On 26/03/21 1:56 am, Shreeya Patel wrote:
On 26/03/21 1:10 am, Eric Biggers wrote:
On Thu, Mar 25, 2021 at 05:38:11AM +0530, Shreeya Patel wrote:
Also, indirect calls using function pointers are easily exploitable by
speculative execution attacks, hence use static_call() in unicode.h and
unicode-core.c files inorder to prevent these attacks by making direct
calls and also to improve the performance of function pointers.
I don't think you need to worry about avoiding indirect calls to prevent
speculative execution attacks. That's what the mitigations like
Retpoline are
for. Instead my concern was just that indirect calls are *slow*,
especially
when those mitigations are enabled. Some of the casefolding
operations are
called a lot (e.g., repeatedly during path resolution), and it would be
desirable to avoid adding more overhead there.
diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
index 2c27b9a5cd6c..2961b0206b4d 100644
--- a/fs/unicode/Kconfig
+++ b/fs/unicode/Kconfig
@@ -8,7 +8,16 @@ config UNICODE
Say Y here to enable UTF-8 NFD normalization and NFD+CF
casefolding
support.
+# UTF-8 encoding can be compiled as a module using UNICODE_UTF8
option.
+# Having UTF-8 encoding as a module will avoid carrying large
+# database table present in utf8data.h_shipped into the kernel
+# by being able to load it only when it is required by the filesystem.
+config UNICODE_UTF8
+ tristate "UTF-8 module"
+ depends on UNICODE
+ default m
+
The help for UNICODE still says that it enables UTF-8 support. But
now there is
a separate option that people will need to remember to enable.
Please document each of these options properly.
Perhaps EXT4_FS and F2FS_FS just should select UNICODE_UTF8 if
UNICODE, so that
UNICODE_UTF8 doesn't have to be a user-selectable symbol?
It is not a user-selectable symbol. It depends on UNICODE and if
someone enables it,
by default UNICODE_UTF8 will be enabled as a module.
Sorry, I think I misunderstood when you said EXT4_FS and F2FS_FS should
select
UNICODE_UTF8 if UNICODE is enabled. I now get it that you don't want
them to be deselectable.
I'll make this change. Thanks
+DEFINE_STATIC_CALL(validate, unicode_validate_static_call);
+EXPORT_STATIC_CALL(validate);
Global symbols can't have generic names like "validate". Please add an
appropriate prefix like "unicode_".
Also, the thing called "unicode_validate_static_call" isn't actually
a static
call as the name suggests, but rather the default function used by
the static
call. It should be called something like unicode_validate_default.
Likewise for all the others.
Thanks for your reviews, I'll make the change suggested by you in v5.
- Eric
