// SPDX-License-Identifier: GPL-2.0-only/* Copyright (c) 2016 Facebook */#include <linux/bpf.h>#include <linux/jhash.h>#include <linux/filter.h>#include <linux/stacktrace.h>#include <linux/perf_event.h>#include <linux/elf.h>#include <linux/pagemap.h>#include <linux/irq_work.h>#include "percpu_freelist.h" #define STACK_CREATE_FLAG_MASK \ (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \ BPF_F_STACK_BUILD_ID) struct stack_map_bucket { struct pcpu_freelist_node fnode; u32 hash; u32 nr; u64 data[];}; struct bpf_stack_map { struct bpf_map map; void *elems; struct pcpu_freelist freelist; u32 n_buckets; struct stack_map_bucket *buckets[];}; /* irq_work to run up_read() for build_id lookup in nmi context */struct stack_map_irq_work { struct irq_work irq_work; struct mm_struct *mm;}; static void do_up_read(struct irq_work *entry){ struct stack_map_irq_work *work; if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT))) return; work = container_of(entry, struct stack_map_irq_work, irq_work); mmap_read_unlock_non_owner(work->mm);} static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work); static inline bool stack_map_use_build_id(struct bpf_map *map){ return (map->map_flags & BPF_F_STACK_BUILD_ID);} static inline int stack_map_data_size(struct bpf_map *map){ return stack_map_use_build_id(map) ? sizeof(struct bpf_stack_build_id) : sizeof(u64);} static int prealloc_elems_and_freelist(struct bpf_stack_map *smap){ u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size; int err; smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries, smap->map.numa_node); if (!smap->elems) return -ENOMEM; err = pcpu_freelist_init(&smap->freelist); if (err) goto free_elems; pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size, smap->map.max_entries); return 0; free_elems: bpf_map_area_free(smap->elems); return err;} /* Called from syscall */static struct bpf_map *stack_map_alloc(union bpf_attr *attr){ u32 value_size = attr->value_size; struct bpf_stack_map *smap; struct bpf_map_memory mem; u64 cost, n_buckets; int err; if (!bpf_capable()) return ERR_PTR(-EPERM); if (attr->map_flags & ~STACK_CREATE_FLAG_MASK) return ERR_PTR(-EINVAL); /* check sanity of attributes */ if (attr->max_entries == 0 || attr->key_size != 4 || value_size < 8 || value_size % 8) return ERR_PTR(-EINVAL); BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64)); if (attr->map_flags & BPF_F_STACK_BUILD_ID) { if (value_size % sizeof(struct bpf_stack_build_id) || value_size / sizeof(struct bpf_stack_build_id) > sysctl_perf_event_max_stack) return ERR_PTR(-EINVAL); } else if (value_size / 8 > sysctl_perf_event_max_stack) return ERR_PTR(-EINVAL); /* hash table size must be power of 2 */ n_buckets = roundup_pow_of_two(attr->max_entries); cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap); cost += n_buckets * (value_size + sizeof(struct stack_map_bucket)); err = bpf_map_charge_init(&mem, cost); if (err) return ERR_PTR(err); smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr)); if (!smap) { bpf_map_charge_finish(&mem); return ERR_PTR(-ENOMEM); } bpf_map_init_from_attr(&smap->map, attr); smap->map.value_size = value_size; smap->n_buckets = n_buckets; err = get_callchain_buffers(sysctl_perf_event_max_stack); if (err) goto free_charge; err = prealloc_elems_and_freelist(smap); if (err) goto put_buffers; bpf_map_charge_move(&smap->map.memory, &mem); return &smap->map; put_buffers: put_callchain_buffers();free_charge: bpf_map_charge_finish(&mem); bpf_map_area_free(smap); return ERR_PTR(err);} #define BPF_BUILD_ID 3/* * Parse build id from the note segment. This logic can be shared between * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are * identical. */static inline int stack_map_parse_build_id(void *page_addr, unsigned char *build_id, void *note_start, Elf32_Word note_size){ Elf32_Word note_offs = 0, new_offs; /* check for overflow */ if (note_start < page_addr || note_start + note_size < note_start) return -EINVAL; /* only supports note that fits in the first page */ if (note_start + note_size > page_addr + PAGE_SIZE) return -EINVAL; while (note_offs + sizeof(Elf32_Nhdr) < note_size) { Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs); if (nhdr->n_type == BPF_BUILD_ID && nhdr->n_namesz == sizeof("GNU") && nhdr->n_descsz > 0 && nhdr->n_descsz <= BPF_BUILD_ID_SIZE) { memcpy(build_id, note_start + note_offs + ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr), nhdr->n_descsz); memset(build_id + nhdr->n_descsz, 0, BPF_BUILD_ID_SIZE - nhdr->n_descsz); return 0; } new_offs = note_offs + sizeof(Elf32_Nhdr) + ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4); if (new_offs <= note_offs) /* overflow */ break; note_offs = new_offs; } return -EINVAL;} /* Parse build ID from 32-bit ELF */static int stack_map_get_build_id_32(void *page_addr, unsigned char *build_id){ Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr; Elf32_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr)) return -EINVAL; phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) if (phdr[i].p_type == PT_NOTE) return stack_map_parse_build_id(page_addr, build_id, page_addr + phdr[i].p_offset, phdr[i].p_filesz); return -EINVAL;} /* Parse build ID from 64-bit ELF */static int stack_map_get_build_id_64(void *page_addr, unsigned char *build_id){ Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr; Elf64_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr)) return -EINVAL; phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) if (phdr[i].p_type == PT_NOTE) return stack_map_parse_build_id(page_addr, build_id, page_addr + phdr[i].p_offset, phdr[i].p_filesz); return -EINVAL;} /* Parse build ID of ELF file mapped to vma */static int stack_map_get_build_id(struct vm_area_struct *vma, unsigned char *build_id){ Elf32_Ehdr *ehdr; struct page *page; void *page_addr; int ret; /* only works for page backed storage */ if (!vma->vm_file) return -EINVAL; page = find_get_page(vma->vm_file->f_mapping, 0); if (!page) return -EFAULT; /* page not mapped */ ret = -EINVAL; page_addr = kmap_atomic(page); ehdr = (Elf32_Ehdr *)page_addr; /* compare magic x7f "ELF" */ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) goto out; /* only support executable file and shared object file */ if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) goto out; if (ehdr->e_ident[EI_CLASS] == ELFCLASS32) ret = stack_map_get_build_id_32(page_addr, build_id); else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) ret = stack_map_get_build_id_64(page_addr, build_id);out: kunmap_atomic(page_addr); put_page(page); return ret;} static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, u64 *ips, u32 trace_nr, bool user){ int i; struct vm_area_struct *vma; bool irq_work_busy = false; struct stack_map_irq_work *work = NULL; if (irqs_disabled()) { if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { work = this_cpu_ptr(&up_read_work); if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) { /* cannot queue more up_read, fallback */ irq_work_busy = true; } } else { /* * PREEMPT_RT does not allow to trylock mmap sem in * interrupt disabled context. Force the fallback code. */ irq_work_busy = true; } } /* * We cannot do up_read() when the irq is disabled, because of * risk to deadlock with rq_lock. To do build_id lookup when the * irqs are disabled, we need to run up_read() in irq_work. We use * a percpu variable to do the irq_work. If the irq_work is * already used by another lookup, we fall back to report ips. * * Same fallback is used for kernel stack (!user) on a stackmap * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || !mmap_read_trylock_non_owner(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); } return; } for (i = 0; i < trace_nr; i++) { vma = find_vma(current->mm, ips[i]); if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { /* per entry fall back to ips */ id_offs[i].status = BPF_STACK_BUILD_ID_IP; id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); continue; } id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] - vma->vm_start; id_offs[i].status = BPF_STACK_BUILD_ID_VALID; } if (!work) { mmap_read_unlock_non_owner(current->mm); } else { work->mm = current->mm; irq_work_queue(&work->irq_work); }} BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, u64, flags){ struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct perf_callchain_entry *trace; struct stack_map_bucket *bucket, *new_bucket, *old_bucket; u32 max_depth = map->value_size / stack_map_data_size(map); /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ u32 init_nr = sysctl_perf_event_max_stack - max_depth; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; u32 hash, id, trace_nr, trace_len; bool user = flags & BPF_F_USER_STACK; bool kernel = !user; u64 *ips; bool hash_matches; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) return -EINVAL; trace = get_perf_callchain(regs, init_nr, kernel, user, sysctl_perf_event_max_stack, false, false); if (unlikely(!trace)) /* couldn't fetch the stack trace */ return -EFAULT; /* get_perf_callchain() guarantees that trace->nr >= init_nr * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth */ trace_nr = trace->nr - init_nr; if (trace_nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; trace_nr -= skip; trace_len = trace_nr * sizeof(u64); ips = trace->ip + skip + init_nr; hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); id = hash & (smap->n_buckets - 1); bucket = READ_ONCE(smap->buckets[id]); hash_matches = bucket && bucket->hash == hash; /* fast cmp */ if (hash_matches && flags & BPF_F_FAST_STACK_CMP) return id; if (stack_map_use_build_id(map)) { /* for build_id+offset, pop a bucket before slow cmp */ new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; new_bucket->nr = trace_nr; stack_map_get_build_id_offset( (struct bpf_stack_build_id *)new_bucket->data, ips, trace_nr, user); trace_len = trace_nr * sizeof(struct bpf_stack_build_id); if (hash_matches && bucket->nr == trace_nr && memcmp(bucket->data, new_bucket->data, trace_len) == 0) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return id; } if (bucket && !(flags & BPF_F_REUSE_STACKID)) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return -EEXIST; } } else { if (hash_matches && bucket->nr == trace_nr && memcmp(bucket->data, ips, trace_len) == 0) return id; if (bucket && !(flags & BPF_F_REUSE_STACKID)) return -EEXIST; new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; memcpy(new_bucket->data, ips, trace_len); } new_bucket->hash = hash; new_bucket->nr = trace_nr; old_bucket = xchg(&smap->buckets[id], new_bucket); if (old_bucket) pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); return id;} const struct bpf_func_proto bpf_get_stackid_proto = { .func = bpf_get_stackid, .gpl_only = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_CTX, .arg2_type = ARG_CONST_MAP_PTR, .arg3_type = ARG_ANYTHING,}; BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, u64, flags){ u32 init_nr, trace_nr, copy_len, elem_size, num_elem; bool user_build_id = flags & BPF_F_USER_BUILD_ID; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; bool kernel = !user; int err = -EINVAL; u64 *ips; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_USER_BUILD_ID))) goto clear; if (kernel && user_build_id) goto clear; elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id) : sizeof(u64); if (unlikely(size % elem_size)) goto clear; num_elem = size / elem_size; if (sysctl_perf_event_max_stack < num_elem) init_nr = 0; else init_nr = sysctl_perf_event_max_stack - num_elem; trace = get_perf_callchain(regs, init_nr, kernel, user, sysctl_perf_event_max_stack, false, false); if (unlikely(!trace)) goto err_fault; trace_nr = trace->nr - init_nr; if (trace_nr < skip) goto err_fault; trace_nr -= skip; trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem; copy_len = trace_nr * elem_size; ips = trace->ip + skip + init_nr; if (user && user_build_id) stack_map_get_build_id_offset(buf, ips, trace_nr, user); else memcpy(buf, ips, copy_len); if (size > copy_len) memset(buf + copy_len, 0, size - copy_len); return copy_len; Lines 1–500 of 637. 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// SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2016 Facebook */ #include <linux/bpf.h> #include <linux/jhash.h> #include <linux/filter.h> #include <linux/stacktrace.h> #include <linux/perf_event.h> #include <linux/elf.h> #include <linux/pagemap.h> #include <linux/irq_work.h> #include "percpu_freelist.h" #define STACK_CREATE_FLAG_MASK \ (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \ BPF_F_STACK_BUILD_ID) struct stack_map_bucket { struct pcpu_freelist_node fnode; u32 hash; u32 nr; u64 data[]; }; struct bpf_stack_map { struct bpf_map map; void *elems; struct pcpu_freelist freelist; u32 n_buckets; struct stack_map_bucket *buckets[]; }; /* irq_work to run up_read() for build_id lookup in nmi context */ struct stack_map_irq_work { struct irq_work irq_work; struct mm_struct *mm; }; static void do_up_read(struct irq_work *entry) { struct stack_map_irq_work *work; if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT))) return; work = container_of(entry, struct stack_map_irq_work, irq_work); mmap_read_unlock_non_owner(work->mm); } static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work); static inline bool stack_map_use_build_id(struct bpf_map *map) { return (map->map_flags & BPF_F_STACK_BUILD_ID); } static inline int stack_map_data_size(struct bpf_map *map) { return stack_map_use_build_id(map) ? sizeof(struct bpf_stack_build_id) : sizeof(u64); } static int prealloc_elems_and_freelist(struct bpf_stack_map *smap) { u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size; int err; smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries, smap->map.numa_node); if (!smap->elems) return -ENOMEM; err = pcpu_freelist_init(&smap->freelist); if (err) goto free_elems; pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size, smap->map.max_entries); return 0; free_elems: bpf_map_area_free(smap->elems); return err; } /* Called from syscall */ static struct bpf_map *stack_map_alloc(union bpf_attr *attr) { u32 value_size = attr->value_size; struct bpf_stack_map *smap; struct bpf_map_memory mem; u64 cost, n_buckets; int err; if (!bpf_capable()) return ERR_PTR(-EPERM); if (attr->map_flags & ~STACK_CREATE_FLAG_MASK) return ERR_PTR(-EINVAL); /* check sanity of attributes */ if (attr->max_entries == 0 || attr->key_size != 4 || value_size < 8 || value_size % 8) return ERR_PTR(-EINVAL); BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64)); if (attr->map_flags & BPF_F_STACK_BUILD_ID) { if (value_size % sizeof(struct bpf_stack_build_id) || value_size / sizeof(struct bpf_stack_build_id) > sysctl_perf_event_max_stack) return ERR_PTR(-EINVAL); } else if (value_size / 8 > sysctl_perf_event_max_stack) return ERR_PTR(-EINVAL); /* hash table size must be power of 2 */ n_buckets = roundup_pow_of_two(attr->max_entries); cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap); cost += n_buckets * (value_size + sizeof(struct stack_map_bucket)); err = bpf_map_charge_init(&mem, cost); if (err) return ERR_PTR(err); smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr)); if (!smap) { bpf_map_charge_finish(&mem); return ERR_PTR(-ENOMEM); } bpf_map_init_from_attr(&smap->map, attr); smap->map.value_size = value_size; smap->n_buckets = n_buckets; err = get_callchain_buffers(sysctl_perf_event_max_stack); if (err) goto free_charge; err = prealloc_elems_and_freelist(smap); if (err) goto put_buffers; bpf_map_charge_move(&smap->map.memory, &mem); return &smap->map; put_buffers: put_callchain_buffers(); free_charge: bpf_map_charge_finish(&mem); bpf_map_area_free(smap); return ERR_PTR(err); } #define BPF_BUILD_ID 3 /* * Parse build id from the note segment. This logic can be shared between * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are * identical. */ static inline int stack_map_parse_build_id(void *page_addr, unsigned char *build_id, void *note_start, Elf32_Word note_size) { Elf32_Word note_offs = 0, new_offs; /* check for overflow */ if (note_start < page_addr || note_start + note_size < note_start) return -EINVAL; /* only supports note that fits in the first page */ if (note_start + note_size > page_addr + PAGE_SIZE) return -EINVAL; while (note_offs + sizeof(Elf32_Nhdr) < note_size) { Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs); if (nhdr->n_type == BPF_BUILD_ID && nhdr->n_namesz == sizeof("GNU") && nhdr->n_descsz > 0 && nhdr->n_descsz <= BPF_BUILD_ID_SIZE) { memcpy(build_id, note_start + note_offs + ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr), nhdr->n_descsz); memset(build_id + nhdr->n_descsz, 0, BPF_BUILD_ID_SIZE - nhdr->n_descsz); return 0; } new_offs = note_offs + sizeof(Elf32_Nhdr) + ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4); if (new_offs <= note_offs) /* overflow */ break; note_offs = new_offs; } return -EINVAL; } /* Parse build ID from 32-bit ELF */ static int stack_map_get_build_id_32(void *page_addr, unsigned char *build_id) { Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr; Elf32_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr)) return -EINVAL; phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) if (phdr[i].p_type == PT_NOTE) return stack_map_parse_build_id(page_addr, build_id, page_addr + phdr[i].p_offset, phdr[i].p_filesz); return -EINVAL; } /* Parse build ID from 64-bit ELF */ static int stack_map_get_build_id_64(void *page_addr, unsigned char *build_id) { Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr; Elf64_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr)) return -EINVAL; phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) if (phdr[i].p_type == PT_NOTE) return stack_map_parse_build_id(page_addr, build_id, page_addr + phdr[i].p_offset, phdr[i].p_filesz); return -EINVAL; } /* Parse build ID of ELF file mapped to vma */ static int stack_map_get_build_id(struct vm_area_struct *vma, unsigned char *build_id) { Elf32_Ehdr *ehdr; struct page *page; void *page_addr; int ret; /* only works for page backed storage */ if (!vma->vm_file) return -EINVAL; page = find_get_page(vma->vm_file->f_mapping, 0); if (!page) return -EFAULT; /* page not mapped */ ret = -EINVAL; page_addr = kmap_atomic(page); ehdr = (Elf32_Ehdr *)page_addr; /* compare magic x7f "ELF" */ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) goto out; /* only support executable file and shared object file */ if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) goto out; if (ehdr->e_ident[EI_CLASS] == ELFCLASS32) ret = stack_map_get_build_id_32(page_addr, build_id); else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) ret = stack_map_get_build_id_64(page_addr, build_id); out: kunmap_atomic(page_addr); put_page(page); return ret; } static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, u64 *ips, u32 trace_nr, bool user) { int i; struct vm_area_struct *vma; bool irq_work_busy = false; struct stack_map_irq_work *work = NULL; if (irqs_disabled()) { if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { work = this_cpu_ptr(&up_read_work); if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) { /* cannot queue more up_read, fallback */ irq_work_busy = true; } } else { /* * PREEMPT_RT does not allow to trylock mmap sem in * interrupt disabled context. Force the fallback code. */ irq_work_busy = true; } } /* * We cannot do up_read() when the irq is disabled, because of * risk to deadlock with rq_lock. To do build_id lookup when the * irqs are disabled, we need to run up_read() in irq_work. We use * a percpu variable to do the irq_work. If the irq_work is * already used by another lookup, we fall back to report ips. * * Same fallback is used for kernel stack (!user) on a stackmap * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || !mmap_read_trylock_non_owner(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); } return; } for (i = 0; i < trace_nr; i++) { vma = find_vma(current->mm, ips[i]); if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { /* per entry fall back to ips */ id_offs[i].status = BPF_STACK_BUILD_ID_IP; id_offs[i].ip = ips[i]; memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); continue; } id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] - vma->vm_start; id_offs[i].status = BPF_STACK_BUILD_ID_VALID; } if (!work) { mmap_read_unlock_non_owner(current->mm); } else { work->mm = current->mm; irq_work_queue(&work->irq_work); } } BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, u64, flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct perf_callchain_entry *trace; struct stack_map_bucket *bucket, *new_bucket, *old_bucket; u32 max_depth = map->value_size / stack_map_data_size(map); /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ u32 init_nr = sysctl_perf_event_max_stack - max_depth; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; u32 hash, id, trace_nr, trace_len; bool user = flags & BPF_F_USER_STACK; bool kernel = !user; u64 *ips; bool hash_matches; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) return -EINVAL; trace = get_perf_callchain(regs, init_nr, kernel, user, sysctl_perf_event_max_stack, false, false); if (unlikely(!trace)) /* couldn't fetch the stack trace */ return -EFAULT; /* get_perf_callchain() guarantees that trace->nr >= init_nr * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth */ trace_nr = trace->nr - init_nr; if (trace_nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; trace_nr -= skip; trace_len = trace_nr * sizeof(u64); ips = trace->ip + skip + init_nr; hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); id = hash & (smap->n_buckets - 1); bucket = READ_ONCE(smap->buckets[id]); hash_matches = bucket && bucket->hash == hash; /* fast cmp */ if (hash_matches && flags & BPF_F_FAST_STACK_CMP) return id; if (stack_map_use_build_id(map)) { /* for build_id+offset, pop a bucket before slow cmp */ new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; new_bucket->nr = trace_nr; stack_map_get_build_id_offset( (struct bpf_stack_build_id *)new_bucket->data, ips, trace_nr, user); trace_len = trace_nr * sizeof(struct bpf_stack_build_id); if (hash_matches && bucket->nr == trace_nr && memcmp(bucket->data, new_bucket->data, trace_len) == 0) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return id; } if (bucket && !(flags & BPF_F_REUSE_STACKID)) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return -EEXIST; } } else { if (hash_matches && bucket->nr == trace_nr && memcmp(bucket->data, ips, trace_len) == 0) return id; if (bucket && !(flags & BPF_F_REUSE_STACKID)) return -EEXIST; new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; memcpy(new_bucket->data, ips, trace_len); } new_bucket->hash = hash; new_bucket->nr = trace_nr; old_bucket = xchg(&smap->buckets[id], new_bucket); if (old_bucket) pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); return id; } const struct bpf_func_proto bpf_get_stackid_proto = { .func = bpf_get_stackid, .gpl_only = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_CTX, .arg2_type = ARG_CONST_MAP_PTR, .arg3_type = ARG_ANYTHING, }; BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, u64, flags) { u32 init_nr, trace_nr, copy_len, elem_size, num_elem; bool user_build_id = flags & BPF_F_USER_BUILD_ID; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; bool kernel = !user; int err = -EINVAL; u64 *ips; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_USER_BUILD_ID))) goto clear; if (kernel && user_build_id) goto clear; elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id) : sizeof(u64); if (unlikely(size % elem_size)) goto clear; num_elem = size / elem_size; if (sysctl_perf_event_max_stack < num_elem) init_nr = 0; else init_nr = sysctl_perf_event_max_stack - num_elem; trace = get_perf_callchain(regs, init_nr, kernel, user, sysctl_perf_event_max_stack, false, false); if (unlikely(!trace)) goto err_fault; trace_nr = trace->nr - init_nr; if (trace_nr < skip) goto err_fault; trace_nr -= skip; trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem; copy_len = trace_nr * elem_size; ips = trace->ip + skip + init_nr; if (user && user_build_id) stack_map_get_build_id_offset(buf, ips, trace_nr, user); else memcpy(buf, ips, copy_len); if (size > copy_len) memset(buf + copy_len, 0, size - copy_len); return copy_len;