| Message ID | 057c40164084bfc7d77c0b2ff78d95dbf6a2a21b.1632503622.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc: Activate CONFIG_STRICT_KERNEL_RWX by default | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 24 jobs. |
On Fri, 24 Sep 2021 19:13:53 +0200, Christophe Leroy wrote: > CONFIG_STRICT_KERNEL_RWX should be set by default on every > architectures (See https://github.com/KSPP/linux/issues/4) > > On PPC32 we have to find a compromise between performance and/or > memory wasting and selection of strict_kernel_rwx, because it implies > either smaller memory chunks or larger alignment between RO memory > and RW memory. > > [...] Applied to powerpc/next. [1/1] powerpc: Activate CONFIG_STRICT_KERNEL_RWX by default https://git.kernel.org/powerpc/c/fdacae8a84024474afff234bdd1dbe19ad597a10 cheers
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index ba5b66189358..79332f51185d 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -148,6 +148,7 @@ config PPC select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX + select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT select ARCH_STACKWALK select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEBUG_PAGEALLOC if PPC32 || PPC_BOOK3S_64
CONFIG_STRICT_KERNEL_RWX should be set by default on every architectures (See https://github.com/KSPP/linux/issues/4) On PPC32 we have to find a compromise between performance and/or memory wasting and selection of strict_kernel_rwx, because it implies either smaller memory chunks or larger alignment between RO memory and RW memory. For instance the 8xx maps memory with 8M pages. So either the limit between RO and RW must be 8M aligned or it falls back or 512k pages which implies more pressure on the TLB. book3s/32 maps memory with BATs as much as possible. BATS can have any power-of-two size between 128k and 256M but we have only 4 to 8 BATs so the alignment must be good enough to allow efficient use of the BATs and avoid falling back on standard page mapping which would kill performance. So let's go one step forward and make it the default but still allow users to unset it when wanted. Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- arch/powerpc/Kconfig | 1 + 1 file changed, 1 insertion(+)