diff options
| -rw-r--r-- | arch/parisc/kernel/signal.c | 64 |
1 files changed, 52 insertions, 12 deletions
diff --git a/arch/parisc/kernel/signal.c b/arch/parisc/kernel/signal.c index dc1ea796fd60..2264f68f3c2f 100644 --- a/arch/parisc/kernel/signal.c +++ b/arch/parisc/kernel/signal.c @@ -435,6 +435,55 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs, int in_syscall) regs->gr[28]); } +/* + * 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) { @@ -457,10 +506,7 @@ 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); break; } } @@ -510,15 +556,9 @@ 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); return; - } default: break; } |