ for (i = 0; i < core_num_brps; ++i) {
+ bp = slots[i];
+ if (bp == NULL)
+ continue;
+ perf_bp_event(bp, regs);
+ }
+ update_bp_registers(regs, 0);
+
+ return 0;
+}
+NOKPROBE_SYMBOL(breakpoint_handler);
+
+int watchpoint_handler(struct pt_regs *regs)
+{
+ int i;
+ struct perf_event *wp, **slots;
+
+ slots = this_cpu_ptr(wp_on_reg);
+
+ for (i = 0; i < core_num_wrps; ++i) {
+ wp = slots[i];
+ if (wp == NULL)
+ continue;
+ perf_bp_event(wp, regs);
+ }
+ update_bp_registers(regs, 0);
+
+ return 0;
+}
+NOKPROBE_SYMBOL(watchpoint_handler);
+
+/*
+ * One-time initialisation.
+ */
+static int __init arch_hw_breakpoint_init(void)
+{
+ core_num_brps = get_num_brps();
+ core_num_wrps = get_num_wrps();
+
+ pr_info("found %d breakpoint and %d watchpoint registers.\n",
+ core_num_brps, core_num_wrps);
+ return 0;
+}
+arch_initcall(arch_hw_breakpoint_init);
+
+void hw_breakpoint_thread_switch(struct task_struct *next)
+{
+ struct pt_regs *regs = task_pt_regs(next);
+
+ /* Update breakpoints/watchpoints. */
+ update_bp_registers(regs, 1);
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+}
+
+/*
+ * Dummy function to register with die_notifier.
+ */
+int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+ unsigned long val, void *data)
+{
+ return NOTIFY_DONE;
+}
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 27c8cacbce01..f78574562329 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -37,6 +37,7 @@
#include <asm/cpu.h>
#include <asm/elf.h>
#include <asm/fpu.h>
+#include <linux/hw_breakpoint.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
@@ -100,6 +101,11 @@ void exit_thread(struct task_struct *tsk)
{
}

+void flush_thread(void)
+{
+ flush_ptrace_hw_breakpoint(current);
+}
+
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
/*
@@ -186,6 +192,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
if (clone_flags & CLONE_SETTLS)
childregs->regs[2] = tls;

+ ptrace_hw_copy_thread(p);
+
out:
clear_tsk_thread_flag(p, TIF_USEDFPU);
clear_tsk_thread_flag(p, TIF_USEDSIMD);
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 4d9f77565703..d59cf93a4c31 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -45,6 +45,7 @@
#include <asm/tlb.h>
#include <asm/types.h>
#include <asm/unwind.h>
+#include <asm/hw_breakpoint.h>

#include "access-helper.h"

@@ -514,7 +515,19 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)

asmlinkage void noinstr do_watch(struct pt_regs *regs)
{
- pr_warn("Hardware watch point handler not implemented!\n");
+ enum ctx_state prev_state;
+
+ prev_state = exception_enter();
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ if (breakpoint_handler(regs))
+ return;
+ if (watchpoint_handler(regs))
+ return;
+#endif
+ force_sig(SIGTRAP);
+ exception_exit(prev_state);
+ return;
}

asmlinkage void noinstr do_ri(struct pt_regs *regs)
--
2.36.0