Add ability to setup hw breakpoints using REGSET use the
__riscv_hwdebug_state structure to configure breakpoints.

Signed-off-by: Jesse Taube <jesse@rivosinc.com>
---
RFC -> V1:
 - New commit
V1 -> V2:
 - No change
---
 arch/riscv/kernel/ptrace.c     | 59 ++++++++++++++++++++++++++++++++++
 include/uapi/linux/elf.h       |  2 ++
 tools/include/uapi/linux/elf.h |  1 +
 3 files changed, 62 insertions(+)

diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index e097e6a61910..fbd0097ec168 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -33,6 +33,9 @@ enum riscv_regset {
 #ifdef CONFIG_RISCV_ISA_SUPM
 	REGSET_TAGGED_ADDR_CTRL,
 #endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+	REGSET_HW_BREAK
+#endif
 };
 
 static int riscv_gpr_get(struct task_struct *target,
@@ -280,7 +283,53 @@ static long ptrace_sethbpregs(struct task_struct *child, unsigned long idx,
 		return -EFAULT;
 
 	return ptrace_hbp_set(child, idx, &state);
+}
 
+static int hw_break_set(struct task_struct *target,
+			const struct user_regset *regset,
+			unsigned int pos, unsigned int count,
+			const void *kbuf, const void __user *ubuf)
+{
+	struct __riscv_hwdebug_state state;
+	int ret, idx, offset, limit;
+
+	idx = offset = 0;
+	limit = regset->n * regset->size;
+	while (count && offset < limit) {
+		if (count < sizeof(state))
+			return -EINVAL;
+
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &state,
+					 offset, offset + sizeof(state));
+		if (ret)
+			return ret;
+		ret = ptrace_hbp_set(target, idx, &state);
+		if (ret)
+			return ret;
+		offset += sizeof(state);
+		idx++;
+	}
+
+	return 0;
+}
+
+static int hw_break_get(struct task_struct *target,
+			const struct user_regset *regset,
+			struct membuf to)
+{
+	int ret, idx = 0;
+	struct __riscv_hwdebug_state state;
+
+	while (to.left) {
+		ret = ptrace_hbp_get(target, idx, &state);
+		if (ret)
+			return ret;
+
+		membuf_write(&to, &state, sizeof(state));
+		idx++;
+	}
+
+	return 0;
 }
 #endif
 
@@ -324,6 +373,16 @@ static const struct user_regset riscv_user_regset[] = {
 		.set = tagged_addr_ctrl_set,
 	},
 #endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+	[REGSET_HW_BREAK] = {
+		.core_note_type = NT_RISCV_HW_BREAK,
+		.n = sizeof(struct __riscv_hwdebug_state) / sizeof(unsigned long),
+		.size = sizeof(unsigned long),
+		.align = sizeof(unsigned long),
+		.regset_get = hw_break_get,
+		.set = hw_break_set,
+	},
+#endif
 };
 
 static const struct user_regset_view riscv_user_native_view = {
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 819ded2d39de..7a32073e0d68 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -545,6 +545,8 @@ typedef struct elf64_shdr {
 #define NT_RISCV_VECTOR	0x901		/* RISC-V vector registers */
 #define NN_RISCV_TAGGED_ADDR_CTRL "LINUX"
 #define NT_RISCV_TAGGED_ADDR_CTRL 0x902	/* RISC-V tagged address control (prctl()) */
+#define NN_RISCV_HW_BREAK	"LINUX"
+#define NT_RISCV_HW_BREAK	0x903	/* RISC-V hardware breakpoint registers */
 #define NN_LOONGARCH_CPUCFG	"LINUX"
 #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
 #define NN_LOONGARCH_CSR	"LINUX"
diff --git a/tools/include/uapi/linux/elf.h b/tools/include/uapi/linux/elf.h
index 5834b83d7f9a..b5f35df1de7a 100644
--- a/tools/include/uapi/linux/elf.h
+++ b/tools/include/uapi/linux/elf.h
@@ -460,6 +460,7 @@ typedef struct elf64_shdr {
 #define NT_RISCV_CSR	0x900		/* RISC-V Control and Status Registers */
 #define NT_RISCV_VECTOR	0x901		/* RISC-V vector registers */
 #define NT_RISCV_TAGGED_ADDR_CTRL 0x902	/* RISC-V tagged address control (prctl()) */
+#define NT_RISCV_HW_BREAK	0x903	/* RISC-V hardware breakpoint registers */
 #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
 #define NT_LOONGARCH_CSR	0xa01	/* LoongArch control and status registers */
 #define NT_LOONGARCH_LSX	0xa02	/* LoongArch Loongson SIMD Extension registers */
-- 
2.43.0