diff options
| author | Sven Schnelle <svens@linux.ibm.com> | 2021-04-07 09:20:17 +0200 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2021-10-26 15:21:29 +0200 |
| commit | 3b051e89da70d464a036a86d70ce2ed61c73f792 (patch) | |
| tree | ad9a4dc6ce89d26aaf92d530d48df8e992c629e6 /arch/s390/kernel/syscall.c | |
| parent | s390: introduce nospec_uses_trampoline() (diff) | |
| download | linux-3b051e89da70d464a036a86d70ce2ed61c73f792.tar.xz linux-3b051e89da70d464a036a86d70ce2ed61c73f792.zip | |
s390: add support for BEAR enhancement facility
The Breaking-Event-Address-Register (BEAR) stores the address of the
last breaking event instruction. Breaking events are usually instructions
that change the program flow - for example branches, and instructions
that modify the address in the PSW like lpswe. This is useful for debugging
wild branches, because one could easily figure out where the wild branch
was originating from.
What is problematic is that lpswe is considered a breaking event, and
therefore overwrites BEAR on kernel exit. The BEAR enhancement facility
adds new instructions that allow to save/restore BEAR and also an lpswey
instruction that doesn't cause a breaking event. So we can save BEAR on
kernel entry and restore it on exit to user space.
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>
Diffstat (limited to 'arch/s390/kernel/syscall.c')
| -rw-r--r-- | arch/s390/kernel/syscall.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/kernel/syscall.c b/arch/s390/kernel/syscall.c index 8fe2d23b64f4..dc2355c623d6 100644 --- a/arch/s390/kernel/syscall.c +++ b/arch/s390/kernel/syscall.c @@ -154,6 +154,8 @@ void noinstr __do_syscall(struct pt_regs *regs, int per_trap) regs->psw = S390_lowcore.svc_old_psw; regs->int_code = S390_lowcore.svc_int_code; update_timer_sys(); + if (static_branch_likely(&cpu_has_bear)) + current->thread.last_break = regs->last_break; local_irq_enable(); regs->orig_gpr2 = regs->gprs[2]; |