From 69e6fe89fa9baafeca3e3515bb50897cd8ee7c35 Mon Sep 17 00:00:00 2001
From: Kacper <kacper@mail.openlinux.dev>
Date: Mon, 15 Dec 2025 18:24:54 +0100
Subject: Add getauxval and cleanup libc startup

---
 lib/libc/internal/Kbuild      |  2 ++
 lib/libc/internal/init/Kbuild |  1 +
 lib/libc/internal/init/vdso.c | 56 +++++++++++++++++++++++++++++++++++++++++++
 lib/libc/internal/libc_main.c | 40 +++++++++++++++++++++++++++++++
 4 files changed, 99 insertions(+)
 create mode 100644 lib/libc/internal/Kbuild
 create mode 100644 lib/libc/internal/init/Kbuild
 create mode 100644 lib/libc/internal/init/vdso.c
 create mode 100644 lib/libc/internal/libc_main.c

(limited to 'lib/libc/internal')

diff --git a/lib/libc/internal/Kbuild b/lib/libc/internal/Kbuild
new file mode 100644
index 00000000..5015f987
--- /dev/null
+++ b/lib/libc/internal/Kbuild
@@ -0,0 +1,2 @@
+obj-y += init/
+obj-y += libc_main.o
diff --git a/lib/libc/internal/init/Kbuild b/lib/libc/internal/init/Kbuild
new file mode 100644
index 00000000..dd27261a
--- /dev/null
+++ b/lib/libc/internal/init/Kbuild
@@ -0,0 +1 @@
+obj-y += vdso.o
diff --git a/lib/libc/internal/init/vdso.c b/lib/libc/internal/init/vdso.c
new file mode 100644
index 00000000..f94401f6
--- /dev/null
+++ b/lib/libc/internal/init/vdso.c
@@ -0,0 +1,56 @@
+#include <asm/vdso.h>
+#include <elf.h>
+#include <string.h>
+#include <sys/auxv.h>
+
+void __init_vdso(void)
+{
+	Elf64_Ehdr *ehdr = (Elf64_Ehdr *)getauxval(AT_SYSINFO_EHDR);
+	Elf64_Phdr *phdr = (Elf64_Phdr *)(ehdr + ehdr->e_phoff);
+
+	for (int i = 0; i < ehdr->e_phnum; i++) {
+		Elf64_Dyn *dyn;
+		Elf64_Sym *symtab;
+		const char *strtab;
+
+		if (phdr[i].p_type == PT_DYNAMIC) {
+			Elf64_Sym *sym;
+
+			dyn = (Elf64_Dyn *)((char *)ehdr + phdr[i].p_offset);
+			symtab = 0;
+			strtab = 0;
+
+			while (dyn->d_tag != DT_NULL) {
+				if (dyn->d_tag == DT_STRTAB) {
+					strtab = (const char *)(ehdr + dyn->d_un.d_ptr);
+				} else if (dyn->d_tag == DT_SYMTAB) {
+					symtab = (Elf64_Sym *)(ehdr + dyn->d_un.d_ptr);
+				}
+
+				if (strtab && symtab) {
+					break;
+				}
+
+				dyn++;
+			}
+
+			sym = symtab;
+			while ((char *)sym < strtab) {
+				if (sym->st_name != 0 && sym->st_value != 0) {
+					const char *name = strtab + sym->st_name;
+
+					for (int i = 0; __vdso_symtab[i].name != 0; i++) {
+						if (strcmp(name, __vdso_symtab[i].name) == 0) {
+							__vdso_symtab[i].func = (void *)(ehdr + sym->st_value);
+							break;
+						}
+					}
+				}
+
+				sym = (Elf64_Sym *)((char *)sym + sizeof(Elf64_Sym));
+			}
+
+			break;
+		}
+	}
+}
diff --git a/lib/libc/internal/libc_main.c b/lib/libc/internal/libc_main.c
new file mode 100644
index 00000000..7ac15ab4
--- /dev/null
+++ b/lib/libc/internal/libc_main.c
@@ -0,0 +1,40 @@
+#include <libc.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/cdefs.h>
+
+extern void __init_vdso(void);
+
+struct libc __libc;
+char **environ;
+char *__progname;
+
+extern int main(int, char **, char **);
+
+__used void __libc_main(uintptr_t *rsp)
+{
+	char **argv;
+	size_t *auxv;
+	int argc;
+
+	argc = (int)(*rsp);
+	argv = (char **)(++rsp);
+
+	rsp += argc;
+
+	environ = (char **)(++rsp);
+	__progname = argv[0];
+
+	while (*rsp)
+		rsp++;
+
+	auxv = (size_t *)++rsp;
+
+	for (size_t i = 0; auxv[i]; i += 2)
+		__libc.auxv[auxv[i]] = auxv[i + 1];
+
+	__init_vdso();
+
+	exit(main(argc, argv, environ));
+}
-- 
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