[PATCH 0/9] Function Granular Kernel Address Space Layout Randomization

[PATCH 0/9] Function Granular Kernel Address Space Layout Randomization

[Kristen Carlson Accardi]

This patch set is an implementation of finer grained kernel address space
randomization. It rearranges your kernel code at load time 
on a per-function level granularity, with only around a second added to
boot time.

Background
----------
KASLR was merged into the kernel with the objective of increasing the
difficulty of code reuse attacks. Code reuse attacks reused existing code
snippets to get around existing memory protections. They exploit software bugs
which expose addresses of useful code snippets to control the flow of
execution for their own nefarious purposes. KASLR moves the entire kernel
code text as a unit at boot time in order to make addresses less predictable.
The order of the code within the segment is unchanged - only the base address
is shifted. There are a few shortcomings to this algorithm.

1. Low Entropy - there are only so many locations the kernel can fit in. This
   means an attacker could guess without too much trouble.
2. Knowledge of a single address can reveal the offset of the base address,
   exposing all other locations for a published/known kernel image.
3. Info leaks abound.

Finer grained ASLR has been proposed as a way to make ASLR more resistant
to info leaks. It is not a new concept at all, and there are many variations
possible. Function reordering is an implementation of finer grained ASLR
which randomizes the layout of an address space on a function level
granularity. We use the term "fgkaslr" in this document to refer to the
technique of function reordering when used with KASLR, as well as finer grained
KASLR in general.

Proposed Improvement
--------------------
This patch set proposes adding function reordering on top of the existing
KASLR base address randomization. The over-arching objective is incremental
improvement over what we already have, as well as something that can be
merged and deployed with as little disruption to our existing kernel/ecosystem
as possible. It is designed to work with the existing solution, although it
can be used independently (not sure why you would do that though...). The
implementation is really pretty simple, and there are 2 main area where
changes occur:

* Build time

GCC has an option to place functions into individual .text sections. We can
use this option to implement function reordering at load time. The final
compiled vmlinux retains all the section headers, which can be used to help
us find the address ranges of each function. Using this information and
an expanded table of relocation addresses, we can shuffle the individual
text sections immediately after decompression. You are probably asking
yourself how this could possibly work given the number of tables of
addresses that exist inside the kernel today for features such as exception
handling and kprobes. Most of these tables generate relocations and
require a simple update, and some tables that have assumptions about order
require sorting after the update. In order to modify these tables, we
preserve a few key symbols from the objcopy symbol stripping process for use
after shuffling the text segments.

Some highlights from the build time changes to look for:

The top level kernel Makefile was modified to add the gcc flag if it
is supported. Currently, I am applying this flag to everything it is
possible to randomize. Future work could turn off this flags for selected
files or even entire subsystems, although obviously at the cost of security.

The relocs tool is updated to add relative relocations. This information
previously wasn't included because it wasn't necessary when moving the
entire .text segment as a unit. 

A new file was created to contain a list of symbols that objcopy should
keep. We use those symbols at load time as described below.

* Load time

The boot kernel was modified to parse the vmlinux elf file after
decompression to check for our interesting symbols that we kept, and to
look for any .text.* sections to randomize. We then shuffle the sections
and update any tables that need to be updated or resorted. The existing
code which updated relocation addresses was modified to account for not
just a fixed delta from the load address, but the offset that the function
section was moved to. This requires inspection of each address to see if
it was impacted by a randomization. We use a bsearch to make this less
horrible on performance.

In order to hide our new layout, symbols reported through /proc/kallsyms
will be sorted by name alphabetically rather than by address.

Security Considerations
-----------------------
The objective of this patch set is to improve a technology that is already
merged into the kernel (KASLR). Obviously, this code is not a one stop
shopping place for blocking code reuse attacks, but should instead be
considered as one of several tools that can be used. In particular, this
code is meant to make KASLR more effective in the presence of info leaks.
A key point to note is that we are basically accepting that there are
many and various ways to leak address today and in the future, and rather
than assume that we can stop them all, we should find a method which makes
individual info leaks less important. How much entropy we are adding to
the existing entropy of standard KASLR will depend on a few variables.
Firstly and most obviously, the number of functions you randomize matters.
This implementation keeps the existing .text section for code that cannot be
randomized - for example, because it was assembly code, or we opted out of
randomization for performance reasons. The less sections to randomize, the
less entropy. In addition, due to alignment (16 bytes for x86_64), the number
of bits in a address that the attacker needs to guess is reduced, as the lower
bits are identical.

Performance Impact
------------------
There are two areas where function reordering can impact performance: boot
time latency, and run time performance.

* Boot time latency
This implementation of finer grained KASLR impacts the boot time of the kernel
in several places. It requires additional parsing of the kernel ELF file to
obtain the section headers of the sections to be randomized. It calls the
random number generator for each section to be randomized to determine that
section's new memory location. It copies the decompressed kernel into a new
area of memory to avoid corruption when laying out the newly randomized
sections. It increases the number of relocations the kernel has to perform at
boot time vs. standard KASLR, and it also requires a lookup on each address
that needs to be relocated to see if it was in a randomized section and needs
to be adjusted by a new offset. Finally, it re-sorts a few data tables that
are required to be sorted by address.

Booting a test VM on a modern, well appointed system showed an increase in
latency of approximately 1 second.

* Run time
The performance impact at run-time of function reordering varies by workload.
Using kcbench, a kernel compilation benchmark, the performance of a kernel
build with finer grained KASLR was about 1% slower than a kernel with standard
KASLR. Analysis with perf showed a slightly higher percentage of 
L1-icache-load-misses. Other workloads were examined as well, with varied
results. Some workloads performed significantly worse under FGKASLR, while
others stayed the same or were mysteriously better. In general, it will
depend on the code flow whether or not finer grained KASLR will impact
your workload, and how the underlying code was designed. Future work could
identify hot areas that may not be randomized and either leave them in the
.text section or group them together into a single section that may be
randomized. If grouping things together helps, one other thing to consider
is that if we could identify text blobs that should be grouped together
to benefit a particular code flow, it could be interesting to explore
whether this security feature could be also be used as a performance
feature if you are interested in optimizing your kernel layout for a
particular workload at boot time. Optimizing function layout for a particular
workload has been researched and proven effective - for more information
read the Facebook paper "Optimizing Function Placement for Large-Scale
Data-Center Applications" (see references section below).

Image Size
----------
Adding additional section headers as a result of compiling with
-ffunction-sections will increase the size of the vmlinux ELF file.
With a standard distro config, the resulting vmlinux was increased by
about 3%. The compressed image is also increased due to the header files,
as well as the extra relocations that must be added. You can expect fgkaslr
to increase the size of the compressed image by about 15%.

Building
--------
To enable fine grained KASLR, you need to have the following config options
set (including all the ones you would use to build normal KASLR)

CONFIG_FG_KASLR=y

In addition, fgkaslr is only supported for the X86_64 architecture.

Modules
-------
Modules are randomized similarly to the rest of the kernel by shuffling
the sections at load time prior to moving them into memory. The module must
also have been build with the -ffunction-sections compiler option.

References
----------
There are a lot of academic papers which explore finer grained ASLR.
This paper in particular contributed the most to my implementation design
as well as my overall understanding of the problem space:

Selfrando: Securing the Tor Browser against De-anonymization Exploits,
M. Conti, S. Crane, T. Frassetto, et al.

For more information on how function layout impacts performance, see:

Optimizing Function Placement for Large-Scale Data-Center Applications,
G. Ottoni, B. Maher

Kees Cook (1):
  x86/boot: Allow a "silent" kaslr random byte fetch

Kristen Carlson Accardi (8):
  objtool: do not assume order of parent/child functions
  x86: tools/relocs: Support >64K section headers
  x86: Makefile: Add build and config option for CONFIG_FG_KASLR
  x86: make sure _etext includes function sections
  x86/tools: Adding relative relocs for randomized functions
  x86: Add support for function granular KASLR
  kallsyms: hide layout
  module: Reorder functions

 Documentation/security/fgkaslr.rst       | 151 +++++
 Documentation/security/index.rst         |   1 +
 Makefile                                 |   4 +
 arch/x86/Kconfig                         |  13 +
 arch/x86/boot/compressed/Makefile        |  10 +-
 arch/x86/boot/compressed/fgkaslr.c       | 809 +++++++++++++++++++++++
 arch/x86/boot/compressed/kaslr.c         |   7 +-
 arch/x86/boot/compressed/misc.c          | 107 ++-
 arch/x86/boot/compressed/misc.h          |  31 +
 arch/x86/boot/compressed/utils.c         |  12 +
 arch/x86/boot/compressed/vmlinux.symbols |  18 +
 arch/x86/include/asm/boot.h              |  15 +-
 arch/x86/kernel/vmlinux.lds.S            |  18 +-
 arch/x86/lib/kaslr.c                     |  18 +-
 arch/x86/tools/relocs.c                  | 143 +++-
 arch/x86/tools/relocs.h                  |   4 +-
 arch/x86/tools/relocs_common.c           |  14 +-
 include/asm-generic/vmlinux.lds.h        |   2 +-
 include/uapi/linux/elf.h                 |   1 +
 kernel/kallsyms.c                        | 138 +++-
 kernel/module.c                          |  82 +++
 tools/objtool/elf.c                      |   8 +-
 22 files changed, 1543 insertions(+), 63 deletions(-)
 create mode 100644 Documentation/security/fgkaslr.rst
 create mode 100644 arch/x86/boot/compressed/fgkaslr.c
 create mode 100644 arch/x86/boot/compressed/utils.c
 create mode 100644 arch/x86/boot/compressed/vmlinux.symbols

-- 
2.20.1

[PATCH 1/9] objtool: do not assume order of parent/child functions

[Kristen Carlson Accardi]

If a .cold function is examined prior to it's parent, the link
to the parent/child function can be overwritten when the parent
is examined. Only update pfunc and cfunc if they were previously
nil to prevent this from happening.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/elf.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 09ddc8f1def3..2aa40f344392 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -408,7 +408,13 @@ static int read_symbols(struct elf *elf)
 			size_t pnamelen;
 			if (sym->type != STT_FUNC)
 				continue;
-			sym->pfunc = sym->cfunc = sym;
+
+			if (sym->pfunc == NULL)
+				sym->pfunc = sym;
+
+			if (sym->cfunc == NULL)
+				sym->cfunc = sym;
+
 			coldstr = strstr(sym->name, ".cold");
 			if (!coldstr)
 				continue;
-- 
2.20.1

[PATCH 2/9] x86: tools/relocs: Support >64K section headers

[Kristen Carlson Accardi]

While it is already supported to find the total number of section
headers if we exceed 64K sections, we need to support the
extended symbol table to get section header indexes for symbols
when there are > 64K sections. Parse the elf file to read
the extended symbol table info, and then replace all direct references
to st_shndx with calls to sym_index(), which will determine whether
we can read the value directly or whether we need to pull it out of
the extended table.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/tools/relocs.c | 104 ++++++++++++++++++++++++++++++----------
 1 file changed, 78 insertions(+), 26 deletions(-)

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index ce7188cbdae5..a00dc133f109 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -14,6 +14,10 @@
 static Elf_Ehdr		ehdr;
 static unsigned long	shnum;
 static unsigned int	shstrndx;
+static unsigned int	shsymtabndx;
+static unsigned int	shxsymtabndx;
+
+static int sym_index(Elf_Sym *sym);
 
 struct relocs {
 	uint32_t	*offset;
@@ -32,6 +36,7 @@ struct section {
 	Elf_Shdr       shdr;
 	struct section *link;
 	Elf_Sym        *symtab;
+	Elf32_Word     *xsymtab;
 	Elf_Rel        *reltab;
 	char           *strtab;
 };
@@ -265,7 +270,7 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym)
 		name = sym_strtab + sym->st_name;
 	}
 	else {
-		name = sec_name(sym->st_shndx);
+		name = sec_name(sym_index(sym));
 	}
 	return name;
 }
@@ -335,6 +340,23 @@ static uint64_t elf64_to_cpu(uint64_t val)
 #define elf_xword_to_cpu(x)	elf32_to_cpu(x)
 #endif
 
+static int sym_index(Elf_Sym *sym)
+{
+	Elf_Sym *symtab = secs[shsymtabndx].symtab;
+	Elf32_Word *xsymtab = secs[shxsymtabndx].xsymtab;
+	unsigned long offset;
+	int index;
+
+	if (sym->st_shndx != SHN_XINDEX)
+		return sym->st_shndx;
+
+	/* calculate offset of sym from head of table. */
+	offset = (unsigned long) sym - (unsigned long) symtab;
+	index = offset/sizeof(*sym);
+
+	return elf32_to_cpu(xsymtab[index]);
+}
+
 static void read_ehdr(FILE *fp)
 {
 	if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) {
@@ -468,31 +490,60 @@ static void read_strtabs(FILE *fp)
 static void read_symtabs(FILE *fp)
 {
 	int i,j;
+
 	for (i = 0; i < shnum; i++) {
 		struct section *sec = &secs[i];
-		if (sec->shdr.sh_type != SHT_SYMTAB) {
+		int num_syms;
+
+		switch (sec->shdr.sh_type) {
+		case SHT_SYMTAB_SHNDX:
+			sec->xsymtab = malloc(sec->shdr.sh_size);
+			if (!sec->xsymtab) {
+				die("malloc of %d bytes for xsymtab failed\n",
+					sec->shdr.sh_size);
+			}
+			if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
+				die("Seek to %d failed: %s\n",
+					sec->shdr.sh_offset, strerror(errno));
+			}
+			if (fread(sec->xsymtab, 1, sec->shdr.sh_size, fp)
+					!= sec->shdr.sh_size) {
+				die("Cannot read extended symbol table: %s\n",
+					strerror(errno));
+			}
+			shxsymtabndx = i;
+			continue;
+
+		case SHT_SYMTAB:
+			num_syms = sec->shdr.sh_size/sizeof(Elf_Sym);
+
+			sec->symtab = malloc(sec->shdr.sh_size);
+			if (!sec->symtab) {
+				die("malloc of %d bytes for symtab failed\n",
+					sec->shdr.sh_size);
+			}
+			if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
+				die("Seek to %d failed: %s\n",
+					sec->shdr.sh_offset, strerror(errno));
+			}
+			if (fread(sec->symtab, 1, sec->shdr.sh_size, fp)
+					!= sec->shdr.sh_size) {
+				die("Cannot read symbol table: %s\n",
+					strerror(errno));
+			}
+			for (j = 0; j < num_syms; j++) {
+				Elf_Sym *sym = &sec->symtab[j];
+
+				sym->st_name  = elf_word_to_cpu(sym->st_name);
+				sym->st_value = elf_addr_to_cpu(sym->st_value);
+				sym->st_size  = elf_xword_to_cpu(sym->st_size);
+				sym->st_shndx = elf_half_to_cpu(sym->st_shndx);
+			}
+			shsymtabndx = i;
+			continue;
+
+		default:
 			continue;
-		}
-		sec->symtab = malloc(sec->shdr.sh_size);
-		if (!sec->symtab) {
-			die("malloc of %d bytes for symtab failed\n",
-				sec->shdr.sh_size);
-		}
-		if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
-			die("Seek to %d failed: %s\n",
-				sec->shdr.sh_offset, strerror(errno));
-		}
-		if (fread(sec->symtab, 1, sec->shdr.sh_size, fp)
-		    != sec->shdr.sh_size) {
-			die("Cannot read symbol table: %s\n",
-				strerror(errno));
-		}
-		for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Sym); j++) {
-			Elf_Sym *sym = &sec->symtab[j];
-			sym->st_name  = elf_word_to_cpu(sym->st_name);
-			sym->st_value = elf_addr_to_cpu(sym->st_value);
-			sym->st_size  = elf_xword_to_cpu(sym->st_size);
-			sym->st_shndx = elf_half_to_cpu(sym->st_shndx);
 		}
 	}
 }
@@ -759,13 +810,14 @@ static void percpu_init(void)
  */
 static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
 {
-	return (sym->st_shndx == per_cpu_shndx) &&
+	int shndx = sym_index(sym);
+
+	return (shndx == per_cpu_shndx) &&
 		strcmp(symname, "__init_begin") &&
 		strcmp(symname, "__per_cpu_load") &&
 		strncmp(symname, "init_per_cpu_", 13);
 }
 
-
 static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 		      const char *symname)
 {
@@ -1088,7 +1140,7 @@ static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 		sec_name(sec->shdr.sh_info),
 		rel_type(ELF_R_TYPE(rel->r_info)),
 		symname,
-		sec_name(sym->st_shndx));
+		sec_name(sym_index(sym)));
 	return 0;
 }
 
-- 
2.20.1

[PATCH 3/9] x86/boot: Allow a "silent" kaslr random byte fetch

[Kristen Carlson Accardi]

From: Kees Cook <keescook@chromium.org>

Under earlyprintk, each RNG call produces a debug report line. When
shuffling hundreds of functions, this is not useful information (each
line is identical and tells us nothing new). Instead, allow for a NULL
"purpose" to suppress the debug reporting.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 arch/x86/lib/kaslr.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/lib/kaslr.c b/arch/x86/lib/kaslr.c
index a53665116458..2b3eb8c948a3 100644
--- a/arch/x86/lib/kaslr.c
+++ b/arch/x86/lib/kaslr.c
@@ -56,11 +56,14 @@ unsigned long kaslr_get_random_long(const char *purpose)
 	unsigned long raw, random = get_boot_seed();
 	bool use_i8254 = true;
 
-	debug_putstr(purpose);
-	debug_putstr(" KASLR using");
+	if (purpose) {
+		debug_putstr(purpose);
+		debug_putstr(" KASLR using");
+	}
 
 	if (has_cpuflag(X86_FEATURE_RDRAND)) {
-		debug_putstr(" RDRAND");
+		if (purpose)
+			debug_putstr(" RDRAND");
 		if (rdrand_long(&raw)) {
 			random ^= raw;
 			use_i8254 = false;
@@ -68,7 +71,8 @@ unsigned long kaslr_get_random_long(const char *purpose)
 	}
 
 	if (has_cpuflag(X86_FEATURE_TSC)) {
-		debug_putstr(" RDTSC");
+		if (purpose)
+			debug_putstr(" RDTSC");
 		raw = rdtsc();
 
 		random ^= raw;
@@ -76,7 +80,8 @@ unsigned long kaslr_get_random_long(const char *purpose)
 	}
 
 	if (use_i8254) {
-		debug_putstr(" i8254");
+		if (purpose)
+			debug_putstr(" i8254");
 		random ^= i8254();
 	}
 
@@ -86,7 +91,8 @@ unsigned long kaslr_get_random_long(const char *purpose)
 	    : "a" (random), "rm" (mix_const));
 	random += raw;
 
-	debug_putstr("...\n");
+	if (purpose)
+		debug_putstr("...\n");
 
 	return random;
 }
-- 
2.20.1

[PATCH 4/9] x86: Makefile: Add build and config option for CONFIG_FG_KASLR

[Kristen Carlson Accardi]

Allow user to select CONFIG_FG_KASLR if dependencies are met. Change
the make file to build with -ffunction-sections if CONFIG_FG_KASLR

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 Makefile         |  4 ++++
 arch/x86/Kconfig | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/Makefile b/Makefile
index 70def4907036..337b72787200 100644
--- a/Makefile
+++ b/Makefile
@@ -866,6 +866,10 @@ ifdef CONFIG_LIVEPATCH
 KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone)
 endif
 
+ifdef CONFIG_FG_KASLR
+KBUILD_CFLAGS += -ffunction-sections
+endif
+
 # arch Makefile may override CC so keep this after arch Makefile is included
 NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1d6104ea8af0..6aaece89f712 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2182,6 +2182,19 @@ config RANDOMIZE_BASE
 
 	  If unsure, say Y.
 
+config FG_KASLR
+	bool "Function Granular Kernel Address Space Layout Randomization"
+	depends on $(cc-option, -ffunction-sections)
+	depends on RANDOMIZE_BASE && X86_64
+	help
+	  This option improves the randomness of the kernel text
+	  over basic Kernel Address Space Layout Randomization (KASLR)
+	  by reordering the kernel text at boot time. This feature
+	  uses information generated at compile time to re-layout the
+	  kernel text section at boot time at function level granularity.
+
+	  If unsure, say N.
+
 # Relocation on x86 needs some additional build support
 config X86_NEED_RELOCS
 	def_bool y
-- 
2.20.1

[PATCH 5/9] x86: make sure _etext includes function sections

[Kristen Carlson Accardi]

We will be using -ffunction-sections to place each function in
it's own text section so it can be randomized at load time. The
linker considers these .text.* sections "orphaned sections", and
will place them after the first similar section (.text). However,
we need to move _etext so that it is after both .text and .text.*
We also need to calculate text size to include .text AND .text.*

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 arch/x86/kernel/vmlinux.lds.S     | 18 +++++++++++++++++-
 include/asm-generic/vmlinux.lds.h |  2 +-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 1bf7e312361f..044f7528a2f0 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -147,8 +147,24 @@ SECTIONS
 #endif
 	} :text =0xcccc
 
-	/* End of text section, which should occupy whole number of pages */
+#ifdef CONFIG_FG_KASLR
+	/*
+	 * -ffunction-sections creates .text.* sections, which are considered
+	 * "orphan sections" and added after the first similar section (.text).
+	 * Adding this ALIGN statement causes the address of _etext
+	 * to be below that of all the .text.* orphaned sections
+	 */
+	. = ALIGN(PAGE_SIZE);
+#endif
 	_etext = .;
+
+	/*
+	 * the size of the .text section is used to calculate the address
+	 * range for orc lookups. If we just use SIZEOF(.text), we will
+	 * miss all the .text.* sections. Calculate the size using _etext
+	 * and _stext and save the value for later.
+	 */
+	text_size = _etext - _stext;
 	. = ALIGN(PAGE_SIZE);
 
 	X86_ALIGN_RODATA_BEGIN
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 71e387a5fe90..f5baee74854c 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -813,7 +813,7 @@
 	. = ALIGN(4);							\
 	.orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) {		\
 		orc_lookup = .;						\
-		. += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) /	\
+		. += (((text_size + LOOKUP_BLOCK_SIZE - 1) /	\
 			LOOKUP_BLOCK_SIZE) + 1) * 4;			\
 		orc_lookup_end = .;					\
 	}
-- 
2.20.1

[PATCH 6/9] x86/tools: Adding relative relocs for randomized functions

[Kristen Carlson Accardi]

If we are randomizing function sections, we are going to need
to recalculate relative offsets for relocs that are either in
the randomized sections, or refer to the randomized sections.
Add code to detect whether a reloc satisifies these cases, and if
so, add them to the appropriate reloc list.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 arch/x86/boot/compressed/Makefile |  7 +++++-
 arch/x86/tools/relocs.c           | 41 ++++++++++++++++++++++++++++---
 arch/x86/tools/relocs.h           |  4 +--
 arch/x86/tools/relocs_common.c    | 14 +++++++----
 4 files changed, 54 insertions(+), 12 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 5f7c262bcc99..3a5a004498de 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -117,6 +117,11 @@ $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
 	$(call if_changed,check-and-link-vmlinux)
 
 OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
+
+ifdef CONFIG_FG_KASLR
+	RELOCS_ARGS += --fg-kaslr
+endif
+
 $(obj)/vmlinux.bin: vmlinux FORCE
 	$(call if_changed,objcopy)
 
@@ -124,7 +129,7 @@ targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relo
 
 CMD_RELOCS = arch/x86/tools/relocs
 quiet_cmd_relocs = RELOCS  $@
-      cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $<
+      cmd_relocs = $(CMD_RELOCS) $(RELOCS_ARGS) $< > $@;$(CMD_RELOCS) $(RELOCS_ARGS) --abs-relocs $<
 $(obj)/vmlinux.relocs: vmlinux FORCE
 	$(call if_changed,relocs)
 
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index a00dc133f109..33c7a0f5e22b 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -42,6 +42,8 @@ struct section {
 };
 static struct section *secs;
 
+static int fg_kaslr;
+
 static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 /*
  * Following symbols have been audited. There values are constant and do
@@ -818,6 +820,32 @@ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
 		strncmp(symname, "init_per_cpu_", 13);
 }
 
+static int is_function_section(struct section *sec)
+{
+	const char *name;
+
+	if (!fg_kaslr)
+		return 0;
+
+	name = sec_name(sec->shdr.sh_info);
+
+	return(!strncmp(name, ".text.", 6));
+}
+
+static int is_randomized_sym(ElfW(Sym) *sym)
+{
+	const char *name;
+
+	if (!fg_kaslr)
+		return 0;
+
+	if (sym->st_shndx > shnum)
+		return 0;
+
+	name = sec_name(sym_index(sym));
+	return(!strncmp(name, ".text.", 6));
+}
+
 static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 		      const char *symname)
 {
@@ -842,13 +870,17 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 	case R_X86_64_PC32:
 	case R_X86_64_PLT32:
 		/*
-		 * PC relative relocations don't need to be adjusted unless
-		 * referencing a percpu symbol.
+		 * we need to keep pc relative relocations for sections which
+		 * might be randomized, and for the percpu section.
+		 * We also need to keep relocations for any offset which might
+		 * reference an address in a section which has been randomized.
 		 *
 		 * NB: R_X86_64_PLT32 can be treated as R_X86_64_PC32.
 		 */
-		if (is_percpu_sym(sym, symname))
+		if (is_function_section(sec) || is_randomized_sym(sym) ||
+		    is_percpu_sym(sym, symname))
 			add_reloc(&relocs32neg, offset);
+
 		break;
 
 	case R_X86_64_PC64:
@@ -1158,8 +1190,9 @@ static void print_reloc_info(void)
 
 void process(FILE *fp, int use_real_mode, int as_text,
 	     int show_absolute_syms, int show_absolute_relocs,
-	     int show_reloc_info)
+	     int show_reloc_info, int fgkaslr)
 {
+	fg_kaslr = fgkaslr;
 	regex_init(use_real_mode);
 	read_ehdr(fp);
 	read_shdrs(fp);
diff --git a/arch/x86/tools/relocs.h b/arch/x86/tools/relocs.h
index 43c83c0fd22c..05504052c846 100644
--- a/arch/x86/tools/relocs.h
+++ b/arch/x86/tools/relocs.h
@@ -31,8 +31,8 @@ enum symtype {
 
 void process_32(FILE *fp, int use_real_mode, int as_text,
 		int show_absolute_syms, int show_absolute_relocs,
-		int show_reloc_info);
+		int show_reloc_info, int fg_kaslr);
 void process_64(FILE *fp, int use_real_mode, int as_text,
 		int show_absolute_syms, int show_absolute_relocs,
-		int show_reloc_info);
+		int show_reloc_info, int fg_kaslr);
 #endif /* RELOCS_H */
diff --git a/arch/x86/tools/relocs_common.c b/arch/x86/tools/relocs_common.c
index 6634352a20bc..513e67a84280 100644
--- a/arch/x86/tools/relocs_common.c
+++ b/arch/x86/tools/relocs_common.c
@@ -12,14 +12,13 @@ void die(char *fmt, ...)
 
 static void usage(void)
 {
-	die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode]" \
-	    " vmlinux\n");
+	die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode|--fg-kaslr] vmlinux\n");
 }
 
 int main(int argc, char **argv)
 {
 	int show_absolute_syms, show_absolute_relocs, show_reloc_info;
-	int as_text, use_real_mode;
+	int as_text, use_real_mode, fg_kaslr;
 	const char *fname;
 	FILE *fp;
 	int i;
@@ -30,6 +29,7 @@ int main(int argc, char **argv)
 	show_reloc_info = 0;
 	as_text = 0;
 	use_real_mode = 0;
+	fg_kaslr = 0;
 	fname = NULL;
 	for (i = 1; i < argc; i++) {
 		char *arg = argv[i];
@@ -54,6 +54,10 @@ int main(int argc, char **argv)
 				use_real_mode = 1;
 				continue;
 			}
+			if (strcmp(arg, "--fg-kaslr") == 0) {
+				fg_kaslr = 1;
+				continue;
+			}
 		}
 		else if (!fname) {
 			fname = arg;
@@ -75,11 +79,11 @@ int main(int argc, char **argv)
 	if (e_ident[EI_CLASS] == ELFCLASS64)
 		process_64(fp, use_real_mode, as_text,
 			   show_absolute_syms, show_absolute_relocs,
-			   show_reloc_info);
+			   show_reloc_info, fg_kaslr);
 	else
 		process_32(fp, use_real_mode, as_text,
 			   show_absolute_syms, show_absolute_relocs,
-			   show_reloc_info);
+			   show_reloc_info, fg_kaslr);
 	fclose(fp);
 	return 0;
 }
-- 
2.20.1

[PATCH 7/9] x86: Add support for function granular KASLR

[Kristen Carlson Accardi]

At boot time, find all the function sections that have separate .text
sections, shuffle them, and then copy them to new locations. Adjust
any relocations accordingly.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 Documentation/security/fgkaslr.rst       | 151 +++++
 Documentation/security/index.rst         |   1 +
 arch/x86/boot/compressed/Makefile        |   3 +
 arch/x86/boot/compressed/fgkaslr.c       | 809 +++++++++++++++++++++++
 arch/x86/boot/compressed/kaslr.c         |   7 +-
 arch/x86/boot/compressed/misc.c          | 107 ++-
 arch/x86/boot/compressed/misc.h          |  31 +
 arch/x86/boot/compressed/utils.c         |  12 +
 arch/x86/boot/compressed/vmlinux.symbols |  18 +
 arch/x86/include/asm/boot.h              |  15 +-
 include/uapi/linux/elf.h                 |   1 +
 11 files changed, 1139 insertions(+), 16 deletions(-)
 create mode 100644 Documentation/security/fgkaslr.rst
 create mode 100644 arch/x86/boot/compressed/fgkaslr.c
 create mode 100644 arch/x86/boot/compressed/utils.c
 create mode 100644 arch/x86/boot/compressed/vmlinux.symbols

diff --git a/Documentation/security/fgkaslr.rst b/Documentation/security/fgkaslr.rst
new file mode 100644
index 000000000000..d08a2fbdb475
--- /dev/null
+++ b/Documentation/security/fgkaslr.rst
@@ -0,0 +1,151 @@
+=====================================================================
+Function Granular Kernel Address Space Layout Randomization (fgkaslr)
+=====================================================================
+
+:Date: 6 April 2020
+:Author: Kristen Accardi
+
+Kernel Address Space Layout Randomization (KASLR) was merged into the kernel
+with the objective of increasing the difficulty of code reuse attacks. Code
+reuse attacks reused existing code snippets to get around existing memory
+protections. They exploit software bugs which expose addresses of useful code
+snippets to control the flow of execution for their own nefarious purposes.
+KASLR as it was originally implemented moves the entire kernel code text as a
+unit at boot time in order to make addresses less predictable. The order of the
+code within the segment is unchanged - only the base address is shifted. There
+are a few shortcomings to this algorithm.
+
+1. Low Entropy - there are only so many locations the kernel can fit in. This
+   means an attacker could guess without too much trouble.
+2. Knowledge of a single address can reveal the offset of the base address,
+   exposing all other locations for a published/known kernel image.
+3. Info leaks abound.
+
+Finer grained ASLR has been proposed as a way to make ASLR more resistant
+to info leaks. It is not a new concept at all, and there are many variations
+possible. Function reordering is an implementation of finer grained ASLR
+which randomizes the layout of an address space on a function level
+granularity. We use the term "fgkaslr" in this document to refer to the
+technique of function reordering when used with KASLR, as well as finer grained
+KASLR in general.
+
+Implementation Details
+======================
+
+The over-arching objective of the fgkaslr implementation is incremental
+improvement over what we already have, as well as something that can be
+merged and deployed with as little disruption to our existing kernel/ecosystem
+as possible. It is designed to work with the existing solution, and there are
+two main area where code changes occur: Build time, and Load time.
+
+Build time
+----------
+
+GCC has an option to place functions into individual .text sections. We can
+use this option to implement function reordering at load time. The final
+compiled vmlinux retains all the section headers, which can be used to help
+us find the address ranges of each function. Using this information and
+an expanded table of relocation addresses, we can shuffle the individual
+text sections immediately after decompression. You are probably asking
+yourself how this could possibly work given the number of tables of
+addresses that exist inside the kernel today for features such as exception
+handling and kprobes. Most of these tables generate relocations and
+require a simple update, and some tables that have assumptions about order
+require sorting after the update. In order to modify these tables, we
+preserve a few key symbols from the objcopy symbol stripping process for use
+after shuffling the text segments.
+
+Load time
+---------
+
+The boot kernel was modified to parse the vmlinux elf file after
+decompression to check for our interesting symbols that we kept, and to
+look for any .text.* sections to randomize. We then shuffle the sections
+and update any tables that need to be updated or resorted. The existing
+code which updated relocation addresses was modified to account for not
+just a fixed delta from the load address, but the offset that the function
+section was moved to. This requires inspection of each address to see if
+it was impacted by a randomization. In order to hide our new layout,
+symbols reported through /proc/kallsyms will be sorted by name alphabetically
+rather than by address.
+
+Security Considerations
+=======================
+
+The objective of this patch set is to improve a technology that is already
+merged into the kernel (KASLR). Obviously, this code is not a one stop
+shopping place for blocking code reuse attacks, but should instead be
+considered as one of several tools that can be used. In particular, this
+code is meant to make KASLR more effective in the presence of info leaks.
+A key point to note is that we are basically accepting that there are
+many and various ways to leak address today and in the future, and rather
+than assume that we can stop them all, we should find a method which makes
+individual info leaks less important. How much entropy we are adding to
+the existing entropy of standard KASLR will depend on a few variables.
+Firstly and most obviously, the number of functions you randomize matters.
+This implementation keeps the existing .text section for code that cannot be
+randomized - for example, because it was assembly code, or we opted out of
+randomization for performance reasons. The less sections to randomize, the
+less entropy. In addition, due to alignment (16 bytes for x86_64), the number
+of bits in a address that the attacker needs to guess is reduced, as the lower
+bits are identical.
+
+Performance Impact
+==================
+
+There are two areas where function reordering can impact performance: boot
+time latency, and run time performance.
+
+Boot time latency
+-----------------
+
+This implementation of finer grained KASLR impacts the boot time of the kernel
+in several places. It requires additional parsing of the kernel ELF file to
+obtain the section headers of the sections to be randomized. It calls the
+random number generator for each section to be randomized to determine that
+section's new memory location. It copies the decompressed kernel into a new
+area of memory to avoid corruption when laying out the newly randomized
+sections. It increases the number of relocations the kernel has to perform at
+boot time vs. standard KASLR, and it also requires a lookup on each address
+that needs to be relocated to see if it was in a randomized section and needs
+to be adjusted by a new offset. Finally, it re-sorts a few data tables that
+are required to be sorted by address.
+
+Booting a test VM on a modern, well appointed system showed an increase in
+latency of approximately 1 second.
+
+Run time
+--------
+
+The performance impact at run-time of function reordering varies by workload.
+Randomly reordering the functions will cause an increase in cache misses
+for some workloads. You should expect to see some workloads perform
+significantly worse under FGKASLR, while others stay the same or even
+mysteriously improve. In general, it will depend on the code flow whether or
+not finer grained KASLR will impact your workload, and how the underlying code
+was designed.
+
+Image Size
+==========
+
+fgkaslr increases the size of the kernel binary due to the extra section
+headers that are included, as well as the extra relocations that need to
+be added. You can expect fgkaslr to increase the size of the resulting
+vmlinux by about 3%, and the compressed image (bzImage) by 15%.
+
+Building
+========
+
+To enable fine grained KASLR, you need to have the following config options
+set (including all the ones you would use to build normal KASLR)
+
+``CONFIG_FG_KASLR=y``
+
+In addition, fgkaslr is only supported for the X86_64 architecture.
+
+Modules
+=======
+
+Modules are randomized similarly to the rest of the kernel by shuffling
+the sections at load time prior to moving them into memory. The module must
+also have been build with the -ffunction-sections compiler option.
diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst
index fc503dd689a7..5e370c409ad2 100644
--- a/Documentation/security/index.rst
+++ b/Documentation/security/index.rst
@@ -7,6 +7,7 @@ Security Documentation
 
    credentials
    IMA-templates
+   fgkaslr
    keys/index
    lsm
    lsm-development
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 3a5a004498de..0ad5a31f1f0a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -80,10 +80,12 @@ vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/kernel_info.o $(obj)/head_$(BITS).o
 
 vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
+vmlinux-objs-$(CONFIG_FG_KASLR) += $(obj)/utils.o
 ifdef CONFIG_X86_64
 	vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr_64.o
 	vmlinux-objs-y += $(obj)/mem_encrypt.o
 	vmlinux-objs-y += $(obj)/pgtable_64.o
+	vmlinux-objs-$(CONFIG_FG_KASLR) += $(obj)/fgkaslr.o
 endif
 
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
@@ -120,6 +122,7 @@ OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 
 ifdef CONFIG_FG_KASLR
 	RELOCS_ARGS += --fg-kaslr
+	OBJCOPYFLAGS += --keep-symbols=$(srctree)/$(src)/vmlinux.symbols
 endif
 
 $(obj)/vmlinux.bin: vmlinux FORCE
diff --git a/arch/x86/boot/compressed/fgkaslr.c b/arch/x86/boot/compressed/fgkaslr.c
new file mode 100644
index 000000000000..d45016840cdd
--- /dev/null
+++ b/arch/x86/boot/compressed/fgkaslr.c
@@ -0,0 +1,809 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fgkaslr.c
+ *
+ * This contains the routines needed to reorder the kernel text section
+ * at boot time.
+ */
+#include "misc.h"
+#include "error.h"
+#include "pgtable.h"
+#include "../string.h"
+#include "../voffset.h"
+#include <linux/sort.h>
+#include <linux/bsearch.h>
+#include "../../include/asm/extable.h"
+#include "../../include/asm/orc_types.h"
+
+/*
+ * Longest parameter of 'fgkaslr=' is 'off' right now, plus an extra '\0'
+ * for termination.
+ */
+#define MAX_FGKASLR_ARG_LENGTH 4
+int nofgkaslr;
+
+/*
+ * Use normal definitions of mem*() from string.c. There are already
+ * included header files which expect a definition of memset() and by
+ * the time we define memset macro, it is too late.
+ */
+#undef memcpy
+#undef memset
+#define memzero(s, n)	memset((s), 0, (n))
+#define memmove		memmove
+
+void *memmove(void *dest, const void *src, size_t n);
+
+static unsigned long percpu_start;
+static unsigned long percpu_end;
+
+static long kallsyms_names;
+static long kallsyms_offsets;
+static long kallsyms_num_syms;
+static long kallsyms_relative_base;
+static long kallsyms_markers;
+static long __start___ex_table_addr;
+static long __stop___ex_table_addr;
+static long _stext;
+static long _etext;
+static long _sinittext;
+static long _einittext;
+static long __start_orc_unwind_ip;
+static long __stop_orc_unwind_ip;
+static long __start_orc_unwind;
+static long __stop_orc_unwind;
+
+/* addresses in mapped address space */
+static int *base;
+static u8 *names;
+static unsigned long relative_base;
+static unsigned int *markers_addr;
+
+struct kallsyms_name {
+	u8 len;
+	u8 indecis[256];
+};
+struct kallsyms_name *names_table;
+
+struct orc_entry *cur_orc_table;
+int *cur_orc_ip_table;
+
+/*
+ * This is an array of pointers to sections headers for randomized sections
+ */
+Elf64_Shdr **sections;
+
+/*
+ * This is an array of all section headers, randomized or otherwise.
+ */
+Elf64_Shdr *sechdrs;
+
+/*
+ * The number of elements in the randomized section header array (sections)
+ */
+int sections_size;
+
+static bool is_text(long addr)
+{
+	if ((addr >= _stext && addr < _etext) ||
+	   (addr >= _sinittext && addr < _einittext))
+		return true;
+	return false;
+}
+
+bool is_percpu_addr(long pc, long offset)
+{
+	unsigned long ptr;
+	long address;
+
+	address = pc + offset + 4;
+
+	ptr = (unsigned long) address;
+
+	if (ptr >= percpu_start && ptr < percpu_end)
+		return true;
+
+	return false;
+}
+
+static int cmp_section_addr(const void *a, const void *b)
+{
+	unsigned long ptr = (unsigned long)a;
+	Elf64_Shdr *s = *(Elf64_Shdr **)b;
+	unsigned long end = s->sh_addr + s->sh_size;
+
+	if (ptr >= s->sh_addr && ptr < end)
+		return 0;
+
+	if (ptr < s->sh_addr)
+		return -1;
+
+	return 1;
+}
+
+/*
+ * Discover if the address is in a randomized section and if so, adjust
+ * by the saved offset.
+ */
+Elf64_Shdr *adjust_address(long *address)
+{
+	Elf64_Shdr **s;
+	Elf64_Shdr *shdr;
+
+	if (nofgkaslr)
+		return NULL;
+
+	s = bsearch((const void *)*address, sections, sections_size, sizeof(*s),
+			cmp_section_addr);
+	if (s != NULL) {
+		shdr = *s;
+		*address += shdr->sh_offset;
+		return shdr;
+	}
+
+	return NULL;
+}
+
+void adjust_relative_offset(long pc, long *value, Elf64_Shdr *section)
+{
+	Elf64_Shdr *s;
+	long address;
+
+	if (nofgkaslr)
+		return;
+
+	/*
+	 * sometimes we are updating a relative offset that would
+	 * normally be relative to the next instruction (such as a call).
+	 * In this case to calculate the target, you need to add 32bits to
+	 * the pc to get the next instruction value. However, sometimes
+	 * targets are just data that was stored in a table such as ksymtab
+	 * or cpu alternatives. In this case our target is not relative to
+	 * the next instruction.
+	 */
+
+	/*
+	 * Calculate the address that this offset would call.
+	 */
+	if (!is_text(pc))
+		address = pc + *value;
+	else
+		address = pc + *value + 4;
+
+	/*
+	 * if the address is in section that was randomized,
+	 * we need to adjust the offset.
+	 */
+	s = adjust_address(&address);
+	if (s != NULL)
+		*value += s->sh_offset;
+
+	/*
+	 * If the PC that this offset was calculated for was in a section
+	 * that has been randomized, the value needs to be adjusted by the
+	 * same amount as the randomized section was adjusted from it's original
+	 * location.
+	 */
+	if (section != NULL)
+		*value -= section->sh_offset;
+
+}
+
+static void kallsyms_swp(void *a, void *b, int size)
+{
+	int idx1, idx2;
+	int temp;
+	struct kallsyms_name name_a;
+
+	/* determine our index into the array */
+	idx1 = (int *)a - base;
+	idx2 = (int *)b - base;
+	temp = base[idx1];
+	base[idx1] = base[idx2];
+	base[idx2] = temp;
+
+	/* also swap the names table */
+	memcpy(&name_a, &names_table[idx1], sizeof(name_a));
+	memcpy(&names_table[idx1], &names_table[idx2],
+		sizeof(struct kallsyms_name));
+	memcpy(&names_table[idx2], &name_a, sizeof(struct kallsyms_name));
+}
+
+static int kallsyms_cmp(const void *a, const void *b)
+{
+	int addr_a, addr_b;
+	unsigned long uaddr_a, uaddr_b;
+
+	addr_a = *(int *)a;
+	addr_b = *(int *)b;
+
+	if (addr_a >= 0)
+		uaddr_a = addr_a;
+	if (addr_b >= 0)
+		uaddr_b = addr_b;
+
+	if (addr_a < 0)
+		uaddr_a = relative_base - 1 - addr_a;
+	if (addr_b < 0)
+		uaddr_b = relative_base - 1 - addr_b;
+
+	if (uaddr_b > uaddr_a)
+		return -1;
+
+	return 0;
+}
+
+static void deal_with_names(int num_syms)
+{
+	int num_bytes;
+	int i, j;
+	int offset;
+
+
+	/* we should have num_syms kallsyms_name entries */
+	num_bytes = num_syms * sizeof(*names_table);
+	names_table = malloc(num_syms * sizeof(*names_table));
+	if (names_table == NULL) {
+		debug_putstr("\nbytes requested: ");
+		debug_puthex(num_bytes);
+		error("\nunable to allocate space for names table\n");
+	}
+
+	/* read all the names entries */
+	offset = 0;
+	for (i = 0; i < num_syms; i++) {
+		names_table[i].len = names[offset];
+		offset++;
+		for (j = 0; j < names_table[i].len; j++) {
+			names_table[i].indecis[j] = names[offset];
+			offset++;
+		}
+	}
+}
+
+static void write_sorted_names(int num_syms)
+{
+	int i, j;
+	int offset = 0;
+	unsigned int *markers;
+
+	/*
+	 * we are going to need to regenerate the markers table, which is a
+	 * table of offsets into the compressed stream every 256 symbols.
+	 * this code copied almost directly from scripts/kallsyms.c
+	 */
+	markers = malloc(sizeof(unsigned int) * ((num_syms + 255) / 256));
+	if (!markers) {
+		debug_putstr("\nfailed to allocate heap space of ");
+		debug_puthex(((num_syms + 255) / 256));
+		debug_putstr(" bytes\n");
+		error("Unable to allocate space for markers table");
+	}
+
+	for (i = 0; i < num_syms; i++) {
+		if ((i & 0xFF) == 0)
+			markers[i >> 8] = offset;
+
+		names[offset] = (u8) names_table[i].len;
+		offset++;
+		for (j = 0; j < names_table[i].len; j++) {
+			names[offset] = (u8) names_table[i].indecis[j];
+			offset++;
+		}
+	}
+
+	/* write new markers table over old one */
+	for (i = 0; i < ((num_syms + 255) >> 8); i++)
+		markers_addr[i] = markers[i];
+
+	free(markers);
+	free(names_table);
+}
+
+static void sort_kallsyms(unsigned long map)
+{
+	int num_syms;
+	int i;
+
+	debug_putstr("\nRe-sorting kallsyms ...");
+
+	num_syms = *(int *)(kallsyms_num_syms + map);
+	base = (int *)(kallsyms_offsets + map);
+	relative_base = *(unsigned long *)(kallsyms_relative_base + map);
+	markers_addr = (unsigned int *)(kallsyms_markers + map);
+	names = (u8 *)(kallsyms_names + map);
+
+	/*
+	 * the kallsyms table was generated prior to any randomization.
+	 * it is a bunch of offsets from "relative base". In order for
+	 * us to check if a symbol has an address that was in a randomized
+	 * section, we need to reconstruct the address to it's original
+	 * value prior to handle_relocations.
+	 */
+	for (i = 0; i < num_syms; i++) {
+		unsigned long addr;
+		int new_base;
+
+		/*
+		 * according to kernel/kallsyms.c, positive offsets are absolute
+		 * values and negative offsets are relative to the base.
+		 */
+		if (base[i] >= 0)
+			addr = base[i];
+		else
+			addr = relative_base - 1 - base[i];
+
+		if (adjust_address(&addr)) {
+			/* here we need to recalcuate the offset */
+			new_base = relative_base - 1 - addr;
+			base[i] = new_base;
+		}
+	}
+
+	/*
+	 * here we need to read in all the kallsyms_names info
+	 * so that we can regenerate it.
+	 */
+	deal_with_names(num_syms);
+
+	sort(base, num_syms, sizeof(int), kallsyms_cmp, kallsyms_swp);
+
+	/* write the newly sorted names table over the old one */
+	write_sorted_names(num_syms);
+}
+
+#define ARCH_HAS_SEARCH_EXTABLE
+#include "../../../../lib/extable.c"
+
+static inline unsigned long
+ex_fixup_handler(const struct exception_table_entry *x)
+{
+	return ((unsigned long)&x->handler + x->handler);
+}
+
+static inline unsigned long
+ex_fixup_addr(const struct exception_table_entry *x)
+{
+	return ((unsigned long)&x->fixup + x->fixup);
+}
+
+static void update_ex_table(unsigned long map)
+{
+	struct exception_table_entry *start_ex_table = (struct exception_table_entry *) (__start___ex_table_addr + map);
+	struct exception_table_entry *stop_ex_table = (struct exception_table_entry *) (__stop___ex_table_addr + map);
+	int num_entries = (__stop___ex_table_addr - __start___ex_table_addr) / sizeof(struct exception_table_entry);
+	int i;
+
+	debug_putstr("\nUpdating exception table...\n");
+	for (i = 0; i < num_entries; i++) {
+		unsigned long insn = ex_to_insn(&start_ex_table[i]);
+		unsigned long fixup = ex_fixup_addr(&start_ex_table[i]);
+		unsigned long handler = ex_fixup_handler(&start_ex_table[i]);
+		unsigned long addr;
+		Elf64_Shdr *s;
+
+		/* check each address to see if it needs adjusting */
+		addr = insn - map;
+		s = adjust_address(&addr);
+		if (s != NULL)
+			start_ex_table[i].insn += s->sh_offset;
+
+		addr = fixup - map;
+		s = adjust_address(&addr);
+		if (s != NULL)
+			start_ex_table[i].fixup += s->sh_offset;
+
+		addr = handler - map;
+		s = adjust_address(&addr);
+		if (s != NULL)
+			start_ex_table[i].handler += s->sh_offset;
+	}
+}
+
+static void sort_ex_table(unsigned long map)
+{
+	struct exception_table_entry *start_ex_table = (struct exception_table_entry *) (__start___ex_table_addr + map);
+	struct exception_table_entry *stop_ex_table = (struct exception_table_entry *) (__stop___ex_table_addr + map);
+
+	debug_putstr("\nRe-sorting exception table...\n");
+
+	sort_extable(start_ex_table, stop_ex_table);
+}
+
+static inline unsigned long orc_ip(const int *ip)
+{
+	return (unsigned long)ip + *ip;
+}
+
+static void orc_sort_swap(void *_a, void *_b, int size)
+{
+	struct orc_entry *orc_a, *orc_b;
+	struct orc_entry orc_tmp;
+	int *a = _a, *b = _b, tmp;
+	int delta = _b - _a;
+
+	/* Swap the .orc_unwind_ip entries: */
+	tmp = *a;
+	*a = *b + delta;
+	*b = tmp - delta;
+
+	/* Swap the corresponding .orc_unwind entries: */
+	orc_a = cur_orc_table + (a - cur_orc_ip_table);
+	orc_b = cur_orc_table + (b - cur_orc_ip_table);
+	orc_tmp = *orc_a;
+	*orc_a = *orc_b;
+	*orc_b = orc_tmp;
+}
+
+static int orc_sort_cmp(const void *_a, const void *_b)
+{
+	struct orc_entry *orc_a;
+	const int *a = _a, *b = _b;
+	unsigned long a_val = orc_ip(a);
+	unsigned long b_val = orc_ip(b);
+
+	if (a_val > b_val)
+		return 1;
+	if (a_val < b_val)
+		return -1;
+
+	/*
+	 * The "weak" section terminator entries need to always be on the left
+	 * to ensure the lookup code skips them in favor of real entries.
+	 * These terminator entries exist to handle any gaps created by
+	 * whitelisted .o files which didn't get objtool generation.
+	 */
+	orc_a = cur_orc_table + (a - cur_orc_ip_table);
+	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+}
+
+static void sort_orc_table(unsigned long map)
+{
+	int num_entries = (__stop_orc_unwind_ip - __start_orc_unwind_ip) / sizeof(int);
+
+	cur_orc_ip_table = (int *)(__start_orc_unwind_ip + map);
+	cur_orc_table = (struct orc_entry *)(__start_orc_unwind + map);
+
+	debug_putstr("\nRe-sorting orc tables...\n");
+	sort(cur_orc_ip_table, num_entries, sizeof(int),
+		orc_sort_cmp, orc_sort_swap);
+}
+
+void post_relocations_cleanup(unsigned long map)
+{
+	if (!nofgkaslr) {
+		update_ex_table(map);
+		sort_ex_table(map);
+		sort_orc_table(map);
+	}
+
+	/*
+	 * maybe one day free will do something. So, we "free" this memory
+	 * in either case
+	 */
+	free(sections);
+	free(sechdrs);
+}
+
+void pre_relocations_cleanup(unsigned long map)
+{
+	if (nofgkaslr)
+		return;
+
+	sort_kallsyms(map);
+}
+
+static void shuffle_sections(int *list, int size)
+{
+	int i;
+	unsigned long j;
+	int temp;
+
+	for (i = size - 1; i > 0; i--) {
+		j = kaslr_get_random_long(NULL) % (i + 1);
+
+		temp = list[i];
+		list[i] = list[j];
+		list[j] = temp;
+	}
+}
+
+static void move_text(int num_sections, char *secstrings, Elf64_Shdr *text,
+			void *source, void *dest, Elf64_Phdr *phdr)
+{
+	unsigned long adjusted_addr;
+	int copy_bytes;
+	void *stash;
+	Elf64_Shdr **sorted_sections;
+	int *index_list;
+
+	memmove(dest, source + text->sh_offset, text->sh_size);
+	copy_bytes = text->sh_size;
+	dest += text->sh_size;
+	adjusted_addr = text->sh_addr + text->sh_size;
+
+	/*
+	 * we leave the sections sorted in their original order
+	 * by s->sh_addr, but shuffle the indexes in a random
+	 * order for copying.
+	 */
+	index_list = malloc(sizeof(int) * num_sections);
+	if (!index_list)
+		error("Failed to allocate space for index list");
+
+	for (int i = 0; i < num_sections; i++)
+		index_list[i] = i;
+
+	shuffle_sections(index_list, num_sections);
+
+	/*
+	 * to avoid overwriting earlier sections before they can get
+	 * copied to dest, stash everything into a buffer first.
+	 * this will cause our source address to be off by
+	 * phdr->p_offset though, so we'll adjust s->sh_offset below.
+	 *
+	 * TBD: ideally we'd simply decompress higher up so that our
+	 * copy wasn't in danger of overwriting anything important.
+	 */
+	stash = malloc(phdr->p_filesz);
+	if (!stash)
+		error("Failed to allocate space for text stash");
+
+	memcpy(stash, source + phdr->p_offset, phdr->p_filesz);
+
+	/* now we'd walk through the sections. */
+	for (int j = 0; j < num_sections; j++) {
+		unsigned long aligned_addr;
+		Elf64_Shdr *s;
+		const char *sname;
+		void *src;
+		int pad_bytes;
+
+		s = sections[index_list[j]];
+
+		sname = secstrings + s->sh_name;
+
+		/* align addr for this section */
+		aligned_addr = ALIGN(adjusted_addr, s->sh_addralign);
+
+		/*
+		 * copy out of stash, so adjust offset
+		 */
+		src = stash + s->sh_offset - phdr->p_offset;
+
+		/*
+		 * Fill any space between sections with int3
+		 */
+		pad_bytes = aligned_addr - adjusted_addr;
+		for (int i = 0; i < pad_bytes; i++)
+			((u8 *)dest)[i] = 0xcc;
+
+		dest = (void *) ALIGN((unsigned long)dest, s->sh_addralign);
+
+		memmove(dest, src, s->sh_size);
+
+		dest += s->sh_size;
+		copy_bytes += s->sh_size + pad_bytes;
+		adjusted_addr = aligned_addr + s->sh_size;
+
+		/* we can blow away sh_offset for our own uses */
+		s->sh_offset = aligned_addr - s->sh_addr;
+	}
+
+	free(index_list);
+
+	/*
+	 * move remainder of text segment. Ok to just use original source
+	 * here since this area is untouched.
+	 */
+	memmove(dest, source + text->sh_offset + copy_bytes,
+		phdr->p_filesz - copy_bytes);
+	free(stash);
+}
+
+#define GET_SYM(name) \
+	do { \
+		if (strcmp(#name, strtab + sym->st_name) == 0) {\
+			name = sym->st_value;			\
+			continue;				\
+		}						\
+	} while (0)
+
+static void parse_symtab(Elf64_Sym *symtab, char *strtab, long num_syms)
+{
+	Elf64_Sym *sym;
+
+	if (symtab == NULL || strtab == NULL)
+		return;
+
+	debug_putstr("\nLooking for symbols... ");
+
+	/*
+	 * walk through the symbol table looking for the symbols
+	 * that we care about.
+	 */
+	for (sym = symtab; --num_syms >= 0; sym++) {
+		if (!sym->st_name)
+			continue;
+
+		GET_SYM(kallsyms_num_syms);
+		GET_SYM(kallsyms_offsets);
+		GET_SYM(kallsyms_relative_base);
+		GET_SYM(kallsyms_names);
+		GET_SYM(kallsyms_markers);
+		GET_SYM(_stext);
+		GET_SYM(_etext);
+		GET_SYM(_sinittext);
+		GET_SYM(_einittext);
+		GET_SYM(__start_orc_unwind_ip);
+		GET_SYM(__stop_orc_unwind_ip);
+		GET_SYM(__start_orc_unwind);
+		GET_SYM(__stop_orc_unwind);
+
+		/* these have to be renamed */
+		if (strcmp("__start___ex_table", strtab + sym->st_name) == 0) {
+			 __start___ex_table_addr = sym->st_value;
+			continue;
+		}
+
+		if (strcmp("__stop___ex_table", strtab + sym->st_name) == 0) {
+			 __stop___ex_table_addr = sym->st_value;
+			continue;
+		}
+	}
+}
+
+void parse_sections_headers(void *output, Elf64_Ehdr *ehdr, Elf64_Phdr *phdrs)
+{
+	Elf64_Phdr *phdr;
+	Elf64_Shdr *s;
+	Elf64_Shdr *text = NULL;
+	Elf64_Shdr *percpu = NULL;
+	char *secstrings;
+	const char *sname;
+	int num_sections = 0;
+	Elf64_Sym *symtab = NULL;
+	char *strtab = NULL;
+	long num_syms = 0;
+	void *dest;
+	int i;
+	char arg[MAX_FGKASLR_ARG_LENGTH];
+	Elf64_Shdr shdr;
+	unsigned long shnum;
+	unsigned int shstrndx;
+
+	debug_putstr("\nParsing ELF section headers... ");
+
+	/*
+	 * Even though fgkaslr may have been disabled, we still
+	 * need to parse through the section headers to get the
+	 * start and end of the percpu section. This is because
+	 * if we were built with CONFIG_FG_KASLR, there are more
+	 * relative relocations present in vmlinux.relocs than
+	 * just the percpu, and only the percpu relocs need to be
+	 * adjusted when using just normal base address kaslr.
+	 */
+	if (cmdline_find_option("fgkaslr", arg, sizeof(arg)) == 3 &&
+		!strncmp(arg, "off", 3)) {
+		warn("FG_KASLR disabled on cmdline.");
+		nofgkaslr = 1;
+	}
+
+	/* read the first section header */
+	shnum = ehdr->e_shnum;
+	shstrndx = ehdr->e_shstrndx;
+	if (shnum == SHN_UNDEF || shstrndx == SHN_XINDEX) {
+		memcpy(&shdr, output + ehdr->e_shoff, sizeof(shdr));
+		if (shnum == SHN_UNDEF)
+			shnum = shdr.sh_size;
+		if (shstrndx == SHN_XINDEX)
+			shstrndx = shdr.sh_link;
+	}
+
+	/* we are going to need to allocate space for the section headers */
+	sechdrs = malloc(sizeof(*sechdrs) * shnum);
+	if (!sechdrs)
+		error("Failed to allocate space for shdrs");
+
+	sections = malloc(sizeof(*sections) * shnum);
+	if (!sections)
+		error("Failed to allocate space for section pointers");
+
+	memcpy(sechdrs, output + ehdr->e_shoff,
+		sizeof(*sechdrs) * shnum);
+
+	/* we need to allocate space for the section string table */
+	s = &sechdrs[shstrndx];
+
+	secstrings = malloc(s->sh_size);
+	if (!secstrings)
+		error("Failed to allocate space for shstr");
+
+	memcpy(secstrings, output + s->sh_offset, s->sh_size);
+
+	/*
+	 * now we need to walk through the section headers and collect the
+	 * sizes of the .text sections to be randomized.
+	 */
+	for (i = 0; i < shnum; i++) {
+		s = &sechdrs[i];
+		sname = secstrings + s->sh_name;
+
+		if (s->sh_type == SHT_SYMTAB) {
+			/* only one symtab per image */
+			symtab = malloc(s->sh_size);
+			if (!symtab)
+				error("Failed to allocate space for symtab");
+
+			memcpy(symtab, output + s->sh_offset, s->sh_size);
+			num_syms = s->sh_size/sizeof(*symtab);
+			continue;
+		}
+
+		if (s->sh_type == SHT_STRTAB && (i != ehdr->e_shstrndx)) {
+			strtab = malloc(s->sh_size);
+			if (!strtab)
+				error("Failed to allocate space for strtab");
+
+			memcpy(strtab, output + s->sh_offset, s->sh_size);
+		}
+
+		if (!strcmp(sname, ".text")) {
+			text = s;
+			continue;
+		}
+
+		if (!strcmp(sname, ".data..percpu")) {
+			/* get start addr for later */
+			percpu = s;
+		}
+
+		if (!(s->sh_flags & SHF_ALLOC) ||
+		    !(s->sh_flags & SHF_EXECINSTR) ||
+		    !(strstarts(sname, ".text")))
+			continue;
+
+		sections[num_sections] = s;
+
+		num_sections++;
+	}
+	sections[num_sections] = NULL;
+	sections_size = num_sections;
+
+	parse_symtab(symtab, strtab, num_syms);
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		phdr = &phdrs[i];
+
+		switch (phdr->p_type) {
+		case PT_LOAD:
+			if ((phdr->p_align % 0x200000) != 0)
+				error("Alignment of LOAD segment isn't multiple of 2MB");
+			dest = output;
+			dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR);
+			if (!nofgkaslr &&
+			    (text && (phdr->p_offset == text->sh_offset))) {
+				move_text(num_sections, secstrings, text,
+					  output, dest, phdr);
+			} else {
+				if (percpu &&
+				    (phdr->p_offset == percpu->sh_offset)) {
+					percpu_start = percpu->sh_addr;
+					percpu_end = percpu_start +
+							phdr->p_filesz;
+				}
+				memmove(dest, output + phdr->p_offset,
+					phdr->p_filesz);
+			}
+			break;
+		default: /* Ignore other PT_* */
+			break;
+		}
+	}
+
+	/* we need to keep the section info to redo relocs */
+	free(secstrings);
+
+	free(phdrs);
+}
+
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index d7408af55738..07ef5d2ea49a 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -39,10 +39,6 @@
 #include <generated/utsrelease.h>
 #include <asm/efi.h>
 
-/* Macros used by the included decompressor code below. */
-#define STATIC
-#include <linux/decompress/mm.h>
-
 #ifdef CONFIG_X86_5LEVEL
 unsigned int __pgtable_l5_enabled;
 unsigned int pgdir_shift __ro_after_init = 39;
@@ -897,7 +893,8 @@ void choose_random_location(unsigned long input,
 {
 	unsigned long random_addr, min_addr;
 
-	if (cmdline_find_option_bool("nokaslr")) {
+	nokaslr = cmdline_find_option_bool("nokaslr");
+	if (nokaslr) {
 		warn("KASLR disabled: 'nokaslr' on cmdline.");
 		return;
 	}
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 9652d5c2afda..2e108fdc7757 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -26,9 +26,6 @@
  * it is not safe to place pointers in static structures.
  */
 
-/* Macros used by the included decompressor code below. */
-#define STATIC		static
-
 /*
  * Use normal definitions of mem*() from string.c. There are already
  * included header files which expect a definition of memset() and by
@@ -49,6 +46,8 @@ struct boot_params *boot_params;
 
 memptr free_mem_ptr;
 memptr free_mem_end_ptr;
+unsigned long malloc_ptr;
+int malloc_count;
 
 static char *vidmem;
 static int vidport;
@@ -203,10 +202,20 @@ static void handle_relocations(void *output, unsigned long output_len,
 	if (IS_ENABLED(CONFIG_X86_64))
 		delta = virt_addr - LOAD_PHYSICAL_ADDR;
 
-	if (!delta) {
-		debug_putstr("No relocation needed... ");
-		return;
+	/*
+	 * it is possible to have delta be zero and
+	 * still have enabled fg kaslr. We need to perform relocations
+	 * for fgkaslr regardless of whether the base address has moved.
+	 */
+	if (!IS_ENABLED(CONFIG_FG_KASLR) || nokaslr) {
+		if (!delta) {
+			debug_putstr("No relocation needed... ");
+			return;
+		}
 	}
+
+	pre_relocations_cleanup(map);
+
 	debug_putstr("Performing relocations... ");
 
 	/*
@@ -230,35 +239,106 @@ static void handle_relocations(void *output, unsigned long output_len,
 	 */
 	for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
 		long extended = *reloc;
+		long value;
+
+		/*
+		 * if using fgkaslr, we might have moved the address
+		 * of the relocation. Check it to see if it needs adjusting
+		 * from the original address.
+		 */
+		(void) adjust_address(&extended);
+
 		extended += map;
 
 		ptr = (unsigned long)extended;
 		if (ptr < min_addr || ptr > max_addr)
 			error("32-bit relocation outside of kernel!\n");
 
-		*(uint32_t *)ptr += delta;
+		value = *(int32_t *)ptr;
+
+		/*
+		 * If using fgkaslr, the value of the relocation
+		 * might need to be changed because it referred
+		 * to an address that has moved.
+		 */
+		adjust_address(&value);
+
+		value += delta;
+
+		*(uint32_t *)ptr = value;
 	}
 #ifdef CONFIG_X86_64
 	while (*--reloc) {
 		long extended = *reloc;
+		long value;
+		long oldvalue;
+		Elf64_Shdr *s;
+
+		/*
+		 * if using fgkaslr, we might have moved the address
+		 * of the relocation. Check it to see if it needs adjusting
+		 * from the original address.
+		 */
+		s = adjust_address(&extended);
+
 		extended += map;
 
 		ptr = (unsigned long)extended;
 		if (ptr < min_addr || ptr > max_addr)
 			error("inverse 32-bit relocation outside of kernel!\n");
 
-		*(int32_t *)ptr -= delta;
+		value = *(int32_t *)ptr;
+		oldvalue = value;
+
+		/*
+		 * If using fgkaslr, these relocs will contain
+		 * relative offsets which might need to be
+		 * changed because it referred
+		 * to an address that has moved.
+		 */
+		adjust_relative_offset(*reloc, &value, s);
+
+		/*
+		 * only percpu symbols need to have their values adjusted for
+		 * base address kaslr since relative offsets within the .text
+		 * and .text.* sections are ok wrt each other.
+		 */
+		if (is_percpu_addr(*reloc, oldvalue))
+			value -= delta;
+
+		*(int32_t *)ptr = value;
 	}
 	for (reloc--; *reloc; reloc--) {
 		long extended = *reloc;
+		long value;
+
+		/*
+		 * if using fgkaslr, we might have moved the address
+		 * of the relocation. Check it to see if it needs adjusting
+		 * from the original address.
+		 */
+		(void) adjust_address(&extended);
+
 		extended += map;
 
 		ptr = (unsigned long)extended;
 		if (ptr < min_addr || ptr > max_addr)
 			error("64-bit relocation outside of kernel!\n");
 
-		*(uint64_t *)ptr += delta;
+		value = *(int64_t *)ptr;
+
+		/*
+		 * If using fgkaslr, the value of the relocation
+		 * might need to be changed because it referred
+		 * to an address that has moved.
+		 */
+		(void) adjust_address(&value);
+
+		value += delta;
+
+		*(uint64_t *)ptr = value;
 	}
+	post_relocations_cleanup(map);
 #endif
 }
 #else
@@ -296,6 +376,15 @@ static void parse_elf(void *output)
 
 	memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
 
+	if (IS_ENABLED(CONFIG_FG_KASLR)) {
+		if (!nokaslr) {
+			parse_sections_headers(output, &ehdr, phdrs);
+			return;
+		} else {
+			warn("FG_KASLR disabled: 'nokaslr' on cmdline.");
+		}
+	}
+
 	for (i = 0; i < ehdr.e_phnum; i++) {
 		phdr = &phdrs[i];
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 726e264410ff..f68f7fc39543 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -39,7 +39,12 @@
 /* misc.c */
 extern memptr free_mem_ptr;
 extern memptr free_mem_end_ptr;
+#define STATIC
+#define STATIC_RW_DATA extern
+#include <linux/decompress/mm.h>
+
 extern struct boot_params *boot_params;
+extern int nokaslr;
 void __putstr(const char *s);
 void __puthex(unsigned long value);
 #define error_putstr(__x)  __putstr(__x)
@@ -74,6 +79,32 @@ struct mem_vector {
 	unsigned long long size;
 };
 
+#ifdef CONFIG_X86_64
+#define Elf_Ehdr Elf64_Ehdr
+#define Elf_Phdr Elf64_Phdr
+#define Elf_Shdr Elf64_Shdr
+#else
+#define Elf_Ehdr Elf32_Ehdr
+#define Elf_Phdr Elf32_Phdr
+#define Elf_Shdr Elf32_Shdr
+#endif
+
+#if CONFIG_FG_KASLR
+void parse_sections_headers(void *output, Elf_Ehdr *ehdr, Elf_Phdr *phdrs);
+void pre_relocations_cleanup(unsigned long map);
+void post_relocations_cleanup(unsigned long map);
+Elf_Shdr *adjust_address(long *address);
+void adjust_relative_offset(long pc, long *value, Elf_Shdr *section);
+bool is_percpu_addr(long pc, long offset);
+#else
+static inline void parse_sections_headers(void *output, Elf_Ehdr *ehdr, Elf_Phdr *phdrs) { }
+static inline void pre_relocations_cleanup(unsigned long map) { }
+static inline void post_relocations_cleanup(unsigned long map) { }
+static inline Elf_Shdr *adjust_address(long *address) { return NULL; }
+static inline void adjust_relative_offset(long pc, long *value, Elf_Shdr *section) { }
+static inline bool is_percpu_addr(long pc, long offset) { return true; }
+#endif /* CONFIG_FG_KASLR */
+
 #if CONFIG_RANDOMIZE_BASE
 /* kaslr.c */
 void choose_random_location(unsigned long input,
diff --git a/arch/x86/boot/compressed/utils.c b/arch/x86/boot/compressed/utils.c
new file mode 100644
index 000000000000..ceefc58d7c71
--- /dev/null
+++ b/arch/x86/boot/compressed/utils.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * utils.c
+ *
+ * This contains various libraries that are needed for fgkaslr
+ */
+#define __DISABLE_EXPORTS
+#define _LINUX_KPROBES_H
+#define NOKPROBE_SYMBOL(fname)
+#include "../../../../lib/sort.c"
+#include "../../../../lib/bsearch.c"
+
diff --git a/arch/x86/boot/compressed/vmlinux.symbols b/arch/x86/boot/compressed/vmlinux.symbols
new file mode 100644
index 000000000000..f48a4c396966
--- /dev/null
+++ b/arch/x86/boot/compressed/vmlinux.symbols
@@ -0,0 +1,18 @@
+kallsyms_offsets
+kallsyms_addresses
+kallsyms_num_syms
+kallsyms_relative_base
+kallsyms_names
+kallsyms_token_table
+kallsyms_token_index
+kallsyms_markers
+__start___ex_table
+__stop___ex_table
+_sinittext
+_einittext
+_stext
+_etext
+__start_orc_unwind_ip
+__stop_orc_unwind_ip
+__stop_orc_unwind
+__start_orc_unwind
diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
index 680c320363db..6918d33eb5ef 100644
--- a/arch/x86/include/asm/boot.h
+++ b/arch/x86/include/asm/boot.h
@@ -26,8 +26,19 @@
 
 #ifdef CONFIG_KERNEL_BZIP2
 # define BOOT_HEAP_SIZE		0x400000
-#else /* !CONFIG_KERNEL_BZIP2 */
-# define BOOT_HEAP_SIZE		 0x10000
+#elif CONFIG_FG_KASLR
+/*
+ * We need extra boot heap when using fgkaslr because we make a copy
+ * of the original decompressed kernel to avoid issues with writing
+ * over ourselves when shuffling the sections. We also need extra
+ * space for resorting kallsyms after shuffling. This value could
+ * be decreased if free() would release memory properly, or if we
+ * could avoid the kernel copy. It would need to be increased if we
+ * find additional tables that need to be resorted.
+ */
+# define BOOT_HEAP_SIZE		0x4000000
+#else /* !CONFIG_KERNEL_BZIP2 && !CONFIG_FG_KASLR */
+# define BOOT_HEAP_SIZE		0x10000
 #endif
 
 #ifdef CONFIG_X86_64
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 34c02e4290fe..a85d1792d5a8 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -298,6 +298,7 @@ typedef struct elf64_phdr {
 #define SHN_LIVEPATCH	0xff20
 #define SHN_ABS		0xfff1
 #define SHN_COMMON	0xfff2
+#define SHN_XINDEX	0xffff
 #define SHN_HIRESERVE	0xffff
  
 typedef struct elf32_shdr {
-- 
2.20.1

[PATCH 8/9] kallsyms: hide layout

[Kristen Carlson Accardi]

To support finer grained kaslr (fgkaslr), we need to hide our sorted
list of symbols, since this will give away our new layout.
This patch makes /proc/kallsyms only visible to priviledged users.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 kernel/kallsyms.c | 138 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 137 insertions(+), 1 deletion(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 16c8c605f4b0..861972b6a879 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -25,6 +25,7 @@
 #include <linux/filter.h>
 #include <linux/ftrace.h>
 #include <linux/compiler.h>
+#include <linux/list_sort.h>
 
 /*
  * These will be re-linked against their real values
@@ -446,6 +447,11 @@ struct kallsym_iter {
 	int show_value;
 };
 
+struct kallsyms_iter_list {
+	struct kallsym_iter iter;
+	struct list_head next;
+};
+
 int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
 			    char *type, char *name)
 {
@@ -660,6 +666,121 @@ int kallsyms_show_value(void)
 	}
 }
 
+static int sorted_show(struct seq_file *m, void *p)
+{
+	struct list_head *list = m->private;
+	struct kallsyms_iter_list *iter;
+	int rc;
+
+	if (list_empty(list))
+		return 0;
+
+	iter = list_first_entry(list, struct kallsyms_iter_list, next);
+
+	m->private = iter;
+	rc = s_show(m, p);
+	m->private = list;
+
+	list_del(&iter->next);
+	kfree(iter);
+
+	return rc;
+}
+
+static void *sorted_start(struct seq_file *m, loff_t *pos)
+{
+	return m->private;
+}
+
+static void *sorted_next(struct seq_file *m, void *p, loff_t *pos)
+{
+	struct list_head *list = m->private;
+
+	(*pos)++;
+
+	if (list_empty(list))
+		return NULL;
+
+	return p;
+}
+
+static const struct seq_operations kallsyms_sorted_op = {
+	.start = sorted_start,
+	.next = sorted_next,
+	.stop = s_stop,
+	.show = sorted_show
+};
+
+static int kallsyms_list_cmp(void *priv, struct list_head *a,
+				struct list_head *b)
+{
+	struct kallsyms_iter_list *iter_a, *iter_b;
+
+	iter_a = list_entry(a, struct kallsyms_iter_list, next);
+	iter_b = list_entry(b, struct kallsyms_iter_list, next);
+
+	return strcmp(iter_a->iter.name, iter_b->iter.name);
+}
+
+int get_all_symbol_name(void *data, const char *name, struct module *mod,
+			unsigned long addr)
+{
+	unsigned long sym_pos;
+	struct kallsyms_iter_list *node, *last;
+	struct list_head *head = (struct list_head *)data;
+
+	node = kmalloc(sizeof(*node), GFP_KERNEL);
+	if (!node)
+		return -ENOMEM;
+
+	if (list_empty(head)) {
+		sym_pos = 0;
+		memset(node, 0, sizeof(*node));
+		reset_iter(&node->iter, 0);
+		node->iter.show_value = kallsyms_show_value();
+	} else {
+		last = list_first_entry(head, struct kallsyms_iter_list, next);
+		memcpy(node, last, sizeof(*node));
+		sym_pos = last->iter.pos;
+	}
+
+	INIT_LIST_HEAD(&node->next);
+	list_add(&node->next, head);
+
+	/*
+	 * update_iter returns false when at end of file
+	 * which in this case we don't care about and can
+	 * safely ignore. update_iter() will increment
+	 * the value of iter->pos, for ksymbol_core.
+	 */
+	if (sym_pos >= kallsyms_num_syms)
+		sym_pos++;
+
+	(void) update_iter(&node->iter, sym_pos);
+
+	return 0;
+}
+
+static int kallsyms_sorted_open(struct inode *inode, struct file *file)
+{
+	int ret;
+	struct list_head *list;
+
+	list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list));
+	if (!list)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(list);
+
+	ret = kallsyms_on_each_symbol(get_all_symbol_name, list);
+	if (ret != 0)
+		return ret;
+
+	list_sort(NULL, list, kallsyms_list_cmp);
+
+	return 0;
+}
+
 static int kallsyms_open(struct inode *inode, struct file *file)
 {
 	/*
@@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = {
 	.proc_release	= seq_release_private,
 };
 
+static const struct proc_ops kallsyms_sorted_proc_ops = {
+	.proc_open = kallsyms_sorted_open,
+	.proc_read = seq_read,
+	.proc_lseek = seq_lseek,
+	.proc_release = seq_release_private,
+};
+
 static int __init kallsyms_init(void)
 {
-	proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
+	/*
+	 * When fine grained kaslr is enabled, we need to
+	 * print out the symbols sorted by name rather than by
+	 * by address, because this reveals the randomization order.
+	 */
+	if (!IS_ENABLED(CONFIG_FG_KASLR))
+		proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
+	else
+		proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops);
 	return 0;
 }
 device_initcall(kallsyms_init);
-- 
2.20.1

[PATCH 9/9] module: Reorder functions

[Kristen Carlson Accardi]

If a module has functions split out into separate text sections
(i.e. compiled with the -ffunction-sections flag), reorder the
functions to provide some code diversification to modules.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 kernel/module.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 646f1e2330d2..e432ec5f6df4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -53,6 +53,8 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/random.h>
+#include <asm/setup.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
@@ -2370,6 +2372,83 @@ static long get_offset(struct module *mod, unsigned int *size,
 	return ret;
 }
 
+/*
+ * shuffle_text_list()
+ * Use a Fisher Yates algorithm to shuffle a list of text sections.
+ */
+static void shuffle_text_list(Elf_Shdr **list, int size)
+{
+	int i;
+	unsigned int j;
+	Elf_Shdr *temp;
+
+	for (i = size - 1; i > 0; i--) {
+		/*
+		 * pick a random index from 0 to i
+		 */
+		get_random_bytes(&j, sizeof(j));
+		j = j % (i + 1);
+
+		temp = list[i];
+		list[i] = list[j];
+		list[j] = temp;
+	}
+}
+
+/*
+ * randomize_text()
+ * Look through the core section looking for executable code sections.
+ * Store sections in an array and then shuffle the sections
+ * to reorder the functions.
+ */
+static void randomize_text(struct module *mod, struct load_info *info)
+{
+	int i;
+	int num_text_sections = 0;
+	Elf_Shdr **text_list;
+	int size = 0;
+	int max_sections = info->hdr->e_shnum;
+	unsigned int sec = find_sec(info, ".text");
+
+	if (sec == 0)
+		return;
+
+	text_list = kmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL);
+	if (text_list == NULL)
+		return;
+
+	for (i = 0; i < max_sections; i++) {
+		Elf_Shdr *shdr = &info->sechdrs[i];
+		const char *sname = info->secstrings + shdr->sh_name;
+
+		if (!(shdr->sh_flags & SHF_ALLOC) ||
+		    !(shdr->sh_flags & SHF_EXECINSTR) ||
+		    strstarts(sname, ".init"))
+			continue;
+
+		text_list[num_text_sections] = shdr;
+		num_text_sections++;
+	}
+
+	shuffle_text_list(text_list, num_text_sections);
+
+	for (i = 0; i < num_text_sections; i++) {
+		Elf_Shdr *shdr = text_list[i];
+
+		/*
+		 * get_offset has a section index for it's last
+		 * argument, that is only used by arch_mod_section_prepend(),
+		 * which is only defined by parisc. Since this this type
+		 * of randomization isn't supported on parisc, we can
+		 * safely pass in zero as the last argument, as it is
+		 * ignored.
+		 */
+		shdr->sh_entsize = get_offset(mod, &size, shdr, 0);
+	}
+
+	kfree(text_list);
+}
+
 /* Lay out the SHF_ALLOC sections in a way not dissimilar to how ld
    might -- code, read-only data, read-write data, small data.  Tally
    sizes, and place the offsets into sh_entsize fields: high bit means it
@@ -2460,6 +2539,9 @@ static void layout_sections(struct module *mod, struct load_info *info)
 			break;
 		}
 	}
+
+	if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())
+		randomize_text(mod, info);
 }
 
 static void set_license(struct module *mod, const char *license)
-- 
2.20.1

Re: [PATCH 7/9] x86: Add support for function granular KASLR

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1851 bytes --]

Hi Kristen,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kees/for-next/pstore]
[also build test ERROR on tip/auto-latest linus/master tip/x86/core v5.7-rc1 next-20200415]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Kristen-Carlson-Accardi/Function-Granular-Kernel-Address-Space-Layout-Randomization/20200416-072741
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/pstore
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   ld: arch/x86/boot/compressed/misc.o: in function `index_update.isra.12':
>> misc.c:(.text+0x102c): undefined reference to `xz_crc32_table'
   ld: arch/x86/boot/compressed/misc.o: in function `xz_crc32_init':
   misc.c:(.text+0x11c0): undefined reference to `xz_crc32_table'
   ld: arch/x86/boot/compressed/misc.o: in function `xz_crc32':
   misc.c:(.text+0x1213): undefined reference to `xz_crc32_table'
   ld: arch/x86/boot/compressed/misc.o: in function `xz_dec_run':
   misc.c:(.text+0x1e69): undefined reference to `xz_crc32_table'
>> ld: misc.c:(.text+0x1f2d): undefined reference to `xz_crc32_table'
   ld: arch/x86/boot/compressed/misc.o:misc.c:(.text+0x1ff3): more undefined references to `xz_crc32_table' follow

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 7244 bytes --]

Re: [PATCH 8/9] kallsyms: hide layout

[Ard Biesheuvel]

On Wed, 15 Apr 2020 at 23:06, Kristen Carlson Accardi
<kristen@linux.intel.com> wrote:
>
> To support finer grained kaslr (fgkaslr), we need to hide our sorted
> list of symbols, since this will give away our new layout.
> This patch makes /proc/kallsyms only visible to priviledged users.
>

Does it?

> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> ---
>  kernel/kallsyms.c | 138 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 137 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 16c8c605f4b0..861972b6a879 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -25,6 +25,7 @@
>  #include <linux/filter.h>
>  #include <linux/ftrace.h>
>  #include <linux/compiler.h>
> +#include <linux/list_sort.h>
>
>  /*
>   * These will be re-linked against their real values
> @@ -446,6 +447,11 @@ struct kallsym_iter {
>         int show_value;
>  };
>
> +struct kallsyms_iter_list {
> +       struct kallsym_iter iter;
> +       struct list_head next;
> +};
> +
>  int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
>                             char *type, char *name)
>  {
> @@ -660,6 +666,121 @@ int kallsyms_show_value(void)
>         }
>  }
>
> +static int sorted_show(struct seq_file *m, void *p)
> +{
> +       struct list_head *list = m->private;
> +       struct kallsyms_iter_list *iter;
> +       int rc;
> +
> +       if (list_empty(list))
> +               return 0;
> +
> +       iter = list_first_entry(list, struct kallsyms_iter_list, next);
> +
> +       m->private = iter;
> +       rc = s_show(m, p);
> +       m->private = list;
> +
> +       list_del(&iter->next);
> +       kfree(iter);
> +
> +       return rc;
> +}
> +
> +static void *sorted_start(struct seq_file *m, loff_t *pos)
> +{
> +       return m->private;
> +}
> +
> +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos)
> +{
> +       struct list_head *list = m->private;
> +
> +       (*pos)++;
> +
> +       if (list_empty(list))
> +               return NULL;
> +
> +       return p;
> +}
> +
> +static const struct seq_operations kallsyms_sorted_op = {
> +       .start = sorted_start,
> +       .next = sorted_next,
> +       .stop = s_stop,
> +       .show = sorted_show
> +};
> +
> +static int kallsyms_list_cmp(void *priv, struct list_head *a,
> +                               struct list_head *b)
> +{
> +       struct kallsyms_iter_list *iter_a, *iter_b;
> +
> +       iter_a = list_entry(a, struct kallsyms_iter_list, next);
> +       iter_b = list_entry(b, struct kallsyms_iter_list, next);
> +
> +       return strcmp(iter_a->iter.name, iter_b->iter.name);
> +}
> +
> +int get_all_symbol_name(void *data, const char *name, struct module *mod,
> +                       unsigned long addr)
> +{
> +       unsigned long sym_pos;
> +       struct kallsyms_iter_list *node, *last;
> +       struct list_head *head = (struct list_head *)data;
> +
> +       node = kmalloc(sizeof(*node), GFP_KERNEL);
> +       if (!node)
> +               return -ENOMEM;
> +
> +       if (list_empty(head)) {
> +               sym_pos = 0;
> +               memset(node, 0, sizeof(*node));
> +               reset_iter(&node->iter, 0);
> +               node->iter.show_value = kallsyms_show_value();
> +       } else {
> +               last = list_first_entry(head, struct kallsyms_iter_list, next);
> +               memcpy(node, last, sizeof(*node));
> +               sym_pos = last->iter.pos;
> +       }
> +
> +       INIT_LIST_HEAD(&node->next);
> +       list_add(&node->next, head);
> +
> +       /*
> +        * update_iter returns false when at end of file
> +        * which in this case we don't care about and can
> +        * safely ignore. update_iter() will increment
> +        * the value of iter->pos, for ksymbol_core.
> +        */
> +       if (sym_pos >= kallsyms_num_syms)
> +               sym_pos++;
> +
> +       (void) update_iter(&node->iter, sym_pos);
> +
> +       return 0;
> +}
> +
> +static int kallsyms_sorted_open(struct inode *inode, struct file *file)
> +{
> +       int ret;
> +       struct list_head *list;
> +
> +       list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list));
> +       if (!list)
> +               return -ENOMEM;
> +
> +       INIT_LIST_HEAD(list);
> +
> +       ret = kallsyms_on_each_symbol(get_all_symbol_name, list);
> +       if (ret != 0)
> +               return ret;
> +
> +       list_sort(NULL, list, kallsyms_list_cmp);
> +

Could we do the sort at init time rather than open time?

> +       return 0;
> +}
> +
>  static int kallsyms_open(struct inode *inode, struct file *file)
>  {
>         /*
> @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = {
>         .proc_release   = seq_release_private,
>  };
>
> +static const struct proc_ops kallsyms_sorted_proc_ops = {
> +       .proc_open = kallsyms_sorted_open,
> +       .proc_read = seq_read,
> +       .proc_lseek = seq_lseek,
> +       .proc_release = seq_release_private,
> +};
> +
>  static int __init kallsyms_init(void)
>  {
> -       proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
> +       /*
> +        * When fine grained kaslr is enabled, we need to
> +        * print out the symbols sorted by name rather than by
> +        * by address, because this reveals the randomization order.
> +        */
> +       if (!IS_ENABLED(CONFIG_FG_KASLR))
> +               proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
> +       else
> +               proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops);

Can we just switch to the sorted version unconditionally instead? Or
is the output order of /proc/kallsyms considered kernel ABI?

>         return 0;
>  }
>  device_initcall(kallsyms_init);
> --
> 2.20.1
>

Re: [PATCH 9/9] module: Reorder functions

[Ard Biesheuvel]

On Wed, 15 Apr 2020 at 23:07, Kristen Carlson Accardi
<kristen@linux.intel.com> wrote:
>
> If a module has functions split out into separate text sections
> (i.e. compiled with the -ffunction-sections flag), reorder the
> functions to provide some code diversification to modules.
>

Is that the only prerequisite? I.e., is it sufficient for another
architecture to add -ffunction-sections to the module CFLAGS to get
this functionality? (assuming it defines CONFIG_FG_KASLR=y)

> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
>  kernel/module.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 82 insertions(+)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 646f1e2330d2..e432ec5f6df4 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -53,6 +53,8 @@
>  #include <linux/bsearch.h>
>  #include <linux/dynamic_debug.h>
>  #include <linux/audit.h>
> +#include <linux/random.h>
> +#include <asm/setup.h>
>  #include <uapi/linux/module.h>
>  #include "module-internal.h"
>
> @@ -2370,6 +2372,83 @@ static long get_offset(struct module *mod, unsigned int *size,
>         return ret;
>  }
>
> +/*
> + * shuffle_text_list()
> + * Use a Fisher Yates algorithm to shuffle a list of text sections.
> + */
> +static void shuffle_text_list(Elf_Shdr **list, int size)
> +{
> +       int i;
> +       unsigned int j;
> +       Elf_Shdr *temp;
> +
> +       for (i = size - 1; i > 0; i--) {
> +               /*
> +                * pick a random index from 0 to i
> +                */
> +               get_random_bytes(&j, sizeof(j));
> +               j = j % (i + 1);
> +
> +               temp = list[i];
> +               list[i] = list[j];
> +               list[j] = temp;
> +       }
> +}
> +
> +/*
> + * randomize_text()
> + * Look through the core section looking for executable code sections.
> + * Store sections in an array and then shuffle the sections
> + * to reorder the functions.
> + */
> +static void randomize_text(struct module *mod, struct load_info *info)
> +{
> +       int i;
> +       int num_text_sections = 0;
> +       Elf_Shdr **text_list;
> +       int size = 0;
> +       int max_sections = info->hdr->e_shnum;
> +       unsigned int sec = find_sec(info, ".text");
> +
> +       if (sec == 0)
> +               return;
> +
> +       text_list = kmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL);
> +       if (text_list == NULL)
> +               return;
> +
> +       for (i = 0; i < max_sections; i++) {
> +               Elf_Shdr *shdr = &info->sechdrs[i];
> +               const char *sname = info->secstrings + shdr->sh_name;
> +
> +               if (!(shdr->sh_flags & SHF_ALLOC) ||
> +                   !(shdr->sh_flags & SHF_EXECINSTR) ||
> +                   strstarts(sname, ".init"))
> +                       continue;
> +
> +               text_list[num_text_sections] = shdr;
> +               num_text_sections++;
> +       }
> +
> +       shuffle_text_list(text_list, num_text_sections);
> +
> +       for (i = 0; i < num_text_sections; i++) {
> +               Elf_Shdr *shdr = text_list[i];
> +
> +               /*
> +                * get_offset has a section index for it's last
> +                * argument, that is only used by arch_mod_section_prepend(),
> +                * which is only defined by parisc. Since this this type
> +                * of randomization isn't supported on parisc, we can
> +                * safely pass in zero as the last argument, as it is
> +                * ignored.
> +                */
> +               shdr->sh_entsize = get_offset(mod, &size, shdr, 0);
> +       }
> +
> +       kfree(text_list);
> +}
> +
>  /* Lay out the SHF_ALLOC sections in a way not dissimilar to how ld
>     might -- code, read-only data, read-write data, small data.  Tally
>     sizes, and place the offsets into sh_entsize fields: high bit means it
> @@ -2460,6 +2539,9 @@ static void layout_sections(struct module *mod, struct load_info *info)
>                         break;
>                 }
>         }
> +
> +       if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())

kaslr_enabled() only exists [as a function] on x86


> +               randomize_text(mod, info);
>  }
>
>  static void set_license(struct module *mod, const char *license)
> --
> 2.20.1
>

Re: [PATCH 9/9] module: Reorder functions

[Arjan van de Ven]

On 4/20/2020 5:01 AM, Ard Biesheuvel wrote:
> Is that the only prerequisite? I.e., is it sufficient for another
> architecture to add -ffunction-sections to the module CFLAGS to get
> this functionality? (assuming it defines CONFIG_FG_KASLR=y)

I suspect you also need/want at least normal KASLR enabled as
a "does it even make sense" common sense threshold

Re: [PATCH 9/9] module: Reorder functions

[Ard Biesheuvel]

On Mon, 20 Apr 2020 at 15:37, Arjan van de Ven <arjan@linux.intel.com> wrote:
>
> On 4/20/2020 5:01 AM, Ard Biesheuvel wrote:
> > Is that the only prerequisite? I.e., is it sufficient for another
> > architecture to add -ffunction-sections to the module CFLAGS to get
> > this functionality? (assuming it defines CONFIG_FG_KASLR=y)
>
> I suspect you also need/want at least normal KASLR enabled as
> a "does it even make sense" common sense threshold

Fair enough. But that is more of a policy concern than a functional concern.

FWIW I took patches #8 and #9, hardwired a couple of CONFIG_FG_KASLR=y
checks and added the -ffunction-sections GCC option for the modules,
and everything appears to be working as expected on arm64. I was just
wondering if I was missing something.

Note that arm64 does not have a decompressor, so there the fine
grained randomization of the core kernel is not really feasible using
the approach presented here.

Re: [PATCH 9/9] module: Reorder functions

[Arjan van de Ven]

On 4/20/2020 6:43 AM, Ard Biesheuvel wrote:

> 
> Note that arm64 does not have a decompressor, so there the fine
> grained randomization of the core kernel is not really feasible using
> the approach presented here.

maybe do a "memcpy" decompressor as an option? :-)

> 

Re: [PATCH 8/9] kallsyms: hide layout

[Kristen Carlson Accardi]

On Mon, 2020-04-20 at 13:58 +0200, Ard Biesheuvel wrote:
> On Wed, 15 Apr 2020 at 23:06, Kristen Carlson Accardi
> <kristen@linux.intel.com> wrote:
> > To support finer grained kaslr (fgkaslr), we need to hide our
> > sorted
> > list of symbols, since this will give away our new layout.
> > This patch makes /proc/kallsyms only visible to priviledged users.
> > 
> 
> Does it?

Oops, I forgot to update my commit message since I changed algorithms.
Thanks for catching that. I'll fix it in the next version.

> 
> > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> > ---
> >  kernel/kallsyms.c | 138
> > +++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 137 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > index 16c8c605f4b0..861972b6a879 100644
> > --- a/kernel/kallsyms.c
> > +++ b/kernel/kallsyms.c
> > @@ -25,6 +25,7 @@
> >  #include <linux/filter.h>
> >  #include <linux/ftrace.h>
> >  #include <linux/compiler.h>
> > +#include <linux/list_sort.h>
> > 
> >  /*
> >   * These will be re-linked against their real values
> > @@ -446,6 +447,11 @@ struct kallsym_iter {
> >         int show_value;
> >  };
> > 
> > +struct kallsyms_iter_list {
> > +       struct kallsym_iter iter;
> > +       struct list_head next;
> > +};
> > +
> >  int __weak arch_get_kallsym(unsigned int symnum, unsigned long
> > *value,
> >                             char *type, char *name)
> >  {
> > @@ -660,6 +666,121 @@ int kallsyms_show_value(void)
> >         }
> >  }
> > 
> > +static int sorted_show(struct seq_file *m, void *p)
> > +{
> > +       struct list_head *list = m->private;
> > +       struct kallsyms_iter_list *iter;
> > +       int rc;
> > +
> > +       if (list_empty(list))
> > +               return 0;
> > +
> > +       iter = list_first_entry(list, struct kallsyms_iter_list,
> > next);
> > +
> > +       m->private = iter;
> > +       rc = s_show(m, p);
> > +       m->private = list;
> > +
> > +       list_del(&iter->next);
> > +       kfree(iter);
> > +
> > +       return rc;
> > +}
> > +
> > +static void *sorted_start(struct seq_file *m, loff_t *pos)
> > +{
> > +       return m->private;
> > +}
> > +
> > +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos)
> > +{
> > +       struct list_head *list = m->private;
> > +
> > +       (*pos)++;
> > +
> > +       if (list_empty(list))
> > +               return NULL;
> > +
> > +       return p;
> > +}
> > +
> > +static const struct seq_operations kallsyms_sorted_op = {
> > +       .start = sorted_start,
> > +       .next = sorted_next,
> > +       .stop = s_stop,
> > +       .show = sorted_show
> > +};
> > +
> > +static int kallsyms_list_cmp(void *priv, struct list_head *a,
> > +                               struct list_head *b)
> > +{
> > +       struct kallsyms_iter_list *iter_a, *iter_b;
> > +
> > +       iter_a = list_entry(a, struct kallsyms_iter_list, next);
> > +       iter_b = list_entry(b, struct kallsyms_iter_list, next);
> > +
> > +       return strcmp(iter_a->iter.name, iter_b->iter.name);
> > +}
> > +
> > +int get_all_symbol_name(void *data, const char *name, struct
> > module *mod,
> > +                       unsigned long addr)
> > +{
> > +       unsigned long sym_pos;
> > +       struct kallsyms_iter_list *node, *last;
> > +       struct list_head *head = (struct list_head *)data;
> > +
> > +       node = kmalloc(sizeof(*node), GFP_KERNEL);
> > +       if (!node)
> > +               return -ENOMEM;
> > +
> > +       if (list_empty(head)) {
> > +               sym_pos = 0;
> > +               memset(node, 0, sizeof(*node));
> > +               reset_iter(&node->iter, 0);
> > +               node->iter.show_value = kallsyms_show_value();
> > +       } else {
> > +               last = list_first_entry(head, struct
> > kallsyms_iter_list, next);
> > +               memcpy(node, last, sizeof(*node));
> > +               sym_pos = last->iter.pos;
> > +       }
> > +
> > +       INIT_LIST_HEAD(&node->next);
> > +       list_add(&node->next, head);
> > +
> > +       /*
> > +        * update_iter returns false when at end of file
> > +        * which in this case we don't care about and can
> > +        * safely ignore. update_iter() will increment
> > +        * the value of iter->pos, for ksymbol_core.
> > +        */
> > +       if (sym_pos >= kallsyms_num_syms)
> > +               sym_pos++;
> > +
> > +       (void) update_iter(&node->iter, sym_pos);
> > +
> > +       return 0;
> > +}
> > +
> > +static int kallsyms_sorted_open(struct inode *inode, struct file
> > *file)
> > +{
> > +       int ret;
> > +       struct list_head *list;
> > +
> > +       list = __seq_open_private(file, &kallsyms_sorted_op,
> > sizeof(*list));
> > +       if (!list)
> > +               return -ENOMEM;
> > +
> > +       INIT_LIST_HEAD(list);
> > +
> > +       ret = kallsyms_on_each_symbol(get_all_symbol_name, list);
> > +       if (ret != 0)
> > +               return ret;
> > +
> > +       list_sort(NULL, list, kallsyms_list_cmp);
> > +
> 
> Could we do the sort at init time rather than open time

I could do this, but module symbols would not be included, and also we
would have to maintain a separate symbol list in memory forever since
we have to keep the list sorted by address for bsearch. So, it does
increase memory consumption vs. just allocating space, sorting, and
then deallocating. I personally feel it's a better trade off to sort at
open.

> 
> > +       return 0;
> > +}
> > +
> >  static int kallsyms_open(struct inode *inode, struct file *file)
> >  {
> >         /*
> > @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops
> > = {
> >         .proc_release   = seq_release_private,
> >  };
> > 
> > +static const struct proc_ops kallsyms_sorted_proc_ops = {
> > +       .proc_open = kallsyms_sorted_open,
> > +       .proc_read = seq_read,
> > +       .proc_lseek = seq_lseek,
> > +       .proc_release = seq_release_private,
> > +};
> > +
> >  static int __init kallsyms_init(void)
> >  {
> > -       proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
> > +       /*
> > +        * When fine grained kaslr is enabled, we need to
> > +        * print out the symbols sorted by name rather than by
> > +        * by address, because this reveals the randomization
> > order.
> > +        */
> > +       if (!IS_ENABLED(CONFIG_FG_KASLR))
> > +               proc_create("kallsyms", 0444, NULL,
> > &kallsyms_proc_ops);
> > +       else
> > +               proc_create("kallsyms", 0444, NULL,
> > &kallsyms_sorted_proc_ops);
> 
> Can we just switch to the sorted version unconditionally instead? Or
> is the output order of /proc/kallsyms considered kernel ABI?

I didn't know the answer to this question, which is why to be safe I
maintained the existing behavior when my feature is not enabled.

> 

Re: [PATCH 0/9] Function Granular Kernel Address Space Layout Randomization

[Kees Cook]

On Wed, Apr 15, 2020 at 02:04:42PM -0700, Kristen Carlson Accardi wrote:
> Kristen Carlson Accardi (8):
>   objtool: do not assume order of parent/child functions
>   x86: tools/relocs: Support >64K section headers

Can these two patches land separately (i.e. "now")? CFI will need the
relocs fix too, so better to have this landed upstream for both
features. I see Josh's Ack in the first...

-- 
Kees Cook

Re: [PATCH 9/9] module: Reorder functions

[Kristen Carlson Accardi]

On Mon, 2020-04-20 at 14:01 +0200, Ard Biesheuvel wrote:
> On Wed, 15 Apr 2020 at 23:07, Kristen Carlson Accardi
> <kristen@linux.intel.com> wrote:
> > If a module has functions split out into separate text sections
> > (i.e. compiled with the -ffunction-sections flag), reorder the
> > functions to provide some code diversification to modules.
> > 
> 
> Is that the only prerequisite? I.e., is it sufficient for another
> architecture to add -ffunction-sections to the module CFLAGS to get
> this functionality? (assuming it defines CONFIG_FG_KASLR=y)

I think it would work for modules. I've not tested this of course. It
might not make sense for some architectures (like 32 bit), but it would
probably work.

> 
> > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > ---
> >  kernel/module.c | 82
> > +++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 82 insertions(+)
> > 
> > diff --git a/kernel/module.c b/kernel/module.c
> > index 646f1e2330d2..e432ec5f6df4 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -53,6 +53,8 @@
> >  #include <linux/bsearch.h>
> >  #include <linux/dynamic_debug.h>
> >  #include <linux/audit.h>
> > +#include <linux/random.h>
> > +#include <asm/setup.h>
> >  #include <uapi/linux/module.h>
> >  #include "module-internal.h"
> > 
> > @@ -2370,6 +2372,83 @@ static long get_offset(struct module *mod,
> > unsigned int *size,
> >         return ret;
> >  }
> > 
> > +/*
> > + * shuffle_text_list()
> > + * Use a Fisher Yates algorithm to shuffle a list of text
> > sections.
> > + */
> > +static void shuffle_text_list(Elf_Shdr **list, int size)
> > +{
> > +       int i;
> > +       unsigned int j;
> > +       Elf_Shdr *temp;
> > +
> > +       for (i = size - 1; i > 0; i--) {
> > +               /*
> > +                * pick a random index from 0 to i
> > +                */
> > +               get_random_bytes(&j, sizeof(j));
> > +               j = j % (i + 1);
> > +
> > +               temp = list[i];
> > +               list[i] = list[j];
> > +               list[j] = temp;
> > +       }
> > +}
> > +
> > +/*
> > + * randomize_text()
> > + * Look through the core section looking for executable code
> > sections.
> > + * Store sections in an array and then shuffle the sections
> > + * to reorder the functions.
> > + */
> > +static void randomize_text(struct module *mod, struct load_info
> > *info)
> > +{
> > +       int i;
> > +       int num_text_sections = 0;
> > +       Elf_Shdr **text_list;
> > +       int size = 0;
> > +       int max_sections = info->hdr->e_shnum;
> > +       unsigned int sec = find_sec(info, ".text");
> > +
> > +       if (sec == 0)
> > +               return;
> > +
> > +       text_list = kmalloc_array(max_sections, sizeof(*text_list),
> > GFP_KERNEL);
> > +       if (text_list == NULL)
> > +               return;
> > +
> > +       for (i = 0; i < max_sections; i++) {
> > +               Elf_Shdr *shdr = &info->sechdrs[i];
> > +               const char *sname = info->secstrings + shdr-
> > >sh_name;
> > +
> > +               if (!(shdr->sh_flags & SHF_ALLOC) ||
> > +                   !(shdr->sh_flags & SHF_EXECINSTR) ||
> > +                   strstarts(sname, ".init"))
> > +                       continue;
> > +
> > +               text_list[num_text_sections] = shdr;
> > +               num_text_sections++;
> > +       }
> > +
> > +       shuffle_text_list(text_list, num_text_sections);
> > +
> > +       for (i = 0; i < num_text_sections; i++) {
> > +               Elf_Shdr *shdr = text_list[i];
> > +
> > +               /*
> > +                * get_offset has a section index for it's last
> > +                * argument, that is only used by
> > arch_mod_section_prepend(),
> > +                * which is only defined by parisc. Since this this
> > type
> > +                * of randomization isn't supported on parisc, we
> > can
> > +                * safely pass in zero as the last argument, as it
> > is
> > +                * ignored.
> > +                */
> > +               shdr->sh_entsize = get_offset(mod, &size, shdr, 0);
> > +       }
> > +
> > +       kfree(text_list);
> > +}
> > +
> >  /* Lay out the SHF_ALLOC sections in a way not dissimilar to how
> > ld
> >     might -- code, read-only data, read-write data, small
> > data.  Tally
> >     sizes, and place the offsets into sh_entsize fields: high bit
> > means it
> > @@ -2460,6 +2539,9 @@ static void layout_sections(struct module
> > *mod, struct load_info *info)
> >                         break;
> >                 }
> >         }
> > +
> > +       if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())
> 
> kaslr_enabled() only exists [as a function] on x86

CONFIG_FG_KASLR is dependant on x86_64. If people really think there is
value in having the module randomization not dependent on the kernel
randomization it can be changed to a different config option - but I am
not sure that there is a ton of value in the module randomization on
it's own.

> 
> 
> > +               randomize_text(mod, info);
> >  }
> > 
> >  static void set_license(struct module *mod, const char *license)
> > --
> > 2.20.1
> > 

Re: [PATCH 9/9] module: Reorder functions

[Kristen Carlson Accardi]

On Mon, 2020-04-20 at 10:56 -0700, Kristen Carlson Accardi wrote:
> On Mon, 2020-04-20 at 14:01 +0200, Ard Biesheuvel wrote:
> > On Wed, 15 Apr 2020 at 23:07, Kristen Carlson Accardi
> > <kristen@linux.intel.com> wrote:
> > > If a module has functions split out into separate text sections
> > > (i.e. compiled with the -ffunction-sections flag), reorder the
> > > functions to provide some code diversification to modules.
> > > 
> > 
> > Is that the only prerequisite? I.e., is it sufficient for another
> > architecture to add -ffunction-sections to the module CFLAGS to get
> > this functionality? (assuming it defines CONFIG_FG_KASLR=y)
> 
> I think it would work for modules. I've not tested this of course. It
> might not make sense for some architectures (like 32 bit), but it
> would
> probably work.
> 
> > > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > ---
> > >  kernel/module.c | 82
> > > +++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 82 insertions(+)
> > > 
> > > diff --git a/kernel/module.c b/kernel/module.c
> > > index 646f1e2330d2..e432ec5f6df4 100644
> > > --- a/kernel/module.c
> > > +++ b/kernel/module.c
> > > @@ -53,6 +53,8 @@
> > >  #include <linux/bsearch.h>
> > >  #include <linux/dynamic_debug.h>
> > >  #include <linux/audit.h>
> > > +#include <linux/random.h>
> > > +#include <asm/setup.h>
> > >  #include <uapi/linux/module.h>
> > >  #include "module-internal.h"
> > > 
> > > @@ -2370,6 +2372,83 @@ static long get_offset(struct module *mod,
> > > unsigned int *size,
> > >         return ret;
> > >  }
> > > 
> > > +/*
> > > + * shuffle_text_list()
> > > + * Use a Fisher Yates algorithm to shuffle a list of text
> > > sections.
> > > + */
> > > +static void shuffle_text_list(Elf_Shdr **list, int size)
> > > +{
> > > +       int i;
> > > +       unsigned int j;
> > > +       Elf_Shdr *temp;
> > > +
> > > +       for (i = size - 1; i > 0; i--) {
> > > +               /*
> > > +                * pick a random index from 0 to i
> > > +                */
> > > +               get_random_bytes(&j, sizeof(j));
> > > +               j = j % (i + 1);
> > > +
> > > +               temp = list[i];
> > > +               list[i] = list[j];
> > > +               list[j] = temp;
> > > +       }
> > > +}
> > > +
> > > +/*
> > > + * randomize_text()
> > > + * Look through the core section looking for executable code
> > > sections.
> > > + * Store sections in an array and then shuffle the sections
> > > + * to reorder the functions.
> > > + */
> > > +static void randomize_text(struct module *mod, struct load_info
> > > *info)
> > > +{
> > > +       int i;
> > > +       int num_text_sections = 0;
> > > +       Elf_Shdr **text_list;
> > > +       int size = 0;
> > > +       int max_sections = info->hdr->e_shnum;
> > > +       unsigned int sec = find_sec(info, ".text");
> > > +
> > > +       if (sec == 0)
> > > +               return;
> > > +
> > > +       text_list = kmalloc_array(max_sections,
> > > sizeof(*text_list),
> > > GFP_KERNEL);
> > > +       if (text_list == NULL)
> > > +               return;
> > > +
> > > +       for (i = 0; i < max_sections; i++) {
> > > +               Elf_Shdr *shdr = &info->sechdrs[i];
> > > +               const char *sname = info->secstrings + shdr-
> > > > sh_name;
> > > +
> > > +               if (!(shdr->sh_flags & SHF_ALLOC) ||
> > > +                   !(shdr->sh_flags & SHF_EXECINSTR) ||
> > > +                   strstarts(sname, ".init"))
> > > +                       continue;
> > > +
> > > +               text_list[num_text_sections] = shdr;
> > > +               num_text_sections++;
> > > +       }
> > > +
> > > +       shuffle_text_list(text_list, num_text_sections);
> > > +
> > > +       for (i = 0; i < num_text_sections; i++) {
> > > +               Elf_Shdr *shdr = text_list[i];
> > > +
> > > +               /*
> > > +                * get_offset has a section index for it's last
> > > +                * argument, that is only used by
> > > arch_mod_section_prepend(),
> > > +                * which is only defined by parisc. Since this
> > > this
> > > type
> > > +                * of randomization isn't supported on parisc, we
> > > can
> > > +                * safely pass in zero as the last argument, as
> > > it
> > > is
> > > +                * ignored.
> > > +                */
> > > +               shdr->sh_entsize = get_offset(mod, &size, shdr,
> > > 0);
> > > +       }
> > > +
> > > +       kfree(text_list);
> > > +}
> > > +
> > >  /* Lay out the SHF_ALLOC sections in a way not dissimilar to how
> > > ld
> > >     might -- code, read-only data, read-write data, small
> > > data.  Tally
> > >     sizes, and place the offsets into sh_entsize fields: high bit
> > > means it
> > > @@ -2460,6 +2539,9 @@ static void layout_sections(struct module
> > > *mod, struct load_info *info)
> > >                         break;
> > >                 }
> > >         }
> > > +
> > > +       if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())
> > 
> > kaslr_enabled() only exists [as a function] on x86
> 
> CONFIG_FG_KASLR is dependant on x86_64. If people really think there
> is
> value in having the module randomization not dependent on the kernel
> randomization it can be changed to a different config option - but I
> am
> not sure that there is a ton of value in the module randomization on
> it's own.

I should have added - thank you for pointing this out, I will fix it in
the next version. I was on a tangent about whether you should even use
this without the main kernel randomization :).

Re: [PATCH 9/9] module: Reorder functions

[Ard Biesheuvel]

On Mon, 20 Apr 2020 at 19:59, Kristen Carlson Accardi
<kristen@linux.intel.com> wrote:
>
> On Mon, 2020-04-20 at 10:56 -0700, Kristen Carlson Accardi wrote:
> > On Mon, 2020-04-20 at 14:01 +0200, Ard Biesheuvel wrote:
> > > On Wed, 15 Apr 2020 at 23:07, Kristen Carlson Accardi
> > > <kristen@linux.intel.com> wrote:
> > > > If a module has functions split out into separate text sections
> > > > (i.e. compiled with the -ffunction-sections flag), reorder the
> > > > functions to provide some code diversification to modules.
> > > >
> > >
> > > Is that the only prerequisite? I.e., is it sufficient for another
> > > architecture to add -ffunction-sections to the module CFLAGS to get
> > > this functionality? (assuming it defines CONFIG_FG_KASLR=y)
> >
> > I think it would work for modules. I've not tested this of course. It
> > might not make sense for some architectures (like 32 bit), but it
> > would
> > probably work.
> >
> > > > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> > > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > > ---
> > > >  kernel/module.c | 82
> > > > +++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 82 insertions(+)
> > > >
> > > > diff --git a/kernel/module.c b/kernel/module.c
> > > > index 646f1e2330d2..e432ec5f6df4 100644
> > > > --- a/kernel/module.c
> > > > +++ b/kernel/module.c
> > > > @@ -53,6 +53,8 @@
> > > >  #include <linux/bsearch.h>
> > > >  #include <linux/dynamic_debug.h>
> > > >  #include <linux/audit.h>
> > > > +#include <linux/random.h>
> > > > +#include <asm/setup.h>
> > > >  #include <uapi/linux/module.h>
> > > >  #include "module-internal.h"
> > > >
> > > > @@ -2370,6 +2372,83 @@ static long get_offset(struct module *mod,
> > > > unsigned int *size,
> > > >         return ret;
> > > >  }
> > > >
> > > > +/*
> > > > + * shuffle_text_list()
> > > > + * Use a Fisher Yates algorithm to shuffle a list of text
> > > > sections.
> > > > + */
> > > > +static void shuffle_text_list(Elf_Shdr **list, int size)
> > > > +{
> > > > +       int i;
> > > > +       unsigned int j;
> > > > +       Elf_Shdr *temp;
> > > > +
> > > > +       for (i = size - 1; i > 0; i--) {
> > > > +               /*
> > > > +                * pick a random index from 0 to i
> > > > +                */
> > > > +               get_random_bytes(&j, sizeof(j));
> > > > +               j = j % (i + 1);
> > > > +
> > > > +               temp = list[i];
> > > > +               list[i] = list[j];
> > > > +               list[j] = temp;
> > > > +       }
> > > > +}
> > > > +
> > > > +/*
> > > > + * randomize_text()
> > > > + * Look through the core section looking for executable code
> > > > sections.
> > > > + * Store sections in an array and then shuffle the sections
> > > > + * to reorder the functions.
> > > > + */
> > > > +static void randomize_text(struct module *mod, struct load_info
> > > > *info)
> > > > +{
> > > > +       int i;
> > > > +       int num_text_sections = 0;
> > > > +       Elf_Shdr **text_list;
> > > > +       int size = 0;
> > > > +       int max_sections = info->hdr->e_shnum;
> > > > +       unsigned int sec = find_sec(info, ".text");
> > > > +
> > > > +       if (sec == 0)
> > > > +               return;
> > > > +
> > > > +       text_list = kmalloc_array(max_sections,
> > > > sizeof(*text_list),
> > > > GFP_KERNEL);
> > > > +       if (text_list == NULL)
> > > > +               return;
> > > > +
> > > > +       for (i = 0; i < max_sections; i++) {
> > > > +               Elf_Shdr *shdr = &info->sechdrs[i];
> > > > +               const char *sname = info->secstrings + shdr-
> > > > > sh_name;
> > > > +
> > > > +               if (!(shdr->sh_flags & SHF_ALLOC) ||
> > > > +                   !(shdr->sh_flags & SHF_EXECINSTR) ||
> > > > +                   strstarts(sname, ".init"))
> > > > +                       continue;
> > > > +
> > > > +               text_list[num_text_sections] = shdr;
> > > > +               num_text_sections++;
> > > > +       }
> > > > +
> > > > +       shuffle_text_list(text_list, num_text_sections);
> > > > +
> > > > +       for (i = 0; i < num_text_sections; i++) {
> > > > +               Elf_Shdr *shdr = text_list[i];
> > > > +
> > > > +               /*
> > > > +                * get_offset has a section index for it's last
> > > > +                * argument, that is only used by
> > > > arch_mod_section_prepend(),
> > > > +                * which is only defined by parisc. Since this
> > > > this
> > > > type
> > > > +                * of randomization isn't supported on parisc, we
> > > > can
> > > > +                * safely pass in zero as the last argument, as
> > > > it
> > > > is
> > > > +                * ignored.
> > > > +                */
> > > > +               shdr->sh_entsize = get_offset(mod, &size, shdr,
> > > > 0);
> > > > +       }
> > > > +
> > > > +       kfree(text_list);
> > > > +}
> > > > +
> > > >  /* Lay out the SHF_ALLOC sections in a way not dissimilar to how
> > > > ld
> > > >     might -- code, read-only data, read-write data, small
> > > > data.  Tally
> > > >     sizes, and place the offsets into sh_entsize fields: high bit
> > > > means it
> > > > @@ -2460,6 +2539,9 @@ static void layout_sections(struct module
> > > > *mod, struct load_info *info)
> > > >                         break;
> > > >                 }
> > > >         }
> > > > +
> > > > +       if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())
> > >
> > > kaslr_enabled() only exists [as a function] on x86
> >
> > CONFIG_FG_KASLR is dependant on x86_64. If people really think there
> > is
> > value in having the module randomization not dependent on the kernel
> > randomization it can be changed to a different config option - but I
> > am
> > not sure that there is a ton of value in the module randomization on
> > it's own.
>

I think there is. The modules are a sizable attack surface, and made
up of drivers for a large part, many of which are not as carefully
reviewed as core code. Also, as I pointed out, the ELF loading trick
from the decompressor is simply infeasible on arm64, given that there
is no decompressor in the first place.

> I should have added - thank you for pointing this out, I will fix it in
> the next version. I was on a tangent about whether you should even use
> this without the main kernel randomization :).
>

Yeah. I was just pointing out that this breaks the build for all other
architectures :-)

Re: [PATCH 9/9] module: Reorder functions

[Kristen Carlson Accardi]

On Wed, 2020-04-22 at 18:22 +0200, Ard Biesheuvel wrote:
> On Mon, 20 Apr 2020 at 19:59, Kristen Carlson Accardi
> <kristen@linux.intel.com> wrote:
> > On Mon, 2020-04-20 at 10:56 -0700, Kristen Carlson Accardi wrote:
> > > On Mon, 2020-04-20 at 14:01 +0200, Ard Biesheuvel wrote:
> > > > On Wed, 15 Apr 2020 at 23:07, Kristen Carlson Accardi
> > > > <kristen@linux.intel.com> wrote:
> > > > > If a module has functions split out into separate text
> > > > > sections
> > > > > (i.e. compiled with the -ffunction-sections flag), reorder
> > > > > the
> > > > > functions to provide some code diversification to modules.
> > > > > 
> > > > 
> > > > Is that the only prerequisite? I.e., is it sufficient for
> > > > another
> > > > architecture to add -ffunction-sections to the module CFLAGS to
> > > > get
> > > > this functionality? (assuming it defines CONFIG_FG_KASLR=y)
> > > 
> > > I think it would work for modules. I've not tested this of
> > > course. It
> > > might not make sense for some architectures (like 32 bit), but it
> > > would
> > > probably work.
> > > 
> > > > > Signed-off-by: Kristen Carlson Accardi <
> > > > > kristen@linux.intel.com>
> > > > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > > > ---
> > > > >  kernel/module.c | 82
> > > > > +++++++++++++++++++++++++++++++++++++++++++++++++
> > > > >  1 file changed, 82 insertions(+)
> > > > > 
> > > > > diff --git a/kernel/module.c b/kernel/module.c
> > > > > index 646f1e2330d2..e432ec5f6df4 100644
> > > > > --- a/kernel/module.c
> > > > > +++ b/kernel/module.c
> > > > > @@ -53,6 +53,8 @@
> > > > >  #include <linux/bsearch.h>
> > > > >  #include <linux/dynamic_debug.h>
> > > > >  #include <linux/audit.h>
> > > > > +#include <linux/random.h>
> > > > > +#include <asm/setup.h>
> > > > >  #include <uapi/linux/module.h>
> > > > >  #include "module-internal.h"
> > > > > 
> > > > > @@ -2370,6 +2372,83 @@ static long get_offset(struct module
> > > > > *mod,
> > > > > unsigned int *size,
> > > > >         return ret;
> > > > >  }
> > > > > 
> > > > > +/*
> > > > > + * shuffle_text_list()
> > > > > + * Use a Fisher Yates algorithm to shuffle a list of text
> > > > > sections.
> > > > > + */
> > > > > +static void shuffle_text_list(Elf_Shdr **list, int size)
> > > > > +{
> > > > > +       int i;
> > > > > +       unsigned int j;
> > > > > +       Elf_Shdr *temp;
> > > > > +
> > > > > +       for (i = size - 1; i > 0; i--) {
> > > > > +               /*
> > > > > +                * pick a random index from 0 to i
> > > > > +                */
> > > > > +               get_random_bytes(&j, sizeof(j));
> > > > > +               j = j % (i + 1);
> > > > > +
> > > > > +               temp = list[i];
> > > > > +               list[i] = list[j];
> > > > > +               list[j] = temp;
> > > > > +       }
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * randomize_text()
> > > > > + * Look through the core section looking for executable code
> > > > > sections.
> > > > > + * Store sections in an array and then shuffle the sections
> > > > > + * to reorder the functions.
> > > > > + */
> > > > > +static void randomize_text(struct module *mod, struct
> > > > > load_info
> > > > > *info)
> > > > > +{
> > > > > +       int i;
> > > > > +       int num_text_sections = 0;
> > > > > +       Elf_Shdr **text_list;
> > > > > +       int size = 0;
> > > > > +       int max_sections = info->hdr->e_shnum;
> > > > > +       unsigned int sec = find_sec(info, ".text");
> > > > > +
> > > > > +       if (sec == 0)
> > > > > +               return;
> > > > > +
> > > > > +       text_list = kmalloc_array(max_sections,
> > > > > sizeof(*text_list),
> > > > > GFP_KERNEL);
> > > > > +       if (text_list == NULL)
> > > > > +               return;
> > > > > +
> > > > > +       for (i = 0; i < max_sections; i++) {
> > > > > +               Elf_Shdr *shdr = &info->sechdrs[i];
> > > > > +               const char *sname = info->secstrings + shdr-
> > > > > > sh_name;
> > > > > +
> > > > > +               if (!(shdr->sh_flags & SHF_ALLOC) ||
> > > > > +                   !(shdr->sh_flags & SHF_EXECINSTR) ||
> > > > > +                   strstarts(sname, ".init"))
> > > > > +                       continue;
> > > > > +
> > > > > +               text_list[num_text_sections] = shdr;
> > > > > +               num_text_sections++;
> > > > > +       }
> > > > > +
> > > > > +       shuffle_text_list(text_list, num_text_sections);
> > > > > +
> > > > > +       for (i = 0; i < num_text_sections; i++) {
> > > > > +               Elf_Shdr *shdr = text_list[i];
> > > > > +
> > > > > +               /*
> > > > > +                * get_offset has a section index for it's
> > > > > last
> > > > > +                * argument, that is only used by
> > > > > arch_mod_section_prepend(),
> > > > > +                * which is only defined by parisc. Since
> > > > > this
> > > > > this
> > > > > type
> > > > > +                * of randomization isn't supported on
> > > > > parisc, we
> > > > > can
> > > > > +                * safely pass in zero as the last argument,
> > > > > as
> > > > > it
> > > > > is
> > > > > +                * ignored.
> > > > > +                */
> > > > > +               shdr->sh_entsize = get_offset(mod, &size,
> > > > > shdr,
> > > > > 0);
> > > > > +       }
> > > > > +
> > > > > +       kfree(text_list);
> > > > > +}
> > > > > +
> > > > >  /* Lay out the SHF_ALLOC sections in a way not dissimilar to
> > > > > how
> > > > > ld
> > > > >     might -- code, read-only data, read-write data, small
> > > > > data.  Tally
> > > > >     sizes, and place the offsets into sh_entsize fields: high
> > > > > bit
> > > > > means it
> > > > > @@ -2460,6 +2539,9 @@ static void layout_sections(struct
> > > > > module
> > > > > *mod, struct load_info *info)
> > > > >                         break;
> > > > >                 }
> > > > >         }
> > > > > +
> > > > > +       if (IS_ENABLED(CONFIG_FG_KASLR) && kaslr_enabled())
> > > > 
> > > > kaslr_enabled() only exists [as a function] on x86
> > > 
> > > CONFIG_FG_KASLR is dependant on x86_64. If people really think
> > > there
> > > is
> > > value in having the module randomization not dependent on the
> > > kernel
> > > randomization it can be changed to a different config option -
> > > but I
> > > am
> > > not sure that there is a ton of value in the module randomization
> > > on
> > > it's own.
> 
> I think there is. The modules are a sizable attack surface, and made
> up of drivers for a large part, many of which are not as carefully
> reviewed as core code. Also, as I pointed out, the ELF loading trick
> from the decompressor is simply infeasible on arm64, given that there
> is no decompressor in the first place.

I can make a separate config option for modules so that you can enable
this separately from the main kernel text randomization. I'll make that
change for v2.

Re: [PATCH 1/9] objtool: do not assume order of parent/child functions

[Josh Poimboeuf]

On Wed, Apr 15, 2020 at 02:04:43PM -0700, Kristen Carlson Accardi wrote:
> If a .cold function is examined prior to it's parent, the link
> to the parent/child function can be overwritten when the parent
> is examined. Only update pfunc and cfunc if they were previously
> nil to prevent this from happening.
> 
> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>

Hi Kristen,

I grabbed this one and it will be merged into the -tip tree soon.
Thanks!

-- 
Josh

Re: [PATCH 7/9] x86: Add support for function granular KASLR

[Baoquan He]

On 04/15/20 at 02:04pm, Kristen Carlson Accardi wrote:
...
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 9652d5c2afda..2e108fdc7757 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -26,9 +26,6 @@
>   * it is not safe to place pointers in static structures.
>   */
>  
> -/* Macros used by the included decompressor code below. */
> -#define STATIC		static
> -

Here removing STATIC definition might be the reason why the LKP
reported build error to patch 7/9.

>  /*
>   * Use normal definitions of mem*() from string.c. There are already
>   * included header files which expect a definition of memset() and by
> @@ -49,6 +46,8 @@ struct boot_params *boot_params;
>  
>  memptr free_mem_ptr;
>  memptr free_mem_end_ptr;
> +unsigned long malloc_ptr;
> +int malloc_count;
>  
>  static char *vidmem;
>  static int vidport;
> @@ -203,10 +202,20 @@ static void handle_relocations(void *output, unsigned long output_len,
>  	if (IS_ENABLED(CONFIG_X86_64))
>  		delta = virt_addr - LOAD_PHYSICAL_ADDR;
>  
> -	if (!delta) {
> -		debug_putstr("No relocation needed... ");
> -		return;
> +	/*
> +	 * it is possible to have delta be zero and
> +	 * still have enabled fg kaslr. We need to perform relocations
> +	 * for fgkaslr regardless of whether the base address has moved.
> +	 */
> +	if (!IS_ENABLED(CONFIG_FG_KASLR) || nokaslr) {
> +		if (!delta) {
> +			debug_putstr("No relocation needed... ");
> +			return;
> +		}
>  	}
> +
> +	pre_relocations_cleanup(map);
> +
>  	debug_putstr("Performing relocations... ");

I testes this patchset on x86_64 machine, it works well. Seems the
debug printing need a little bit adjustment.

-  	debug_putstr("Performing relocations... ");
+  	debug_putstr("\nPerforming relocations... ");

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Decompressing Linux... Parsing ELF... 
Parsing ELF section headers... 
Looking for symbols... 
Re-sorting kallsyms ...Performing relocations... 
                       ~~~~~~~~^
Updating exception table...

Re-sorting exception table...

>  
>  	/*
> @@ -230,35 +239,106 @@ static void handle_relocations(void *output, unsigned long output_len,
>  	 */
>  	for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
>  		long extended = *reloc;
> +		long value;
> +
> +		/*
> +		 * if using fgkaslr, we might have moved the address
> +		 * of the relocation. Check it to see if it needs adjusting
> +		 * from the original address.
> +		 */
> +		(void) adjust_address(&extended);
> +
>  		extended += map;
>  
>  		ptr = (unsigned long)extended;
>  		if (ptr < min_addr || ptr > max_addr)
>  			error("32-bit relocation outside of kernel!\n");
>  
> -		*(uint32_t *)ptr += delta;
> +		value = *(int32_t *)ptr;
> +
> +		/*
> +		 * If using fgkaslr, the value of the relocation
> +		 * might need to be changed because it referred
> +		 * to an address that has moved.
> +		 */
> +		adjust_address(&value);
> +
> +		value += delta;
> +
> +		*(uint32_t *)ptr = value;
>  	}
>  #ifdef CONFIG_X86_64
>  	while (*--reloc) {
>  		long extended = *reloc;
> +		long value;
> +		long oldvalue;
> +		Elf64_Shdr *s;
> +
> +		/*
> +		 * if using fgkaslr, we might have moved the address
> +		 * of the relocation. Check it to see if it needs adjusting
> +		 * from the original address.
> +		 */
> +		s = adjust_address(&extended);
> +
>  		extended += map;
>  
>  		ptr = (unsigned long)extended;
>  		if (ptr < min_addr || ptr > max_addr)
>  			error("inverse 32-bit relocation outside of kernel!\n");
>  
> -		*(int32_t *)ptr -= delta;
> +		value = *(int32_t *)ptr;
> +		oldvalue = value;
> +
> +		/*
> +		 * If using fgkaslr, these relocs will contain
> +		 * relative offsets which might need to be
> +		 * changed because it referred
> +		 * to an address that has moved.
> +		 */
> +		adjust_relative_offset(*reloc, &value, s);
> +
> +		/*
> +		 * only percpu symbols need to have their values adjusted for
> +		 * base address kaslr since relative offsets within the .text
> +		 * and .text.* sections are ok wrt each other.
> +		 */
> +		if (is_percpu_addr(*reloc, oldvalue))
> +			value -= delta;
> +
> +		*(int32_t *)ptr = value;
>  	}
>  	for (reloc--; *reloc; reloc--) {
>  		long extended = *reloc;
> +		long value;
> +
> +		/*
> +		 * if using fgkaslr, we might have moved the address
> +		 * of the relocation. Check it to see if it needs adjusting
> +		 * from the original address.
> +		 */
> +		(void) adjust_address(&extended);
> +
>  		extended += map;
>  
>  		ptr = (unsigned long)extended;
>  		if (ptr < min_addr || ptr > max_addr)
>  			error("64-bit relocation outside of kernel!\n");
>  
> -		*(uint64_t *)ptr += delta;
> +		value = *(int64_t *)ptr;
> +
> +		/*
> +		 * If using fgkaslr, the value of the relocation
> +		 * might need to be changed because it referred
> +		 * to an address that has moved.
> +		 */
> +		(void) adjust_address(&value);
> +
> +		value += delta;
> +
> +		*(uint64_t *)ptr = value;
>  	}
> +	post_relocations_cleanup(map);
>  #endif
>  }
>  #else
> @@ -296,6 +376,15 @@ static void parse_elf(void *output)
>  
>  	memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
>  
> +	if (IS_ENABLED(CONFIG_FG_KASLR)) {
> +		if (!nokaslr) {
> +			parse_sections_headers(output, &ehdr, phdrs);
> +			return;
> +		} else {
> +			warn("FG_KASLR disabled: 'nokaslr' on cmdline.");
> +		}
> +	}
> +
>  	for (i = 0; i < ehdr.e_phnum; i++) {
>  		phdr = &phdrs[i];
>  
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index 726e264410ff..f68f7fc39543 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -39,7 +39,12 @@
>  /* misc.c */
>  extern memptr free_mem_ptr;
>  extern memptr free_mem_end_ptr;
> +#define STATIC
> +#define STATIC_RW_DATA extern
> +#include <linux/decompress/mm.h>
> +
>  extern struct boot_params *boot_params;
> +extern int nokaslr;
>  void __putstr(const char *s);
>  void __puthex(unsigned long value);
>  #define error_putstr(__x)  __putstr(__x)
> @@ -74,6 +79,32 @@ struct mem_vector {
>  	unsigned long long size;
>  };
>  
> +#ifdef CONFIG_X86_64
> +#define Elf_Ehdr Elf64_Ehdr
> +#define Elf_Phdr Elf64_Phdr
> +#define Elf_Shdr Elf64_Shdr
> +#else
> +#define Elf_Ehdr Elf32_Ehdr
> +#define Elf_Phdr Elf32_Phdr
> +#define Elf_Shdr Elf32_Shdr
> +#endif
> +
> +#if CONFIG_FG_KASLR
> +void parse_sections_headers(void *output, Elf_Ehdr *ehdr, Elf_Phdr *phdrs);
> +void pre_relocations_cleanup(unsigned long map);
> +void post_relocations_cleanup(unsigned long map);
> +Elf_Shdr *adjust_address(long *address);
> +void adjust_relative_offset(long pc, long *value, Elf_Shdr *section);
> +bool is_percpu_addr(long pc, long offset);
> +#else
> +static inline void parse_sections_headers(void *output, Elf_Ehdr *ehdr, Elf_Phdr *phdrs) { }
> +static inline void pre_relocations_cleanup(unsigned long map) { }
> +static inline void post_relocations_cleanup(unsigned long map) { }
> +static inline Elf_Shdr *adjust_address(long *address) { return NULL; }
> +static inline void adjust_relative_offset(long pc, long *value, Elf_Shdr *section) { }
> +static inline bool is_percpu_addr(long pc, long offset) { return true; }
> +#endif /* CONFIG_FG_KASLR */
> +
>  #if CONFIG_RANDOMIZE_BASE
>  /* kaslr.c */
>  void choose_random_location(unsigned long input,
> diff --git a/arch/x86/boot/compressed/utils.c b/arch/x86/boot/compressed/utils.c
> new file mode 100644
> index 000000000000..ceefc58d7c71
> --- /dev/null
> +++ b/arch/x86/boot/compressed/utils.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * utils.c
> + *
> + * This contains various libraries that are needed for fgkaslr
> + */
> +#define __DISABLE_EXPORTS
> +#define _LINUX_KPROBES_H
> +#define NOKPROBE_SYMBOL(fname)
> +#include "../../../../lib/sort.c"
> +#include "../../../../lib/bsearch.c"
> +
> diff --git a/arch/x86/boot/compressed/vmlinux.symbols b/arch/x86/boot/compressed/vmlinux.symbols
> new file mode 100644
> index 000000000000..f48a4c396966
> --- /dev/null
> +++ b/arch/x86/boot/compressed/vmlinux.symbols
> @@ -0,0 +1,18 @@
> +kallsyms_offsets
> +kallsyms_addresses
> +kallsyms_num_syms
> +kallsyms_relative_base
> +kallsyms_names
> +kallsyms_token_table
> +kallsyms_token_index
> +kallsyms_markers
> +__start___ex_table
> +__stop___ex_table
> +_sinittext
> +_einittext
> +_stext
> +_etext
> +__start_orc_unwind_ip
> +__stop_orc_unwind_ip
> +__stop_orc_unwind
> +__start_orc_unwind
> diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
> index 680c320363db..6918d33eb5ef 100644
> --- a/arch/x86/include/asm/boot.h
> +++ b/arch/x86/include/asm/boot.h
> @@ -26,8 +26,19 @@
>  
>  #ifdef CONFIG_KERNEL_BZIP2
>  # define BOOT_HEAP_SIZE		0x400000
> -#else /* !CONFIG_KERNEL_BZIP2 */
> -# define BOOT_HEAP_SIZE		 0x10000
> +#elif CONFIG_FG_KASLR
> +/*
> + * We need extra boot heap when using fgkaslr because we make a copy
> + * of the original decompressed kernel to avoid issues with writing
> + * over ourselves when shuffling the sections. We also need extra
> + * space for resorting kallsyms after shuffling. This value could
> + * be decreased if free() would release memory properly, or if we
> + * could avoid the kernel copy. It would need to be increased if we
> + * find additional tables that need to be resorted.
> + */
> +# define BOOT_HEAP_SIZE		0x4000000
> +#else /* !CONFIG_KERNEL_BZIP2 && !CONFIG_FG_KASLR */
> +# define BOOT_HEAP_SIZE		0x10000
>  #endif
>  
>  #ifdef CONFIG_X86_64
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index 34c02e4290fe..a85d1792d5a8 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -298,6 +298,7 @@ typedef struct elf64_phdr {
>  #define SHN_LIVEPATCH	0xff20
>  #define SHN_ABS		0xfff1
>  #define SHN_COMMON	0xfff2
> +#define SHN_XINDEX	0xffff
>  #define SHN_HIRESERVE	0xffff
>   
>  typedef struct elf32_shdr {
> -- 
> 2.20.1
>