parasite-syscall: use the ptrace requests PTRACE_(GET|SET)REGSET to retrieve and set CPU registers

This patch introduces the routines ptrace_get_gpregs() and ptrace_set_gpregs()
that wrap the ptrace interface to get and set CPU registers respectively.
The motivation is to make the CRIU code be compatible with architectures that
don't support the PTRACE_GETREGS and PTRACE_SETREGS ptrace calls ---
the requests PTRACE_GETREGSET and PTRACE_SETREGSET are implemented instead.
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/ptrace.h

@@ -27,6 +27,11 @@ struct ptrace_peeksiginfo_args {
 #define PTRACE_PEEKSIGINFO_SHARED       (1 << 0)
 #endif
 
+#ifndef PTRACE_GETREGSET
+# define PTRACE_GETREGSET	0x4204
+# define PTRACE_SETREGSET	0x4205
+#endif
+
 #define PTRACE_GETSIGMASK	0x420a
 #define PTRACE_SETSIGMASK	0x420b
 

parasite-syscall.c

@@ -30,6 +30,7 @@
 
 #include <string.h>
 #include <stdlib.h>
+#include <elf.h>
 
 #include "asm/parasite-syscall.h"
 #include "asm/dump.h"
@@ -67,12 +68,20 @@ static struct vma_area *get_vma_by_ip(struct list_head *vma_area_list, unsigned
 
 static inline int ptrace_get_regs(int pid, user_regs_struct_t *regs)
 {
-	return ptrace(PTRACE_GETREGS, pid, NULL, regs);
+	struct iovec iov;
+
+	iov.iov_base = regs;
+	iov.iov_len = sizeof(user_regs_struct_t);
+	return ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov);
 }
 
 static inline int ptrace_set_regs(int pid, user_regs_struct_t *regs)
 {
-	return ptrace(PTRACE_SETREGS, pid, NULL, regs);
+	struct iovec iov;
+
+	iov.iov_base = regs;
+	iov.iov_len = sizeof(user_regs_struct_t);
+	return ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov);
 }
 
 static int get_thread_ctx(int pid, struct thread_ctx *ctx)