Messages in this thread Patch in this message | | | Date | Fri, 5 Feb 2021 16:22:12 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH 6/8] preempt/dynamic: Provide preempt_schedule[_notrace]() static calls |
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On Wed, Jan 27, 2021 at 05:18:37PM -0600, Josh Poimboeuf wrote:
> +static struct static_call_tramp_key *tramp_key_lookup(unsigned long addr) > +{ > + struct static_call_tramp_key *start = __start_static_call_tramp_key; > + struct static_call_tramp_key *stop = __stop_static_call_tramp_key; > + struct static_call_tramp_key *tramp_key; > + > + for (tramp_key = start; tramp_key != stop; tramp_key++) { > + unsigned long tramp; > + > + tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp; > + if (tramp == addr) > + return tramp_key; > + } > + > + return NULL; > +} > + > static int static_call_add_module(struct module *mod) > { > - return __static_call_init(mod, mod->static_call_sites, > - mod->static_call_sites + mod->num_static_call_sites); > + struct static_call_site *start = mod->static_call_sites; > + struct static_call_site *stop = start + mod->num_static_call_sites; > + struct static_call_site *site; > + > + for (site = start; site != stop; site++) { > + unsigned long addr = (unsigned long)static_call_key(site); > + struct static_call_tramp_key *tramp_key; > + > + /* > + * Is the key is exported, 'addr' points to the key, which > + * means modules are allowed to call static_call_update() on > + * it. > + * > + * Otherwise, the key isn't exported, and 'addr' points to the > + * trampoline so we need to lookup the key. > + * > + * We go through this dance to prevent crazy modules from > + * abusing sensitive static calls. > + */ > + if (!kernel_text_address(addr)) > + continue; > + > + tramp_key = tramp_key_lookup(addr); > + if (!tramp_key) { > + pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n", > + static_call_addr(site)); > + return -EINVAL; > + } > + > + site->key = ((long)tramp_key->key - (long)&tramp_key->key) | > + (site->key & STATIC_CALL_SITE_FLAGS); > + } > + > + return __static_call_init(mod, start, stop); > }
I find it works better with this on..
--- diff --git a/kernel/static_call.c b/kernel/static_call.c index 5e6f567976c1..6906c6ec4c97 100644 --- a/kernel/static_call.c +++ b/kernel/static_call.c @@ -325,7 +325,7 @@ static int __static_call_mod_text_reserved(void *start, void *end) return ret; } -static struct static_call_tramp_key *tramp_key_lookup(unsigned long addr) +static unsigned long tramp_key_lookup(unsigned long addr) { struct static_call_tramp_key *start = __start_static_call_tramp_key; struct static_call_tramp_key *stop = __stop_static_call_tramp_key; @@ -336,10 +336,10 @@ static struct static_call_tramp_key *tramp_key_lookup(unsigned long addr) tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp; if (tramp == addr) - return tramp_key; + return (long)tramp_key->key + (long)&tramp_key->key; } - return NULL; + return 0; } static int static_call_add_module(struct module *mod) @@ -350,7 +350,7 @@ static int static_call_add_module(struct module *mod) for (site = start; site != stop; site++) { unsigned long addr = (unsigned long)static_call_key(site); - struct static_call_tramp_key *tramp_key; + unsigned long key; /* * Is the key is exported, 'addr' points to the key, which @@ -366,14 +366,14 @@ static int static_call_add_module(struct module *mod) if (!kernel_text_address(addr)) continue; - tramp_key = tramp_key_lookup(addr); - if (!tramp_key) { + key = tramp_key_lookup(addr); + if (!key) { pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n", static_call_addr(site)); return -EINVAL; } - site->key = ((long)tramp_key->key - (long)&tramp_key->key) | + site->key = (key - (long)&site->key) | (site->key & STATIC_CALL_SITE_FLAGS); }
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