uml: floating point signal delivery fixes

Handle floating point state in across signals correctly.  UML/i386 needs to
know whether the host does PTRACE_[GS]ETFPXREGS, so an arch_init_registers
hook is added, which on x86_64 does nothing.

UML doesn't save and restore floating point registers on kernel entry and
exit, so they need to be copied between the host process and the sigcontext.
save_fpx_registers and restore_fpx_registers are added for this purpose.
save_fp_registers and restore_fp_registers already exist.

There was a bunch of floating point state conversion code in
arch/um/sys-i386/ptrace.c which isn't needed there, but is needed in signal.c,
so it is moved over.

The i386 code now distinguishes between fp and fpx state and handles them
correctly.  The x86_64 code just needs to copy state as-is between the host
process and the stack.  There are also some fixes there to pass the correct
address of the floating point state around.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 34 insertions, 3 deletions

diff --git a/arch/um/os-Linux/registers.c b/arch/um/os-Linux/registers.c
index b06c780..a32ba6a 100644
--- a/arch/um/os-Linux/registers.c
+++ b/arch/um/os-Linux/registers.c
@@ -47,6 +47,8 @@ void init_registers(int pid)
 	if (err)
 		panic("check_ptrace : PTRACE_GETREGS failed, errno = %d",
 		      errno);
+
+	arch_init_registers(pid);
 }
 
 void get_safe_registers(unsigned long *regs)
diff --git a/arch/um/os-Linux/sys-i386/registers.c b/arch/um/os-Linux/sys-i386/registers.c
index f171204..8f1f0ab 100644
--- a/arch/um/os-Linux/sys-i386/registers.c
+++ b/arch/um/os-Linux/sys-i386/registers.c
@@ -8,9 +8,6 @@
 #include "longjmp.h"
 #include "user.h"
 
-/* XXX These need to use [GS]ETFPXREGS and copy_sc_{to,from}_user_skas needs
- * to pass in a sufficiently large buffer
- */
 int save_fp_registers(int pid, unsigned long *fp_regs)
 {
 	if(ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
@@ -25,6 +22,20 @@ int restore_fp_registers(int pid, unsigned long *fp_regs)
 	return 0;
 }
 
+int save_fpx_registers(int pid, unsigned long *fp_regs)
+{
+	if(ptrace(PTRACE_GETFPXREGS, pid, 0, fp_regs) < 0)
+		return -errno;
+	return 0;
+}
+
+int restore_fpx_registers(int pid, unsigned long *fp_regs)
+{
+	if(ptrace(PTRACE_SETFPXREGS, pid, 0, fp_regs) < 0)
+		return -errno;
+	return 0;
+}
+
 unsigned long get_thread_reg(int reg, jmp_buf *buf)
 {
 	switch(reg){
@@ -36,3 +47,21 @@ unsigned long get_thread_reg(int reg, jmp_buf *buf)
 		return 0;
 	}
 }
+
+int have_fpx_regs = 1;
+
+void arch_init_registers(int pid)
+{
+	unsigned long fpx_regs[HOST_XFP_SIZE];
+	int err;
+
+	err = ptrace(PTRACE_GETFPXREGS, pid, 0, fpx_regs);
+	if(!err)
+		return;
+
+	if(errno != EIO)
+		panic("check_ptrace : PTRACE_GETFPXREGS failed, errno = %d",
+		      errno);
+
+	have_fpx_regs = 0;
+}