signal: Add unsafe_put_compat_sigset()

Implement 'unsafe' version of put_compat_sigset()

For the bigendian, use unsafe_put_user() directly
to avoid intermediate copy through the stack.

For the littleendian, use a straight unsafe_copy_to_user().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/537c7082ee309a0bb9c67a50c5d9dd929aedb82d.1597770847.git.christophe.leroy@csgroup.eu

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 14d514233e1d4007230a83529bd61ce8da1334fd..400c0941c8aff65d2914bf40568a620bdd8f1b4d 100644 (file)
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -442,6 +442,38 @@ put_compat_sigset(compat_sigset_t __user *compat, const sigset_t *set,
 #endif
 }
 
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#define unsafe_put_compat_sigset(compat, set, label) do {              \
+       compat_sigset_t __user *__c = compat;                           \
+       const sigset_t *__s = set;                                      \
+                                                                       \
+       switch (_NSIG_WORDS) {                                          \
+       case 4:                                                         \
+               unsafe_put_user(__s->sig[3] >> 32, &__c->sig[7], label);        \
+               unsafe_put_user(__s->sig[3], &__c->sig[6], label);      \
+               fallthrough;                                            \
+       case 3:                                                         \
+               unsafe_put_user(__s->sig[2] >> 32, &__c->sig[5], label);        \
+               unsafe_put_user(__s->sig[2], &__c->sig[4], label);      \
+               fallthrough;                                            \
+       case 2:                                                         \
+               unsafe_put_user(__s->sig[1] >> 32, &__c->sig[3], label);        \
+               unsafe_put_user(__s->sig[1], &__c->sig[2], label);      \
+               fallthrough;                                            \
+       case 1:                                                         \
+               unsafe_put_user(__s->sig[0] >> 32, &__c->sig[1], label);        \
+               unsafe_put_user(__s->sig[0], &__c->sig[0], label);      \
+       }                                                               \
+} while (0)
+#else
+#define unsafe_put_compat_sigset(compat, set, label) do {              \
+       compat_sigset_t __user *__c = compat;                           \
+       const sigset_t *__s = set;                                      \
+                                                                       \
+       unsafe_copy_to_user(__c, __s, sizeof(*__c), label);             \
+} while (0)
+#endif
+
 extern int compat_ptrace_request(struct task_struct *child,
                                 compat_long_t request,
                                 compat_ulong_t addr, compat_ulong_t data);