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s390: move restart of execve() syscall

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On s390, execve might have to be restarted for PGSTE binaries
like kvm. In the past this was done via the PIF_SYSCALL_RESTART
bit. However, with the recent changes, syscalls are now restarted
differently. Now that execve() is the only call that might get
restarted via PIF_SYSCALL_RESTART, move the loop to do_syscall().
This also has the advantage that the restart is no longer visible
to userspace.

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 2021-06-30 13:50:55 +02:00 committed by Vasily Gorbik
parent fbf50f47ea
commit e3c7a8d7f4
2 changed files with 20 additions and 15 deletions
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8
arch/s390/include/asm/ptrace.h
View File

@ -162,6 +162,14 @@ static inline int test_pt_regs_flag(struct pt_regs *regs, int flag)
return !!(regs->flags & (1UL << flag));
}
static inline int test_and_clear_pt_regs_flag(struct pt_regs *regs, int flag)
{
int ret = test_pt_regs_flag(regs, flag);
clear_pt_regs_flag(regs, flag);
return ret;
}
/*
* These are defined as per linux/ptrace.h, which see.
*/

27
arch/s390/kernel/syscall.c
View File

@ -134,13 +134,15 @@ static void do_syscall(struct pt_regs *regs)
* work, the ptrace code sets PIF_SYSCALL_RET_SET, which is checked here
* and if set, the syscall will be skipped.
*/
if (!test_pt_regs_flag(regs, PIF_SYSCALL_RET_SET)) {
regs->gprs[2] = -ENOSYS;
if (likely(nr < NR_syscalls))
regs->gprs[2] = current->thread.sys_call_table[nr](regs);
} else {
clear_pt_regs_flag(regs, PIF_SYSCALL_RET_SET);
}
if (unlikely(test_and_clear_pt_regs_flag(regs, PIF_SYSCALL_RET_SET)))
goto out;
regs->gprs[2] = -ENOSYS;
if (likely(nr >= NR_syscalls))
goto out;
do {
regs->gprs[2] = current->thread.sys_call_table[nr](regs);
} while (test_and_clear_pt_regs_flag(regs, PIF_SYSCALL_RESTART));
out:
syscall_exit_to_user_mode_work(regs);
}
@ -158,13 +160,8 @@ void noinstr __do_syscall(struct pt_regs *regs, int per_trap)
if (per_trap)
set_thread_flag(TIF_PER_TRAP);
for (;;) {
regs->flags = 0;
set_pt_regs_flag(regs, PIF_SYSCALL);
do_syscall(regs);
if (!test_pt_regs_flag(regs, PIF_SYSCALL_RESTART))
break;
local_irq_enable();
}
regs->flags = 0;
set_pt_regs_flag(regs, PIF_SYSCALL);
do_syscall(regs);
exit_to_user_mode();
}