arch/tile: Change struct sigcontext to be more useful

Rather than just using pt_regs, it now contains the actual saved
state explicitly, similar to pt_regs.  By doing it this way, we
provide a cleaner API for userspace (or equivalently, we avoid the
need for libc to provide its own definition of sigcontext).

While we're at it, move PT_FLAGS_xxx to where they are not visible
from userspace.  And always pass siginfo and mcontext to signal
handlers, even if they claim they don't need it, since sometimes
they actually try to use it anyway in practice.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

2 files changed, 16 insertions, 13 deletions

diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index 45b66a3c991f..ce183aa1492c 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -61,13 +61,19 @@ int restore_sigcontext(struct pt_regs *regs,
         /* Always make any pending restarted system calls return -EINTR */
         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 
+        /*
+         * Enforce that sigcontext is like pt_regs, and doesn't mess
+         * up our stack alignment rules.
+         */
+        BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
+        BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
+
         for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
-                err |= __get_user(((long *)regs)[i],
-                                  &((long __user *)(&sc->regs))[i]);
+                err |= __get_user(regs->regs[i], &sc->gregs[i]);
 
         regs->faultnum = INT_SWINT_1_SIGRETURN;
 
-        err |= __get_user(*pr0, &sc->regs.regs[0]);
+        err |= __get_user(*pr0, &sc->gregs[0]);
         return err;
 }
 
@@ -112,8 +118,7 @@ int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
         int i, err = 0;
 
         for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
-                err |= __put_user(((long *)regs)[i],
-                                  &((long __user *)(&sc->regs))[i]);
+                err |= __put_user(regs->regs[i], &sc->gregs[i]);
 
         return err;
 }
@@ -203,19 +208,17 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
          * Set up registers for signal handler.
          * Registers that we don't modify keep the value they had from
          * user-space at the time we took the signal.
+         * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
+         * since some things rely on this (e.g. glibc's debug/segfault.c).
          */
         regs->pc = (unsigned long) ka->sa.sa_handler;
         regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
         regs->sp = (unsigned long) frame;
         regs->lr = restorer;
         regs->regs[0] = (unsigned long) usig;
-
-        if (ka->sa.sa_flags & SA_SIGINFO) {
-                /* Need extra arguments, so mark to restore caller-saves. */
-                regs->regs[1] = (unsigned long) &frame->info;
-                regs->regs[2] = (unsigned long) &frame->uc;
-                regs->flags |= PT_FLAGS_CALLER_SAVES;
-        }
+        regs->regs[1] = (unsigned long) &frame->info;
+        regs->regs[2] = (unsigned long) &frame->uc;
+        regs->flags |= PT_FLAGS_CALLER_SAVES;
 
         /*
          * Notify any tracer that was single-stepping it.
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index 38a68b0b4581..ea2e0ce28380 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -175,7 +175,7 @@ static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt)
                         pr_err("  <received signal %d>\n",
                                frame->info.si_signo);
                 }
-                return &frame->uc.uc_mcontext.regs;
+                return (struct pt_regs *)&frame->uc.uc_mcontext;
         }
         return NULL;
 }