diff options
| author | Christophe Leroy <christophe.leroy@c-s.fr> | 2020-04-15 14:57:09 +0000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-06-02 20:59:13 +1000 |
| commit | 547e687b2981a115814962506068873d24983af7 (patch) | |
| tree | c6f5e405135e2b21d3fb8bb0397a03f841c13507 | |
| parent | 332ce969b763553e9c4d55069e1e15aba4ea560f (diff) | |
powerpc/uaccess: Don't set KUAP by default on book3s/32
On book3s/32, KUAP is an heavy process as it requires to
determine which segments are impacted and unlock/lock
each of them.
And since the implementation of user_access_begin/end, it
is even worth for the time being because unlike __get_user(),
user_access_begin doesn't make difference between read and write
and unlocks access also for read allthought that's unneeded
on book3s/32.
As shown by the size of a kernel built with KUAP and one without,
the overhead is 64k bytes of code. As a comparison a similar
build on an 8xx has an overhead of only 8k bytes of code.
text data bss dec hex filename
7230416 1425868 837376 9493660 90dc9c vmlinux.kuap6xx
7165012 1425548 837376 9427936 8fdbe0 vmlinux.nokuap6xx
6519796 1960028 477464 8957288 88ad68 vmlinux.kuap8xx
6511664 1959864 477464 8948992 888d00 vmlinux.nokuap8xx
Until a more optimised KUAP is implemented on book3s/32,
don't select it by default.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/154a99399317b096ac1f04827b9f8d7a9179ddc1.1586962586.git.christophe.leroy@c-s.fr
| -rw-r--r-- | arch/powerpc/platforms/Kconfig.cputype | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index e3fb0ef5129f..9a7baf31d276 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype @@ -389,7 +389,7 @@ config PPC_HAVE_KUAP config PPC_KUAP bool "Kernel Userspace Access Protection" depends on PPC_HAVE_KUAP - default y + default y if !PPC_BOOK3S_32 help Enable support for Kernel Userspace Access Protection (KUAP) |