powerpc/signal64: Remove TM ifdefery in middle of if/else block

Both rt_sigreturn() and handle_rt_signal_64() contain TM-related ifdefs
which break-up an if/else block. Provide stubs for the ifdef-guarded TM
functions and remove the need for an ifdef in rt_sigreturn().

Rework the remaining TM ifdef in handle_rt_signal64() similar to
commit f1cf4f93de2f ("powerpc/signal32: Remove ifdefery in middle of if/else").

Unlike in the commit for ppc32, the ifdef can't be removed entirely
since uc_transact in sigframe depends on CONFIG_PPC_TRANSACTIONAL_MEM.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-6-cmr@codefail.de

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 3231c2d..afb334d 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1117,9 +1117,10 @@ void restore_tm_state(struct pt_regs *regs)
        regs->msr |= msr_diff;
 }
 
-#else
+#else /* !CONFIG_PPC_TRANSACTIONAL_MEM */
 #define tm_recheckpoint_new_task(new)
 #define __switch_to_tm(prev, new)
+void tm_reclaim_current(uint8_t cause) {}
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 
 static inline void save_sprs(struct thread_struct *t)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 6ca5461..bd8d210 100644 (file)
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -594,6 +594,12 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 
        return err;
 }
+#else /* !CONFIG_PPC_TRANSACTIONAL_MEM */
+static long restore_tm_sigcontexts(struct task_struct *tsk, struct sigcontext __user *sc,
+                                  struct sigcontext __user *tm_sc)
+{
+       return -EINVAL;
+}
 #endif
 
 /*
@@ -710,9 +716,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
        struct pt_regs *regs = current_pt_regs();
        struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
        sigset_t set;
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        unsigned long msr;
-#endif
 
        /* Always make any pending restarted system calls return -EINTR */
        current->restart_block.fn = do_no_restart_syscall;
@@ -724,48 +728,50 @@ SYSCALL_DEFINE0(rt_sigreturn)
                goto badframe;
        set_current_blocked(&set);
 
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-       /*
-        * If there is a transactional state then throw it away.
-        * The purpose of a sigreturn is to destroy all traces of the
-        * signal frame, this includes any transactional state created
-        * within in. We only check for suspended as we can never be
-        * active in the kernel, we are active, there is nothing better to
-        * do than go ahead and Bad Thing later.
-        * The cause is not important as there will never be a
-        * recheckpoint so it's not user visible.
-        */
-       if (MSR_TM_SUSPENDED(mfmsr()))
-               tm_reclaim_current(0);
+       if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM)) {
+               /*
+                * If there is a transactional state then throw it away.
+                * The purpose of a sigreturn is to destroy all traces of the
+                * signal frame, this includes any transactional state created
+                * within in. We only check for suspended as we can never be
+                * active in the kernel, we are active, there is nothing better to
+                * do than go ahead and Bad Thing later.
+                * The cause is not important as there will never be a
+                * recheckpoint so it's not user visible.
+                */
+               if (MSR_TM_SUSPENDED(mfmsr()))
+                       tm_reclaim_current(0);
 
-       /*
-        * Disable MSR[TS] bit also, so, if there is an exception in the
-        * code below (as a page fault in copy_ckvsx_to_user()), it does
-        * not recheckpoint this task if there was a context switch inside
-        * the exception.
-        *
-        * A major page fault can indirectly call schedule(). A reschedule
-        * process in the middle of an exception can have a side effect
-        * (Changing the CPU MSR[TS] state), since schedule() is called
-        * with the CPU MSR[TS] disable and returns with MSR[TS]=Suspended
-        * (switch_to() calls tm_recheckpoint() for the 'new' process). In
-        * this case, the process continues to be the same in the CPU, but
-        * the CPU state just changed.
-        *
-        * This can cause a TM Bad Thing, since the MSR in the stack will
-        * have the MSR[TS]=0, and this is what will be used to RFID.
-        *
-        * Clearing MSR[TS] state here will avoid a recheckpoint if there
-        * is any process reschedule in kernel space. The MSR[TS] state
-        * does not need to be saved also, since it will be replaced with
-        * the MSR[TS] that came from user context later, at
-        * restore_tm_sigcontexts.
-        */
-       regs->msr &= ~MSR_TS_MASK;
+               /*
+                * Disable MSR[TS] bit also, so, if there is an exception in the
+                * code below (as a page fault in copy_ckvsx_to_user()), it does
+                * not recheckpoint this task if there was a context switch inside
+                * the exception.
+                *
+                * A major page fault can indirectly call schedule(). A reschedule
+                * process in the middle of an exception can have a side effect
+                * (Changing the CPU MSR[TS] state), since schedule() is called
+                * with the CPU MSR[TS] disable and returns with MSR[TS]=Suspended
+                * (switch_to() calls tm_recheckpoint() for the 'new' process). In
+                * this case, the process continues to be the same in the CPU, but
+                * the CPU state just changed.
+                *
+                * This can cause a TM Bad Thing, since the MSR in the stack will
+                * have the MSR[TS]=0, and this is what will be used to RFID.
+                *
+                * Clearing MSR[TS] state here will avoid a recheckpoint if there
+                * is any process reschedule in kernel space. The MSR[TS] state
+                * does not need to be saved also, since it will be replaced with
+                * the MSR[TS] that came from user context later, at
+                * restore_tm_sigcontexts.
+                */
+               regs->msr &= ~MSR_TS_MASK;
 
-       if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR]))
-               goto badframe;
-       if (MSR_TM_ACTIVE(msr)) {
+               if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR]))
+                       goto badframe;
+       }
+
+       if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) && MSR_TM_ACTIVE(msr)) {
                /* We recheckpoint on return. */
                struct ucontext __user *uc_transact;
 
@@ -778,9 +784,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
                if (restore_tm_sigcontexts(current, &uc->uc_mcontext,
                                           &uc_transact->uc_mcontext))
                        goto badframe;
-       } else
-#endif
-       {
+       } else {
                /*
                 * Fall through, for non-TM restore
                 *
@@ -818,10 +822,8 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
        unsigned long newsp = 0;
        long err = 0;
        struct pt_regs *regs = tsk->thread.regs;
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        /* Save the thread's msr before get_tm_stackpointer() changes it */
        unsigned long msr = regs->msr;
-#endif
 
        frame = get_sigframe(ksig, tsk, sizeof(*frame), 0);
        if (!access_ok(frame, sizeof(*frame)))
@@ -836,8 +838,9 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
        /* Create the ucontext.  */
        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __save_altstack(&frame->uc.uc_stack, regs->gpr[1]);
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+
        if (MSR_TM_ACTIVE(msr)) {
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
                /* The ucontext_t passed to userland points to the second
                 * ucontext_t (for transactional state) with its uc_link ptr.
                 */
@@ -847,9 +850,8 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
                                            tsk, ksig->sig, NULL,
                                            (unsigned long)ksig->ka.sa.sa_handler,
                                            msr);
-       } else
 #endif
-       {
+       } else {
                err |= __put_user(0, &frame->uc.uc_link);
                prepare_setup_sigcontext(tsk);
                err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,