Le 03/04/2019 à 05:38, Christopher M Riedl a écrit :
On March 29, 2019 at 3:41 AM Christophe Leroy <christophe.le...@c-s.fr> wrote:
Le 29/03/2019 à 05:21, cmr a écrit :
Operations which write to memory should be restricted on secure systems
and optionally to avoid self-destructive behaviors.
Add a config option, XMON_RO, to control default xmon behavior along
with kernel cmdline options xmon=ro and xmon=rw for explicit control.
The default is to enable read-only mode.
The following xmon operations are affected:
memops:
disable memmove
disable memset
memex:
no-op'd mwrite
super_regs:
no-op'd write_spr
bpt_cmds:
disable
proc_call:
disable
Signed-off-by: cmr <c...@informatik.wtf>
A Fully qualified name should be used.
What do you mean by fully-qualified here? PPC_XMON_RO? (PPC_)XMON_READONLY?
I mean it should be
Signed-off-by: Christopher M Riedl <c...@informatik.wtf>
instead of
Signed-off-by: cmr <c...@informatik.wtf>
---
arch/powerpc/Kconfig.debug | 7 +++++++
arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++++++
2 files changed, 31 insertions(+)
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 4e00cb0a5464..33cc01adf4cb 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -117,6 +117,13 @@ config XMON_DISASSEMBLY
to say Y here, unless you're building for a memory-constrained
system.
+config XMON_RO
+ bool "Set xmon read-only mode"
+ depends on XMON
+ default y
Should it really be always default y ?
I would set default 'y' only when some security options are also set.
This is a good point, I based this on an internal Slack suggestion but giving
this more thought, disabling read-only mode by default makes more sense. I'm
not sure what security options could be set though?
Maybe starting with CONFIG_STRICT_KERNEL_RWX
Another point that may also be addressed by your patch is the definition
of PAGE_KERNEL_TEXT:
#if defined(CONFIG_KGDB) || defined(CONFIG_XMON) ||
defined(CONFIG_BDI_SWITCH) ||\
defined(CONFIG_KPROBES) || defined(CONFIG_DYNAMIC_FTRACE)
#define PAGE_KERNEL_TEXT PAGE_KERNEL_X
#else
#define PAGE_KERNEL_TEXT PAGE_KERNEL_ROX
#endif
The above let me think that it would be better if you add a config
XMON_RW instead of XMON_RO, with default !STRICT_KERNEL_RWX
Christophe
