| Message ID | 20240325215502.660-1-jarkko@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v5,1/2] kprobes: textmem API | expand |
s/textmem/execmem/ (also in long description) will hold sending a new version as not a functional issue, will fix after review. BR, Jarkko
On Mon Mar 25, 2024 at 11:55 PM EET, Jarkko Sakkinen wrote: > +#ifdef CONFIG_MODULES > if (register_module_notifier(&trace_kprobe_module_nb)) > return -EINVAL; > +#endif /* CONFIG_MODULES */ register_module_notifier() does have "dummy" version but what would I pass to it. It makes more mess than it cleans to declare also a "dummy" version of trace_kprobe_module_nb. The callback itself has too tight module subsystem bindings so that they could be simply flagged with IS_DEFINED() (or correct if I'm mistaken, this the conclusion I've ended up with). BR, Jarkko
On Tue Mar 26, 2024 at 12:09 AM EET, Jarkko Sakkinen wrote: > On Mon Mar 25, 2024 at 11:55 PM EET, Jarkko Sakkinen wrote: > > +#ifdef CONFIG_MODULES > > if (register_module_notifier(&trace_kprobe_module_nb)) > > return -EINVAL; > > +#endif /* CONFIG_MODULES */ > > register_module_notifier() does have "dummy" version but what > would I pass to it. It makes more mess than it cleans to declare > also a "dummy" version of trace_kprobe_module_nb. > > The callback itself has too tight module subsystem bindings so > that they could be simply flagged with IS_DEFINED() (or correct > if I'm mistaken, this the conclusion I've ended up with). One way to clean that up would be to create trace_kprobe_module.c and move kernel module specific code over there and then change kernel/trace/Makefile as follows: ifeq ($(CONFIG_PERF_EVENTS),y) obj-y += trace_kprobe.o obj-$(CONFIG_MODULES) += trace_kprobe_module.o endif and define trace_kprobe_module_init() or similar to do all the dance with notifiers etc. This crossed my mind but did not want to do it without feedback. BR, Jarkko
On Tue, 26 Mar 2024 00:09:42 +0200 "Jarkko Sakkinen" <jarkko@kernel.org> wrote: > On Mon Mar 25, 2024 at 11:55 PM EET, Jarkko Sakkinen wrote: > > +#ifdef CONFIG_MODULES > > if (register_module_notifier(&trace_kprobe_module_nb)) > > return -EINVAL; > > +#endif /* CONFIG_MODULES */ > > register_module_notifier() does have "dummy" version but what > would I pass to it. It makes more mess than it cleans to declare > also a "dummy" version of trace_kprobe_module_nb. That is better than having #ifdef in the function. > > The callback itself has too tight module subsystem bindings so > that they could be simply flagged with IS_DEFINED() (or correct > if I'm mistaken, this the conclusion I've ended up with). Please try this. ----- diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 70dc6179086e..bc98db14927f 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -2625,6 +2625,7 @@ static void remove_module_kprobe_blacklist(struct module *mod) } } +#ifdef CONFIG_MODULES /* Module notifier call back, checking kprobes on the module */ static int kprobes_module_callback(struct notifier_block *nb, unsigned long val, void *data) @@ -2675,6 +2676,9 @@ static int kprobes_module_callback(struct notifier_block *nb, mutex_unlock(&kprobe_mutex); return NOTIFY_DONE; } +#else +#define kprobes_module_callback (NULL) +#endif static struct notifier_block kprobe_module_nb = { .notifier_call = kprobes_module_callback, @@ -2739,7 +2743,7 @@ static int __init init_kprobes(void) err = arch_init_kprobes(); if (!err) err = register_die_notifier(&kprobe_exceptions_nb); - if (!err) + if (!err && IS_ENABLED(CONFIG_MODULES)) err = register_module_notifier(&kprobe_module_nb); kprobes_initialized = (err == 0); ----- Thank you,
On Tue Mar 26, 2024 at 1:50 AM EET, Masami Hiramatsu (Google) wrote: > On Tue, 26 Mar 2024 00:09:42 +0200 > "Jarkko Sakkinen" <jarkko@kernel.org> wrote: > > > On Mon Mar 25, 2024 at 11:55 PM EET, Jarkko Sakkinen wrote: > > > +#ifdef CONFIG_MODULES > > > if (register_module_notifier(&trace_kprobe_module_nb)) > > > return -EINVAL; > > > +#endif /* CONFIG_MODULES */ > > > > register_module_notifier() does have "dummy" version but what > > would I pass to it. It makes more mess than it cleans to declare > > also a "dummy" version of trace_kprobe_module_nb. > > That is better than having #ifdef in the function. > > > > > The callback itself has too tight module subsystem bindings so > > that they could be simply flagged with IS_DEFINED() (or correct > > if I'm mistaken, this the conclusion I've ended up with). > > Please try this. > > ----- > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 70dc6179086e..bc98db14927f 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -2625,6 +2625,7 @@ static void remove_module_kprobe_blacklist(struct module *mod) > } > } > > +#ifdef CONFIG_MODULES > /* Module notifier call back, checking kprobes on the module */ > static int kprobes_module_callback(struct notifier_block *nb, > unsigned long val, void *data) > @@ -2675,6 +2676,9 @@ static int kprobes_module_callback(struct notifier_block *nb, > mutex_unlock(&kprobe_mutex); > return NOTIFY_DONE; > } > +#else > +#define kprobes_module_callback (NULL) > +#endif > > static struct notifier_block kprobe_module_nb = { > .notifier_call = kprobes_module_callback, > @@ -2739,7 +2743,7 @@ static int __init init_kprobes(void) > err = arch_init_kprobes(); > if (!err) > err = register_die_notifier(&kprobe_exceptions_nb); > - if (!err) > + if (!err && IS_ENABLED(CONFIG_MODULES)) > err = register_module_notifier(&kprobe_module_nb); > > kprobes_initialized = (err == 0); OK, thanks for the suggestion WFM. I'll give this also a spin with VisionFive2 RISC-V SBC before sending v6. BR, Jarkko
On Mon, 25 Mar 2024 23:55:01 +0200 Jarkko Sakkinen <jarkko@kernel.org> wrote: > Tracing with kprobes while running a monolithic kernel is currently > impossible because CONFIG_KPROBES depends on CONFIG_MODULES because it uses > the kernel module allocator. > > Introduce alloc_textmem() and free_textmem() for allocating executable > memory. If an arch implements these functions, it can mark this up with > the HAVE_ALLOC_EXECMEM kconfig flag. > > At first this feature will be used for enabling kprobes without > modules support for arch/riscv. > > Link: https://lore.kernel.org/all/20240325115632.04e37297491cadfbbf382767@kernel.org/ > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> > --- > v5: > - alloc_execmem() was missing GFP_KERNEL parameter. The patch set did > compile because 2/2 had the fixup (leaked there when rebasing the > patch set). > v4: > - Squashed a couple of unrequired CONFIG_MODULES checks. > - See https://lore.kernel.org/all/D034M18D63EC.2Y11D954YSZYK@kernel.org/ > v3: > - A new patch added. > - For IS_DEFINED() I need advice as I could not really find that many > locations where it would be applicable. > --- > arch/Kconfig | 16 +++++++++++++++- > include/linux/execmem.h | 13 +++++++++++++ > kernel/kprobes.c | 17 ++++++++++++++--- > kernel/trace/trace_kprobe.c | 8 ++++++++ > 4 files changed, 50 insertions(+), 4 deletions(-) > create mode 100644 include/linux/execmem.h > > diff --git a/arch/Kconfig b/arch/Kconfig > index a5af0edd3eb8..33ba68b7168f 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -52,8 +52,8 @@ config GENERIC_ENTRY > > config KPROBES > bool "Kprobes" > - depends on MODULES > depends on HAVE_KPROBES > + select ALLOC_EXECMEM > select KALLSYMS > select TASKS_RCU if PREEMPTION > help > @@ -215,6 +215,20 @@ config HAVE_OPTPROBES > config HAVE_KPROBES_ON_FTRACE > bool > > +config HAVE_ALLOC_EXECMEM > + bool > + help > + Architectures that select this option are capable of allocating executable > + memory, which can be used by subsystems but is not dependent of any of its > + clients. > + > +config ALLOC_EXECMEM > + bool "Executable (trampoline) memory allocation" > + depends on MODULES || HAVE_ALLOC_EXECMEM > + help > + Select this for executable (trampoline) memory. Can be enabled when either > + module allocator or arch-specific allocator is available. > + > config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE > bool > help > diff --git a/include/linux/execmem.h b/include/linux/execmem.h > new file mode 100644 > index 000000000000..ae2ff151523a > --- /dev/null > +++ b/include/linux/execmem.h > @@ -0,0 +1,13 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _LINUX_EXECMEM_H > +#define _LINUX_EXECMEM_H > + > +#ifdef CONFIG_HAVE_ALLOC_EXECMEM > +void *alloc_execmem(unsigned long size, gfp_t gfp); > +void free_execmem(void *region); > +#else > +#define alloc_execmem(size, gfp) module_alloc(size) > +#define free_execmem(region) module_memfree(region) > +#endif > + > +#endif /* _LINUX_EXECMEM_H */ > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 9d9095e81792..87fd8c14a938 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -44,6 +44,7 @@ > #include <asm/cacheflush.h> > #include <asm/errno.h> > #include <linux/uaccess.h> > +#include <linux/execmem.h> > > #define KPROBE_HASH_BITS 6 > #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) > @@ -113,17 +114,17 @@ enum kprobe_slot_state { > void __weak *alloc_insn_page(void) > { > /* > - * Use module_alloc() so this page is within +/- 2GB of where the > + * Use alloc_execmem() so this page is within +/- 2GB of where the > * kernel image and loaded module images reside. This is required > * for most of the architectures. > * (e.g. x86-64 needs this to handle the %rip-relative fixups.) > */ > - return module_alloc(PAGE_SIZE); > + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); > } > > static void free_insn_page(void *page) > { > - module_memfree(page); > + free_execmem(page); > } > > struct kprobe_insn_cache kprobe_insn_slots = { > @@ -1580,6 +1581,7 @@ static int check_kprobe_address_safe(struct kprobe *p, > goto out; > } > > +#ifdef CONFIG_MODULES You don't need this block, because these APIs have dummy functions. > /* Check if 'p' is probing a module. */ > *probed_mod = __module_text_address((unsigned long) p->addr); > if (*probed_mod) { So this block never be true if !CONFIG_MODULES automatically, and it should be optimized out by compiler. > @@ -1603,6 +1605,8 @@ static int check_kprobe_address_safe(struct kprobe *p, > ret = -ENOENT; > } > } > +#endif > + > out: > preempt_enable(); > jump_label_unlock(); > @@ -2482,6 +2486,7 @@ 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 +2504,7 @@ static void kprobe_remove_ksym_blacklist(unsigned long entry) > { > kprobe_remove_area_blacklist(entry, entry + 1); > } > +#endif /* CONFIG_MODULES */ I think this block should be moved right before remove_module_kprobe_blacklist(). Then we can gather the code depending on modules in one place. > > int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value, > char *type, char *sym) > @@ -2564,6 +2570,7 @@ 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 +2672,7 @@ static struct notifier_block kprobe_module_nb = { > .notifier_call = kprobes_module_callback, > .priority = 0 > }; > +#endif /* CONFIG_MODULES */ So, keep the kprobe_module_nb outside of this #ifdef as I sed. > > void kprobe_free_init_mem(void) > { > @@ -2724,8 +2732,11 @@ 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 Then we don't need this #ifdef. > > kprobes_initialized = (err == 0); > kprobe_sysctls_init(); > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index c4c6e0e0068b..af70bb1e9c3a 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 +130,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) > > return ret; > } > +#else > +#define trace_kprobe_module_exist(tk) false /* aka a module never exists */ > +#endif /* CONFIG_MODULES */ > > static bool trace_kprobe_is_busy(struct dyn_event *ev) > { > @@ -670,6 +674,7 @@ 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 +709,7 @@ static struct notifier_block trace_kprobe_module_nb = { > .notifier_call = trace_kprobe_module_callback, > .priority = 1 /* Invoked after kprobe module callback */ > }; > +#endif /* CONFIG_MODULES */ As I similar to the above, let's move trace_kprobe_module_nb outside of #ifdef. > > static int count_symbols(void *data, unsigned long unused) > { > @@ -1897,8 +1903,10 @@ 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 */ And remove this #ifdef. Thank you! > > return 0; > } > -- > 2.44.0 >
On Tue Mar 26, 2024 at 2:58 AM EET, Masami Hiramatsu (Google) wrote: > On Mon, 25 Mar 2024 23:55:01 +0200 > Jarkko Sakkinen <jarkko@kernel.org> wrote: > > > Tracing with kprobes while running a monolithic kernel is currently > > impossible because CONFIG_KPROBES depends on CONFIG_MODULES because it uses > > the kernel module allocator. > > > > Introduce alloc_textmem() and free_textmem() for allocating executable > > memory. If an arch implements these functions, it can mark this up with > > the HAVE_ALLOC_EXECMEM kconfig flag. > > > > At first this feature will be used for enabling kprobes without > > modules support for arch/riscv. > > > > Link: https://lore.kernel.org/all/20240325115632.04e37297491cadfbbf382767@kernel.org/ > > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> > > --- > > v5: > > - alloc_execmem() was missing GFP_KERNEL parameter. The patch set did > > compile because 2/2 had the fixup (leaked there when rebasing the > > patch set). > > v4: > > - Squashed a couple of unrequired CONFIG_MODULES checks. > > - See https://lore.kernel.org/all/D034M18D63EC.2Y11D954YSZYK@kernel.org/ > > v3: > > - A new patch added. > > - For IS_DEFINED() I need advice as I could not really find that many > > locations where it would be applicable. > > --- > > arch/Kconfig | 16 +++++++++++++++- > > include/linux/execmem.h | 13 +++++++++++++ > > kernel/kprobes.c | 17 ++++++++++++++--- > > kernel/trace/trace_kprobe.c | 8 ++++++++ > > 4 files changed, 50 insertions(+), 4 deletions(-) > > create mode 100644 include/linux/execmem.h > > > > diff --git a/arch/Kconfig b/arch/Kconfig > > index a5af0edd3eb8..33ba68b7168f 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -52,8 +52,8 @@ config GENERIC_ENTRY > > > > config KPROBES > > bool "Kprobes" > > - depends on MODULES > > depends on HAVE_KPROBES > > + select ALLOC_EXECMEM > > select KALLSYMS > > select TASKS_RCU if PREEMPTION > > help > > @@ -215,6 +215,20 @@ config HAVE_OPTPROBES > > config HAVE_KPROBES_ON_FTRACE > > bool > > > > +config HAVE_ALLOC_EXECMEM > > + bool > > + help > > + Architectures that select this option are capable of allocating executable > > + memory, which can be used by subsystems but is not dependent of any of its > > + clients. > > + > > +config ALLOC_EXECMEM > > + bool "Executable (trampoline) memory allocation" > > + depends on MODULES || HAVE_ALLOC_EXECMEM > > + help > > + Select this for executable (trampoline) memory. Can be enabled when either > > + module allocator or arch-specific allocator is available. > > + > > config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE > > bool > > help > > diff --git a/include/linux/execmem.h b/include/linux/execmem.h > > new file mode 100644 > > index 000000000000..ae2ff151523a > > --- /dev/null > > +++ b/include/linux/execmem.h > > @@ -0,0 +1,13 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#ifndef _LINUX_EXECMEM_H > > +#define _LINUX_EXECMEM_H > > + > > +#ifdef CONFIG_HAVE_ALLOC_EXECMEM > > +void *alloc_execmem(unsigned long size, gfp_t gfp); > > +void free_execmem(void *region); > > +#else > > +#define alloc_execmem(size, gfp) module_alloc(size) > > +#define free_execmem(region) module_memfree(region) > > +#endif > > + > > +#endif /* _LINUX_EXECMEM_H */ > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index 9d9095e81792..87fd8c14a938 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -44,6 +44,7 @@ > > #include <asm/cacheflush.h> > > #include <asm/errno.h> > > #include <linux/uaccess.h> > > +#include <linux/execmem.h> > > > > #define KPROBE_HASH_BITS 6 > > #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) > > @@ -113,17 +114,17 @@ enum kprobe_slot_state { > > void __weak *alloc_insn_page(void) > > { > > /* > > - * Use module_alloc() so this page is within +/- 2GB of where the > > + * Use alloc_execmem() so this page is within +/- 2GB of where the > > * kernel image and loaded module images reside. This is required > > * for most of the architectures. > > * (e.g. x86-64 needs this to handle the %rip-relative fixups.) > > */ > > - return module_alloc(PAGE_SIZE); > > + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); > > } > > > > static void free_insn_page(void *page) > > { > > - module_memfree(page); > > + free_execmem(page); > > } > > > > struct kprobe_insn_cache kprobe_insn_slots = { > > @@ -1580,6 +1581,7 @@ static int check_kprobe_address_safe(struct kprobe *p, > > goto out; > > } > > > > +#ifdef CONFIG_MODULES > > You don't need this block, because these APIs have dummy functions. Hmm... I'll verify this tomorrow. > > > /* Check if 'p' is probing a module. */ > > *probed_mod = __module_text_address((unsigned long) p->addr); > > if (*probed_mod) { > > So this block never be true if !CONFIG_MODULES automatically, and it should be > optimized out by compiler. Yeah sure, was not done for saving cycles. Just wanted to make sure that my stuff compiles with different config flag combinations related but I'll check tomorrow morning if I can relax this further. > > > @@ -1603,6 +1605,8 @@ static int check_kprobe_address_safe(struct kprobe *p, > > ret = -ENOENT; > > } > > } > > +#endif > > + > > out: > > preempt_enable(); > > jump_label_unlock(); > > @@ -2482,6 +2486,7 @@ 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 +2504,7 @@ static void kprobe_remove_ksym_blacklist(unsigned long entry) > > { > > kprobe_remove_area_blacklist(entry, entry + 1); > > } > > +#endif /* CONFIG_MODULES */ > > I think this block should be moved right before remove_module_kprobe_blacklist(). > Then we can gather the code depending on modules in one place. Agree with this without verification :-) > > > > > int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value, > > char *type, char *sym) > > @@ -2564,6 +2570,7 @@ 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 +2672,7 @@ static struct notifier_block kprobe_module_nb = { > > .notifier_call = kprobes_module_callback, > > .priority = 0 > > }; > > +#endif /* CONFIG_MODULES */ > > So, keep the kprobe_module_nb outside of this #ifdef as I sed. Yup, already done in v6. > > > > > > void kprobe_free_init_mem(void) > > { > > @@ -2724,8 +2732,11 @@ 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 > > Then we don't need this #ifdef. Addressed in v6. > > > > > kprobes_initialized = (err == 0); > > kprobe_sysctls_init(); > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index c4c6e0e0068b..af70bb1e9c3a 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 +130,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) > > > > return ret; > > } > > +#else > > +#define trace_kprobe_module_exist(tk) false /* aka a module never exists */ > > +#endif /* CONFIG_MODULES */ > > > > static bool trace_kprobe_is_busy(struct dyn_event *ev) > > { > > @@ -670,6 +674,7 @@ 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 +709,7 @@ static struct notifier_block trace_kprobe_module_nb = { > > .notifier_call = trace_kprobe_module_callback, > > .priority = 1 /* Invoked after kprobe module callback */ > > }; > > +#endif /* CONFIG_MODULES */ > > As I similar to the above, let's move trace_kprobe_module_nb outside > of #ifdef. Ditto (also in v6). > > > > > static int count_symbols(void *data, unsigned long unused) > > { > > @@ -1897,8 +1903,10 @@ 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 */ > > And remove this #ifdef. > > Thank you! Thanks for quick reviews and sorry for the spam. I just try to move this forward with small pushes because with compilation flags it is easy to blow up compilation. I'll do the aforementioned suggestions that were missing from v6 to v7. > > > > > return 0; > > } > > -- > > 2.44.0 > > BR, Jarkko
On Tue Mar 26, 2024 at 3:31 AM EET, Jarkko Sakkinen wrote: > > > +#endif /* _LINUX_EXECMEM_H */ > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > index 9d9095e81792..87fd8c14a938 100644 > > > --- a/kernel/kprobes.c > > > +++ b/kernel/kprobes.c > > > @@ -44,6 +44,7 @@ > > > #include <asm/cacheflush.h> > > > #include <asm/errno.h> > > > #include <linux/uaccess.h> > > > +#include <linux/execmem.h> > > > > > > #define KPROBE_HASH_BITS 6 > > > #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) > > > @@ -113,17 +114,17 @@ enum kprobe_slot_state { > > > void __weak *alloc_insn_page(void) > > > { > > > /* > > > - * Use module_alloc() so this page is within +/- 2GB of where the > > > + * Use alloc_execmem() so this page is within +/- 2GB of where the > > > * kernel image and loaded module images reside. This is required > > > * for most of the architectures. > > > * (e.g. x86-64 needs this to handle the %rip-relative fixups.) > > > */ > > > - return module_alloc(PAGE_SIZE); > > > + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); > > > } > > > > > > static void free_insn_page(void *page) > > > { > > > - module_memfree(page); > > > + free_execmem(page); > > > } > > > > > > struct kprobe_insn_cache kprobe_insn_slots = { > > > @@ -1580,6 +1581,7 @@ static int check_kprobe_address_safe(struct kprobe *p, > > > goto out; > > > } > > > > > > +#ifdef CONFIG_MODULES > > > > You don't need this block, because these APIs have dummy functions. > > Hmm... I'll verify this tomorrow. It depends on having struct module available given "(*probed_mod)->state". It is non-existent unless CONFIG_MODULES is set given how things are flagged in include/linux/module.h. BR, Jarkko
On Tue Mar 26, 2024 at 4:01 AM EET, Jarkko Sakkinen wrote: > On Tue Mar 26, 2024 at 3:31 AM EET, Jarkko Sakkinen wrote: > > > > +#endif /* _LINUX_EXECMEM_H */ > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > > index 9d9095e81792..87fd8c14a938 100644 > > > > --- a/kernel/kprobes.c > > > > +++ b/kernel/kprobes.c > > > > @@ -44,6 +44,7 @@ > > > > #include <asm/cacheflush.h> > > > > #include <asm/errno.h> > > > > #include <linux/uaccess.h> > > > > +#include <linux/execmem.h> > > > > > > > > #define KPROBE_HASH_BITS 6 > > > > #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) > > > > @@ -113,17 +114,17 @@ enum kprobe_slot_state { > > > > void __weak *alloc_insn_page(void) > > > > { > > > > /* > > > > - * Use module_alloc() so this page is within +/- 2GB of where the > > > > + * Use alloc_execmem() so this page is within +/- 2GB of where the > > > > * kernel image and loaded module images reside. This is required > > > > * for most of the architectures. > > > > * (e.g. x86-64 needs this to handle the %rip-relative fixups.) > > > > */ > > > > - return module_alloc(PAGE_SIZE); > > > > + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); > > > > } > > > > > > > > static void free_insn_page(void *page) > > > > { > > > > - module_memfree(page); > > > > + free_execmem(page); > > > > } > > > > > > > > struct kprobe_insn_cache kprobe_insn_slots = { > > > > @@ -1580,6 +1581,7 @@ static int check_kprobe_address_safe(struct kprobe *p, > > > > goto out; > > > > } > > > > > > > > +#ifdef CONFIG_MODULES > > > > > > You don't need this block, because these APIs have dummy functions. > > > > Hmm... I'll verify this tomorrow. > > It depends on having struct module available given "(*probed_mod)->state". > > It is non-existent unless CONFIG_MODULES is set given how things are > flagged in include/linux/module.h. Hey, noticed kconfig issue. According to kconfig-language.txt: "select should be used with care. select will force a symbol to a value without visiting the dependencies." So the problem here lies in KPROBES config entry using select statement to pick ALLOC_EXECMEM. It will not take the depends on statement into account and thus will allow to select kprobes without any allocator in place. So to address this I'd suggest to use depends on statement also for describing relation between KPROBES and ALLOC_EXECMEM. It does not make life worse than before for anyone because even with the current kernel you have to select MODULES before you can move forward with kprobes. BR, Jarkko
On Tue, 26 Mar 2024 15:18:21 +0200 "Jarkko Sakkinen" <jarkko@kernel.org> wrote: > On Tue Mar 26, 2024 at 4:01 AM EET, Jarkko Sakkinen wrote: > > On Tue Mar 26, 2024 at 3:31 AM EET, Jarkko Sakkinen wrote: > > > > > +#endif /* _LINUX_EXECMEM_H */ > > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > > > index 9d9095e81792..87fd8c14a938 100644 > > > > > --- a/kernel/kprobes.c > > > > > +++ b/kernel/kprobes.c > > > > > @@ -44,6 +44,7 @@ > > > > > #include <asm/cacheflush.h> > > > > > #include <asm/errno.h> > > > > > #include <linux/uaccess.h> > > > > > +#include <linux/execmem.h> > > > > > > > > > > #define KPROBE_HASH_BITS 6 > > > > > #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) > > > > > @@ -113,17 +114,17 @@ enum kprobe_slot_state { > > > > > void __weak *alloc_insn_page(void) > > > > > { > > > > > /* > > > > > - * Use module_alloc() so this page is within +/- 2GB of where the > > > > > + * Use alloc_execmem() so this page is within +/- 2GB of where the > > > > > * kernel image and loaded module images reside. This is required > > > > > * for most of the architectures. > > > > > * (e.g. x86-64 needs this to handle the %rip-relative fixups.) > > > > > */ > > > > > - return module_alloc(PAGE_SIZE); > > > > > + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); > > > > > } > > > > > > > > > > static void free_insn_page(void *page) > > > > > { > > > > > - module_memfree(page); > > > > > + free_execmem(page); > > > > > } > > > > > > > > > > struct kprobe_insn_cache kprobe_insn_slots = { > > > > > @@ -1580,6 +1581,7 @@ static int check_kprobe_address_safe(struct kprobe *p, > > > > > goto out; > > > > > } > > > > > > > > > > +#ifdef CONFIG_MODULES > > > > > > > > You don't need this block, because these APIs have dummy functions. > > > > > > Hmm... I'll verify this tomorrow. > > > > It depends on having struct module available given "(*probed_mod)->state". Ah, indeed. We need module_state() function to avoid it. > > > > It is non-existent unless CONFIG_MODULES is set given how things are > > flagged in include/linux/module.h. > > Hey, noticed kconfig issue. > > According to kconfig-language.txt: > > "select should be used with care. select will force a symbol to a value > without visiting the dependencies." > > So the problem here lies in KPROBES config entry using select statement > to pick ALLOC_EXECMEM. It will not take the depends on statement into > account and thus will allow to select kprobes without any allocator in > place. OK, in that case "depend on" is good. > > So to address this I'd suggest to use depends on statement also for > describing relation between KPROBES and ALLOC_EXECMEM. It does not make > life worse than before for anyone because even with the current kernel > you have to select MODULES before you can move forward with kprobes. Yeah, since ALLOC_EXECMEM is enabled by default. Thank you! > > BR, Jarkko
On Tue Mar 26, 2024 at 5:05 PM EET, Masami Hiramatsu (Google) wrote: > > According to kconfig-language.txt: > > > > "select should be used with care. select will force a symbol to a value > > without visiting the dependencies." > > > > So the problem here lies in KPROBES config entry using select statement > > to pick ALLOC_EXECMEM. It will not take the depends on statement into > > account and thus will allow to select kprobes without any allocator in > > place. > > OK, in that case "depend on" is good. Yeah, did not remember this at all. Only recalled when I started to get linking errors when compiling just the first patch... It's a bit uninituitive twist in kconfig :-) BR, Jarkko
diff --git a/arch/Kconfig b/arch/Kconfig index a5af0edd3eb8..33ba68b7168f 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -52,8 +52,8 @@ config GENERIC_ENTRY config KPROBES bool "Kprobes" - depends on MODULES depends on HAVE_KPROBES + select ALLOC_EXECMEM select KALLSYMS select TASKS_RCU if PREEMPTION help @@ -215,6 +215,20 @@ config HAVE_OPTPROBES config HAVE_KPROBES_ON_FTRACE bool +config HAVE_ALLOC_EXECMEM + bool + help + Architectures that select this option are capable of allocating executable + memory, which can be used by subsystems but is not dependent of any of its + clients. + +config ALLOC_EXECMEM + bool "Executable (trampoline) memory allocation" + depends on MODULES || HAVE_ALLOC_EXECMEM + help + Select this for executable (trampoline) memory. Can be enabled when either + module allocator or arch-specific allocator is available. + config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE bool help diff --git a/include/linux/execmem.h b/include/linux/execmem.h new file mode 100644 index 000000000000..ae2ff151523a --- /dev/null +++ b/include/linux/execmem.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_EXECMEM_H +#define _LINUX_EXECMEM_H + +#ifdef CONFIG_HAVE_ALLOC_EXECMEM +void *alloc_execmem(unsigned long size, gfp_t gfp); +void free_execmem(void *region); +#else +#define alloc_execmem(size, gfp) module_alloc(size) +#define free_execmem(region) module_memfree(region) +#endif + +#endif /* _LINUX_EXECMEM_H */ diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 9d9095e81792..87fd8c14a938 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -44,6 +44,7 @@ #include <asm/cacheflush.h> #include <asm/errno.h> #include <linux/uaccess.h> +#include <linux/execmem.h> #define KPROBE_HASH_BITS 6 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) @@ -113,17 +114,17 @@ enum kprobe_slot_state { void __weak *alloc_insn_page(void) { /* - * Use module_alloc() so this page is within +/- 2GB of where the + * Use alloc_execmem() so this page is within +/- 2GB of where the * kernel image and loaded module images reside. This is required * for most of the architectures. * (e.g. x86-64 needs this to handle the %rip-relative fixups.) */ - return module_alloc(PAGE_SIZE); + return alloc_execmem(PAGE_SIZE, GFP_KERNEL); } static void free_insn_page(void *page) { - module_memfree(page); + free_execmem(page); } struct kprobe_insn_cache kprobe_insn_slots = { @@ -1580,6 +1581,7 @@ 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 +1605,8 @@ static int check_kprobe_address_safe(struct kprobe *p, ret = -ENOENT; } } +#endif + out: preempt_enable(); jump_label_unlock(); @@ -2482,6 +2486,7 @@ 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 +2504,7 @@ 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 +2570,7 @@ 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 +2672,7 @@ 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 +2732,11 @@ 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..af70bb1e9c3a 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 +130,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) return ret; } +#else +#define trace_kprobe_module_exist(tk) false /* aka a module never exists */ +#endif /* CONFIG_MODULES */ static bool trace_kprobe_is_busy(struct dyn_event *ev) { @@ -670,6 +674,7 @@ 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 +709,7 @@ 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 +1903,10 @@ 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; }
Tracing with kprobes while running a monolithic kernel is currently impossible because CONFIG_KPROBES depends on CONFIG_MODULES because it uses the kernel module allocator. Introduce alloc_textmem() and free_textmem() for allocating executable memory. If an arch implements these functions, it can mark this up with the HAVE_ALLOC_EXECMEM kconfig flag. At first this feature will be used for enabling kprobes without modules support for arch/riscv. Link: https://lore.kernel.org/all/20240325115632.04e37297491cadfbbf382767@kernel.org/ Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> --- v5: - alloc_execmem() was missing GFP_KERNEL parameter. The patch set did compile because 2/2 had the fixup (leaked there when rebasing the patch set). v4: - Squashed a couple of unrequired CONFIG_MODULES checks. - See https://lore.kernel.org/all/D034M18D63EC.2Y11D954YSZYK@kernel.org/ v3: - A new patch added. - For IS_DEFINED() I need advice as I could not really find that many locations where it would be applicable. --- arch/Kconfig | 16 +++++++++++++++- include/linux/execmem.h | 13 +++++++++++++ kernel/kprobes.c | 17 ++++++++++++++--- kernel/trace/trace_kprobe.c | 8 ++++++++ 4 files changed, 50 insertions(+), 4 deletions(-) create mode 100644 include/linux/execmem.h