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FROMLIST: scs: add support for stack usage debugging

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Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. When enabled,
also prints out the highest shadow stack usage per process.

Bug: 145210207
Change-Id: I4c085b51e1432e8d52e54126ffd8bf7b6e35b529
(am from https://lore.kernel.org/patchwork/patch/1149056/)
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Sami Tolvanen 2018-09-06 13:09:06 -07:00 committed by Alistair Delva
parent 9c265248fa
commit 32518aee30
1 changed files with 39 additions and 0 deletions
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39
kernel/scs.c
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@ -184,6 +184,44 @@ int scs_prepare(struct task_struct *tsk, int node)
return 0; return 0;
} }
#ifdef CONFIG_DEBUG_STACK_USAGE
static inline unsigned long scs_used(struct task_struct *tsk)
{
unsigned long *p = __scs_base(tsk);
unsigned long *end = scs_magic(p);
unsigned long s = (unsigned long)p;
while (p < end && READ_ONCE_NOCHECK(*p))
p++;
return (unsigned long)p - s;
}
static void scs_check_usage(struct task_struct *tsk)
{
static DEFINE_SPINLOCK(lock);
static unsigned long highest;
unsigned long used = scs_used(tsk);
if (used <= highest)
return;
spin_lock(&lock);
if (used > highest) {
pr_info("%s (%d): highest shadow stack usage: %lu bytes\n",
tsk->comm, task_pid_nr(tsk), used);
highest = used;
}
spin_unlock(&lock);
}
#else
static inline void scs_check_usage(struct task_struct *tsk)
{
}
#endif
bool scs_corrupted(struct task_struct *tsk) bool scs_corrupted(struct task_struct *tsk)
{ {
unsigned long *magic = scs_magic(__scs_base(tsk)); unsigned long *magic = scs_magic(__scs_base(tsk));
@ -200,6 +238,7 @@ void scs_release(struct task_struct *tsk)
return; return;
WARN_ON(scs_corrupted(tsk)); WARN_ON(scs_corrupted(tsk));
scs_check_usage(tsk);
scs_account(tsk, -1); scs_account(tsk, -1);
task_set_scs(tsk, NULL); task_set_scs(tsk, NULL);