s390/ptrace: Preserve ILC when updating system call number

When an attached debugger changes gpr2 via PTRACE_POKEUSR while the
traced process has PIF_SYSCALL set, the int_code in pt_regs is also
updated. In case of an svc it contains the instruction length code
(ILC), as well as the system call number.

The ptrace code sets the ILC unconditionally to a value which matches the
svc instruction. However the svc instruction also may have been executed
via the execute or execute relative long instruction, which have a
different length. Therefore preserve the ILC and only change the system
call number using syscall_set_nr().

This makes sure that in case of a PSW rewind the instruction address
points to the correct instruction.

Fixes: 56e62a737028 ("s390: convert to generic entry")
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions