kernel/linux.git/include/linux/execmem.h, branch v6.19.11

execmem: drop writable parameter from execmem_fill_trapping_insns()

2025-08-02T19:06:12+00:00

After update of execmem_cache_free() that made memory writable before updating it, there is no need to update read only memory, so the writable parameter to execmem_fill_trapping_insns() is not needed. Drop it. Link: https://lkml.kernel.org/r/20250713071730.4117334-7-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Acked-by: Peter Zijlstra (Intel) Cc: Daniel Gomez Cc: Masami Hiramatsu (Google) Cc: Petr Pavlu Cc: Steven Rostedt (Google) Signed-off-by: Andrew Morton

execmem: introduce execmem_alloc_rw()

2025-08-02T19:06:11+00:00

Some callers of execmem_alloc() require the memory to be temporarily writable even when it is allocated from ROX cache. These callers use execemem_make_temp_rw() right after the call to execmem_alloc(). Wrap this sequence in execmem_alloc_rw() API. Link: https://lkml.kernel.org/r/20250713071730.4117334-3-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Daniel Gomez Reviewed-by: Petr Pavlu Acked-by: Peter Zijlstra (Intel) Cc: Masami Hiramatsu (Google) Cc: Steven Rostedt (Google) Signed-off-by: Andrew Morton

execmem: drop unused execmem_update_copy()

2025-08-02T19:06:11+00:00

Patch series "x86: enable EXECMEM_ROX_CACHE for ftrace and kprobes", v3. These patches enable use of EXECMEM_ROX_CACHE for ftrace and kprobes allocations on x86. They also include some ground work in execmem. Since the execmem model for caching large ROX pages changed from the initial assumption that the memory that is allocated from ROX cache is always ROX to the current state where memory can be temporarily made RW and then restored to ROX, we can stop using text poking to update it. This also saves the hassle of trying lock text_mutex in execmem_cache_free() when kprobes already hold that mutex. This patch (of 8): The execmem_update_copy() that used text poking was required when memory allocated from ROX cache was always read-only. Since now its permissions can be switched to read-write there is no need in a function that updates memory with text poking. Remove it. Link: https://lkml.kernel.org/r/20250713071730.4117334-1-rppt@kernel.org Link: https://lkml.kernel.org/r/20250713071730.4117334-2-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Acked-by: Peter Zijlstra (Intel) Cc: Daniel Gomez Cc: Masami Hiramatsu (Google) Cc: Petr Pavlu Cc: Steven Rostedt (Google) Signed-off-by: Andrew Morton

Revert "mm/execmem: Unify early execmem_cache behaviour"

2025-06-11T09:20:52+00:00

The commit d6d1e3e6580c ("mm/execmem: Unify early execmem_cache behaviour") changed early behaviour of execemem ROX cache to allow its usage in early x86 code that allocates text pages when CONFIG_MITGATION_ITS is enabled. The permission management of the pages allocated from execmem for ITS mitigation is now completely contained in arch/x86/kernel/alternatives.c and therefore there is no need to special case early allocations in execmem. This reverts commit d6d1e3e6580ca35071ad474381f053cbf1fb6414. Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250603111446.2609381-6-rppt@kernel.org

x86/its: Use dynamic thunks for indirect branches

2025-05-09T20:36:58+00:00

ITS mitigation moves the unsafe indirect branches to a safe thunk. This could degrade the prediction accuracy as the source address of indirect branches becomes same for different execution paths. To improve the predictions, and hence the performance, assign a separate thunk for each indirect callsite. This is also a defense-in-depth measure to avoid indirect branches aliasing with each other. As an example, 5000 dynamic thunks would utilize around 16 bits of the address space, thereby gaining entropy. For a BTB that uses 32 bits for indexing, dynamic thunks could provide better prediction accuracy over fixed thunks. Have ITS thunks be variable sized and use EXECMEM_MODULE_TEXT such that they are both more flexible (got to extend them later) and live in 2M TLBs, just like kernel code, avoiding undue TLB pressure. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Alexandre Chartre

mm/execmem: Unify early execmem_cache behaviour

2025-05-09T20:33:20+00:00

Early kernel memory is RWX, only at the end of early boot (before SMP) do we mark things ROX. Have execmem_cache mirror this behaviour for early users. This avoids having to remember what code is execmem and what is not -- we can poke everything with impunity ;-) Also performance for not having to do endless text_poke_mm switches. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Alexandre Chartre

execmem: add API for temporal remapping as RW and restoring ROX afterwards

2025-02-03T10:46:02+00:00

Using a writable copy for ROX memory is cumbersome and error prone. Add API that allow temporarily remapping of ranges in the ROX cache as writable and then restoring their read-only-execute permissions. This API will be later used in modules code and will allow removing nasty games with writable copy in alternatives patching on x86. The restoring of the ROX permissions relies on the ability of architecture to reconstruct large pages in its set_memory_rox() method. Signed-off-by: "Mike Rapoport (Microsoft)" Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250126074733.1384926-6-rppt@kernel.org

alloc_tag: populate memory for module tags as needed

2024-11-07T22:25:16+00:00

The memory reserved for module tags does not need to be backed by physical pages until there are tags to store there. Change the way we reserve this memory to allocate only virtual area for the tags and populate it with physical pages as needed when we load a module. [surenb@google.com: avoid execmem_vmap() when !MMU] Link: https://lkml.kernel.org/r/20241031233611.3833002-1-surenb@google.com Link: https://lkml.kernel.org/r/20241023170759.999909-5-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: Pasha Tatashin Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Borislav Petkov (AMD) Cc: Christoph Hellwig Cc: Daniel Gomez Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: David Rientjes Cc: Dennis Zhou Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joonsoo Kim Cc: Kalesh Singh Cc: Kees Cook Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Luis Chamberlain Cc: Matthew Wilcox Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: Minchan Kim Cc: Paul E. McKenney Cc: Petr Pavlu Cc: Roman Gushchin Cc: Sami Tolvanen Cc: Sourav Panda Cc: Steven Rostedt (Google) Cc: Thomas Gleixner Cc: Thomas Huth Cc: Uladzislau Rezki (Sony) Cc: Vlastimil Babka Cc: Xiongwei Song Cc: Yu Zhao Signed-off-by: Andrew Morton

execmem: add support for cache of large ROX pages

2024-11-07T22:25:16+00:00

Using large pages to map text areas reduces iTLB pressure and improves performance. Extend execmem_alloc() with an ability to use huge pages with ROX permissions as a cache for smaller allocations. To populate the cache, a writable large page is allocated from vmalloc with VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as ROX. The direct map alias of that large page is exculded from the direct map. Portions of that large page are handed out to execmem_alloc() callers without any changes to the permissions. When the memory is freed with execmem_free() it is invalidated again so that it won't contain stale instructions. An architecture has to implement execmem_fill_trapping_insns() callback and select ARCH_HAS_EXECMEM_ROX configuration option to be able to use the ROX cache. The cache is enabled on per-range basis when an architecture sets EXECMEM_ROX_CACHE flag in definition of an execmem_range. Link: https://lkml.kernel.org/r/20241023162711.2579610-8-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Luis Chamberlain Tested-by: kdevops Cc: Andreas Larsson Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Borislav Petkov (AMD) Cc: Brian Cain Cc: Catalin Marinas Cc: Christophe Leroy Cc: Christoph Hellwig Cc: Dave Hansen Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Helge Deller Cc: Huacai Chen Cc: Ingo Molnar Cc: Johannes Berg Cc: John Paul Adrian Glaubitz Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Mark Rutland Cc: Masami Hiramatsu (Google) Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Oleg Nesterov Cc: Palmer Dabbelt Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Russell King Cc: Song Liu Cc: Stafford Horne Cc: Steven Rostedt (Google) Cc: Suren Baghdasaryan Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Uladzislau Rezki (Sony) Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton

module: prepare to handle ROX allocations for text

2024-11-07T22:25:15+00:00

In order to support ROX allocations for module text, it is necessary to handle modifications to the code, such as relocations and alternatives patching, without write access to that memory. One option is to use text patching, but this would make module loading extremely slow and will expose executable code that is not finally formed. A better way is to have memory allocated with ROX permissions contain invalid instructions and keep a writable, but not executable copy of the module text. The relocations and alternative patches would be done on the writable copy using the addresses of the ROX memory. Once the module is completely ready, the updated text will be copied to ROX memory using text patching in one go and the writable copy will be freed. Add support for that to module initialization code and provide necessary interfaces in execmem. Link: https://lkml.kernel.org/r/20241023162711.2579610-5-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewd-by: Luis Chamberlain Tested-by: kdevops Cc: Andreas Larsson Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Borislav Petkov (AMD) Cc: Brian Cain Cc: Catalin Marinas Cc: Christophe Leroy Cc: Christoph Hellwig Cc: Dave Hansen Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Helge Deller Cc: Huacai Chen Cc: Ingo Molnar Cc: Johannes Berg Cc: John Paul Adrian Glaubitz Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Mark Rutland Cc: Masami Hiramatsu (Google) Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Oleg Nesterov Cc: Palmer Dabbelt Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Russell King Cc: Song Liu Cc: Stafford Horne Cc: Steven Rostedt (Google) Cc: Suren Baghdasaryan Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Uladzislau Rezki (Sony) Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton