• Eric Paris's avatar
    Audit: push audit success and retcode into arch ptrace.h · d7e7528b
    Eric Paris authored
    The audit system previously expected arches calling to audit_syscall_exit to
    supply as arguments if the syscall was a success and what the return code was.
    Audit also provides a helper AUDITSC_RESULT which was supposed to simplify things
    by converting from negative retcodes to an audit internal magic value stating
    success or failure.  This helper was wrong and could indicate that a valid
    pointer returned to userspace was a failed syscall.  The fix is to fix the
    layering foolishness.  We now pass audit_syscall_exit a struct pt_reg and it
    in turns calls back into arch code to collect the return value and to
    determine if the syscall was a success or failure.  We also define a generic
    is_syscall_success() macro which determines success/failure based on if the
    value is < -MAX_ERRNO.  This works for arches like x86 which do not use a
    separate mechanism to indicate syscall failure.
    
    We make both the is_syscall_success() and regs_return_value() static inlines
    instead of macros.  The reason is because the audit function must take a void*
    for the regs.  (uml calls theirs struct uml_pt_regs instead of just struct
    pt_regs so audit_syscall_exit can't take a struct pt_regs).  Since the audit
    function takes a void* we need to use static inlines to cast it back to the
    arch correct structure to dereference it.
    
    The other major change is that on some arches, like ia64, MIPS and ppc, we
    change regs_return_value() to give us the negative value on syscall failure.
    THE only other user of this macro, kretprobe_example.c, won't notice and it
    makes the value signed consistently for the audit functions across all archs.
    
    In arch/sh/kernel/ptrace_64.c I see that we were using regs[9] in the old
    audit code as the return value.  But the ptrace_64.h code defined the macro
    regs_return_value() as regs[3].  I have no idea which one is correct, but this
    patch now uses the regs_return_value() function, so it now uses regs[3].
    
    For powerpc we previously used regs->result but now use the
    regs_return_value() function which uses regs->gprs[3].  regs->gprs[3] is
    always positive so the regs_return_value(), much like ia64 makes it negative
    before calling the audit code when appropriate.
    Signed-off-by: default avatarEric Paris <eparis@redhat.com>
    Acked-by: H. Peter Anvin <hpa@zytor.com> [for x86 portion]
    Acked-by: Tony Luck <tony.luck@intel.com> [for ia64]
    Acked-by: Richard Weinberger <richard@nod.at> [for uml]
    Acked-by: David S. Miller <davem@davemloft.net> [for sparc]
    Acked-by: Ralf Baechle <ralf@linux-mips.org> [for mips]
    Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [for ppc]
    d7e7528b
ptrace.h 2 KB