wireguard-linux/arch/arm64/kernel/asm-offsets.c, branch update-toolchain

KVM: arm64: Fix clobbered ELR in sync abort/SError

2024-06-20T17:40:53Z

When the hypervisor receives a SError or synchronous exception (EL2h) while running with the __kvm_hyp_vector and if ELR_EL2 doesn't point to an extable entry, it panics indirectly by overwriting ELR with the address of a panic handler in order for the asm routine it returns to to ERET into the handler. However, this clobbers ELR_EL2 for the handler itself. As a result, hyp_panic(), when retrieving what it believes to be the PC where the exception happened, actually ends up reading the address of the panic handler that called it! This results in an erroneous and confusing panic message where the source of any synchronous exception (e.g. BUG() or kCFI) appears to be __guest_exit_panic, making it hard to locate the actual BRK instruction. Therefore, store the original ELR_EL2 in the per-CPU kvm_hyp_ctxt and point the sysreg to a routine that first restores it to its previous value before running __guest_exit_panic. Fixes: 7db21530479f ("KVM: arm64: Restore hyp when panicking in guest context") Signed-off-by: Pierre-Clément Tosi Acked-by: Will Deacon Link: https://lore.kernel.org/r/20240610063244.2828978-2-ptosi@google.com Signed-off-by: Oliver Upton

arm64: make member of struct pt_regs and it's offset macro in the same order

2024-02-22T19:07:49Z

In struct pt_regs, member pstate is after member pc. Move offset macro of pstate after offset macro of pc to improve readability a little. Signed-off-by: Kemeng Shi Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20240130175504.106364-1-shikemeng@huaweicloud.com Signed-off-by: Catalin Marinas

arm64: fpsimd: Bring cond_yield asm macro in line with new rules

2024-01-12T12:48:27Z

We no longer disable softirqs or preemption when doing kernel mode SIMD, and so for fully preemptible kernels, there is no longer a need to do any explicit yielding (and for non-preemptible kernels, yielding is not needed either). That leaves voluntary preemption, where only explicit yield calls may result in a reschedule. To retain the existing behavior for such a configuration, we should take the new situation into account, where the preempt count will be zero rather than one, and yielding to pending softirqs is unnecessary. Fixes: aefbab8e77eb ("arm64: fpsimd: Preserve/restore kernel mode NEON at context switch") Signed-off-by: Ard Biesheuvel Reviewed-by: Mark Brown Link: https://lore.kernel.org/r/20240111112447.577640-2-ardb+git@google.com Signed-off-by: Will Deacon

arm64: ftrace: fix build error with CONFIG_FUNCTION_GRAPH_TRACER=n

2023-07-05T13:46:19Z

It appears that a merge conflict ended up hiding a newly added constant in some configurations: arch/arm64/kernel/entry-ftrace.S: Assembler messages: arch/arm64/kernel/entry-ftrace.S:59: Error: undefined symbol FTRACE_OPS_DIRECT_CALL used as an immediate value FTRACE_OPS_DIRECT_CALL is still used when CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS is enabled, even if CONFIG_FUNCTION_GRAPH_TRACER is disabled, so change the ifdef accordingly. Link: https://lkml.kernel.org/r/20230623152204.2216297-1-arnd@kernel.org Cc: Will Deacon Cc: Mark Rutland Cc: Donglin Peng Fixes: 3646970322464 ("arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL") Signed-off-by: Arnd Bergmann Acked-by: Florent Revest Reviewed-by: Randy Dunlap Tested-by: Randy Dunlap # build-tested Acked-by: Catalin Marinas Signed-off-by: Steven Rostedt (Google)

arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

2023-06-20T22:38:37Z

The previous patch ("function_graph: Support recording and printing the return value of function") has laid the groundwork for the for the funcgraph-retval, and this modification makes it available on the ARM64 platform. We introduce a new structure called fgraph_ret_regs for the ARM64 platform to hold return registers and the frame pointer. We then fill its content in the return_to_handler and pass its address to the function ftrace_return_to_handler to record the return value. Link: https://lkml.kernel.org/r/c78366416ce93f704ae7000c4ee60eb4258c38f7.1680954589.git.pengdonglin@sangfor.com.cn Reviewed-by: Mark Rutland Tested-by: Mark Rutland Acked-by: Catalin Marinas Signed-off-by: Donglin Peng Signed-off-by: Steven Rostedt (Google)

arm64: ftrace: Add direct call support

2023-04-11T17:06:39Z

This builds up on the CALL_OPS work which extends the ftrace patchsite on arm64 with an ops pointer usable by the ftrace trampoline. This ops pointer is valid at all time. Indeed, it is either pointing to ftrace_list_ops or to the single ops which should be called from that patchsite. There are a few cases to distinguish: - If a direct call ops is the only one tracing a function: - If the direct called trampoline is within the reach of a BL instruction -> the ftrace patchsite jumps to the trampoline - Else -> the ftrace patchsite jumps to the ftrace_caller trampoline which reads the ops pointer in the patchsite and jumps to the direct call address stored in the ops - Else -> the ftrace patchsite jumps to the ftrace_caller trampoline and its ops literal points to ftrace_list_ops so it iterates over all registered ftrace ops, including the direct call ops and calls its call_direct_funcs handler which stores the direct called trampoline's address in the ftrace_regs and the ftrace_caller trampoline will return to that address instead of returning to the traced function Signed-off-by: Florent Revest Co-developed-by: Mark Rutland Signed-off-by: Mark Rutland Link: https://lore.kernel.org/r/20230405180250.2046566-2-revest@chromium.org Signed-off-by: Will Deacon

arm64: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS

2023-01-24T11:49:43Z

This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on arm64. This allows each ftrace callsite to provide an ftrace_ops to the common ftrace trampoline, allowing each callsite to invoke distinct tracer functions without the need to fall back to list processing or to allocate custom trampolines for each callsite. This significantly speeds up cases where multiple distinct trace functions are used and callsites are mostly traced by a single tracer. The main idea is to place a pointer to the ftrace_ops as a literal at a fixed offset from the function entry point, which can be recovered by the common ftrace trampoline. Using a 64-bit literal avoids branch range limitations, and permits the ops to be swapped atomically without special considerations that apply to code-patching. In future this will also allow for the implementation of DYNAMIC_FTRACE_WITH_DIRECT_CALLS without branch range limitations by using additional fields in struct ftrace_ops. As noted in the core patch adding support for DYNAMIC_FTRACE_WITH_CALL_OPS, this approach allows for directly invoking ftrace_ops::func even for ftrace_ops which are dynamically-allocated (or part of a module), without going via ftrace_ops_list_func. Currently, this approach is not compatible with CLANG_CFI, as the presence/absence of pre-function NOPs changes the offset of the pre-function type hash, and there's no existing mechanism to ensure a consistent offset for instrumented and uninstrumented functions. When CLANG_CFI is enabled, the existing scheme with a global ops->func pointer is used, and there should be no functional change. I am currently working with others to allow the two to work together in future (though this will liekly require updated compiler support). I've benchamrked this with the ftrace_ops sample module [1], which is not currently upstream, but available at: https://lore.kernel.org/lkml/20230103124912.2948963-1-mark.rutland@arm.com git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git ftrace-ops-sample-20230109 Using that module I measured the total time taken for 100,000 calls to a trivial instrumented function, with a number of tracers enabled with relevant filters (which would apply to the instrumented function) and a number of tracers enabled with irrelevant filters (which would not apply to the instrumented function). I tested on an M1 MacBook Pro, running under a HVF-accelerated QEMU VM (i.e. on real hardware). Before this patch: Number of tracers || Total time | Per-call average time (ns) Relevant | Irrelevant || (ns) | Total | Overhead =========+============++=============+==============+============ 0 | 0 || 94,583 | 0.95 | - 0 | 1 || 93,709 | 0.94 | - 0 | 2 || 93,666 | 0.94 | - 0 | 10 || 93,709 | 0.94 | - 0 | 100 || 93,792 | 0.94 | - ---------+------------++-------------+--------------+------------ 1 | 1 || 6,467,833 | 64.68 | 63.73 1 | 2 || 7,509,708 | 75.10 | 74.15 1 | 10 || 23,786,792 | 237.87 | 236.92 1 | 100 || 106,432,500 | 1,064.43 | 1063.38 ---------+------------++-------------+--------------+------------ 1 | 0 || 1,431,875 | 14.32 | 13.37 2 | 0 || 6,456,334 | 64.56 | 63.62 10 | 0 || 22,717,000 | 227.17 | 226.22 100 | 0 || 103,293,667 | 1032.94 | 1031.99 ---------+------------++-------------+--------------+-------------- Note: per-call overhead is estimated relative to the baseline case with 0 relevant tracers and 0 irrelevant tracers. After this patch Number of tracers || Total time | Per-call average time (ns) Relevant | Irrelevant || (ns) | Total | Overhead =========+============++=============+==============+============ 0 | 0 || 94,541 | 0.95 | - 0 | 1 || 93,666 | 0.94 | - 0 | 2 || 93,709 | 0.94 | - 0 | 10 || 93,667 | 0.94 | - 0 | 100 || 93,792 | 0.94 | - ---------+------------++-------------+--------------+------------ 1 | 1 || 281,000 | 2.81 | 1.86 1 | 2 || 281,042 | 2.81 | 1.87 1 | 10 || 280,958 | 2.81 | 1.86 1 | 100 || 281,250 | 2.81 | 1.87 ---------+------------++-------------+--------------+------------ 1 | 0 || 280,959 | 2.81 | 1.86 2 | 0 || 6,502,708 | 65.03 | 64.08 10 | 0 || 18,681,209 | 186.81 | 185.87 100 | 0 || 103,550,458 | 1,035.50 | 1034.56 ---------+------------++-------------+--------------+------------ Note: per-call overhead is estimated relative to the baseline case with 0 relevant tracers and 0 irrelevant tracers. As can be seen from the above: a) Whenever there is a single relevant tracer function associated with a tracee, the overhead of invoking the tracer is constant, and does not scale with the number of tracers which are *not* associated with that tracee. b) The overhead for a single relevant tracer has dropped to ~1/7 of the overhead prior to this series (from 13.37ns to 1.86ns). This is largely due to permitting calls to dynamically-allocated ftrace_ops without going through ftrace_ops_list_func. I've run the ftrace selftests from v6.2-rc3, which reports: | # of passed: 110 | # of failed: 0 | # of unresolved: 3 | # of untested: 0 | # of unsupported: 0 | # of xfailed: 1 | # of undefined(test bug): 0 ... where the unresolved entries were the tests for DIRECT functions (which are not supported), and the checkbashisms selftest (which is irrelevant here): | [8] Test ftrace direct functions against tracers [UNRESOLVED] | [9] Test ftrace direct functions against kprobes [UNRESOLVED] | [62] Meta-selftest: Checkbashisms [UNRESOLVED] ... with all other tests passing (or failing as expected). Signed-off-by: Mark Rutland Cc: Florent Revest Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Will Deacon Link: https://lore.kernel.org/r/20230123134603.1064407-9-mark.rutland@arm.com Signed-off-by: Catalin Marinas

ftrace: arm64: move from REGS to ARGS

2022-11-18T13:56:41Z

This commit replaces arm64's support for FTRACE_WITH_REGS with support for FTRACE_WITH_ARGS. This removes some overhead and complexity, and removes some latent issues with inconsistent presentation of struct pt_regs (which can only be reliably saved/restored at exception boundaries). FTRACE_WITH_REGS has been supported on arm64 since commit: 3b23e4991fb66f6d ("arm64: implement ftrace with regs") As noted in the commit message, the major reasons for implementing FTRACE_WITH_REGS were: (1) To make it possible to use the ftrace graph tracer with pointer authentication, where it's necessary to snapshot/manipulate the LR before it is signed by the instrumented function. (2) To make it possible to implement LIVEPATCH in future, where we need to hook function entry before an instrumented function manipulates the stack or argument registers. Practically speaking, we need to preserve the argument/return registers, PC, LR, and SP. Neither of these need a struct pt_regs, and only require the set of registers which are live at function call/return boundaries. Our calling convention is defined by "Procedure Call Standard for the Arm® 64-bit Architecture (AArch64)" (AKA "AAPCS64"), which can currently be found at: https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst Per AAPCS64, all function call argument and return values are held in the following GPRs: * X0 - X7 : parameter / result registers * X8 : indirect result location register * SP : stack pointer (AKA SP) Additionally, ad function call boundaries, the following GPRs hold context/return information: * X29 : frame pointer (AKA FP) * X30 : link register (AKA LR) ... and for ftrace we need to capture the instrumented address: * PC : program counter No other GPRs are relevant, as none of the other arguments hold parameters or return values: * X9 - X17 : temporaries, may be clobbered * X18 : shadow call stack pointer (or temorary) * X19 - X28 : callee saved This patch implements FTRACE_WITH_ARGS for arm64, only saving/restoring the minimal set of registers necessary. This is always sufficient to manipulate control flow (e.g. for live-patching) or to manipulate function arguments and return values. This reduces the necessary stack usage from 336 bytes for pt_regs down to 112 bytes for ftrace_regs + 32 bytes for two frame records, freeing up 188 bytes. This could be reduced further with changes to the unwinder. As there is no longer a need to save different sets of registers for different features, we no longer need distinct `ftrace_caller` and `ftrace_regs_caller` trampolines. This allows the trampoline assembly to be simpler, and simplifies code which previously had to handle the two trampolines. I've tested this with the ftrace selftests, where there are no unexpected failures. Co-developed-by: Florent Revest Signed-off-by: Mark Rutland Signed-off-by: Florent Revest Cc: Catalin Marinas Cc: Masami Hiramatsu Cc: Steven Rostedt Cc: Will Deacon Reviewed-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt (Google) Link: https://lore.kernel.org/r/20221103170520.931305-5-mark.rutland@arm.com Signed-off-by: Will Deacon

KVM: arm64: Drop unused workaround_flags vcpu field

2021-12-08T14:54:07Z

workaround_flags is a leftover from our earlier Spectre-v4 workaround implementation, and now serves no purpose. Get rid of the field and the corresponding asm-offset definition. Fixes: 29e8910a566a ("KVM: arm64: Simplify handling of ARCH_WORKAROUND_2") Signed-off-by: Marc Zyngier

Merge tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

2021-11-02T00:00:05Z

Pull thread_info update to move 'cpu' back from task_struct from Kees Cook: "Cross-architecture update to move task_struct::cpu back into thread_info on arm64, x86, s390, powerpc, and riscv. All Acked by arch maintainers. Quoting Ard Biesheuvel: 'Move task_struct::cpu back into thread_info Keeping CPU in task_struct is problematic for architectures that define raw_smp_processor_id() in terms of this field, as it requires linux/sched.h to be included, which causes a lot of pain in terms of circular dependencies (aka 'header soup') This series moves it back into thread_info (where it came from) for all architectures that enable THREAD_INFO_IN_TASK, addressing the header soup issue as well as some pointless differences in the implementations of task_cpu() and set_task_cpu()'" * tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: riscv: rely on core code to keep thread_info::cpu updated powerpc: smp: remove hack to obtain offset of task_struct::cpu sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y powerpc: add CPU field to struct thread_info s390: add CPU field to struct thread_info x86: add CPU field to struct thread_info arm64: add CPU field to struct thread_info