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| author | Martin Schwidefsky | 2017-09-12 16:37:33 +0200 |
|---|---|---|
| committer | Martin Schwidefsky | 2018-10-09 11:20:57 +0200 |
| commit | ce3dc447493ff4186b192b38d723ab5e8c1eb52f (patch) | |
| tree | f93f58afcd85087876a1ab9badcdaed76b5a37fe /arch/s390/kernel/entry.h | |
| parent | s390: add stack switch helper (diff) | |
| download | kernel-qcow2-linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.tar.gz kernel-qcow2-linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.tar.xz kernel-qcow2-linux-ce3dc447493ff4186b192b38d723ab5e8c1eb52f.zip | |
s390: add support for virtually mapped kernel stacks
With virtually mapped kernel stacks the kernel stack overflow detection
is now fault based, every stack has a guard page in the vmalloc space.
The panic_stack is renamed to nodat_stack and is used for all function
that need to run without DAT, e.g. memcpy_real or do_start_kdump.
The main effect is a reduction in the kernel image size as with vmap
stacks the old style overflow checking that adds two instructions per
function is not needed anymore. Result from bloat-o-meter:
add/remove: 20/1 grow/shrink: 13/26854 up/down: 2198/-216240 (-214042)
In regard to performance the micro-benchmark for fork has a hit of a
few microseconds, allocating 4 pages in vmalloc space is more expensive
compare to an order-2 page allocation. But with real workload I could
not find a noticeable difference.
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/entry.h')
| -rw-r--r-- | arch/s390/kernel/entry.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h index 472fa2f1a4a5..c3816ae108b0 100644 --- a/arch/s390/kernel/entry.h +++ b/arch/s390/kernel/entry.h @@ -86,4 +86,7 @@ DECLARE_PER_CPU(u64, mt_cycles[8]); void gs_load_bc_cb(struct pt_regs *regs); void set_fs_fixup(void); +unsigned long stack_alloc(void); +void stack_free(unsigned long stack); + #endif /* _ENTRY_H */ |