Adding support to add special mapping for user space trampoline with
following functions:
uprobe_trampoline_get - find or add uprobe_trampoline
uprobe_trampoline_put - remove or destroy uprobe_trampoline
The user space trampoline is exported as arch specific user space special
mapping through tramp_mapping, which is initialized in following changes
with new uprobe syscall.
The uprobe trampoline needs to be callable/reachable from the probed address,
so while searching for available address we use is_reachable_by_call 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. Adding new arch hooks
for that, because this change is x86_64 specific.
Locking is provided by callers in following changes.
Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
arch/x86/kernel/uprobes.c | 115 ++++++++++++++++++++++++++++++++++++++
include/linux/uprobes.h | 6 ++
kernel/events/uprobes.c | 10 ++++
kernel/fork.c | 1 +
4 files changed, 132 insertions(+)
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 77050e5a4680..32a4b88975c4 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -608,6 +608,121 @@ static void riprel_post_xol(struct arch_uprobe *auprobe,
struct pt_regs *regs)
*sr = utask->autask.saved_scratch_register;
}
}
+
+static int tramp_mremap(const struct vm_special_mapping *sm, struct
vm_area_struct *new_vma)
+{
+ return -EPERM;
+}
+
+static struct page *tramp_mapping_pages[2] __ro_after_init;
+
+static struct vm_special_mapping tramp_mapping = {
+ .name = "[uprobes-trampoline]",
+ .mremap = tramp_mremap,
+ .pages = tramp_mapping_pages,
+};
+
+struct uprobe_trampoline {
+ struct hlist_node node;
+ unsigned long vaddr;
+};
+
+static bool is_reachable_by_call(unsigned long vtramp, unsigned long vaddr)
+{
+ long delta = (long)(vaddr + 5 - vtramp);
+
+ return delta >= INT_MIN && delta <= INT_MAX;
+}
+
+static unsigned long find_nearest_page(unsigned long vaddr)
+{
+ struct vm_unmapped_area_info info = {
+ .length = PAGE_SIZE,
+ .align_mask = ~PAGE_MASK,
+ .flags = VM_UNMAPPED_AREA_TOPDOWN,
+ .low_limit = 0,
+ .high_limit = ULONG_MAX,
+ };
+ unsigned long limit, call_end = vaddr + 5;
+
+ if (!check_add_overflow(call_end, INT_MIN, &limit))
+ info.low_limit = limit;
+ if (!check_add_overflow(call_end, INT_MAX, &limit))
+ info.high_limit = limit;
+ return vm_unmapped_area(&info);
+}
+
+static struct uprobe_trampoline *create_uprobe_trampoline(unsigned long vaddr)
+{
+ struct pt_regs *regs = task_pt_regs(current);
+ struct mm_struct *mm = current->mm;
+ struct uprobe_trampoline *tramp;
+ struct vm_area_struct *vma;
+
+ if (!user_64bit_mode(regs))
+ return NULL;
+
+ vaddr = find_nearest_page(vaddr);
+ if (IS_ERR_VALUE(vaddr))
+ return NULL;
+
+ tramp = kzalloc(sizeof(*tramp), GFP_KERNEL);
+ if (unlikely(!tramp))
+ return NULL;
+
+ tramp->vaddr = vaddr;
+ vma = _install_special_mapping(mm, tramp->vaddr, PAGE_SIZE,
+
VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_DONTCOPY|VM_IO,
+ &tramp_mapping);
+ if (IS_ERR(vma))
+ goto free_area;
+ return tramp;
+
+free_area:
+ kfree(tramp);
+ return NULL;
+}
+
+__maybe_unused
+static struct uprobe_trampoline *get_uprobe_trampoline(unsigned long vaddr,
bool *new)
+{
+ struct uprobes_state *state = ¤t->mm->uprobes_state;
+ struct uprobe_trampoline *tramp = NULL;
+
+ hlist_for_each_entry(tramp, &state->head_tramps, node) {
+ if (is_reachable_by_call(tramp->vaddr, vaddr))
+ return tramp;
+ }
+
+ tramp = create_uprobe_trampoline(vaddr);
+ if (!tramp)
+ return NULL;
+
+ *new = true;
+ hlist_add_head(&tramp->node, &state->head_tramps);
+ return tramp;
+}
+
+static void destroy_uprobe_trampoline(struct uprobe_trampoline *tramp)
+{
+ hlist_del(&tramp->node);
+ kfree(tramp);
+}
+
+void arch_uprobe_init_state(struct mm_struct *mm)
+{
+ INIT_HLIST_HEAD(&mm->uprobes_state.head_tramps);
+}
+
+void arch_uprobe_clear_state(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->head_tramps, node)
+ destroy_uprobe_trampoline(tramp);
+}
#else /* 32-bit: */
/*
* No RIP-relative addressing on 32-bit
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 5080619560d4..b40d33aae016 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -17,6 +17,7 @@
#include <linux/wait.h>
#include <linux/timer.h>
#include <linux/seqlock.h>
+#include <linux/mutex.h>
struct uprobe;
struct vm_area_struct;
@@ -185,6 +186,9 @@ struct xol_area;
struct uprobes_state {
struct xol_area *xol_area;
+#ifdef CONFIG_X86_64
+ struct hlist_head head_tramps;
+#endif
};
typedef int (*uprobe_write_verify_t)(struct page *page, unsigned long vaddr,
@@ -233,6 +237,8 @@ extern void uprobe_handle_trampoline(struct pt_regs *regs);
extern void *arch_uretprobe_trampoline(unsigned long *psize);
extern unsigned long uprobe_get_trampoline_vaddr(void);
extern void uprobe_copy_from_page(struct page *page, unsigned long vaddr, void
*dst, int len);
+extern void arch_uprobe_clear_state(struct mm_struct *mm);
+extern void arch_uprobe_init_state(struct mm_struct *mm);
#else /* !CONFIG_UPROBES */
struct uprobes_state {
};
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 6795b8d82b9c..acec91a676b7 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1802,6 +1802,14 @@ static struct xol_area *get_xol_area(void)
return area;
}
+void __weak arch_uprobe_clear_state(struct mm_struct *mm)
+{
+}
+
+void __weak arch_uprobe_init_state(struct mm_struct *mm)
+{
+}
+
/*
* uprobe_clear_state - Free the area allocated for slots.
*/
@@ -1813,6 +1821,8 @@ void uprobe_clear_state(struct mm_struct *mm)
delayed_uprobe_remove(NULL, mm);
mutex_unlock(&delayed_uprobe_lock);
+ arch_uprobe_clear_state(mm);
+
if (!area)
return;
diff --git a/kernel/fork.c b/kernel/fork.c
index f1937a1cda08..0b280d2180dd 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1270,6 +1270,7 @@ static void mm_init_uprobes_state(struct mm_struct *mm)
{
#ifdef CONFIG_UPROBES
mm->uprobes_state.xol_area = NULL;
+ arch_uprobe_init_state(mm);
#endif
}
--
2.49.0
