[PATCH 5.12 231/242] s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall

Greg Kroah-Hartman
2021-07-15T19:20:44Z

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