openrisc: Add HAVE_REGS_AND_STACK_ACCESS_API support

Support for HAVE_REGS_AND_STACK_ACCESS_API needed for restartable
sequences.

The implementation has been copied from riscv and tested with the
restartable sequences self tests.

Note, pt-regs members are 'long' on openrisc which require casts for the
api, someday we should try to update these to be 'unsigned long' as
that's what they really are.

Signed-off-by: Michael Jeanson <[e-mail]>
[stafford: Updated commit message]
Signed-off-by: Stafford Horne <[e-mail]>

arch/openrisc/Kconfig

···
 	select HAVE_PCI
 	select HAVE_UID16
 	select HAVE_PAGE_SIZE_8KB
+	select HAVE_REGS_AND_STACK_ACCESS_API
 	select GENERIC_ATOMIC64
 	select GENERIC_CLOCKEVENTS_BROADCAST
 	select GENERIC_SMP_IDLE_THREAD

arch/openrisc/include/asm/ptrace.h

···
 
 #include <asm/spr_defs.h>
 #include <uapi/asm/ptrace.h>
+#include <linux/compiler.h>
 
 /*
  * Make kernel PTrace/register structures opaque to userspace... userspace can
···
 			/* Named registers */
 			long  sr;	/* Stored in place of r0 */
 			long  sp;	/* r1 */
+			long  gpr2;
+			long  gpr3;
+			long  gpr4;
+			long  gpr5;
+			long  gpr6;
+			long  gpr7;
+			long  gpr8;
+			long  gpr9;
+			long  gpr10;
+			long  gpr11;
+			long  gpr12;
+			long  gpr13;
+			long  gpr14;
+			long  gpr15;
+			long  gpr16;
+			long  gpr17;
+			long  gpr18;
+			long  gpr19;
+			long  gpr20;
+			long  gpr21;
+			long  gpr22;
+			long  gpr23;
+			long  gpr24;
+			long  gpr25;
+			long  gpr26;
+			long  gpr27;
+			long  gpr28;
+			long  gpr29;
+			long  gpr30;
+			long  gpr31;
 		};
 		struct {
 			/* Old style */
···
 /* TODO: Rename this to REDZONE because that's what it is */
 #define STACK_FRAME_OVERHEAD  128  /* size of minimum stack frame */
 
-#define instruction_pointer(regs)	((regs)->pc)
+#define MAX_REG_OFFSET offsetof(struct pt_regs, orig_gpr11)
+
+/* Helpers for working with the instruction pointer */
+static inline unsigned long instruction_pointer(struct pt_regs *regs)
+{
+	return (unsigned long)regs->pc;
+}
+static inline void instruction_pointer_set(struct pt_regs *regs,
+					   unsigned long val)
+{
+	regs->pc = val;
+}
+
 #define user_mode(regs)			(((regs)->sr & SPR_SR_SM) == 0)
 #define user_stack_pointer(regs)	((unsigned long)(regs)->sp)
 #define profile_pc(regs)		instruction_pointer(regs)
 
+/* Valid only for Kernel mode traps. */
+static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
+{
+	return (unsigned long)regs->sp;
+}
+
 static inline long regs_return_value(struct pt_regs *regs)
 {
 	return regs->gpr[11];
+}
+
+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__ */

arch/openrisc/kernel/ptrace.c

···
  * in exit.c or in signal.c.
  */
 
+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(sr),
+	REG_OFFSET_NAME(sp),
+	REG_OFFSET_NAME(gpr2),
+	REG_OFFSET_NAME(gpr3),
+	REG_OFFSET_NAME(gpr4),
+	REG_OFFSET_NAME(gpr5),
+	REG_OFFSET_NAME(gpr6),
+	REG_OFFSET_NAME(gpr7),
+	REG_OFFSET_NAME(gpr8),
+	REG_OFFSET_NAME(gpr9),
+	REG_OFFSET_NAME(gpr10),
+	REG_OFFSET_NAME(gpr11),
+	REG_OFFSET_NAME(gpr12),
+	REG_OFFSET_NAME(gpr13),
+	REG_OFFSET_NAME(gpr14),
+	REG_OFFSET_NAME(gpr15),
+	REG_OFFSET_NAME(gpr16),
+	REG_OFFSET_NAME(gpr17),
+	REG_OFFSET_NAME(gpr18),
+	REG_OFFSET_NAME(gpr19),
+	REG_OFFSET_NAME(gpr20),
+	REG_OFFSET_NAME(gpr21),
+	REG_OFFSET_NAME(gpr22),
+	REG_OFFSET_NAME(gpr23),
+	REG_OFFSET_NAME(gpr24),
+	REG_OFFSET_NAME(gpr25),
+	REG_OFFSET_NAME(gpr26),
+	REG_OFFSET_NAME(gpr27),
+	REG_OFFSET_NAME(gpr28),
+	REG_OFFSET_NAME(gpr29),
+	REG_OFFSET_NAME(gpr30),
+	REG_OFFSET_NAME(gpr31),
+	REG_OFFSET_NAME(pc),
+	REG_OFFSET_NAME(orig_gpr11),
+	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;
+}
 
 /*
  * Called by kernel/ptrace.c when detaching..