Sender: Ingo Molnar <mingo.kernel.org@gmail.com>
Date:   Sat, 8 Jan 2022 11:32:31 +0100
From:   Ingo Molnar <mingo@kernel.org>
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Ard Biesheuvel <ardb@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Al Viro <viro@zeniv.linux.org.uk>, llvm@lists.linux.dev
Subject: [PATCH] headers/deps: Add header dependencies to .c files:
 <linux/ptrace_api.h>
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* Nathan Chancellor <nathan@kernel.org> wrote:

> 1. kernel/stackleak.c build failure:
> 
> $ make -skj"$(nproc)" ARCH=x86_64 allmodconfig kernel/stackleak.o
> kernel/stackleak.c: In function ‘stackleak_erase’:
> kernel/stackleak.c:92:13: error: implicit declaration of function ‘on_thread_stack’; did you mean ‘setup_thread_stack’? [-Werror=implicit-function-declaration]

So it turns out that my build environment didn't have the stackleak code 
enabled at all:

  kepler:~/mingo.tip.git> make ARCH=x86_64 allmodconfig
  #
  # configuration written to .config
  #
  kepler:~/mingo.tip.git> grep -E 'STACKLEAK|GCC_PLUGIN' .config
  CONFIG_HAVE_ARCH_STACKLEAK=y
  CONFIG_HAVE_GCC_PLUGINS=y

... because it failed this condition:

 menuconfig GCC_PLUGINS
 ...
        depends on $(success,test -e $(shell,$(CC) -print-file-name=plugin)/include/plugin-version.h)

... because there were no plugin headers:

  kepler:~/mingo.tip.git> gcc -print-file-name=plugin
  /usr/lib/gcc/x86_64-linux-gnu/10/plugin

  kepler:~/mingo.tip.git> ls $(gcc -print-file-name=plugin)/include/
  ls: cannot access '/usr/lib/gcc/x86_64-linux-gnu/10/plugin/include/': No such file or directory

... because I needed to install the plugin-development packages for gcc-10.

After installing those I have stackleak:

  kepler:~/mingo.tip.git> grep STACKLEAK .config
  CONFIG_HAVE_ARCH_STACKLEAK=y
  CONFIG_GCC_PLUGIN_STACKLEAK=y
  CONFIG_STACKLEAK_TRACK_MIN_SIZE=100
  CONFIG_STACKLEAK_METRICS=y
  CONFIG_STACKLEAK_RUNTIME_DISABLE=y

and was able to reproduce your build failure. :-)

> This is fixed with the following diff although I am unsure if that is as
> minimal as it should be.
> 
> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
> index ce161a8e8d97..d67c5475183b 100644
> --- a/kernel/stackleak.c
> +++ b/kernel/stackleak.c
> @@ -10,8 +10,10 @@
>   * reveal and blocks some uninitialized stack variable attacks.
>   */
>  
> +#include <asm/processor_api.h>
>  #include <linux/stackleak.h>
>  #include <linux/kprobes.h>
> +#include <linux/align.h>

Yeah - I used a simpler & more generic header: <linux/ptrace_api.h> - see 
the patch below.

But your solution is functionally equivalent. This fix will be included in 
-v2, hopefully released later today.

Thanks,

	Ingo

===============>
From: Ingo Molnar <mingo@kernel.org>
Date: Sat, 8 Jan 2022 11:29:17 +0100
Subject: [PATCH] headers/deps: Add header dependencies to .c files: <linux/ptrace_api.h>

Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/stackleak.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/stackleak.c b/kernel/stackleak.c
index ce161a8e8d97..fde49e2f209a 100644
--- a/kernel/stackleak.c
+++ b/kernel/stackleak.c
@@ -10,6 +10,7 @@
  * reveal and blocks some uninitialized stack variable attacks.
  */
 
+#include <linux/ptrace_api.h>
 #include <linux/stackleak.h>
 #include <linux/kprobes.h>