perf s390: add regs_query_register_offset()

The regs_query_register_offset() helper function converts
register name like "%r0" to an offset of a register in user_pt_regs
It is required by the BPF prologue generator.

The user_pt_regs structure was recently added to "asm/ptrace.h".
Hence, update tools/perf/check-headers.sh to keep the header file
in sync with kernel changes.

Suggested-by: Thomas Richter <[e-mail]>
Signed-off-by: Hendrik Brueckner <[e-mail]>
Reviewed-and-tested-by: Thomas Richter <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

tools/perf/arch/s390/Makefile

···
 PERF_HAVE_DWARF_REGS := 1
 endif
 HAVE_KVM_STAT_SUPPORT := 1
+PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET := 1

tools/perf/arch/s390/util/dwarf-regs.c

···
 /*
  * Mapping of DWARF debug register numbers into register names.
  *
- *    Copyright IBM Corp. 2010
- *    Author(s): Heiko Carstens <[e-mail]>,
+ * Copyright IBM Corp. 2010, 2017
+ * Author(s): Heiko Carstens <[e-mail]>,
+ *	      Hendrik Brueckner <[e-mail]>
  *
  */
 
+#include <errno.h>
 #include <stddef.h>
-#include <dwarf-regs.h>
+#include <stdlib.h>
 #include <linux/kernel.h>
+#include <asm/ptrace.h>
+#include <string.h>
+#include <dwarf-regs.h>
 #include "dwarf-regs-table.h"
 
 const char *get_arch_regstr(unsigned int n)
 {
 	return (n >= ARRAY_SIZE(s390_dwarf_regs)) ? NULL : s390_dwarf_regs[n];
+}
+
+/*
+ * Convert the register name into an offset to struct pt_regs (kernel).
+ * This is required by the BPF prologue generator.  The BPF
+ * program is called in the BPF overflow handler in the perf
+ * core.
+ */
+int regs_query_register_offset(const char *name)
+{
+	unsigned long gpr;
+
+	if (!name || strncmp(name, "%r", 2))
+		return -EINVAL;
+
+	errno = 0;
+	gpr = strtoul(name + 2, NULL, 10);
+	if (errno || gpr >= 16)
+		return -EINVAL;
+
+	return offsetof(user_pt_regs, gprs) + 8 * gpr;
 }

tools/perf/check-headers.sh

···
 arch/powerpc/include/uapi/asm/kvm.h
 arch/s390/include/uapi/asm/kvm.h
 arch/s390/include/uapi/asm/kvm_perf.h
+arch/s390/include/uapi/asm/ptrace.h
 arch/s390/include/uapi/asm/sie.h
 arch/arm/include/uapi/asm/kvm.h
 arch/arm64/include/uapi/asm/kvm.h