m68k: Verify the offsets in struct siginfo never change.

A change to the generic struct siginfo accidentally changed the offset
of si_offset.  Add build time checks to ensure the offsets of all known
fields in struct siginfo never change.  This copies the form of similar
changes on x86.

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

diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
index e79421f..f7cd5ec 100644 (file)
--- a/arch/m68k/kernel/signal.c
+++ b/arch/m68k/kernel/signal.c
@@ -574,6 +574,66 @@ static inline int rt_save_fpu_state(struct ucontext __user *uc, struct pt_regs *
 
 #endif /* CONFIG_FPU */
 
+static inline void siginfo_build_tests(void)
+{
+       /* This needs to be tested on m68k as it has a lesser
+        * alignment requirment than x86 and that can cause surprises.
+        */
+
+       /* This is part of the ABI and can never change in size: */
+       BUILD_BUG_ON(sizeof(siginfo_t) != 128);
+
+       /* Ensure the know fields never change in location */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_signo) != 0);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_errno) != 4);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_code)  != 8);
+
+       /* _kill */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_pid) != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_uid) != 0x10);
+
+       /* _timer */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_tid)     != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_overrun) != 0x10);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_value)   != 0x14);
+
+       /* _rt */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_pid)   != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_uid)   != 0x10);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_value) != 0x14);
+
+       /* _sigchld */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_pid)    != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_uid)    != 0x10);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_status) != 0x14);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_utime)  != 0x18);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_stime)  != 0x1C);
+
+       /* _sigfault */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_addr) != 0x0C);
+
+       /* _sigfault._mcerr */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_addr_lsb) != 0x10);
+
+       /* _sigfault._addr_bnd */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_lower) != 0x12);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_upper) != 0x16);
+
+       /* _sigfault._addr_pkey */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_pkey) != 0x12);
+
+       /* _sigpoll */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_band)   != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_fd)     != 0x10);
+
+       /* _sigsys */
+       BUILD_BUG_ON(offsetof(siginfo_t, si_call_addr) != 0x0C);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_syscall)   != 0x10);
+       BUILD_BUG_ON(offsetof(siginfo_t, si_arch)      != 0x14);
+
+       /* any new si_fields should be added here */
+}
+
 static int mangle_kernel_stack(struct pt_regs *regs, int formatvec,
                               void __user *fp)
 {
@@ -635,6 +695,8 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u
        struct sigcontext context;
        int err = 0;
 
+       siginfo_build_tests();
+
        /* Always make any pending restarted system calls return -EINTR */
        current->restart_block.fn = do_no_restart_syscall;