Linux manages to have three separate orderings of the arguments to
the clone() syscall on different architectures. In the kernel these
are selected via CONFIG_CLONE_BACKWARDS and CONFIG_CLONE_BACKWARDS2.
Clean up our implementation of this to use similar #define names
rather than a TARGET_* ifdef ladder.
This includes behaviour changes fixing bugs on cris, x86-64, m68k,
openrisc and unicore32. cris had explicit but wrong handling; the
others were just incorrectly using QEMU's default, which happened
to be the equivalent of CONFIG_CLONE_BACKWARDS. (unicore32 appears
to be broken in the mainline kernel in that it tries to use arg3 for
both parent_tidptr and newtls simultaneously -- we don't attempt
to emulate this bug...)
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Also fixes a register corruption bug in do_sigreturn. When "returning"
from sigreturn we are actually restoring the virtual cpu state from the
signal frame. This is actually surprisingly hard to observe in practice.
Typically an thread be blocked in a FUTEX_WAIT call when the signal arrives,
so the effect is a spurious syscall success and the introduction of a
subtle race condition.
On x86/arm a syscall modifies a single word sized register, so
do_sigreturn can just return that value. On MIPS a syscall clobbers
multiple registers, so we need additional smarts. My solution is to
invent a magic errno value that means "don't touch CPU state".
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7194 c046a42c-6fe2-441c-8c8c-71466251a162
