From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- kernel/scs.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 158 insertions(+) create mode 100644 kernel/scs.c (limited to 'kernel/scs.c') diff --git a/kernel/scs.c b/kernel/scs.c new file mode 100644 index 000000000..b7e1b096d --- /dev/null +++ b/kernel/scs.c @@ -0,0 +1,158 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Shadow Call Stack support. + * + * Copyright (C) 2019 Google LLC + */ + +#include +#include +#include +#include +#include +#include + +static void __scs_account(void *s, int account) +{ + struct page *scs_page = vmalloc_to_page(s); + + mod_node_page_state(page_pgdat(scs_page), NR_KERNEL_SCS_KB, + account * (SCS_SIZE / SZ_1K)); +} + +/* Matches NR_CACHED_STACKS for VMAP_STACK */ +#define NR_CACHED_SCS 2 +static DEFINE_PER_CPU(void *, scs_cache[NR_CACHED_SCS]); + +static void *__scs_alloc(int node) +{ + int i; + void *s; + + for (i = 0; i < NR_CACHED_SCS; i++) { + s = this_cpu_xchg(scs_cache[i], NULL); + if (s) { + s = kasan_unpoison_vmalloc(s, SCS_SIZE, + KASAN_VMALLOC_PROT_NORMAL); + memset(s, 0, SCS_SIZE); + goto out; + } + } + + s = __vmalloc_node_range(SCS_SIZE, 1, VMALLOC_START, VMALLOC_END, + GFP_SCS, PAGE_KERNEL, 0, node, + __builtin_return_address(0)); + +out: + return kasan_reset_tag(s); +} + +void *scs_alloc(int node) +{ + void *s; + + s = __scs_alloc(node); + if (!s) + return NULL; + + *__scs_magic(s) = SCS_END_MAGIC; + + /* + * Poison the allocation to catch unintentional accesses to + * the shadow stack when KASAN is enabled. + */ + kasan_poison_vmalloc(s, SCS_SIZE); + __scs_account(s, 1); + return s; +} + +void scs_free(void *s) +{ + int i; + + __scs_account(s, -1); + + /* + * We cannot sleep as this can be called in interrupt context, + * so use this_cpu_cmpxchg to update the cache, and vfree_atomic + * to free the stack. + */ + + for (i = 0; i < NR_CACHED_SCS; i++) + if (this_cpu_cmpxchg(scs_cache[i], 0, s) == NULL) + return; + + kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_PROT_NORMAL); + vfree_atomic(s); +} + +static int scs_cleanup(unsigned int cpu) +{ + int i; + void **cache = per_cpu_ptr(scs_cache, cpu); + + for (i = 0; i < NR_CACHED_SCS; i++) { + vfree(cache[i]); + cache[i] = NULL; + } + + return 0; +} + +void __init scs_init(void) +{ + cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "scs:scs_cache", NULL, + scs_cleanup); +} + +int scs_prepare(struct task_struct *tsk, int node) +{ + void *s = scs_alloc(node); + + if (!s) + return -ENOMEM; + + task_scs(tsk) = task_scs_sp(tsk) = s; + return 0; +} + +static void scs_check_usage(struct task_struct *tsk) +{ + static unsigned long highest; + + unsigned long *p, prev, curr = highest, used = 0; + + if (!IS_ENABLED(CONFIG_DEBUG_STACK_USAGE)) + return; + + for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) { + if (!READ_ONCE_NOCHECK(*p)) + break; + used += sizeof(*p); + } + + 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; + } +} + +void scs_release(struct task_struct *tsk) +{ + void *s = task_scs(tsk); + + if (!s) + return; + + WARN(task_scs_end_corrupted(tsk), + "corrupted shadow stack detected when freeing task\n"); + scs_check_usage(tsk); + scs_free(s); +} -- cgit v1.2.3