From 872df34d7c51a79523820ea6a14860398c639b87 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 14 Oct 2024 10:05:48 -0700 Subject: x86/its: Use dynamic thunks for indirect branches ITS mitigation moves the unsafe indirect branches to a safe thunk. This could degrade the prediction accuracy as the source address of indirect branches becomes same for different execution paths. To improve the predictions, and hence the performance, assign a separate thunk for each indirect callsite. This is also a defense-in-depth measure to avoid indirect branches aliasing with each other. As an example, 5000 dynamic thunks would utilize around 16 bits of the address space, thereby gaining entropy. For a BTB that uses 32 bits for indexing, dynamic thunks could provide better prediction accuracy over fixed thunks. Have ITS thunks be variable sized and use EXECMEM_MODULE_TEXT such that they are both more flexible (got to extend them later) and live in 2M TLBs, just like kernel code, avoiding undue TLB pressure. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Alexandre Chartre --- include/linux/module.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/module.h') diff --git a/include/linux/module.h b/include/linux/module.h index b3329110d668..8050f77c3b64 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -586,6 +586,11 @@ struct module { atomic_t refcnt; #endif +#ifdef CONFIG_MITIGATION_ITS + int its_num_pages; + void **its_page_array; +#endif + #ifdef CONFIG_CONSTRUCTORS /* Constructor functions. */ ctor_fn_t *ctors; -- cgit v1.2.3 From 8c21c4111128365f81a88573eeb2844fa696b299 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 2 Jun 2025 19:55:36 +0900 Subject: module: make __mod_device_table__* symbols static The __mod_device_table__* symbols are only parsed by modpost to generate MODULE_ALIAS() entries from MODULE_DEVICE_TABLE(). Therefore, these symbols do not need to be globally visible, or globally unique. If they are in the global scope, we would worry about the symbol uniqueness, but modpost is fine with parsing multiple symbols with the same name. Signed-off-by: Masahiro Yamada Reviewed-by: Petr Pavlu --- include/linux/module.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/module.h') diff --git a/include/linux/module.h b/include/linux/module.h index 8050f77c3b64..92e1420fccdf 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -249,8 +249,8 @@ struct module_kobject *lookup_or_create_module_kobject(const char *name); #ifdef MODULE /* Creates an alias so file2alias.c can find device table. */ #define MODULE_DEVICE_TABLE(type, name) \ -extern typeof(name) __mod_device_table__##type##__##name \ - __attribute__ ((unused, alias(__stringify(name)))) +static typeof(name) __mod_device_table__##type##__##name \ + __attribute__ ((used, alias(__stringify(name)))) #else /* !MODULE */ #define MODULE_DEVICE_TABLE(type, name) #endif -- cgit v1.2.3