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x86: Expose thread features in /proc/$PID/status

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Applications and loaders can have logic to decide whether to enable
shadow stack. They usually don't report whether shadow stack has been
enabled or not, so there is no way to verify whether an application
actually is protected by shadow stack.

Add two lines in /proc/$PID/status to report enabled and locked features.

Since, this involves referring to arch specific defines in asm/prctl.h,
implement an arch breakout to emit the feature lines.

[Switched to CET, added to commit log]

Co-developed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-37-rick.p.edgecombe%40intel.com
This commit is contained in:
Rick Edgecombe 2023-06-12 17:11:02 -07:00 committed by Dave Hansen
parent 1d62c65372
commit 0ee44885fe
3 changed files with 30 additions and 0 deletions
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23
arch/x86/kernel/cpu/proc.c
View file

@ -4,6 +4,8 @@
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/cpufreq.h>
#include <asm/prctl.h>
#include <linux/proc_fs.h>
#include "cpu.h"
@ -175,3 +177,24 @@ const struct seq_operations cpuinfo_op = {
.stop = c_stop,
.show = show_cpuinfo,
};
#ifdef CONFIG_X86_USER_SHADOW_STACK
static void dump_x86_features(struct seq_file *m, unsigned long features)
{
if (features & ARCH_SHSTK_SHSTK)
seq_puts(m, "shstk ");
if (features & ARCH_SHSTK_WRSS)
seq_puts(m, "wrss ");
}
void arch_proc_pid_thread_features(struct seq_file *m, struct task_struct *task)
{
seq_puts(m, "x86_Thread_features:\t");
dump_x86_features(m, task->thread.features);
seq_putc(m, '\n');
seq_puts(m, "x86_Thread_features_locked:\t");
dump_x86_features(m, task->thread.features_locked);
seq_putc(m, '\n');
}
#endif /* CONFIG_X86_USER_SHADOW_STACK */

6
fs/proc/array.c
View file

@ -431,6 +431,11 @@ static inline void task_untag_mask(struct seq_file *m, struct mm_struct *mm)
seq_printf(m, "untag_mask:\t%#lx\n", mm_untag_mask(mm));
}
__weak void arch_proc_pid_thread_features(struct seq_file *m,
struct task_struct *task)
{
}
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
@ -455,6 +460,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
task_cpus_allowed(m, task);
cpuset_task_status_allowed(m, task);
task_context_switch_counts(m, task);
arch_proc_pid_thread_features(m, task);
return 0;
}

1
include/linux/proc_fs.h
View file

@ -159,6 +159,7 @@ int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
#endif /* CONFIG_PROC_PID_ARCH_STATUS */
void arch_report_meminfo(struct seq_file *m);
void arch_proc_pid_thread_features(struct seq_file *m, struct task_struct *task);
#else /* CONFIG_PROC_FS */