[RFC UKL 01/10] kbuild: Add sections and symbols to linker script for UKL support

[Ali Raza <aliraza@bu.edu>]

In order to link a user space executable we will need access to a few
section that are not normally used when linking the kernel.  Add these
sections when we have selected CONFIG_UNIKERNEL_LINUX.

Add case to not throw warnings for COMMON symbols from application code.

Make the KBUILD_VMLINUX_OBJS contain the application library when UKL is
enabled.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>

Co-developed-by: Thomas Unger <tommyu@bu.edu>
Signed-off-by: Thomas Unger <tommyu@bu.edu>
Co-developed-by: Matthew Boyd <mboydmcse@gmail.com>
Signed-off-by: Matthew Boyd <mboydmcse@gmail.com>
Co-developed-by: Eric B Munson <munsoner@bu.edu>
Signed-off-by: Eric B Munson <munsoner@bu.edu>
Co-developed-by: Ali Raza <aliraza@bu.edu>
Signed-off-by: Ali Raza <aliraza@bu.edu>
---
 Makefile                          |  4 ++
 arch/x86/kernel/vmlinux.lds.S     | 98 +++++++++++++++++++++++++++++++
 include/asm-generic/sections.h    |  4 ++
 include/asm-generic/vmlinux.lds.h | 32 +++++++++-
 scripts/mod/modpost.c             |  4 ++
 5 files changed, 141 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 8478e13e9424..d072a52ed856 100644
--- a/Makefile
+++ b/Makefile
@@ -1129,6 +1129,10 @@ KBUILD_VMLINUX_LIBS := $(patsubst %/,%/lib.a, $(libs-y))
 endif
 KBUILD_VMLINUX_OBJS += $(patsubst %/,%/built-in.a, $(drivers-y))
 
+ifdef CONFIG_UNIKERNEL_LINUX
+KBUILD_VMLINUX_OBJS += $(CONFIG_UKL_ARCHIVE_PATH)
+endif
+
 export KBUILD_VMLINUX_OBJS KBUILD_VMLINUX_LIBS
 export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds
 # used by scripts/Makefile.package
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 15f29053cec4..cb8b33955969 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -101,6 +101,9 @@ jiffies = jiffies_64;
 
 PHDRS {
 	text PT_LOAD FLAGS(5);          /* R_E */
+#if defined(CONFIG_UNIKERNEL_LINUX) && defined(CONFIG_UKL_TLS)
+	tls PT_TLS FLAGS(6);            /* RW_ */
+#endif
 	data PT_LOAD FLAGS(6);          /* RW_ */
 #ifdef CONFIG_X86_64
 #ifdef CONFIG_SMP
@@ -146,6 +149,71 @@ SECTIONS
 #endif
 	} :text =0xcccc
 
+#ifdef CONFIG_UNIKERNEL_LINUX
+	/* Added to preserve page alignment */
+	. = ALIGN(PAGE_SIZE);
+
+	/*  */
+	.rela.plt	:
+	{
+		*(.rela.plt)
+		PROVIDE_HIDDEN (__rela_iplt_start = .);
+		*(.rela.iplt)
+		PROVIDE_HIDDEN (__rela_iplt_end = .);
+	} :text =0xcccc
+	.preinit_array	:
+	{
+		PROVIDE_HIDDEN (__preinit_array_start = .);
+		KEEP (*(.preinit_array))
+		PROVIDE_HIDDEN (__preinit_array_end = .);
+	} :text =0xcccc
+	.init_array	:
+	{
+		PROVIDE_HIDDEN (__init_array_start = .);
+		KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
+		KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o
+			*crtend.o *crtend?.o ) .ctors))
+		PROVIDE_HIDDEN (__init_array_end = .);
+	} :text =0xcccc
+	.fini_array	:
+	{
+		PROVIDE_HIDDEN (__fini_array_start = .);
+		KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
+		KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o
+			*crtend.o *crtend?.o ) .dtors))
+		PROVIDE_HIDDEN (__fini_array_end = .);
+	} :text =0xcccc
+	.ctors		:
+	{
+		/* gcc uses crtbegin.o to find the start of
+		   the constructors, so we make sure it is
+		   first.  Because this is a wildcard, it
+		   doesn't matter if the user does not
+		   actually link against crtbegin.o; the
+		   linker won't look for a file to match a
+		   wildcard.  The wildcard also means that it
+		   doesn't matter which directory crtbegin.o
+		   is in.  */
+		KEEP (*crtbegin.o(.ctors))
+		KEEP (*crtbegin?.o(.ctors))
+		/* We don't want to include the .ctor section from
+		   the crtend.o file until after the sorted ctors.
+		   The .ctor section from the crtend file contains the
+		   end of ctors marker and it must be last */
+		KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+		KEEP (*(SORT(.ctors.*)))
+		KEEP (*(.ctors))
+	} :text =0xcccc
+	.dtors		:
+	{
+		KEEP (*crtbegin.o(.dtors))
+		KEEP (*crtbegin?.o(.dtors))
+		KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+		KEEP (*(SORT(.dtors.*)))
+		KEEP (*(.dtors))
+	} :text =0xcccc
+#endif
+
 	/* End of text section, which should occupy whole number of pages */
 	_etext = .;
 	. = ALIGN(PAGE_SIZE);
@@ -208,6 +276,29 @@ SECTIONS
 
 	. = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
 
+#ifdef CONFIG_UNIKERNEL_LINUX
+#ifdef CONFIG_UKL_TLS
+	/* Thread Local Storage sections */
+	. = ALIGN(PAGE_SIZE);
+	.tdata : ALIGN(0x200000){
+		__tls_data_start = .;
+		*(.tdata .tdata.* .gnu.linkonce.td.*)
+		__tls_data_end = .;
+	} :tls
+	.tbss : {
+		__tls_bss_start = .;
+		*(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon)
+		__tls_bss_end = .;
+	} :tls
+#else
+	. = ALIGN(PAGE_SIZE);
+	__tls_data_start = .;
+	__tls_data_end = .;
+	__tls_bss_start = .;
+	__tls_bss_end = .;
+#endif
+#endif
+
 	/* Init code and data - will be freed after init */
 	. = ALIGN(PAGE_SIZE);
 	.init.begin : AT(ADDR(.init.begin) - LOAD_OFFSET) {
@@ -380,8 +471,13 @@ SECTIONS
 		*(BSS_MAIN)
 		BSS_DECRYPTED
 		. = ALIGN(PAGE_SIZE);
+#ifdef CONFIG_UNIKERNEL_LINUX
+	}
+	__bss_stop = .;
+#else
 		__bss_stop = .;
 	}
+#endif
 
 	/*
 	 * The memory occupied from _text to here, __end_of_kernel_reserve, is
@@ -446,6 +542,7 @@ SECTIONS
 #endif
 	       "Unexpected GOT/PLT entries detected!")
 
+#ifndef CONFIG_UNIKERNEL_LINUX
 	/*
 	 * Sections that should stay zero sized, which is safer to
 	 * explicitly check instead of blindly discarding.
@@ -469,6 +566,7 @@ SECTIONS
 		*(.rela.*) *(.rela_*)
 	}
 	ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
+#endif
 }
 
 /*
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index db13bb620f52..42ebf251903c 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -35,6 +35,10 @@
 extern char _text[], _stext[], _etext[];
 extern char _data[], _sdata[], _edata[];
 extern char __bss_start[], __bss_stop[];
+#ifdef CONFIG_UNIKERNEL_LINUX
+extern char __tls_data_start[], __tls_data_end[];
+extern char __tls_bss_start[], __tls_bss_end[];
+#endif
 extern char __init_begin[], __init_end[];
 extern char _sinittext[], _einittext[];
 extern char __start_ro_after_init[], __end_ro_after_init[];
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7c90b1ab3e00..4b0e4f3d4c39 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -568,6 +568,24 @@
  * code elimination is enabled, so these sections should be converted
  * to use ".." first.
  */
+#ifdef CONFIG_UNIKERNEL_LINUX
+#define TEXT_TEXT							\
+		ALIGN_FUNCTION();					\
+		*(.text.hot .text.hot.*)				\
+		*(TEXT_MAIN .text.fixup)				\
+		*(.stub .text.* .gnu.linkonce.t.*)			\
+		*(.text.unlikely .text.*_unlikely .text.unlikely.*)	\
+		*(.text.exit .text.exit.*)				\
+		*(.text.startup .text.startup.*)			\
+		*(.text.unknown .text.unknown.*)			\
+		NOINSTR_TEXT						\
+		*(.text..refcount)					\
+		*(.ref.text)						\
+		*(.text.asan.* .text.tsan.*)				\
+		TEXT_CFI_JT						\
+	MEM_KEEP(init.text*)						\
+	MEM_KEEP(exit.text*)
+#else
 #define TEXT_TEXT							\
 		ALIGN_FUNCTION();					\
 		*(.text.hot .text.hot.*)				\
@@ -580,7 +598,8 @@
 		*(.text.asan.* .text.tsan.*)				\
 		TEXT_CFI_JT						\
 	MEM_KEEP(init.text*)						\
-	MEM_KEEP(exit.text*)						\
+	MEM_KEEP(exit.text*)
+#endif
 
 
 /* sched.text is aling to function alignment to secure we have same
@@ -1029,12 +1048,23 @@
 	/* ld.bfd warns about .gnu.version* even when not emitted */	\
 	*(.gnu.version*)						\
 
+#ifdef CONFIG_UNIKERNEL_LINUX
+#define DISCARDS							\
+	/DISCARD/ : {							\
+	EXIT_DISCARDS							\
+	EXIT_CALL							\
+	COMMON_DISCARDS							\
+	*(.gnu.glibc-stub.*)						\
+	*(.gnu.warning.*)						\
+	}
+#else
 #define DISCARDS							\
 	/DISCARD/ : {							\
 	EXIT_DISCARDS							\
 	EXIT_CALL							\
 	COMMON_DISCARDS							\
 	}
+#endif
 
 /**
  * PERCPU_INPUT - the percpu input sections
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 2c80da0220c3..a6023db6b630 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -626,6 +626,8 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
 	case SHN_COMMON:
 		if (strstarts(symname, "__gnu_lto_")) {
 			/* Should warn here, but modpost runs before the linker */
+		} else if (strstarts(symname, "ukl_")) {
+			/* User code can have common symbols */
 		} else
 			warn("\"%s\" [%s] is COMMON symbol\n", symname, mod->name);
 		break;
@@ -774,6 +776,8 @@ static const char *const section_white_list[] =
 	".fmt_slot*",			/* EZchip */
 	".gnu.lto*",
 	".discard.*",
+	".gnu.warning.*",
+	".gnu.glibc-stub.*",
 	NULL
 };
 
-- 
2.21.3