Add build system scaffolding and libc headers

9 files changed, 307 insertions, 0 deletions

diff --git a/lib/libc/arch/Kbuild b/lib/libc/arch/Kbuild
new file mode 100644
index 00000000..ad3a7486
--- /dev/null
+++ b/lib/libc/arch/Kbuild
@@ -0,0 +1 @@
+obj-y += $(ARCH)/
diff --git a/lib/libc/arch/x86_64/Kbuild b/lib/libc/arch/x86_64/Kbuild
new file mode 100644
index 00000000..fc8a2d3f
--- /dev/null
+++ b/lib/libc/arch/x86_64/Kbuild
@@ -0,0 +1,7 @@
+obj-y += clock_gettime.o
+obj-y += crt0.o
+obj-y += fenv.o
+obj-y += longjmp.o
+obj-y += setjmp.o
+obj-y += sigsetjmp.o
+obj-y += vdso_setup.o
diff --git a/lib/libc/arch/x86_64/clock_gettime.c b/lib/libc/arch/x86_64/clock_gettime.c
new file mode 100644
index 00000000..6a7a3874
--- /dev/null
+++ b/lib/libc/arch/x86_64/clock_gettime.c
@@ -0,0 +1,13 @@
+#include <asm/vdso.h>
+#include <syscall.h>
+#include <time.h>
+
+int clock_gettime(clockid_t clock_id, struct timespec *tp)
+{
+#if defined(__x86_64__)
+	if (__vdso_clock_gettime)
+		return __vdso_clock_gettime(clock_id, tp);
+#endif
+
+	return syscall(clock_gettime, clock_id, tp);
+}
diff --git a/lib/libc/arch/x86_64/crt0.c b/lib/libc/arch/x86_64/crt0.c
new file mode 100644
index 00000000..2c7943ff
--- /dev/null
+++ b/lib/libc/arch/x86_64/crt0.c
@@ -0,0 +1,59 @@
+#include <linux/auxvec.h>
+#include <linux/elf.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <thread.h>
+#include <unistd.h>
+
+#define weak_reference(old, new) \
+	extern __typeof(old) new __attribute__((__weak__, __alias__(#old)))
+
+extern int main(int, char *[]);
+char **environ;
+
+static struct __thread_self thread = { .tid = 0, ._errno = 0 };
+
+struct __attribute__((packed)) auxv_t {
+	uintptr_t a_type;
+	uintptr_t a_val;
+} *__auxv;
+
+static void __vdso_setup(Elf64_Ehdr *vdso_addr __attribute__((unused)))
+{
+}
+
+weak_reference(__vdso_setup, vdso_setup);
+
+__attribute__((used)) void __libc_start(uintptr_t *sp)
+{
+	char **argv;
+	int argc;
+
+	argc = (int)(*sp);
+	argv = (char **)(++sp);
+	sp += argc;
+	environ = (char **)(++sp);
+
+	while (*sp)
+		sp++;
+
+	__auxv = (struct auxv_t *)(++sp);
+	while (__auxv->a_type != AT_NULL) {
+		if (__auxv->a_type == AT_SYSINFO_EHDR) {
+			vdso_setup((Elf64_Ehdr *)__auxv->a_val);
+		}
+
+		__auxv++;
+	}
+
+	__asm__ volatile("wrfsbase %0" ::"r"(thread));
+
+	exit(main(argc, argv));
+}
+
+__attribute__((noreturn, naked)) void _start(void)
+{
+	__asm__ __volatile__("mov %rsp, %rdi\n"
+			     "call __libc_start\n");
+}
diff --git a/lib/libc/arch/x86_64/fenv.s b/lib/libc/arch/x86_64/fenv.s
new file mode 100644
index 00000000..b9a46581
--- /dev/null
+++ b/lib/libc/arch/x86_64/fenv.s
@@ -0,0 +1,97 @@
+.global feclearexcept
+.type feclearexcept,@function
+feclearexcept:
+	mov %edi,%ecx
+	and $0x3f,%ecx
+	fnstsw %ax
+	test %eax,%ecx
+	jz 1f
+	fnclex
+1:	stmxcsr -8(%rsp)
+	and $0x3f,%eax
+	or %eax,-8(%rsp)
+	test %ecx,-8(%rsp)
+	jz 1f
+	not %ecx
+	and %ecx,-8(%rsp)
+	ldmxcsr -8(%rsp)
+1:	xor %eax,%eax
+	ret
+
+.global feraiseexcept
+.type feraiseexcept,@function
+feraiseexcept:
+	and $0x3f,%edi
+	stmxcsr -8(%rsp)
+	or %edi,-8(%rsp)
+	ldmxcsr -8(%rsp)
+	xor %eax,%eax
+	ret
+
+.global __fesetround
+.hidden __fesetround
+.type __fesetround,@function
+__fesetround:
+	push %rax
+	xor %eax,%eax
+	mov %edi,%ecx
+	fnstcw (%rsp)
+	andb $0xf3,1(%rsp)
+	or %ch,1(%rsp)
+	fldcw (%rsp)
+	stmxcsr (%rsp)
+	shl $3,%ch
+	andb $0x9f,1(%rsp)
+	or %ch,1(%rsp)
+	ldmxcsr (%rsp)
+	pop %rcx
+	ret
+
+.global fegetround
+.type fegetround,@function
+fegetround:
+	push %rax
+	stmxcsr (%rsp)
+	pop %rax
+	shr $3,%eax
+	and $0xc00,%eax
+	ret
+
+.global fegetenv
+.type fegetenv,@function
+fegetenv:
+	xor %eax,%eax
+	fnstenv (%rdi)
+	stmxcsr 28(%rdi)
+	ret
+
+.global fesetenv
+.type fesetenv,@function
+fesetenv:
+	xor %eax,%eax
+	inc %rdi
+	jz 1f
+	fldenv -1(%rdi)
+	ldmxcsr 27(%rdi)
+	ret
+1:	push %rax
+	push %rax
+	pushq $0xffff
+	pushq $0x37f
+	fldenv (%rsp)
+	pushq $0x1f80
+	ldmxcsr (%rsp)
+	add $40,%rsp
+	ret
+
+.global fetestexcept
+.type fetestexcept,@function
+fetestexcept:
+	and $0x3f,%edi
+	push %rax
+	stmxcsr (%rsp)
+	pop %rsi
+	fnstsw %ax
+	or %esi,%eax
+	and %edi,%eax
+	ret
diff --git a/lib/libc/arch/x86_64/longjmp.c b/lib/libc/arch/x86_64/longjmp.c
new file mode 100644
index 00000000..6aed69a5
--- /dev/null
+++ b/lib/libc/arch/x86_64/longjmp.c
@@ -0,0 +1,18 @@
+#include <setjmp.h>
+
+__attribute__((noreturn, naked, returns_twice)) void longjmp(jmp_buf env,
+							     int val)
+{
+	__asm__ __volatile__("mov 0(%rdi), %rbx\n"
+			     "mov 8(%rdi), %rbp\n"
+			     "mov 16(%rdi), %r12\n"
+			     "mov 24(%rdi), %r13\n"
+			     "mov 32(%rdi), %r14\n"
+			     "mov 40(%rdi), %r15\n"
+			     "mov 48(%rdi), %rsp\n"
+			     "xor %rax, %rax\n"
+			     "cmp $0, %esi\n"
+			     "setne %al\n"
+			     "mov %eax, %eax\n"
+			     "jmp *56(%rdi)\n");
+}
diff --git a/lib/libc/arch/x86_64/setjmp.c b/lib/libc/arch/x86_64/setjmp.c
new file mode 100644
index 00000000..d268ae25
--- /dev/null
+++ b/lib/libc/arch/x86_64/setjmp.c
@@ -0,0 +1,17 @@
+#include <setjmp.h>
+
+__attribute__((naked, returns_twice)) int setjmp(jmp_buf env)
+{
+	__asm__ __volatile__("mov %rbx,(%rdi)\n"
+			     "mov %rbp,8(%rdi)\n"
+			     "mov %r12,16(%rdi)\n"
+			     "mov %r13,24(%rdi)\n"
+			     "mov %r14,32(%rdi)\n"
+			     "mov %r15,40(%rdi)\n"
+			     "lea 8(%rsp),%rdx\n"
+			     "mov %rdx,48(%rdi)\n"
+			     "mov (%rsp),%rdx\n"
+			     "mov %rdx,56(%rdi)\n"
+			     "xor %eax,%eax\n"
+			     "ret\n");
+}
diff --git a/lib/libc/arch/x86_64/sigsetjmp.c b/lib/libc/arch/x86_64/sigsetjmp.c
new file mode 100644
index 00000000..d4c0a4db
--- /dev/null
+++ b/lib/libc/arch/x86_64/sigsetjmp.c
@@ -0,0 +1,33 @@
+#include <setjmp.h>
+
+int sigsetjmp(sigjmp_buf env, int savemask)
+{
+	__asm__ __volatile__("movq %%rbx, 0(%0)\n"
+			     "movq %%rbp, 8(%0)\n"
+			     "movq %%r12, 16(%0)\n"
+			     "movq %%r13, 24(%0)\n"
+			     "movq %%r14, 32(%0)\n"
+			     "movq %%r15, 40(%0)\n"
+
+			     "leaq 8(%%rsp), %%rax\n"
+			     "movq %%rax, 48(%0)\n"
+			     "movq (%%rsp), %%rax\n"
+			     "movq %%rax, 56(%0)\n"
+
+			     "testl %%esi, %%esi\n"
+			     "jz 1f\n"
+			     "movq $2, %%rdi\n"
+			     "movq $0, %%rsi\n"
+			     "leaq 64(%0), %%rdx\n"
+			     "movq $128, %%r10\n"
+			     "movq $14, %%rax\n"
+			     "syscall\n"
+
+			     "1:\n"
+			     "xor %%eax, %%eax\n"
+			     :
+			     : "r"(env), "S"(savemask)
+			     : "rax", "rdi", "rdx", "r10", "memory");
+
+	return 0;
+}
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));
+			}
+		}
+	}
+}