powerpc: Fix various syscall/signal/swapcontext bugs

A careful reading of the recent changes to the system call entry/exit
paths revealed several problems, plus some things that could be
simplified and improved:

* 32-bit wasn't testing the _TIF_NOERROR bit in the syscall fast exit
  path, so it was only doing anything with it once it saw some other
  bit being set.  In other words, the noerror behaviour would apply to
  the next system call where we had to reschedule or deliver a signal,
  which is not necessarily the current system call.

* 32-bit wasn't doing the call to ptrace_notify in the syscall exit
  path when the _TIF_SINGLESTEP bit was set.

* _TIF_RESTOREALL was in both _TIF_USER_WORK_MASK and
  _TIF_PERSYSCALL_MASK, which is odd since _TIF_RESTOREALL is only set
  by system calls.  I took it out of _TIF_USER_WORK_MASK.

* On 64-bit, _TIF_RESTOREALL wasn't causing the non-volatile registers
  to be restored (unless perhaps a signal was delivered or the syscall
  was traced or single-stepped).  Thus the non-volatile registers
  weren't restored on exit from a signal handler.  We probably got
  away with it mostly because signal handlers written in C wouldn't
  alter the non-volatile registers.

* On 32-bit I simplified the code and made it more like 64-bit by
  making the syscall exit path jump to ret_from_except to handle
  preemption and signal delivery.

* 32-bit was calling do_signal unnecessarily when _TIF_RESTOREALL was
  set - but I think because of that 32-bit was actually restoring the
  non-volatile registers on exit from a signal handler.

* I changed the order of enabling interrupts and saving the
  non-volatile registers before calling do_syscall_trace_leave; now we
  enable interrupts first.

Signed-off-by: Paul Mackerras <paulus@samba.org>

7 files changed, 52 insertions, 173 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 840aad43a98b..c9a660e4c2db 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -92,7 +92,6 @@ int main(void)
 
         DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
         DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count));
-        DEFINE(TI_SIGFRAME, offsetof(struct thread_info, nvgprs_frame));
         DEFINE(TI_TASK, offsetof(struct thread_info, task));
 #ifdef CONFIG_PPC32
         DEFINE(TI_EXECDOMAIN, offsetof(struct thread_info, exec_domain));
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index f20a67261ec7..4827ca1ec89b 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -227,7 +227,7 @@ ret_from_syscall:
         MTMSRD(r10)
         lwz     r9,TI_FLAGS(r12)
         li      r8,-_LAST_ERRNO
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_RESTORE_SIGMASK)
+        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
         bne-    syscall_exit_work
         cmplw   0,r3,r8
         blt+    syscall_exit_cont
@@ -287,8 +287,10 @@ syscall_dotrace:
 
 syscall_exit_work:
         andi.   r0,r9,_TIF_RESTOREALL
-        bne-    2f
-        cmplw   0,r3,r8
+        beq+    0f
+        REST_NVGPRS(r1)
+        b       2f
+0:      cmplw   0,r3,r8
         blt+    1f
         andi.   r0,r9,_TIF_NOERROR
         bne-    1f
@@ -302,9 +304,7 @@ syscall_exit_work:
 2:      andi.   r0,r9,(_TIF_PERSYSCALL_MASK)
         beq     4f
 
-        /* Clear per-syscall TIF flags if any are set, but _leave_
-        _TIF_SAVE_NVGPRS set in r9 since we haven't dealt with that
-        yet.  */
+        /* Clear per-syscall TIF flags if any are set.  */
 
         li      r11,_TIF_PERSYSCALL_MASK
         addi    r12,r12,TI_FLAGS
@@ -318,8 +318,13 @@ syscall_exit_work:
         subi    r12,r12,TI_FLAGS
         
 4:      /* Anything which requires enabling interrupts? */
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SAVE_NVGPRS)
-        beq     7f
+        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
+        beq     ret_from_except
+
+        /* Re-enable interrupts */
+        ori     r10,r10,MSR_EE
+        SYNC
+        MTMSRD(r10)
 
         /* Save NVGPRS if they're not saved already */
         lwz     r4,_TRAP(r1)
@@ -328,71 +333,11 @@ syscall_exit_work:
         SAVE_NVGPRS(r1)
         li      r4,0xc00
         stw     r4,_TRAP(r1)
-
-        /* Re-enable interrupts */
-5:      ori     r10,r10,MSR_EE
-        SYNC
-        MTMSRD(r10)
-
-        andi.   r0,r9,_TIF_SAVE_NVGPRS
-        bne     save_user_nvgprs
-
-save_user_nvgprs_cont:
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
-        beq     7f
-
+5:
         addi    r3,r1,STACK_FRAME_OVERHEAD
         bl      do_syscall_trace_leave
-        REST_NVGPRS(r1)
-
-6:      lwz     r3,GPR3(r1)
-        LOAD_MSR_KERNEL(r10,MSR_KERNEL) /* doesn't include MSR_EE */
-        SYNC
-        MTMSRD(r10)             /* disable interrupts again */
-        rlwinm  r12,r1,0,0,(31-THREAD_SHIFT)    /* current_thread_info() */
-        lwz     r9,TI_FLAGS(r12)
-7:
-        andi.   r0,r9,_TIF_NEED_RESCHED
-        bne     8f
-        lwz     r5,_MSR(r1)
-        andi.   r5,r5,MSR_PR
-        beq     ret_from_except
-        andi.   r0,r9,_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK
-        beq     ret_from_except
-        b       do_user_signal
-8:
-        ori     r10,r10,MSR_EE
-        SYNC
-        MTMSRD(r10)             /* re-enable interrupts */
-        bl      schedule
-        b       6b
-
-save_user_nvgprs:
-        lwz     r8,TI_SIGFRAME(r12)
-
-.macro savewords start, end
-  1:    stw \start,4*(\start)(r8)
-        .section __ex_table,"a"
-        .align  2
-        .long   1b,save_user_nvgprs_fault
-        .previous
-        .if \end - \start
-        savewords "(\start+1)",\end
-        .endif
-.endm   
-        savewords 14,31
-        b       save_user_nvgprs_cont
-
-        
-save_user_nvgprs_fault:
-        li      r3,11           /* SIGSEGV */
-        lwz     r4,TI_TASK(r12)
-        bl      force_sigsegv
+        b       ret_from_except_full
 
-        rlwinm  r12,r1,0,0,(31-THREAD_SHIFT)    /* current_thread_info() */
-        lwz     r9,TI_FLAGS(r12)
-        b       save_user_nvgprs_cont
-        
 #ifdef SHOW_SYSCALLS
 do_show_syscall:
 #ifdef SHOW_SYSCALLS_TASK
@@ -490,6 +435,14 @@ ppc_clone:
         stw     r0,_TRAP(r1)            /* register set saved */
         b       sys_clone
 
+        .globl  ppc_swapcontext
+ppc_swapcontext:
+        SAVE_NVGPRS(r1)
+        lwz     r0,_TRAP(r1)
+        rlwinm  r0,r0,0,0,30            /* clear LSB to indicate full */
+        stw     r0,_TRAP(r1)            /* register set saved */
+        b       sys_swapcontext
+
 /*
  * Top-level page fault handling.
  * This is in assembler because if do_page_fault tells us that
@@ -683,7 +636,7 @@ user_exc_return:		/* r10 contains MSR_KERNEL here */
         /* Check current_thread_info()->flags */
         rlwinm  r9,r1,0,0,(31-THREAD_SHIFT)
         lwz     r9,TI_FLAGS(r9)
-        andi.   r0,r9,(_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_RESTORE_SIGMASK)
+        andi.   r0,r9,(_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK|_TIF_NEED_RESCHED)
         bne     do_work
 
 restore_user:
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 388f861b8ed1..24be0cf86d7f 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -160,7 +160,7 @@ syscall_exit:
         mtmsrd  r10,1
         ld      r9,TI_FLAGS(r12)
         li      r11,-_LAST_ERRNO
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_SAVE_NVGPRS|_TIF_NOERROR|_TIF_RESTORE_SIGMASK)
+        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
         bne-    syscall_exit_work
         cmpld   r3,r11
         ld      r5,_CCR(r1)
@@ -216,8 +216,10 @@ syscall_exit_work:
          If TIF_NOERROR is set, just save r3 as it is. */
 
         andi.   r0,r9,_TIF_RESTOREALL
-        bne-    2f
-        cmpld   r3,r11          /* r10 is -LAST_ERRNO */
+        beq+    0f
+        REST_NVGPRS(r1)
+        b       2f
+0:      cmpld   r3,r11          /* r10 is -LAST_ERRNO */
         blt+    1f
         andi.   r0,r9,_TIF_NOERROR
         bne-    1f
@@ -229,9 +231,7 @@ syscall_exit_work:
 2:      andi.   r0,r9,(_TIF_PERSYSCALL_MASK)
         beq     4f
 
-        /* Clear per-syscall TIF flags if any are set, but _leave_
-        _TIF_SAVE_NVGPRS set in r9 since we haven't dealt with that
-        yet.  */
+        /* Clear per-syscall TIF flags if any are set.  */
 
         li      r11,_TIF_PERSYSCALL_MASK
         addi    r12,r12,TI_FLAGS
@@ -240,10 +240,9 @@ syscall_exit_work:
         stdcx.  r10,0,r12
         bne-    3b
         subi    r12,r12,TI_FLAGS
-        
-4:      bl      .save_nvgprs
-        /* Anything else left to do? */
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SAVE_NVGPRS)
+
+4:      /* Anything else left to do? */
+        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
         beq     .ret_from_except_lite
 
         /* Re-enable interrupts */
@@ -251,26 +250,10 @@ syscall_exit_work:
         ori     r10,r10,MSR_EE
         mtmsrd  r10,1
 
-        andi.   r0,r9,_TIF_SAVE_NVGPRS
-        bne     save_user_nvgprs
-
-        /* If tracing, re-enable interrupts and do it */
-save_user_nvgprs_cont:  
-        andi.   r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
-        beq     5f
-        
+        bl      .save_nvgprs
         addi    r3,r1,STACK_FRAME_OVERHEAD
         bl      .do_syscall_trace_leave
-        REST_NVGPRS(r1)
-        clrrdi  r12,r1,THREAD_SHIFT
-
-        /* Disable interrupts again and handle other work if any */
-5:      mfmsr   r10
-        rldicl  r10,r10,48,1
-        rotldi  r10,r10,16
-        mtmsrd  r10,1
-
-        b       .ret_from_except_lite
+        b       .ret_from_except
 
 /* Save non-volatile GPRs, if not already saved. */
 _GLOBAL(save_nvgprs)
@@ -282,51 +265,6 @@ _GLOBAL(save_nvgprs)
         std     r0,_TRAP(r1)
         blr
 
-
-save_user_nvgprs:
-        ld      r10,TI_SIGFRAME(r12)
-        andi.   r0,r9,_TIF_32BIT
-        beq-    save_user_nvgprs_64
-
-        /* 32-bit save to userspace */
-
-.macro savewords start, end
-  1:    stw \start,4*(\start)(r10)
-        .section __ex_table,"a"
-        .align  3
-        .llong  1b,save_user_nvgprs_fault
-        .previous
-        .if \end - \start
-        savewords "(\start+1)",\end
-        .endif
-.endm   
-        savewords 14,31
-        b       save_user_nvgprs_cont
-
-save_user_nvgprs_64:
-        /* 64-bit save to userspace */
-
-.macro savelongs start, end
-  1:    std \start,8*(\start)(r10)
-        .section __ex_table,"a"
-        .align  3
-        .llong  1b,save_user_nvgprs_fault
-        .previous
-        .if \end - \start
-        savelongs "(\start+1)",\end
-        .endif
-.endm   
-        savelongs 14,31
-        b       save_user_nvgprs_cont
-
-save_user_nvgprs_fault:
-        li      r3,11           /* SIGSEGV */
-        ld      r4,TI_TASK(r12)
-        bl      .force_sigsegv
-
-        clrrdi  r12,r1,THREAD_SHIFT
-        ld      r9,TI_FLAGS(r12)
-        b       save_user_nvgprs_cont
         
 /*
  * The sigsuspend and rt_sigsuspend system calls can call do_signal
@@ -352,6 +290,16 @@ _GLOBAL(ppc_clone)
         bl      .sys_clone
         b       syscall_exit
 
+_GLOBAL(ppc32_swapcontext)
+        bl      .save_nvgprs
+        bl      .compat_sys_swapcontext
+        b       syscall_exit
+
+_GLOBAL(ppc64_swapcontext)
+        bl      .save_nvgprs
+        bl      .sys_swapcontext
+        b       syscall_exit
+
 _GLOBAL(ret_from_fork)
         bl      .schedule_tail
         REST_NVGPRS(r1)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 400793c71304..bcb83574335b 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -561,10 +561,7 @@ void do_syscall_trace_leave(struct pt_regs *regs)
                                    regs->result);
 
         if ((test_thread_flag(TIF_SYSCALL_TRACE)
-#ifdef CONFIG_PPC64
-             || test_thread_flag(TIF_SINGLESTEP)
-#endif
-             )
+             || test_thread_flag(TIF_SINGLESTEP))
             && (current->ptrace & PT_PTRACED))
                 do_syscall_trace();
 }
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index bd837b5dbf06..d7a4e814974d 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -151,10 +151,7 @@ static inline int save_general_regs(struct pt_regs *regs,
         elf_greg_t64 *gregs = (elf_greg_t64 *)regs;
         int i;
 
-        if (!FULL_REGS(regs)) {
-                set_thread_flag(TIF_SAVE_NVGPRS);
-                current_thread_info()->nvgprs_frame = frame->mc_gregs;
-        }
+        WARN_ON(!FULL_REGS(regs));
 
         for (i = 0; i <= PT_RESULT; i ++) {
                 if (i == 14 && !FULL_REGS(regs))
@@ -215,15 +212,7 @@ static inline int get_old_sigaction(struct k_sigaction *new_ka,
 static inline int save_general_regs(struct pt_regs *regs,
                 struct mcontext __user *frame)
 {
-        if (!FULL_REGS(regs)) {
-                /* Zero out the unsaved GPRs to avoid information
-                   leak, and set TIF_SAVE_NVGPRS to ensure that the
-                   registers do actually get saved later. */
-                memset(&regs->gpr[14], 0, 18 * sizeof(unsigned long));
-                current_thread_info()->nvgprs_frame = &frame->mc_gregs;
-                set_thread_flag(TIF_SAVE_NVGPRS);
-        }
-
+        WARN_ON(!FULL_REGS(regs));
         return __copy_to_user(&frame->mc_gregs, regs, GP_REGS_SIZE);
 }
 
@@ -826,8 +815,8 @@ static int do_setcontext(struct ucontext __user *ucp, struct pt_regs *regs, int
 }
 
 long sys_swapcontext(struct ucontext __user *old_ctx,
-                       struct ucontext __user *new_ctx,
-                       int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
+                     struct ucontext __user *new_ctx,
+                     int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
 {
         unsigned char tmp;
 
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 497a5d3df359..4324f8a8ba24 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -118,14 +118,7 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
         err |= __put_user(0, &sc->v_regs);
 #endif /* CONFIG_ALTIVEC */
         err |= __put_user(&sc->gp_regs, &sc->regs);
-        if (!FULL_REGS(regs)) {
-                /* Zero out the unsaved GPRs to avoid information
-                   leak, and set TIF_SAVE_NVGPRS to ensure that the
-                   registers do actually get saved later. */
-                memset(&regs->gpr[14], 0, 18 * sizeof(unsigned long));
-                set_thread_flag(TIF_SAVE_NVGPRS);
-                current_thread_info()->nvgprs_frame = &sc->gp_regs;
-        }
+        WARN_ON(!FULL_REGS(regs));
         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
         err |= __put_user(signr, &sc->signal);
diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.S
index 8a9f994ed917..1ad55f0466fd 100644
--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.S
@@ -288,7 +288,7 @@ COMPAT_SYS(clock_settime)
 COMPAT_SYS(clock_gettime)
 COMPAT_SYS(clock_getres)
 COMPAT_SYS(clock_nanosleep)
-COMPAT_SYS(swapcontext)
+SYSX(ppc64_swapcontext,ppc32_swapcontext,ppc_swapcontext)
 COMPAT_SYS(tgkill)
 COMPAT_SYS(utimes)
 COMPAT_SYS(statfs64)