Add build system scaffolding and libc headers

1 files changed, 62 insertions, 0 deletions

diff --git a/lib/libc/arch/x86_64/vdso_setup.c b/lib/libc/arch/x86_64/vdso_setup.c
new file mode 100644
index 00000000..c410995d
--- /dev/null
+++ b/lib/libc/arch/x86_64/vdso_setup.c
@@ -0,0 +1,62 @@
+#include <linux/auxvec.h>
+#include <linux/elf.h>
+#include <string.h>
+#include <time.h>
+
+int (*__vdso_clock_gettime)(int, struct timespec *) = NULL;
+int (*__vdso_getcpu)(unsigned *, unsigned *, void *) = NULL;
+int (*__vdso_time)(long *) = NULL;
+
+static __inline __attribute__((used)) void vdso_setup(Elf64_Ehdr *vdso_addr)
+{
+	Elf64_Phdr *phdr =
+		(Elf64_Phdr *)((char *)vdso_addr + vdso_addr->e_phoff);
+
+	for (int i = 0; i < vdso_addr->e_phnum; i++) {
+		if (phdr[i].p_type == PT_DYNAMIC) {
+			Elf64_Dyn *dyn = (Elf64_Dyn *)((char *)vdso_addr +
+						       phdr[i].p_offset);
+			const char *strtab = NULL;
+			Elf64_Sym *symtab = NULL;
+			for (; dyn->d_tag != DT_NULL; dyn++) {
+				if (dyn->d_tag == DT_STRTAB) {
+					strtab = (const char *)vdso_addr +
+						 dyn->d_un.d_ptr;
+				} else if (dyn->d_tag == DT_SYMTAB) {
+					symtab =
+						(Elf64_Sym *)((char *)vdso_addr +
+							      dyn->d_un.d_ptr);
+				}
+			}
+
+			if (strtab == NULL || symtab == NULL) {
+				return;
+			}
+
+			Elf64_Sym *sym = symtab;
+			while ((char *)sym < (char *)strtab) {
+				if (sym->st_name != 0 && sym->st_value != 0) {
+					const char *name =
+						strtab + sym->st_name;
+					if (strcmp(name,
+						   "__vdso_clock_gettime") == 0)
+						__vdso_clock_gettime =
+							(void *)(vdso_addr +
+								 sym->st_value);
+					else if (strcmp(name,
+							"__vdso_getcpu") == 0)
+						__vdso_getcpu =
+							(void *)(vdso_addr +
+								 sym->st_value);
+					else if (strcmp(name, "__vdso_time") ==
+						 0)
+						__vdso_time =
+							(void *)(vdso_addr +
+								 sym->st_value);
+				}
+				sym = (Elf64_Sym *)((char *)sym +
+						    sizeof(Elf64_Sym));
+			}
+		}
+	}
+}