• Helge Deller's avatar
    parisc: Fix syscall restarts · 4b1338cc
    Helge Deller authored
    commit 71a71fb5 upstream.
    
    On parisc syscalls which are interrupted by signals sometimes failed to
    restart and instead returned -ENOSYS which in the worst case lead to
    userspace crashes.
    A similiar problem existed on MIPS and was fixed by commit e967ef02
    ("MIPS: Fix restart of indirect syscalls").
    
    On parisc the current syscall restart code assumes that all syscall
    callers load the syscall number in the delay slot of the ble
    instruction. That's how it is e.g. done in the unistd.h header file:
    	ble 0x100(%sr2, %r0)
    	ldi #syscall_nr, %r20
    Because of that assumption the current code never restored %r20 before
    returning to userspace.
    
    This assumption is at least not true for code which uses the glibc
    syscall() function, which instead uses this syntax:
    	ble 0x100(%sr2, %r0)
    	copy regX, %r20
    where regX depend on how the compiler optimizes the code and register
    usage.
    
    This patch fixes this problem by adding code to analyze how the syscall
    number is loaded in the delay branch and - if needed - copy the syscall
    number to regX prior returning to userspace for the syscall restart.
    Signed-off-by: default avatarHelge Deller <deller@gmx.de>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    4b1338cc
signal.c 18 KB