On 06/07/2017 05:35 AM, Igor Stoppa wrote: > The MMU available in many systems running Linux can often provide R/O > protection to the memory pages it handles. > > However, the MMU-based protection works efficiently only when said pages > contain only data that will not need further modifications. > > Statically allocated variables can be segregated into a dedicated > section, however this is not fit too well the case of dynamically > allocated ones. > > Dynamic allocation does not provide, currently, means for grouping > variables in memory pages that would contain exclusively data that can > be made read only. > > The allocator here provided (pmalloc - protectable memory allocator) > introduces the concept of pools of protectable memory. > > A module can request a pool and then refer any allocation request to the > pool handler it has received. > > Once all the memory requested (over various iterations) is initialized, > the pool can be protected. > > After this point, the pool can only be destroyed (it is up to the module > to avoid any further references to the memory from the pool, after > the destruction is invoked). > > The latter case is mainly meant for releasing memory, when a module is > unloaded. > > A module can have as many pools as needed, for example to support the > protection of data that is initialized in sufficiently distinct phases. > > Signed-off-by: Igor Stoppa <igor.sto...@huawei.com> > --- > include/linux/page-flags.h | 2 + > include/linux/pmalloc.h | 20 ++++ > include/trace/events/mmflags.h | 1 + > init/main.c | 2 + > mm/Makefile | 1 + > mm/pmalloc.c | 226 > +++++++++++++++++++++++++++++++++++++++++ > mm/usercopy.c | 24 +++-- > 7 files changed, 267 insertions(+), 9 deletions(-) > create mode 100644 include/linux/pmalloc.h > create mode 100644 mm/pmalloc.c > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 6b5818d..acc0723 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -81,6 +81,7 @@ enum pageflags { > PG_active, > PG_waiters, /* Page has waiters, check its waitqueue. Must > be bit #7 and in the same byte as "PG_locked" */ > PG_slab, > + PG_pmalloc, > PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/ > PG_arch_1, > PG_reserved, > @@ -274,6 +275,7 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, > active, PF_HEAD) > TESTCLEARFLAG(Active, active, PF_HEAD) > __PAGEFLAG(Slab, slab, PF_NO_TAIL) > __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL) > +__PAGEFLAG(Pmalloc, pmalloc, PF_NO_TAIL) > PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems > */ > > /* Xen */ > diff --git a/include/linux/pmalloc.h b/include/linux/pmalloc.h > new file mode 100644 > index 0000000..83d3557 > --- /dev/null > +++ b/include/linux/pmalloc.h > @@ -0,0 +1,20 @@ > +/* > + * pmalloc.h: Header for Protectable Memory Allocator > + * > + * (C) Copyright 2017 Huawei Technologies Co. Ltd. > + * Author: Igor Stoppa <igor.sto...@huawei.com> > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; version 2 > + * of the License. > + */ > + > +#ifndef _PMALLOC_H > +#define _PMALLOC_H > + > +struct pmalloc_pool *pmalloc_create_pool(const char *name); > +void *pmalloc(unsigned long size, struct pmalloc_pool *pool); > +int pmalloc_protect_pool(struct pmalloc_pool *pool); > +int pmalloc_destroy_pool(struct pmalloc_pool *pool); > +#endif > diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h > index 304ff94..41d1587 100644 > --- a/include/trace/events/mmflags.h > +++ b/include/trace/events/mmflags.h > @@ -91,6 +91,7 @@ > {1UL << PG_lru, "lru" }, \ > {1UL << PG_active, "active" }, \ > {1UL << PG_slab, "slab" }, \ > + {1UL << PG_pmalloc, "pmalloc" }, \ > {1UL << PG_owner_priv_1, "owner_priv_1" }, \ > {1UL << PG_arch_1, "arch_1" }, \ > {1UL << PG_reserved, "reserved" }, \ > diff --git a/init/main.c b/init/main.c > index f866510..7850887 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -485,6 +485,7 @@ static void __init mm_init(void) > ioremap_huge_init(); > } > > +extern int __init pmalloc_init(void); > asmlinkage __visible void __init start_kernel(void) > { > char *command_line; > @@ -653,6 +654,7 @@ asmlinkage __visible void __init start_kernel(void) > proc_caches_init(); > buffer_init(); > key_init(); > + pmalloc_init(); > security_init(); > dbg_late_init(); > vfs_caches_init(); > diff --git a/mm/Makefile b/mm/Makefile > index 026f6a8..b47dcf8 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -65,6 +65,7 @@ obj-$(CONFIG_SPARSEMEM) += sparse.o > obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o > obj-$(CONFIG_SLOB) += slob.o > obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o > +obj-$(CONFIG_ARCH_HAS_SET_MEMORY) += pmalloc.o > obj-$(CONFIG_KSM) += ksm.o > obj-$(CONFIG_PAGE_POISONING) += page_poison.o > obj-$(CONFIG_SLAB) += slab.o > diff --git a/mm/pmalloc.c b/mm/pmalloc.c > new file mode 100644 > index 0000000..8050dea > --- /dev/null > +++ b/mm/pmalloc.c > @@ -0,0 +1,226 @@ > +/* > + * pmalloc.c: Protectable Memory Allocator > + * > + * (C) Copyright 2017 Huawei Technologies Co. Ltd. > + * Author: Igor Stoppa <igor.sto...@huawei.com> > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; version 2 > + * of the License. > + */ > + > +#include <linux/printk.h> > +#include <linux/init.h> > +#include <linux/mm.h> > +#include <linux/vmalloc.h> > +#include <linux/list.h> > +#include <linux/rculist.h> > +#include <linux/mutex.h> > +#include <linux/atomic.h> > +#include <asm/set_memory.h> > +#include <asm/page.h> > + > +typedef unsigned long align_t; > +#define WORD_SIZE sizeof(unsigned long) > + > +#define __PMALLOC_ALIGNED __aligned(WORD_SIZE) > + > +#define MAX_POOL_NAME_LEN 20 > + > +struct pmalloc_data { > + struct hlist_head pools_list_head; > + struct mutex pools_list_mutex; > + atomic_t pools_count; > +}; > + > +struct pmalloc_pool { > + struct hlist_node pools_list; > + struct hlist_head nodes_list_head; > + struct mutex nodes_list_mutex; > + atomic_t nodes_count; > + atomic_t protected; > + char name[MAX_POOL_NAME_LEN]; > +}; > + > +struct pmalloc_node { > + struct hlist_node nodes_list; > + atomic_t used_words; > + unsigned int total_words; > + __PMALLOC_ALIGNED align_t data[]; > +}; > + > +#define HEADER_SIZE sizeof(struct pmalloc_node) > + > +static struct pmalloc_data *pmalloc_data; > + > +static struct pmalloc_node *__pmalloc_create_node(int words) > +{ > + struct pmalloc_node *node; > + unsigned long size, i, pages; > + struct page *p; > + > + size = roundup(HEADER_SIZE + WORD_SIZE * words, PAGE_SIZE); > + node = vmalloc(size); > + if (!node) > + return NULL; > + atomic_set(&node->used_words, 0); > + node->total_words = (size - HEADER_SIZE) / WORD_SIZE; > + pages = size / PAGE_SIZE; > + for (i = 0; i < pages; i++) { > + p = vmalloc_to_page((void *)(i * PAGE_SIZE + > + (unsigned long)node)); > + __SetPagePmalloc(p); > + } > + return node; > +} > + > +void *pmalloc(unsigned long size, struct pmalloc_pool *pool) > +{ > + struct pmalloc_node *node; > + int req_words; > + int starting_word; > + > + if (size > INT_MAX || size == 0 || > + !pool || atomic_read(&pool->protected)) > + return NULL; > + req_words = roundup(size, WORD_SIZE) / WORD_SIZE; > + rcu_read_lock(); > + hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list) { > + starting_word = atomic_fetch_add(req_words, &node->used_words); > + if (starting_word + req_words > node->total_words) { > + atomic_sub(req_words, &node->used_words); > + } else { > + rcu_read_unlock(); > + return node->data + starting_word; > + } > + } > + rcu_read_unlock(); > + node = __pmalloc_create_node(req_words); > + if (!node) > + return NULL; > + starting_word = atomic_fetch_add(req_words, &node->used_words); > + mutex_lock(&pool->nodes_list_mutex); > + hlist_add_head_rcu(&node->nodes_list, &pool->nodes_list_head); > + mutex_unlock(&pool->nodes_list_mutex); > + synchronize_rcu(); > + atomic_inc(&pool->nodes_count); > + return node->data + starting_word; > +}
The pool logic looks remarkably similar to genalloc (lib/genalloc.c). It's not a perfect 1-to-1 mapping but it's close enough to be worth a look. > + > +const char msg[] = "Not a valid Pmalloc object."; > +const char *__pmalloc_check_object(const void *ptr, unsigned long n) > +{ > + unsigned long p; > + > + p = (unsigned long)ptr; > + n = p + n - 1; > + for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) { > + if (is_vmalloc_addr((void *)p)) { > + struct page *page; > + > + page = vmalloc_to_page((void *)p); > + if (!(page && PagePmalloc(page))) > + return msg; > + } Should this be an error if is_vmalloc_addr returns false? Thanks, Laura