diff --git a/Userland/DynamicLoader/CMakeLists.txt b/Userland/DynamicLoader/CMakeLists.txt
index 019b7eaf89..dc1d10505f 100644
--- a/Userland/DynamicLoader/CMakeLists.txt
+++ b/Userland/DynamicLoader/CMakeLists.txt
@@ -9,7 +9,13 @@ file(GLOB ELF_SOURCES "../Libraries/LibELF/*.cpp")
 set(ELF_SOURCES ${ELF_SOURCES} ../Libraries/LibELF/Arch/i386/plt_trampoline.S)
 file(GLOB LIBC_SOURCES1 "../Libraries/LibC/*.cpp")
 file(GLOB LIBC_SOURCES2 "../Libraries/LibC/*/*.cpp")
-file(GLOB LIBC_SOURCES3 "../Libraries/LibC/*.S")
+
+if ("${SERENITY_ARCH}" STREQUAL "i686")
+    file(GLOB LIBC_SOURCES3 "../Libraries/LibC/arch/i386/*.S")
+elseif ("${SERENITY_ARCH}" STREQUAL "x86_64")
+    file(GLOB LIBC_SOURCES3 "../Libraries/LibC/arch/x86_64/*.S")
+endif()
+
 file(GLOB LIBSYSTEM_SOURCES "../Libraries/LibSystem/*.cpp")
 
 list(FILTER LIBC_SOURCES1 EXCLUDE REGEX ".+crt0.cpp")
diff --git a/Userland/Libraries/LibC/CMakeLists.txt b/Userland/Libraries/LibC/CMakeLists.txt
index d0e7947fb8..571c384b0c 100644
--- a/Userland/Libraries/LibC/CMakeLists.txt
+++ b/Userland/Libraries/LibC/CMakeLists.txt
@@ -24,7 +24,6 @@ set(LIBC_SOURCES
     sched.cpp
     semaphore.cpp
     serenity.cpp
-    setjmp.S
     signal.cpp
     spawn.cpp
     stat.cpp
@@ -53,7 +52,13 @@ set(LIBC_SOURCES
 
 file(GLOB AK_SOURCES CONFIGURE_DEPENDS "../../../AK/*.cpp")
 file(GLOB ELF_SOURCES CONFIGURE_DEPENDS "../LibELF/*.cpp")
-set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/i386/plt_trampoline.S)
+
+if ("${SERENITY_ARCH}" STREQUAL "i686")
+    set(ASM_SOURCES "arch/i386/setjmp.S")
+    set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/i386/plt_trampoline.S)
+elseif ("${SERENITY_ARCH}" STREQUAL "x86_64")
+    set(ASM_SOURCES "arch/x86_64/setjmp.S")
+endif()
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unknown-warning-option -DSERENITY_LIBC_BUILD")
 
@@ -76,7 +81,7 @@ add_custom_command(
     COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_OBJECTS:ssp> ${CMAKE_INSTALL_PREFIX}/usr/lib/ssp.o
 )
 
-set(SOURCES ${LIBC_SOURCES} ${AK_SOURCES} ${ELF_SOURCES})
+set(SOURCES ${LIBC_SOURCES} ${AK_SOURCES} ${ELF_SOURCES} ${ASM_SOURCES})
 
 serenity_libc_static(LibCStatic c)
 target_link_libraries(LibCStatic crt0 ssp system)
diff --git a/Userland/Libraries/LibC/setjmp.S b/Userland/Libraries/LibC/arch/i386/setjmp.S
similarity index 100%
rename from Userland/Libraries/LibC/setjmp.S
rename to Userland/Libraries/LibC/arch/i386/setjmp.S
diff --git a/Userland/Libraries/LibC/arch/x86_64/setjmp.S b/Userland/Libraries/LibC/arch/x86_64/setjmp.S
new file mode 100644
index 0000000000..6b6df0441a
--- /dev/null
+++ b/Userland/Libraries/LibC/arch/x86_64/setjmp.S
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+.global setjmp
+setjmp:
+    mov %rbx, (%rdi)
+    mov %rbp, 8(%rdi)
+    mov %r12, 16(%rdi)
+    mov %r13, 24(%rdi)
+    mov %r14, 32(%rdi)
+    mov %r15, 40(%rdi)
+    lea 8(%rsp), %rcx
+    mov %rcx, 48(%rdi)
+    mov (%rsp), %rcx
+    mov %rcx, 56(%rdi)
+    xor %eax, %eax
+    ret
+
+.global longjmp
+longjmp:
+    mov (%rdi), %rbx
+    mov 8(%rdi), %rbp
+    mov 16(%rdi), %r12
+    mov 24(%rdi), %r13
+    mov 32(%rdi), %r14
+    mov 40(%rdi), %r15
+    mov 48(%rdi), %rsp
+
+    test %rsi, %rsi
+    jnz .nonzero
+    mov 1, %rax
+.nonzero:
+    jmp *56(%rdi)
+