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s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall

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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>
This commit is contained in:
Sven Schnelle 2021-06-25 14:48:28 +02:00 committed by Vasily Gorbik
parent d57778feb9
commit 686341f254
2 changed files with 20 additions and 0 deletions
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3
arch/s390/kernel/vdso64/vdso64.lds.S
View File

@ -137,6 +137,9 @@ VERSION
__kernel_clock_gettime;
__kernel_clock_getres;
__kernel_getcpu;
__kernel_restart_syscall;
__kernel_rt_sigreturn;
__kernel_sigreturn;
local: *;
};
}

17
arch/s390/kernel/vdso64/vdso_user_wrapper.S
View File

@ -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