[PATCH v5 1/9] RISC-V: Implement ptrace regs and stack API

guoren
2020-12-17T16:03:32Z

From: Patrick Stählin <me@packi.ch>

Needed for kprobes support. Copied and adapted from arm64 code.

Guo Ren fixup pt_regs type for linux-5.8-rc1.

Signed-off-by: Patrick Stählin <me@packi.ch>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Reviewed-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ptrace.h | 29 ++++++++++++
arch/riscv/kernel/ptrace.c | 99 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 129 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 44377fd..62a4958 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -72,6 +72,7 @@ config RISCV
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_STACKPROTECTOR
select HAVE_SYSCALL_TRACEPOINTS
select IRQ_DOMAIN
diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
index ee49f80..23372bb 100644
--- a/arch/riscv/include/asm/ptrace.h
+++ b/arch/riscv/include/asm/ptrace.h
@@ -8,6 +8,7 @@

#include <uapi/asm/ptrace.h>
#include <asm/csr.h>
+#include <linux/compiler.h>

#ifndef __ASSEMBLY__

@@ -60,6 +61,7 @@ struct pt_regs {

#define user_mode(regs) (((regs)->status & SR_PP) == 0)

+#define MAX_REG_OFFSET offsetof(struct pt_regs, orig_a0)

/* Helpers for working with the instruction pointer */
static inline unsigned long instruction_pointer(struct pt_regs *regs)
@@ -85,6 +87,12 @@ static inline void user_stack_pointer_set(struct pt_regs *regs,
regs->sp = val;
}

+/* Valid only for Kernel mode traps. */
+static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
+{
+ return regs->sp;
+}
+
/* Helpers for working with the frame pointer */
static inline unsigned long frame_pointer(struct pt_regs *regs)
{
@@ -101,6 +109,27 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
return regs->a0;
}

+extern int regs_query_register_offset(const char *name);
+extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+ unsigned int n);
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs: pt_regs from which register value is gotten
+ * @offset: offset of the register.
+ *
+ * regs_get_register returns the value of a register whose offset from @regs.
+ * The @offset is the offset of the register in struct pt_regs.
+ * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
+ */
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+ unsigned int offset)
+{
+ if (unlikely(offset > MAX_REG_OFFSET))
+ return 0;
+
+ return *(unsigned long *)((unsigned long)regs + offset);
+}
#endif /* __ASSEMBLY__ */

#endif /* _ASM_RISCV_PTRACE_H */
diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index 2d6395f..1a85305 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -114,6 +114,105 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
return &riscv_user_native_view;
}

+struct pt_regs_offset {
+ const char *name;
+ int offset;
+};
+
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+ REG_OFFSET_NAME(epc),
+ REG_OFFSET_NAME(ra),
+ REG_OFFSET_NAME(sp),
+ REG_OFFSET_NAME(gp),
+ REG_OFFSET_NAME(tp),
+ REG_OFFSET_NAME(t0),
+ REG_OFFSET_NAME(t1),
+ REG_OFFSET_NAME(t2),
+ REG_OFFSET_NAME(s0),
+ REG_OFFSET_NAME(s1),
+ REG_OFFSET_NAME(a0),
+ REG_OFFSET_NAME(a1),
+ REG_OFFSET_NAME(a2),
+ REG_OFFSET_NAME(a3),
+ REG_OFFSET_NAME(a4),
+ REG_OFFSET_NAME(a5),
+ REG_OFFSET_NAME(a6),
+ REG_OFFSET_NAME(a7),
+ REG_OFFSET_NAME(s2),
+ REG_OFFSET_NAME(s3),
+ REG_OFFSET_NAME(s4),
+ REG_OFFSET_NAME(s5),
+ REG_OFFSET_NAME(s6),
+ REG_OFFSET_NAME(s7),
+ REG_OFFSET_NAME(s8),
+ REG_OFFSET_NAME(s9),
+ REG_OFFSET_NAME(s10),
+ REG_OFFSET_NAME(s11),
+ REG_OFFSET_NAME(t3),
+ REG_OFFSET_NAME(t4),
+ REG_OFFSET_NAME(t5),
+ REG_OFFSET_NAME(t6),
+ REG_OFFSET_NAME(status),
+ REG_OFFSET_NAME(badaddr),
+ REG_OFFSET_NAME(cause),
+ REG_OFFSET_NAME(orig_a0),
+ REG_OFFSET_END,
+};
+
+/**
+ * regs_query_register_offset() - query register offset from its name
+ * @name: the name of a register
+ *
+ * regs_query_register_offset() returns the offset of a register in struct
+ * pt_regs from its name. If the name is invalid, this returns -EINVAL;
+ */
+int regs_query_register_offset(const char *name)
+{
+ const struct pt_regs_offset *roff;
+
+ for (roff = regoffset_table; roff->name != NULL; roff++)
+ if (!strcmp(roff->name, name))
+ return roff->offset;
+ return -EINVAL;
+}
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs: pt_regs which contains kernel stack pointer.
+ * @addr: address which is checked.
+ *
+ * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+static bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
+{
+ return (addr & ~(THREAD_SIZE - 1)) ==
+ (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs: pt_regs which contains kernel stack pointer.
+ * @n: stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specified by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
+{
+ unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+
+ addr += n;
+ if (regs_within_kernel_stack(regs, (unsigned long)addr))
+ return *addr;
+ else
+ return 0;
+}
+
void ptrace_disable(struct task_struct *child)
{
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);