Tracing with kprobes while running a monolithic kernel is currently impossible due the kernel module allocator dependency.
Address the issue by allowing architectures to implement module_alloc() and module_memfree() independent of the module subsystem. An arch tree can signal this by setting HAVE_KPROBES_ALLOC in its Kconfig file. Realize the feature on RISC-V by separating allocator to module_alloc.c and implementing module_memfree(). Link: https://www.sochub.fi # for power on testing new SoC's with a minimal stack Link: https://lore.kernel.org/all/20220608000014.3054333-1-jar...@profian.com/ # continuation Signed-off-by: Jarkko Sakkinen <jar...@kernel.org> --- v2: - Better late than never right? :-) - Focus only to RISC-V for now to make the patch more digestable. This is the arch where I use the patch on a daily basis to help with QA. - Introduce HAVE_KPROBES_ALLOC flag to help with more gradual migration. --- arch/Kconfig | 8 +++++++- arch/riscv/Kconfig | 1 + arch/riscv/kernel/Makefile | 5 +++++ arch/riscv/kernel/module.c | 11 ----------- arch/riscv/kernel/module_alloc.c | 28 ++++++++++++++++++++++++++++ kernel/kprobes.c | 10 ++++++++++ kernel/trace/trace_kprobe.c | 18 ++++++++++++++++-- 7 files changed, 67 insertions(+), 14 deletions(-) create mode 100644 arch/riscv/kernel/module_alloc.c diff --git a/arch/Kconfig b/arch/Kconfig index a5af0edd3eb8..c931f1de98a7 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -52,7 +52,7 @@ config GENERIC_ENTRY config KPROBES bool "Kprobes" - depends on MODULES + depends on MODULES || HAVE_KPROBES_ALLOC depends on HAVE_KPROBES select KALLSYMS select TASKS_RCU if PREEMPTION @@ -215,6 +215,12 @@ config HAVE_OPTPROBES config HAVE_KPROBES_ON_FTRACE bool +config HAVE_KPROBES_ALLOC + bool + help + Architectures that select this option are capable of allocating memory + for kprobes withou the kernel module allocator. + config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE bool help diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index e3142ce531a0..4f1b925e83d8 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -132,6 +132,7 @@ config RISCV select HAVE_KPROBES if !XIP_KERNEL select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL select HAVE_KRETPROBES if !XIP_KERNEL + select HAVE_KPROBES_ALLOC if !XIP_KERNEL # https://github.com/ClangBuiltLinux/linux/issues/1881 select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if !LD_IS_LLD select HAVE_MOVE_PMD diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index 604d6bf7e476..46318194bce1 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -73,6 +73,11 @@ obj-$(CONFIG_SMP) += cpu_ops.o obj-$(CONFIG_RISCV_BOOT_SPINWAIT) += cpu_ops_spinwait.o obj-$(CONFIG_MODULES) += module.o +ifeq ($(CONFIG_MODULES),y) +obj-y += module_alloc.o +else +obj-$(CONFIG_KPROBES) += module_alloc.o +endif obj-$(CONFIG_MODULE_SECTIONS) += module-sections.o obj-$(CONFIG_CPU_PM) += suspend_entry.o suspend.o diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c index 5e5a82644451..cc324b450f2e 100644 --- a/arch/riscv/kernel/module.c +++ b/arch/riscv/kernel/module.c @@ -905,17 +905,6 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab, return 0; } -#if defined(CONFIG_MMU) && defined(CONFIG_64BIT) -void *module_alloc(unsigned long size) -{ - return __vmalloc_node_range(size, 1, MODULES_VADDR, - MODULES_END, GFP_KERNEL, - PAGE_KERNEL, VM_FLUSH_RESET_PERMS, - NUMA_NO_NODE, - __builtin_return_address(0)); -} -#endif - int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *me) diff --git a/arch/riscv/kernel/module_alloc.c b/arch/riscv/kernel/module_alloc.c new file mode 100644 index 000000000000..3d9aa8dbca8a --- /dev/null +++ b/arch/riscv/kernel/module_alloc.c @@ -0,0 +1,28 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2017 Zihao Yu + * Copyright (c) 2024 Jarkko Sakkinen + */ + +#include <linux/mm.h> +#include <linux/moduleloader.h> +#include <linux/vmalloc.h> +#include <asm/sections.h> + +#if defined(CONFIG_MMU) && defined(CONFIG_64BIT) +void *module_alloc(unsigned long size) +{ + return __vmalloc_node_range(size, 1, MODULES_VADDR, + MODULES_END, GFP_KERNEL, + PAGE_KERNEL, 0, NUMA_NO_NODE, + __builtin_return_address(0)); +} + +void module_memfree(void *module_region) +{ + if (in_interrupt()) + pr_warn("In interrupt context: vmalloc may not work.\n"); + + vfree(module_region); +} +#endif diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 9d9095e81792..2c583ab6efc4 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1580,6 +1580,7 @@ static int check_kprobe_address_safe(struct kprobe *p, goto out; } +#ifdef CONFIG_MODULES /* Check if 'p' is probing a module. */ *probed_mod = __module_text_address((unsigned long) p->addr); if (*probed_mod) { @@ -1603,6 +1604,8 @@ static int check_kprobe_address_safe(struct kprobe *p, ret = -ENOENT; } } +#endif + out: preempt_enable(); jump_label_unlock(); @@ -2482,6 +2485,7 @@ int kprobe_add_area_blacklist(unsigned long start, unsigned long end) return 0; } +#ifdef CONFIG_MODULES /* Remove all symbols in given area from kprobe blacklist */ static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end) { @@ -2499,6 +2503,7 @@ static void kprobe_remove_ksym_blacklist(unsigned long entry) { kprobe_remove_area_blacklist(entry, entry + 1); } +#endif /* CONFIG_MODULES */ int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value, char *type, char *sym) @@ -2564,6 +2569,7 @@ static int __init populate_kprobe_blacklist(unsigned long *start, return ret ? : arch_populate_kprobe_blacklist(); } +#ifdef CONFIG_MODULES static void add_module_kprobe_blacklist(struct module *mod) { unsigned long start, end; @@ -2665,6 +2671,7 @@ static struct notifier_block kprobe_module_nb = { .notifier_call = kprobes_module_callback, .priority = 0 }; +#endif /* CONFIG_MODULES */ void kprobe_free_init_mem(void) { @@ -2724,8 +2731,11 @@ static int __init init_kprobes(void) err = arch_init_kprobes(); if (!err) err = register_die_notifier(&kprobe_exceptions_nb); + +#ifdef CONFIG_MODULES if (!err) err = register_module_notifier(&kprobe_module_nb); +#endif kprobes_initialized = (err == 0); kprobe_sysctls_init(); diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index c4c6e0e0068b..f8fbd5e76dda 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -111,6 +111,7 @@ static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk, return strncmp(module_name(mod), name, len) == 0 && name[len] == ':'; } +#ifdef CONFIG_MODULES static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) { char *p; @@ -129,6 +130,7 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) return ret; } +#endif /* CONFIG_MODULES */ static bool trace_kprobe_is_busy(struct dyn_event *ev) { @@ -608,7 +610,11 @@ static int append_trace_kprobe(struct trace_kprobe *tk, struct trace_kprobe *to) /* Register k*probe */ ret = __register_trace_kprobe(tk); - if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) { +#ifdef CONFIG_MODULES + if (ret == -ENOENT && trace_kprobe_module_exist(tk)) + ret = 0; +#endif /* CONFIG_MODULES */ + if (ret == -ENOENT) { pr_warn("This probe might be able to register after target module is loaded. Continue.\n"); ret = 0; } @@ -655,7 +661,11 @@ static int register_trace_kprobe(struct trace_kprobe *tk) /* Register k*probe */ ret = __register_trace_kprobe(tk); - if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) { +#ifdef CONFIG_MODULES + if (ret == -ENOENT && trace_kprobe_module_exist(tk)) + ret = 0; +#endif /* CONFIG_MODULES */ + if (ret == -ENOENT) { pr_warn("This probe might be able to register after target module is loaded. Continue.\n"); ret = 0; } @@ -670,6 +680,7 @@ static int register_trace_kprobe(struct trace_kprobe *tk) return ret; } +#ifdef CONFIG_MODULES /* Module notifier call back, checking event on the module */ static int trace_kprobe_module_callback(struct notifier_block *nb, unsigned long val, void *data) @@ -704,6 +715,7 @@ static struct notifier_block trace_kprobe_module_nb = { .notifier_call = trace_kprobe_module_callback, .priority = 1 /* Invoked after kprobe module callback */ }; +#endif /* CONFIG_MODULES */ static int count_symbols(void *data, unsigned long unused) { @@ -1897,8 +1909,10 @@ static __init int init_kprobe_trace_early(void) if (ret) return ret; +#ifdef CONFIG_MODULES if (register_module_notifier(&trace_kprobe_module_nb)) return -EINVAL; +#endif /* CONFIG_MODULES */ return 0; } -- 2.44.0
