From: Sven Schnelle svens@linux.ibm.com
commit 686341f2548b5a4c4ab1ee22427e046027ae1c9c upstream.
Add minimalistic trampolines to vdso64 so we can return from signal without using the stack which requires pgm check handler hacks when NX is enabled.
restart_syscall will be called from vdso to work around the architectural limitation that the syscall number might be encoded in the svc instruction, and therefore can not be changed.
Signed-off-by: Sven Schnelle svens@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/vdso64/vdso64.lds.S | 3 +++ arch/s390/kernel/vdso64/vdso_user_wrapper.S | 17 +++++++++++++++++ 2 files changed, 20 insertions(+)
--- a/arch/s390/kernel/vdso64/vdso64.lds.S +++ b/arch/s390/kernel/vdso64/vdso64.lds.S @@ -137,6 +137,9 @@ VERSION __kernel_clock_gettime; __kernel_clock_getres; __kernel_getcpu; + __kernel_restart_syscall; + __kernel_rt_sigreturn; + __kernel_sigreturn; local: *; }; } --- a/arch/s390/kernel/vdso64/vdso_user_wrapper.S +++ b/arch/s390/kernel/vdso64/vdso_user_wrapper.S @@ -37,3 +37,20 @@ vdso_func gettimeofday vdso_func clock_getres vdso_func clock_gettime vdso_func getcpu + +.macro vdso_syscall func,syscall + .globl __kernel_\func + .type __kernel_\func,@function + .align 8 +__kernel_\func: + CFI_STARTPROC + svc \syscall + /* Make sure we notice when a syscall returns, which shouldn't happen */ + .word 0 + CFI_ENDPROC + .size __kernel_\func,.-__kernel_\func +.endm + +vdso_syscall restart_syscall,__NR_restart_syscall +vdso_syscall sigreturn,__NR_sigreturn +vdso_syscall rt_sigreturn,__NR_rt_sigreturn