um: add extended processor state save/restore support

This patch extends save_fp_registers() and restore_fp_registers() to use
PTRACE_GETREGSET and PTRACE_SETREGSET with the XSTATE note type, adding
support for new processor state extensions between context switches.

When the new ptrace requests are unavailable, it falls back to the old
PTRACE_GETFPREGS and PTRACE_SETFPREGS methods, which have been renamed to
save_i387_registers() and restore_i387_registers().

Now these functions expect *fp_regs to have the space of an _xstate struct.
Thus, this also makes ptrace in UML responde to PTRACE_GETFPREGS/_SETFPREG
requests with a user_i387_struct (thus independent from HOST_FP_SIZE), and
by calling save_i387_registers() and restore_i387_registers() instead of
the extended save_fp_registers() and restore_fp_registers() functions.

Signed-off-by: Eli Cooper <elicooper@gmx.com>

1 files changed, 47 insertions, 2 deletions

diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
index 41bfe84e11ab..00f54a91bb4b 100644
--- a/arch/x86/um/os-Linux/registers.c
+++ b/arch/x86/um/os-Linux/registers.c
@@ -11,21 +11,56 @@
 #endif
 #include <longjmp.h>
 #include <sysdep/ptrace_user.h>
+#include <sys/uio.h>
+#include <asm/sigcontext.h>
+#include <linux/elf.h>
 
-int save_fp_registers(int pid, unsigned long *fp_regs)
+int have_xstate_support;
+
+int save_i387_registers(int pid, unsigned long *fp_regs)
 {
         if (ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
                 return -errno;
         return 0;
 }
 
-int restore_fp_registers(int pid, unsigned long *fp_regs)
+int save_fp_registers(int pid, unsigned long *fp_regs)
+{
+        struct iovec iov;
+
+        if (have_xstate_support) {
+                iov.iov_base = fp_regs;
+                iov.iov_len = sizeof(struct _xstate);
+                if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+                        return -errno;
+                return 0;
+        } else {
+                return save_i387_registers(pid, fp_regs);
+        }
+}
+
+int restore_i387_registers(int pid, unsigned long *fp_regs)
 {
         if (ptrace(PTRACE_SETFPREGS, pid, 0, fp_regs) < 0)
                 return -errno;
         return 0;
 }
 
+int restore_fp_registers(int pid, unsigned long *fp_regs)
+{
+        struct iovec iov;
+
+        if (have_xstate_support) {
+                iov.iov_base = fp_regs;
+                iov.iov_len = sizeof(struct _xstate);
+                if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+                        return -errno;
+                return 0;
+        } else {
+                return restore_i387_registers(pid, fp_regs);
+        }
+}
+
 #ifdef __i386__
 int have_fpx_regs = 1;
 int save_fpx_registers(int pid, unsigned long *fp_regs)
@@ -85,6 +120,16 @@ int put_fp_registers(int pid, unsigned long *regs)
         return restore_fp_registers(pid, regs);
 }
 
+void arch_init_registers(int pid)
+{
+        struct _xstate fp_regs;
+        struct iovec iov;
+
+        iov.iov_base = &fp_regs;
+        iov.iov_len = sizeof(struct _xstate);
+        if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
+                have_xstate_support = 1;
+}
 #endif
 
 unsigned long get_thread_reg(int reg, jmp_buf *buf)