linux_sigreturn() loads the struct trapframe from l_sigcontext members, thus making a signed extension of 32 bit register context. If the register is not touched in usermode between return from signal and next syscall entry, the sign-extension part of 64bit register is not cleared, causing linux32_fetch_syscall_args() to read wrong values.
linux_sigreturn() loads the struct trapframe from l_sigcontext
members, thus making a signed extension of 32 bit register
context. If the register is not touched in usermode between
return from signal and next syscall entry, the sign-extension
part of 64bit register is not cleared, causing
linux32_fetch_syscall_args() to read wrong values.

Use unsigned type for the registers in the linux sigcontext.

Reported by:	Jacob Frelinger <jacob.frelinger duke edu>, arundel
In collaboration with:	dchagin
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase