On Wed, Mar 27, 2024 at 12:24:03AM +0900, Masami Hiramatsu wrote: > On Tue, 26 Mar 2024 14:46:10 +0000 > Mark Rutland <[email protected]> wrote: > > > > On Mon, Mar 25, 2024 at 11:56:32AM +0900, Masami Hiramatsu wrote: > > > I think, we'd better to introduce `alloc_execmem()`, > > > CONFIG_HAVE_ALLOC_EXECMEM and CONFIG_ALLOC_EXECMEM at first > > > > > > config HAVE_ALLOC_EXECMEM > > > bool > > > > > > config ALLOC_EXECMEM > > > bool "Executable trampline memory allocation" > > > depends on MODULES || HAVE_ALLOC_EXECMEM > > > > > > And define fallback macro to module_alloc() like this. > > > > > > #ifndef CONFIG_HAVE_ALLOC_EXECMEM > > > #define alloc_execmem(size, gfp) module_alloc(size) > > > #endif > > > > Please can we *not* do this? I think this is abstracting at the wrong level > > (as > > I mentioned on the prior execmem proposals). > > > > Different exectuable allocations can have different requirements. For > > example, > > on arm64 modules need to be within 2G of the kernel image, but the kprobes > > XOL > > areas can be anywhere in the kernel VA space. > > > > Forcing those behind the same interface makes things *harder* for > > architectures > > and/or makes the common code more complicated (if that ends up having to > > track > > all those different requirements). From my PoV it'd be much better to have > > separate kprobes_alloc_*() functions for kprobes which an architecture can > > then > > choose to implement using a common library if it wants to. > > > > I took a look at doing that using the core ifdeffery fixups from Jarkko's > > v6, > > and it looks pretty clean to me (and works in testing on arm64): > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kprobes/without-modules > > > > Could we please start with that approach, with kprobe-specific alloc/free > > code > > provided by the architecture? > > OK, as far as I can read the code, this method also works and neat! > (and minimum intrusion). I actually found that exposing CONFIG_ALLOC_EXECMEM > to user does not help, it should be an internal change. So hiding this change > from user is better choice. Then there is no reason to introduce the new > alloc_execmem, but just expand kprobe_alloc_insn_page() is reasonable. > > Mark, can you send this series here, so that others can review/test it?
I've written up a cover letter and sent that out: https://lore.kernel.org/lkml/[email protected]/ Mark.
