commit 16dd46bb781a1d37eeb2377e8e48276e9d14d15d
author Catalin Marinas <catalin.marinas@arm.com> Tue Oct 16 17:07:46 2012 +0100
committer Catalin Marinas <catalin.marinas@arm.com> Thu Oct 18 20:14:01 2012 +0100
tree f5f0626fdf4a841ffba5f7ce79e7e8cbfee6a56a
parent f71a1a42667f576ec736bb1200eba2118fee3a22

arm64: No need to set the x0-x2 registers in start_thread()

For historical reasons, ARM used to set r0-r2 in start_thread() to the
first values on the user stack when starting a new user application. The
same logic has been inherited in AArch64. The x0 register is overridden
by the sys_execve() return value so it's always zero on success. The x1
and x2 registers are ignored by AArch64 and EABI AArch32 applications,
so we can safely remove the register setting for both native and compat
user space.

This also fixes a potential fault with the kernel accessing user space
stack directly.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>