Adding support to add special mapping for for user space trampoline with following functions:
uprobe_trampoline_get - find or add related uprobe_trampoline uprobe_trampoline_put - remove ref or destroy uprobe_trampoline The user space trampoline is exported as architecture specific user space special mapping, which is provided by arch_uprobe_trampoline_mapping function. The uprobe trampoline needs to be callable/reachable from the probe address, so while searching for available address we use arch_uprobe_is_callable function to decide if the uprobe trampoline is callable from the probe address. All uprobe_trampoline objects are stored in uprobes_state object and are cleaned up when the process mm_struct goes down. Locking is provided by callers in following changes. Signed-off-by: Jiri Olsa <[email protected]> --- include/linux/uprobes.h | 12 +++++ kernel/events/uprobes.c | 114 ++++++++++++++++++++++++++++++++++++++++ kernel/fork.c | 1 + 3 files changed, 127 insertions(+) diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index 8843b7f99ed0..c4ee755ca2a1 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -16,6 +16,7 @@ #include <linux/types.h> #include <linux/wait.h> #include <linux/timer.h> +#include <linux/mutex.h> struct uprobe; struct vm_area_struct; @@ -172,6 +173,13 @@ struct xol_area; struct uprobes_state { struct xol_area *xol_area; + struct hlist_head tramp_head; +}; + +struct uprobe_trampoline { + struct hlist_node node; + unsigned long vaddr; + atomic64_t ref; }; extern void __init uprobes_init(void); @@ -220,6 +228,10 @@ extern int arch_uprobe_verify_opcode(struct arch_uprobe *auprobe, struct page *p unsigned long vaddr, uprobe_opcode_t *new_opcode, int nbytes); extern bool arch_uprobe_is_register(uprobe_opcode_t *insn, int nbytes); +extern struct uprobe_trampoline *uprobe_trampoline_get(unsigned long vaddr); +extern void uprobe_trampoline_put(struct uprobe_trampoline *area); +extern bool arch_uprobe_is_callable(unsigned long vtramp, unsigned long vaddr); +extern const struct vm_special_mapping *arch_uprobe_trampoline_mapping(void); #else /* !CONFIG_UPROBES */ struct uprobes_state { }; diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 8068f91de9e3..f57918c624da 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -615,6 +615,118 @@ set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long v (uprobe_opcode_t *)&auprobe->insn, UPROBE_SWBP_INSN_SIZE); } +bool __weak arch_uprobe_is_callable(unsigned long vtramp, unsigned long vaddr) +{ + return false; +} + +const struct vm_special_mapping * __weak arch_uprobe_trampoline_mapping(void) +{ + return NULL; +} + +static unsigned long find_nearest_page(unsigned long vaddr) +{ + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma, *prev; + VMA_ITERATOR(vmi, mm, 0); + + prev = vma_next(&vmi); + vma = vma_next(&vmi); + while (vma) { + if (vma->vm_start - prev->vm_end >= PAGE_SIZE) { + if (arch_uprobe_is_callable(prev->vm_end, vaddr)) + return prev->vm_end; + if (arch_uprobe_is_callable(vma->vm_start - PAGE_SIZE, vaddr)) + return vma->vm_start - PAGE_SIZE; + } + + prev = vma; + vma = vma_next(&vmi); + } + + return 0; +} + +static struct uprobe_trampoline *create_uprobe_trampoline(unsigned long vaddr) +{ + const struct vm_special_mapping *mapping; + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma; + struct uprobe_trampoline *tramp; + + mapping = arch_uprobe_trampoline_mapping(); + if (!mapping) + return NULL; + + vaddr = find_nearest_page(vaddr); + if (!vaddr) + return NULL; + + tramp = kzalloc(sizeof(*tramp), GFP_KERNEL); + if (unlikely(!tramp)) + return NULL; + + atomic64_set(&tramp->ref, 1); + tramp->vaddr = vaddr; + + vma = _install_special_mapping(mm, tramp->vaddr, PAGE_SIZE, + VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_DONTCOPY|VM_IO, + mapping); + if (IS_ERR(vma)) + goto free_area; + return tramp; + + free_area: + kfree(tramp); + return NULL; +} + +struct uprobe_trampoline *uprobe_trampoline_get(unsigned long vaddr) +{ + struct uprobes_state *state = ¤t->mm->uprobes_state; + struct uprobe_trampoline *tramp = NULL; + + hlist_for_each_entry(tramp, &state->tramp_head, node) { + if (arch_uprobe_is_callable(tramp->vaddr, vaddr)) { + atomic64_inc(&tramp->ref); + return tramp; + } + } + + tramp = create_uprobe_trampoline(vaddr); + if (!tramp) + return NULL; + + hlist_add_head(&tramp->node, &state->tramp_head); + return tramp; +} + +static void destroy_uprobe_trampoline(struct uprobe_trampoline *tramp) +{ + hlist_del(&tramp->node); + kfree(tramp); +} + +void uprobe_trampoline_put(struct uprobe_trampoline *tramp) +{ + if (tramp == NULL) + return; + + if (atomic64_dec_and_test(&tramp->ref)) + destroy_uprobe_trampoline(tramp); +} + +static void clear_tramp_head(struct mm_struct *mm) +{ + struct uprobes_state *state = &mm->uprobes_state; + struct uprobe_trampoline *tramp; + struct hlist_node *n; + + hlist_for_each_entry_safe(tramp, n, &state->tramp_head, node) + destroy_uprobe_trampoline(tramp); +} + /* uprobe should have guaranteed positive refcount */ static struct uprobe *get_uprobe(struct uprobe *uprobe) { @@ -1787,6 +1899,8 @@ void uprobe_clear_state(struct mm_struct *mm) delayed_uprobe_remove(NULL, mm); mutex_unlock(&delayed_uprobe_lock); + clear_tramp_head(mm); + if (!area) return; diff --git a/kernel/fork.c b/kernel/fork.c index 1450b461d196..b734a172fd6e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1254,6 +1254,7 @@ static void mm_init_uprobes_state(struct mm_struct *mm) { #ifdef CONFIG_UPROBES mm->uprobes_state.xol_area = NULL; + INIT_HLIST_HEAD(&mm->uprobes_state.tramp_head); #endif } -- 2.47.0
