parisc: Fix syscall restarts

[pandora-kernel.git] / arch / parisc / kernel / signal.c

diff --git a/arch/parisc/kernel/signal.c b/arch/parisc/kernel/signal.c
index 12c1ed3..f7c8352 100644 (file)
--- a/arch/parisc/kernel/signal.c
+++ b/arch/parisc/kernel/signal.c
@@ -468,6 +468,55 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
        return 1;
 }
 
+/*
+ * Check how the syscall number gets loaded into %r20 within
+ * the delay branch in userspace and adjust as needed.
+ */
+
+static void check_syscallno_in_delay_branch(struct pt_regs *regs)
+{
+       u32 opcode, source_reg;
+       u32 __user *uaddr;
+       int err;
+
+       /* Usually we don't have to restore %r20 (the system call number)
+        * because it gets loaded in the delay slot of the branch external
+        * instruction via the ldi instruction.
+        * In some cases a register-to-register copy instruction might have
+        * been used instead, in which case we need to copy the syscall
+        * number into the source register before returning to userspace.
+        */
+
+       /* A syscall is just a branch, so all we have to do is fiddle the
+        * return pointer so that the ble instruction gets executed again.
+        */
+       regs->gr[31] -= 8; /* delayed branching */
+
+       /* Get assembler opcode of code in delay branch */
+       uaddr = (unsigned int *) ((regs->gr[31] & ~3) + 4);
+       err = get_user(opcode, uaddr);
+       if (err)
+               return;
+
+       /* Check if delay branch uses "ldi int,%r20" */
+       if ((opcode & 0xffff0000) == 0x34140000)
+               return; /* everything ok, just return */
+
+       /* Check if delay branch uses "nop" */
+       if (opcode == INSN_NOP)
+               return;
+
+       /* Check if delay branch uses "copy %rX,%r20" */
+       if ((opcode & 0xffe0ffff) == 0x08000254) {
+               source_reg = (opcode >> 16) & 31;
+               regs->gr[source_reg] = regs->gr[20];
+               return;
+       }
+
+       pr_warn("syscall restart: %s (pid %d): unexpected opcode 0x%08x\n",
+               current->comm, task_pid_nr(current), opcode);
+}
+
 static inline void
 syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
 {
@@ -489,10 +538,7 @@ syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
                }
                /* fallthrough */
        case -ERESTARTNOINTR:
-               /* A syscall is just a branch, so all
-                * we have to do is fiddle the return pointer.
-                */
-               regs->gr[31] -= 8; /* delayed branching */
+               check_syscallno_in_delay_branch(regs);
                /* Preserve original r28. */
                regs->gr[28] = regs->orig_r28;
                break;
@@ -543,18 +589,12 @@ insert_restart_trampoline(struct pt_regs *regs)
        }
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
-       case -ERESTARTNOINTR: {
-               /* Hooray for delayed branching.  We don't
-                * have to restore %r20 (the system call
-                * number) because it gets loaded in the delay
-                * slot of the branch external instruction.
-                */
-               regs->gr[31] -= 8;
+       case -ERESTARTNOINTR:
+               check_syscallno_in_delay_branch(regs);
                /* Preserve original r28. */
                regs->gr[28] = regs->orig_r28;
 
                return;
-       }
        default:
                break;
        }