Associate .eh_frame_hdr sections with their mm by adding them to a per-mm maple tree which is indexed by the corresponding text address range. A single .eh_frame_hdr section can be associated with multiple text ranges.
Based on Josh Poimboeuf's, Steven Rostedt's, and my unwind user sframe implementation. Signed-off-by: Jens Remus <[email protected]> --- Notes (jremus): Changes in RFC v2: - INIT_MM_EH_FRAME and mm_init_eh_frame(): Use MT_FLAGS_USE_RCU to enable concurrent eh_frame_mt read and write access. (Sashiko AI) - eh_frame_remove_section(): Fix ABA problem by using the advanced maple tree API to hold the internal spinlock while iterating over the eh_frame_mt and removing the eh_frame section(s). (Sashiko AI) arch/x86/include/asm/mmu.h | 2 +- include/linux/eh_frame.h | 22 ++++++++++++ include/linux/mm_types.h | 3 ++ kernel/fork.c | 10 ++++++ kernel/unwind/eh_frame.c | 70 ++++++++++++++++++++++++++++++++++++-- mm/init-mm.c | 2 ++ 6 files changed, 105 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 0fe9c569d171..227a32899a59 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -87,7 +87,7 @@ typedef struct { .context = { \ .ctx_id = 1, \ .lock = __MUTEX_INITIALIZER(mm.context.lock), \ - } + }, void leave_mm(void); #define leave_mm leave_mm diff --git a/include/linux/eh_frame.h b/include/linux/eh_frame.h index aaac2dd663d5..c4279ee77c13 100644 --- a/include/linux/eh_frame.h +++ b/include/linux/eh_frame.h @@ -2,9 +2,14 @@ #ifndef _LINUX_EH_FRAME_H #define _LINUX_EH_FRAME_H +#include <linux/mm_types.h> +#include <linux/srcu.h> + #ifdef CONFIG_HAVE_UNWIND_USER_EH_FRAME struct eh_frame_section { + struct rcu_head rcu; + unsigned long eh_frame_hdr_start; unsigned long eh_frame_hdr_end; unsigned long text_start; @@ -19,14 +24,29 @@ struct eh_frame_section { u8 binary_search_table_enc; }; +#define EH_FRAME_MT_FLAGS (MT_FLAGS_USE_RCU) + +#define INIT_MM_EH_FRAME .eh_frame_mt = MTREE_INIT(eh_frame_mt, EH_FRAME_MT_FLAGS), +extern void eh_frame_free_mm(struct mm_struct *mm); + extern int eh_frame_add_section(unsigned long eh_frame_hdr_start, unsigned long eh_frame_hdr_end, unsigned long text_start, unsigned long text_end); extern int eh_frame_remove_section(unsigned long eh_frame_hdr_start); +static inline bool current_has_eh_frame(void) +{ + struct mm_struct *mm = current->mm; + + return mm && !mtree_empty(&mm->eh_frame_mt); +} + #else /* !CONFIG_HAVE_UNWIND_USER_EH_FRAME */ +#define INIT_MM_EH_FRAME +static inline void eh_frame_free_mm(struct mm_struct *mm) {} + static inline int eh_frame_add_section(unsigned long eh_frame_hdr_start, unsigned long eh_frame_hdr_end, unsigned long text_start, @@ -40,6 +60,8 @@ static inline int eh_frame_remove_section(unsigned long eh_frame_hdr_start) return -ENOSYS; } +static inline bool current_has_eh_frame(void) { return false; } + #endif /* CONFIG_HAVE_UNWIND_USER_EH_FRAME */ #endif /* _LINUX_EH_FRAME_H */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index b18c2b2e7d2c..ac51d6212e86 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1404,6 +1404,9 @@ struct mm_struct { #ifdef CONFIG_MM_ID mm_id_t mm_id; #endif /* CONFIG_MM_ID */ +#ifdef CONFIG_HAVE_UNWIND_USER_EH_FRAME + struct maple_tree eh_frame_mt; +#endif } __randomize_layout; /* diff --git a/kernel/fork.c b/kernel/fork.c index f0e2e131a9a5..dab67d2eb096 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -111,6 +111,7 @@ #include <linux/tick.h> #include <linux/unwind_deferred.h> #include <linux/pgalloc.h> +#include <linux/eh_frame.h> #include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -738,6 +739,7 @@ void __mmdrop(struct mm_struct *mm) mm_pasid_drop(mm); mm_destroy_cid(mm); percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS); + eh_frame_free_mm(mm); free_mm(mm); } @@ -1082,6 +1084,13 @@ static void mmap_init_lock(struct mm_struct *mm) #endif } +static void mm_init_eh_frame(struct mm_struct *mm) +{ +#ifdef CONFIG_HAVE_UNWIND_USER_EH_FRAME + mt_init_flags(&mm->eh_frame_mt, EH_FRAME_MT_FLAGS); +#endif +} + static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) { mt_init_flags(&mm->mm_mt, MM_MT_FLAGS); @@ -1109,6 +1118,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) mm->pmd_huge_pte = NULL; #endif mm_init_uprobes_state(mm); + mm_init_eh_frame(mm); hugetlb_count_init(mm); futex_mm_init(mm); diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c index f25a0923e315..8cf19c5298fd 100644 --- a/kernel/unwind/eh_frame.c +++ b/kernel/unwind/eh_frame.c @@ -19,6 +19,8 @@ #define dbg(fmt, ...) \ pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__) +DEFINE_STATIC_SRCU(eh_frame_srcu); + #define UNSAFE_GET_USER_INC(to, from, end, label) \ ({ \ typeof(to) __to; \ @@ -310,6 +312,7 @@ int eh_frame_add_section(unsigned long eh_frame_hdr_start, unsigned long text_start, unsigned long text_end) { + struct maple_tree *eh_frame_mt = ¤t->mm->eh_frame_mt; struct mm_struct *mm = current->mm; struct eh_frame_section *sec; int ret; @@ -352,15 +355,76 @@ int eh_frame_add_section(unsigned long eh_frame_hdr_start, if (ret) goto err_free; - /* TODO nowhere to store it yet - just free it and return an error */ - ret = -ENOSYS; + ret = mtree_insert_range(eh_frame_mt, sec->text_start, sec->text_end - 1, + sec, GFP_KERNEL_ACCOUNT); + if (ret) { + dbg("mtree_insert_range failed: text=%lx-%lx\n", + sec->text_start, sec->text_end); + goto err_free; + } + + return 0; err_free: free_section(sec); return ret; } +static void eh_frame_free_srcu(struct rcu_head *rcu) +{ + struct eh_frame_section *sec = container_of(rcu, struct eh_frame_section, rcu); + + free_section(sec); +} + +static int __eh_frame_remove_section(struct ma_state *mas, + struct eh_frame_section *sec) +{ + if (mas_erase(mas) != sec) { + dbg("mas_erase failed: text=%lx\n", sec->text_start); + return -EINVAL; + } + + call_srcu(&eh_frame_srcu, &sec->rcu, eh_frame_free_srcu); + + return 0; +} + int eh_frame_remove_section(unsigned long eh_frame_hdr_start) { - return -ENOSYS; + struct mm_struct *mm = current->mm; + struct eh_frame_section *sec; + MA_STATE(mas, &mm->eh_frame_mt, 0, 0); + bool found = false; + int ret = 0; + + guard(srcu)(&eh_frame_srcu); + + mtree_lock(&mm->eh_frame_mt); + mas_for_each(&mas, sec, ULONG_MAX) { + if (sec->eh_frame_hdr_start == eh_frame_hdr_start) { + found = true; + ret |= __eh_frame_remove_section(&mas, sec); + } + } + mtree_unlock(&mm->eh_frame_mt); + + if (!found || ret) + return -EINVAL; + + return 0; +} + +void eh_frame_free_mm(struct mm_struct *mm) +{ + struct eh_frame_section *sec; + unsigned long index = 0; + + if (!mm) + return; + + mt_for_each(&mm->eh_frame_mt, sec, index, ULONG_MAX) + free_section(sec); + + mtree_destroy(&mm->eh_frame_mt); } diff --git a/mm/init-mm.c b/mm/init-mm.c index 3e792aad7626..25c26341fc4f 100644 --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -11,6 +11,7 @@ #include <linux/atomic.h> #include <linux/user_namespace.h> #include <linux/iommu.h> +#include <linux/eh_frame.h> #include <asm/mmu.h> #ifndef INIT_MM_CONTEXT @@ -48,6 +49,7 @@ struct mm_struct init_mm = { #endif .flexible_array = MM_STRUCT_FLEXIBLE_ARRAY_INIT, INIT_MM_CONTEXT(init_mm) + INIT_MM_EH_FRAME }; void setup_initial_init_mm(void *start_code, void *end_code, -- 2.53.0
