signal: Distinguish between kernel_siginfo and siginfo

Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo.  Keeping the
traditional name for the userspace definition.  While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo.  The reduction in size comes in a following change.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index a807ff5cc1a9..c2cee9db5204 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -651,7 +651,7 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data)
         return 0;
 }
 
-static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
+static int ptrace_getsiginfo(struct task_struct *child, kernel_siginfo_t *info)
 {
         unsigned long flags;
         int error = -ESRCH;
@@ -667,7 +667,7 @@ static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
         return error;
 }
 
-static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
+static int ptrace_setsiginfo(struct task_struct *child, const kernel_siginfo_t *info)
 {
         unsigned long flags;
         int error = -ESRCH;
@@ -709,7 +709,7 @@ static int ptrace_peek_siginfo(struct task_struct *child,
                 pending = &child->pending;
 
         for (i = 0; i < arg.nr; ) {
-                siginfo_t info;
+                kernel_siginfo_t info;
                 s32 off = arg.off + i;
 
                 spin_lock_irq(&child->sighand->siglock);
@@ -885,7 +885,7 @@ int ptrace_request(struct task_struct *child, long request,
 {
         bool seized = child->ptrace & PT_SEIZED;
         int ret = -EIO;
-        siginfo_t siginfo, *si;
+        kernel_siginfo_t siginfo, *si;
         void __user *datavp = (void __user *) data;
         unsigned long __user *datalp = datavp;
         unsigned long flags;
@@ -1180,7 +1180,7 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 {
         compat_ulong_t __user *datap = compat_ptr(data);
         compat_ulong_t word;
-        siginfo_t siginfo;
+        kernel_siginfo_t siginfo;
         int ret;
 
         switch (request) {