gcc-plugins/stackleak: Avoid .head.text section

The .head.text section carries the startup code that runs with the MMU
off or with a translation of memory that deviates from the ordinary one.
So avo

gcc-plugins/stackleak: Avoid .head.text section

The .head.text section carries the startup code that runs with the MMU
off or with a translation of memory that deviates from the ordinary one.
So avoid instrumentation with the stackleak plugin, which already avoids
.init.text and .noinstr.text entirely.

Fixes: 48204aba801f1b51 ("x86/sme: Move early SME kernel encryption handling into .head.text")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Signed-off-by: Ard Biesheuvel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

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treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_385.RULE

Based on the normalized pattern:

licensed under the gpl v2

extracted by the scancode license scanner the SPDX license

treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_385.RULE

Based on the normalized pattern:

licensed under the gpl v2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference.

Reviewed-by: Allison Randal <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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gcc-plugins: use KERNELVERSION for plugin version

Commit 61f60bac8c05 ("gcc-plugins: Change all version strings match
kernel") broke parallel builds.

Instead of adding the dependency between GCC pl

gcc-plugins: use KERNELVERSION for plugin version

Commit 61f60bac8c05 ("gcc-plugins: Change all version strings match
kernel") broke parallel builds.

Instead of adding the dependency between GCC plugins and utsrelease.h,
let's use KERNELVERSION, which does not require any build artifact.

Another reason why I want to avoid utsrelease.h is because it depends
on CONFIG_LOCALVERSION(_AUTO) and localversion* files.

(include/generated/utsrelease.h depends on include/config/kernel.release,
which is generated by scripts/setlocalversion)

I want to keep host tools independent of the kernel configuration.

There is no good reason to rebuild GCC plugins just because of
CONFIG_LOCALVERSION being changed.

We just want to associate the plugin versions with the kernel source
version. KERNELVERSION should be enough for our purpose.

Fixes: 61f60bac8c05 ("gcc-plugins: Change all version strings match kernel")
Reported-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/linux-mm/[email protected]
Reported-by: Guenter Roeck <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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gcc-plugins: Change all version strings match kernel

It's not meaningful for the GCC plugins to track their versions separately
from the rest of the kernel. Switch all versions to the kernel version

gcc-plugins: Change all version strings match kernel

It's not meaningful for the GCC plugins to track their versions separately
from the rest of the kernel. Switch all versions to the kernel version.

Fix mismatched indenting while we're at it.

Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins/stackleak: Ignore .noinstr.text and .entry.text

The .noinstr.text section functions may not have "current()" sanely
available. Similarly true for .entry.text, though such a check is
curr

gcc-plugins/stackleak: Ignore .noinstr.text and .entry.text

The .noinstr.text section functions may not have "current()" sanely
available. Similarly true for .entry.text, though such a check is
currently redundant. Add a check for both. In an x86_64 defconfig build,
the following functions no longer receive stackleak instrumentation:

__do_fast_syscall_32()
do_int80_syscall_32()
do_machine_check()
do_syscall_64()
exc_general_protection()
fixup_bad_iret()

Suggested-by: Peter Zijlstra <[email protected]>
Cc: Alexander Popov <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins/stackleak: Exactly match strings instead of prefixes

Since STRING_CST may not be NUL terminated, strncmp() was used for check
for equality. However, this may lead to mismatches for longe

gcc-plugins/stackleak: Exactly match strings instead of prefixes

Since STRING_CST may not be NUL terminated, strncmp() was used for check
for equality. However, this may lead to mismatches for longer section
names where the start matches the tested-for string. Test for exact
equality by checking for the presences of NUL termination.

Cc: Alexander Popov <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins: remove code for GCC versions older than 4.9

Documentation/process/changes.rst says the minimal GCC version is 4.9.
Hence, BUILDING_GCC_VERSION is greater than or equal to 4009.

Signed-

gcc-plugins: remove code for GCC versions older than 4.9

Documentation/process/changes.rst says the minimal GCC version is 4.9.
Hence, BUILDING_GCC_VERSION is greater than or equal to 4009.

Signed-off-by: Masahiro Yamada <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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gcc-plugins/stackleak: Add 'verbose' plugin parameter

Add 'verbose' plugin parameter for stackleak gcc plugin.
It can be used for printing additional info about the kernel code
instrumentation.

For

gcc-plugins/stackleak: Add 'verbose' plugin parameter

Add 'verbose' plugin parameter for stackleak gcc plugin.
It can be used for printing additional info about the kernel code
instrumentation.

For using it add the following to scripts/Makefile.gcc-plugins:
gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
+= -fplugin-arg-stackleak_plugin-verbose

Signed-off-by: Alexander Popov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving

The kernel code instrumentation in stackleak gcc plugin works in two stages.
At first, stack tracking is added to GIMP

gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving

The kernel code instrumentation in stackleak gcc plugin works in two stages.
At first, stack tracking is added to GIMPLE representation of every function
(except some special cases). And later, when stack frame size info is
available, stack tracking is removed from the RTL representation of the
functions with small stack frame. There is an unwanted side-effect for these
functions: some of them do useless work with caller-saved registers.

As an example of such case, proc_sys_write without() instrumentation:
55 push %rbp
41 b8 01 00 00 00 mov $0x1,%r8d
48 89 e5 mov %rsp,%rbp
e8 11 ff ff ff callq ffffffff81284610 <proc_sys_call_handler>
5d pop %rbp
c3 retq
0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
00 00 00

proc_sys_write() with instrumentation:
55 push %rbp
48 89 e5 mov %rsp,%rbp
41 56 push %r14
41 55 push %r13
41 54 push %r12
53 push %rbx
49 89 f4 mov %rsi,%r12
48 89 fb mov %rdi,%rbx
49 89 d5 mov %rdx,%r13
49 89 ce mov %rcx,%r14
4c 89 f1 mov %r14,%rcx
4c 89 ea mov %r13,%rdx
4c 89 e6 mov %r12,%rsi
48 89 df mov %rbx,%rdi
41 b8 01 00 00 00 mov $0x1,%r8d
e8 f2 fe ff ff callq ffffffff81298e80 <proc_sys_call_handler>
5b pop %rbx
41 5c pop %r12
41 5d pop %r13
41 5e pop %r14
5d pop %rbp
c3 retq
66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
00 00

Let's improve the instrumentation to avoid this:

1. Make stackleak_track_stack() save all register that it works with.
Use no_caller_saved_registers attribute for that function. This attribute
is available for x86_64 and i386 starting from gcc-7.

2. Insert calling stackleak_track_stack() in asm:
asm volatile("call stackleak_track_stack" :: "r" (current_stack_pointer))
Here we use ASM_CALL_CONSTRAINT trick from arch/x86/include/asm/asm.h.
The input constraint is taken into account during gcc shrink-wrapping
optimization. It is needed to be sure that stackleak_track_stack() call is
inserted after the prologue of the containing function, when the stack
frame is prepared.

This work is a deep reengineering of the idea described on grsecurity blog
https://grsecurity.net/resolving_an_unfortunate_stackleak_interaction

Signed-off-by: Alexander Popov <[email protected]>
Acked-by: Miguel Ojeda <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins/stackleak: Avoid assignment for unused macro argument

With GCC version >= 8, the cgraph_create_edge() macro argument using
"frequency" goes unused. Instead of assigning a temporary varia

gcc-plugins/stackleak: Avoid assignment for unused macro argument

With GCC version >= 8, the cgraph_create_edge() macro argument using
"frequency" goes unused. Instead of assigning a temporary variable for
the argument, pass the compute_call_stmt_bb_frequency() call directly
as the macro argument so that it will just not be called when it is
not wanted by the macros.

Silences the warning:

scripts/gcc-plugins/stackleak_plugin.c:54:6: warning: variable ‘frequency’ set but not used [-Wunused-but-set-variable]

Now builds cleanly with gcc-7 and gcc-9. Both boot and pass
STACKLEAK_ERASING LKDTM test.

Signed-off-by: Kees Cook <[email protected]>

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stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass

Currently the 'stackleak_cleanup' pass deleting a CALL insn is executed
after the 'reload' pass. That allows gcc to do so

stackleak: Register the 'stackleak_cleanup' pass before the '*free_cfg' pass

Currently the 'stackleak_cleanup' pass deleting a CALL insn is executed
after the 'reload' pass. That allows gcc to do some weird optimization in
function prologues and epilogues, which are generated later [1].

Let's avoid that by registering the 'stackleak_cleanup' pass before
the '*free_cfg' pass. It's the moment when the stack frame size is
already final, function prologues and epilogues are generated, and the
machine-dependent code transformations are not done.

[1] https://www.openwall.com/lists/kernel-hardening/2018/11/23/2

Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Alexander Popov <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack

The STACKLEAK feature erases the kernel stack before returning from
syscalls. That reduces the information which kernel stack leak bug

gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack

The STACKLEAK feature erases the kernel stack before returning from
syscalls. That reduces the information which kernel stack leak bugs can
reveal and blocks some uninitialized stack variable attacks.

This commit introduces the STACKLEAK gcc plugin. It is needed for
tracking the lowest border of the kernel stack, which is important
for the code erasing the used part of the kernel stack at the end
of syscalls (comes in a separate commit).

The STACKLEAK feature is ported from grsecurity/PaX. More information at:
https://grsecurity.net/
https://pax.grsecurity.net/

This code is modified from Brad Spengler/PaX Team's code in the last
public patch of grsecurity/PaX based on our understanding of the code.
Changes or omissions from the original code are ours and don't reflect
the original grsecurity/PaX code.

Signed-off-by: Alexander Popov <[email protected]>
Tested-by: Laura Abbott <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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