| Date | Mon, 27 Apr 2020 09:00:09 -0700 | Subject | [PATCH v13 03/12] scs: add support for stack usage debugging | From | Sami Tolvanen <> |
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Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. When enabled, also prints out the highest shadow stack usage per process.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Will Deacon <will@kernel.org> --- kernel/scs.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/kernel/scs.c b/kernel/scs.c index 8769016c714c..2a96573f2b1b 100644 --- a/kernel/scs.c +++ b/kernel/scs.c @@ -68,6 +68,43 @@ int scs_prepare(struct task_struct *tsk, int node) return 0; } +#ifdef CONFIG_DEBUG_STACK_USAGE +static unsigned long __scs_used(struct task_struct *tsk) +{ + unsigned long *p = task_scs(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 unsigned long highest; + unsigned long used = __scs_used(tsk); + unsigned long prev; + unsigned long curr = highest; + + while (used > curr) { + prev = cmpxchg_relaxed(&highest, curr, used); + + if (prev == curr) { + pr_info("%s (%d): highest shadow stack usage: " + "%lu bytes\n", + tsk->comm, task_pid_nr(tsk), used); + break; + } + + curr = prev; + } +} +#else +static inline void scs_check_usage(struct task_struct *tsk) {} +#endif + void scs_release(struct task_struct *tsk) { void *s; @@ -77,6 +114,7 @@ void scs_release(struct task_struct *tsk) return; WARN_ON(scs_corrupted(tsk)); + scs_check_usage(tsk); scs_account(tsk, -1); scs_free(s); -- 2.26.2.303.gf8c07b1a785-goog
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