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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-03-22 10:54:24 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-02-08 14:13:25 +0100 |
| commit | 57d7f939e7bdd746992f5c318a78697ba837c523 (patch) | |
| tree | 80c01c9c446fc190432798a6d1ecf0c8e5456b57 /arch/s390/kernel/entry.S | |
| parent | 2583b848cad049cf5f3f0a03af8b140668b376f3 (diff) | |
| download | lwn-57d7f939e7bdd746992f5c318a78697ba837c523.tar.gz lwn-57d7f939e7bdd746992f5c318a78697ba837c523.zip | |
s390: add no-execute support
Bit 0x100 of a page table, segment table of region table entry
can be used to disallow code execution for the virtual addresses
associated with the entry.
There is one tricky bit, the system call to return from a signal
is part of the signal frame written to the user stack. With a
non-executable stack this would stop working. To avoid breaking
things the protection fault handler checks the opcode that caused
the fault for 0x0a77 (sys_sigreturn) and 0x0aad (sys_rt_sigreturn)
and injects a system call. This is preferable to the alternative
solution with a stub function in the vdso because it works for
vdso=off and statically linked binaries as well.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/entry.S')
| -rw-r--r-- | arch/s390/kernel/entry.S | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index f687f168c94d..34ab7e8d6a76 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -380,13 +380,11 @@ ENTRY(system_call) brasl %r14,do_signal TSTMSK __PT_FLAGS(%r11),_PIF_SYSCALL jno .Lsysc_return +.Lsysc_do_syscall: + lghi %r13,__TASK_thread lmg %r2,%r7,__PT_R2(%r11) # load svc arguments - lghi %r8,0 # svc 0 returns -ENOSYS - llgh %r1,__PT_INT_CODE+2(%r11) # load new svc number - cghi %r1,NR_syscalls - jnl .Lsysc_nr_ok # invalid svc number -> do svc 0 - slag %r8,%r1,2 - j .Lsysc_nr_ok # restart svc + lghi %r1,0 # svc 0 returns -ENOSYS + j .Lsysc_do_svc # # _TIF_NOTIFY_RESUME is set, call do_notify_resume @@ -528,6 +526,8 @@ ENTRY(pgm_check_handler) LOCKDEP_SYS_EXIT tm __PT_PSW+1(%r11),0x01 # returning to user ? jno .Lsysc_restore + TSTMSK __PT_FLAGS(%r11),_PIF_SYSCALL + jo .Lsysc_do_syscall j .Lsysc_tif # |