Messages in this thread | | | Date | Wed, 3 Apr 2024 18:52:30 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v2 1/4] arm64: patching: always use fixmap |
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On Wed, Apr 03, 2024 at 04:01:51PM +0100, Mark Rutland wrote: > For historical reasons, patch_map() won't bother to fixmap non-image > addresses when CONFIG_STRICT_MODULE_RWX=n, matching the behaviour prior > to the introduction of CONFIG_STRICT_MODULE_RWX. However, as arm64 > doesn't select CONFIG_ARCH_OPTIONAL_KERNEL_RWX, CONFIG_MODULES implies > CONFIG_STRICT_MODULE_RWX, so any kernel built with module support will > use the fixmap for any non-image address. > > Historically we only used patch_map() for the kernel image and modules, > but these days its also used by BPF and KPROBES to write to read-only > pages of executable text. Currently these both depend on CONFIG_MODULES, > but we'd like to change that in subsequent patches, which will require > using the fixmap regardless of CONFIG_STRICT_MODULE_RWX. > > This patch changes patch_map() to always use the fixmap, and simplifies > the logic: > > * Use is_image_text() directly in the if-else, rather than using a > temporary boolean variable. > > * Use offset_in_page() to get the offset within the mapping. > > * Remove uintaddr and cast the address directly when using > is_image_text(). > > For kernels built with CONFIG_MODULES=y, there should be no functional > change as a result of this patch. > > For kernels built with CONFIG_MODULES=n, patch_map() will use the fixmap > for non-image addresses, but there are no extant users with non-image > addresses when CONFIG_MODULES=n, and hence there should be no functional > change as a result of this patch alone. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > --- > arch/arm64/kernel/patching.c | 10 +++------- > 1 file changed, 3 insertions(+), 7 deletions(-) > > Catalin, Will, this is a prerequisite for the final two patches in the > series. Are you happy for this go via the tracing tree?
Fine by me.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
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