* sdt.h (STAP_SEMAPHORE): New. Add guard to utrace probe points.

* itrace.h (__access_process_vm): Moved from here...
* runtime/access_process_vm.h: New.  ...to here.
* translate.cxx (translate_pass): Include access_process_vm.h
* session.h (sdt_semaphore_addr): New.
* tapsets.cxx (sdt_query::record_semaphore): New.  Record sdt_semaphore_addr.
(uprobe_derived_probe_group::emit_module_decls): Allow for uprobe guard variable to be set and unset.
(uprobe_derived_probe_group::emit_module_decls): Likewise.
(uprobe_derived_probe_group::emit_module_exit): Likewise.
* tapset-utrace.cxx (utrace_derived_probe_group::emit_probe_decl): Likewise.
(utrace_derived_probe_group::emit_module_decls): Likewise.
(utrace_derived_probe_group::emit_module_exit): Likewise.

1 files changed, 54 insertions, 0 deletions

diff --git a/runtime/access_process_vm.h b/runtime/access_process_vm.h
new file mode 100644
index 00000000..70489d48
--- /dev/null
+++ b/runtime/access_process_vm.h
@@ -0,0 +1,54 @@
+/*
+ * The kernel's access_process_vm is not exported in kernel.org kernels, although
+ * some distros export it on some architectures.  To workaround this inconsistency,
+ * we copied and pasted it here.  Fortunately, everything it calls is exported.
+ */
+#include <linux/pagemap.h>
+#include <asm/cacheflush.h>
+static int __access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+{
+	struct mm_struct *mm;
+	struct vm_area_struct *vma;
+	struct page *page;
+	void *old_buf = buf;
+
+	mm = get_task_mm(tsk);
+	if (!mm)
+		return 0;
+
+	down_read(&mm->mmap_sem);
+	/* ignore errors, just check how much was sucessfully transfered */
+	while (len) {
+		int bytes, ret, offset;
+		void *maddr;
+
+		ret = get_user_pages(tsk, mm, addr, 1,
+				     write, 1, &page, &vma);
+		if (ret <= 0)
+			break;
+
+		bytes = len;
+		offset = addr & (PAGE_SIZE-1);
+		if (bytes > PAGE_SIZE-offset)
+			bytes = PAGE_SIZE-offset;
+
+		maddr = kmap(page);
+		if (write) {
+			copy_to_user_page(vma, page, addr,
+					  maddr + offset, buf, bytes);
+			set_page_dirty_lock(page);
+		} else {
+			copy_from_user_page(vma, page, addr,
+					    buf, maddr + offset, bytes);
+		}
+		kunmap(page);
+		page_cache_release(page);
+		len -= bytes;
+		buf += bytes;
+		addr += bytes;
+	}
+	up_read(&mm->mmap_sem);
+	mmput(mm);
+
+	return buf - old_buf;
+}