kernel/arch/arm64/include/asm/alternative.h, branch linux-6.2.y

arm64: alternatives: Split up alternative.h

2020-11-09T21:49:34Z

asm/alternative.h contains both the macros needed to use alternatives, as well the type definitions and function prototypes for applying them. Split the header in two, so that alternatives can be used from core header files such as linux/compiler.h without the risk of circular includes Acked-by: Peter Zijlstra (Intel) Acked-by: Mark Rutland Signed-off-by: Will Deacon

arm64: uaccess: move uao_* alternatives to asm-uaccess.h

2020-11-09T21:49:34Z

The uao_* alternative asm macros are only used by the uaccess assembly routines in arch/arm64/lib/, where they are included indirectly via asm-uaccess.h. Since they're specific to the uaccess assembly (and will lose the alternatives in subsequent patches), let's move them into asm-uaccess.h. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Christoph Hellwig Cc: James Morse Cc: Will Deacon [will: update #include in mte.S to pull in uao asm macros] Signed-off-by: Will Deacon

arm64/alternatives: move length validation inside the subsection

2020-07-30T15:50:14Z

Commit f7b93d42945c ("arm64/alternatives: use subsections for replacement sequences") breaks LLVM's integrated assembler, because due to its one-pass design, it cannot compute instruction sequence lengths before the layout for the subsection has been finalized. This change fixes the build by moving the .org directives inside the subsection, so they are processed after the subsection layout is known. Fixes: f7b93d42945c ("arm64/alternatives: use subsections for replacement sequences") Signed-off-by: Sami Tolvanen Link: https://github.com/ClangBuiltLinux/linux/issues/1078 Link: https://lore.kernel.org/r/20200730153701.3892953-1-samitolvanen@google.com Signed-off-by: Will Deacon

arm64/alternatives: use subsections for replacement sequences

2020-07-02T11:57:17Z

When building very large kernels, the logic that emits replacement sequences for alternatives fails when relative branches are present in the code that is emitted into the .altinstr_replacement section and patched in at the original site and fixed up. The reason is that the linker will insert veneers if relative branches go out of range, and due to the relative distance of the .altinstr_replacement from the .text section where its branch targets usually live, veneers may be emitted at the end of the .altinstr_replacement section, with the relative branches in the sequence pointed at the veneers instead of the actual target. The alternatives patching logic will attempt to fix up the branch to point to its original target, which will be the veneer in this case, but given that the patch site is likely to be far away as well, it will be out of range and so patching will fail. There are other cases where these veneers are problematic, e.g., when the target of the branch is in .text while the patch site is in .init.text, in which case putting the replacement sequence inside .text may not help either. So let's use subsections to emit the replacement code as closely as possible to the patch site, to ensure that veneers are only likely to be emitted if they are required at the patch site as well, in which case they will be in range for the replacement sequence both before and after it is transported to the patch site. This will prevent alternative sequences in non-init code from being released from memory after boot, but this is tolerable given that the entire section is only 512 KB on an allyesconfig build (which weighs in at 500+ MB for the entire Image). Also, note that modules today carry the replacement sequences in non-init sections as well, and any of those that target init code will be emitted into init sections after this change. This fixes an early crash when booting an allyesconfig kernel on a system where any of the alternatives sequences containing relative branches are activated at boot (e.g., ARM64_HAS_PAN on TX2) Signed-off-by: Ard Biesheuvel Cc: Suzuki K Poulose Cc: James Morse Cc: Andre Przywara Cc: Dave P Martin Link: https://lore.kernel.org/r/20200630081921.13443-1-ardb@kernel.org Signed-off-by: Will Deacon

arm64: alternative: fix build with clang integrated assembler

2020-03-20T10:01:28Z

Building an arm64 defconfig with clang's integrated assembler, this error occurs: :2:2: error: unrecognized instruction mnemonic _ASM_EXTABLE 9999b, 9f ^ arch/arm64/mm/cache.S:50:1: note: while in macro instantiation user_alt 9f, "dc cvau, x4", "dc civac, x4", 0 ^ While GNU as seems fine with case-sensitive macro instantiations, clang doesn't, so use the actual macro name (_asm_extable) as in the rest of the file. Also checked that the generated assembly matches the GCC output. Reviewed-by: Nick Desaulniers Tested-by: Nick Desaulniers Fixes: 290622efc76e ("arm64: fix "dc cvau" cache operation on errata-affected core") Link: https://github.com/ClangBuiltLinux/linux/issues/924 Signed-off-by: Ilie Halip Signed-off-by: Will Deacon

arm64: fix alternatives with LLVM's integrated assembler

2020-01-16T17:32:34Z

LLVM's integrated assembler fails with the following error when building KVM: :12:6: error: expected absolute expression .if kvm_update_va_mask == 0 ^ :21:6: error: expected absolute expression .if kvm_update_va_mask == 0 ^ :24:2: error: unrecognized instruction mnemonic NOT_AN_INSTRUCTION ^ LLVM ERROR: Error parsing inline asm These errors come from ALTERNATIVE_CB and __ALTERNATIVE_CFG, which test for the existence of the callback parameter in inline assembly using the following expression: " .if " __stringify(cb) " == 0\n" This works with GNU as, but isn't supported by LLVM. This change splits __ALTERNATIVE_CFG and ALTINSTR_ENTRY into separate macros to fix the LLVM build. Link: https://github.com/ClangBuiltLinux/linux/issues/472 Signed-off-by: Sami Tolvanen Tested-by: Nick Desaulniers Reviewed-by: Kees Cook Signed-off-by: Will Deacon

arm64: alternative: Apply alternatives early in boot process

2019-02-06T10:05:20Z

Currently alternatives are applied very late in the boot process (and a long time after we enable scheduling). Some alternative sequences, such as those that alter the way CPU context is stored, must be applied much earlier in the boot sequence. Introduce apply_boot_alternatives() to allow some alternatives to be applied immediately after we detect the CPU features of the boot CPU. Signed-off-by: Daniel Thompson [julien.thierry@arm.com: rename to fit new cpufeature framework better, apply BOOT_SCOPE feature early in boot] Signed-off-by: Julien Thierry Reviewed-by: Suzuki K Poulose Reviewed-by: Marc Zyngier Cc: Will Deacon Cc: Christoffer Dall Cc: Suzuki K Poulose Signed-off-by: Catalin Marinas

arm64: alternative: Allow alternative status checking per cpufeature

2019-02-06T10:05:20Z

In preparation for the application of alternatives at different points during the boot process, provide the possibility to check whether alternatives for a feature of interest was already applied instead of having a global boolean for all alternatives. Make VHE enablement code check for the VHE feature instead of considering all alternatives. Signed-off-by: Julien Thierry Acked-by: Marc Zyngier Cc: Will Deacon Cc: Suzuki K Poulose Cc: Marc Zyngier Cc: Christoffer Dall Signed-off-by: Catalin Marinas

arm64: Avoid flush_icache_range() in alternatives patching code

2018-06-27T17:21:53Z

The implementation of flush_icache_range() includes instruction sequences which are themselves patched at runtime, so it is not safe to call from the patching framework. This patch reworks the alternatives cache-flushing code so that it rolls its own internal D-cache maintenance using DC CIVAC before invalidating the entire I-cache after all alternatives have been applied at boot. Modules don't cause any issues, since flush_icache_range() is safe to call by the time they are loaded. Acked-by: Mark Rutland Reported-by: Rohit Khanna Cc: Alexander Van Brunt Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas

arm64: alternatives: Add dynamic patching feature

2018-03-19T13:03:17Z

We've so far relied on a patching infrastructure that only gave us a single alternative, without any way to provide a range of potential replacement instructions. For a single feature, this is an all or nothing thing. It would be interesting to have a more flexible grained way of patching the kernel though, where we could dynamically tune the code that gets injected. In order to achive this, let's introduce a new form of dynamic patching, assiciating a callback to a patching site. This callback gets source and target locations of the patching request, as well as the number of instructions to be patched. Dynamic patching is declared with the new ALTERNATIVE_CB and alternative_cb directives: asm volatile(ALTERNATIVE_CB("mov %0, #0\n", callback) : "r" (v)); or alternative_cb callback mov x0, #0 alternative_cb_end where callback is the C function computing the alternative. Reviewed-by: Christoffer Dall Reviewed-by: Catalin Marinas Signed-off-by: Marc Zyngier