Merge tag 'x86_urgent_for_6.16-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipHEADmaster

Pull x86 fixes from Dave Hansen:
 "This is a pretty scattered set of fixes. The majority of them are
  further fixups around the recent ITS mitigations.

  The rest don't really have a coherent story:

   - Some flavors of Xen PV guests don't support large pages, but the
     set_memory.c code assumes all CPUs support them.

     Avoid problems with a quick CPU feature check.

   - The TDX code has some wrappers to help retry calls to the TDX
     module. They use function pointers to assembly functions and the
     compiler usually generates direct CALLs. But some new compilers,
     plus -Os turned them in to indirect CALLs and the assembly code was
     not annotated for indirect calls.

     Force inlining of the helper to fix it up.

   - Last, a FRED issue showed up when single-stepping. It's fine when
     using an external debugger, but was getting stuck returning from a
     SIGTRAP handler otherwise.

     Clear the FRED 'swevent' bit to ensure that forward progress is
     made"

* tag 'x86_urgent_for_6.16-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "mm/execmem: Unify early execmem_cache behaviour"
  x86/its: explicitly manage permissions for ITS pages
  x86/its: move its_pages array to struct mod_arch_specific
  x86/Kconfig: only enable ROX cache in execmem when STRICT_MODULE_RWX is set
  x86/mm/pat: don't collapse pages without PSE set
  x86/virt/tdx: Avoid indirect calls to TDX assembly functions
  selftests/x86: Add a test to detect infinite SIGTRAP handler loop
  x86/fred/signal: Prevent immediate repeat of single step trap on return from SIGTRAP handler

1 files changed, 55 insertions, 24 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index ecfe7b497cad..6455f7f751b3 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -116,6 +116,24 @@ static struct module *its_mod;
 #endif
 static void *its_page;
 static unsigned int its_offset;
+struct its_array its_pages;
+
+static void *__its_alloc(struct its_array *pages)
+{
+	void *page __free(execmem) = execmem_alloc(EXECMEM_MODULE_TEXT, PAGE_SIZE);
+	if (!page)
+		return NULL;
+
+	void *tmp = krealloc(pages->pages, (pages->num+1) * sizeof(void *),
+			     GFP_KERNEL);
+	if (!tmp)
+		return NULL;
+
+	pages->pages = tmp;
+	pages->pages[pages->num++] = page;
+
+	return no_free_ptr(page);
+}
 
 /* Initialize a thunk with the "jmp *reg; int3" instructions. */
 static void *its_init_thunk(void *thunk, int reg)
@@ -151,6 +169,21 @@ static void *its_init_thunk(void *thunk, int reg)
 	return thunk + offset;
 }
 
+static void its_pages_protect(struct its_array *pages)
+{
+	for (int i = 0; i < pages->num; i++) {
+		void *page = pages->pages[i];
+		execmem_restore_rox(page, PAGE_SIZE);
+	}
+}
+
+static void its_fini_core(void)
+{
+	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+		its_pages_protect(&its_pages);
+	kfree(its_pages.pages);
+}
+
 #ifdef CONFIG_MODULES
 void its_init_mod(struct module *mod)
 {
@@ -173,10 +206,8 @@ void its_fini_mod(struct module *mod)
 	its_page = NULL;
 	mutex_unlock(&text_mutex);
 
-	for (int i = 0; i < mod->its_num_pages; i++) {
-		void *page = mod->its_page_array[i];
-		execmem_restore_rox(page, PAGE_SIZE);
-	}
+	if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		its_pages_protect(&mod->arch.its_pages);
 }
 
 void its_free_mod(struct module *mod)
@@ -184,37 +215,33 @@ void its_free_mod(struct module *mod)
 	if (!cpu_feature_enabled(X86_FEATURE_INDIRECT_THUNK_ITS))
 		return;
 
-	for (int i = 0; i < mod->its_num_pages; i++) {
-		void *page = mod->its_page_array[i];
+	for (int i = 0; i < mod->arch.its_pages.num; i++) {
+		void *page = mod->arch.its_pages.pages[i];
 		execmem_free(page);
 	}
-	kfree(mod->its_page_array);
+	kfree(mod->arch.its_pages.pages);
 }
 #endif /* CONFIG_MODULES */
 
 static void *its_alloc(void)
 {
-	void *page __free(execmem) = execmem_alloc(EXECMEM_MODULE_TEXT, PAGE_SIZE);
+	struct its_array *pages = &its_pages;
+	void *page;
 
+#ifdef CONFIG_MODULE
+	if (its_mod)
+		pages = &its_mod->arch.its_pages;
+#endif
+
+	page = __its_alloc(pages);
 	if (!page)
 		return NULL;
 
-#ifdef CONFIG_MODULES
-	if (its_mod) {
-		void *tmp = krealloc(its_mod->its_page_array,
-				     (its_mod->its_num_pages+1) * sizeof(void *),
-				     GFP_KERNEL);
-		if (!tmp)
-			return NULL;
-
-		its_mod->its_page_array = tmp;
-		its_mod->its_page_array[its_mod->its_num_pages++] = page;
+	execmem_make_temp_rw(page, PAGE_SIZE);
+	if (pages == &its_pages)
+		set_memory_x((unsigned long)page, 1);
 
-		execmem_make_temp_rw(page, PAGE_SIZE);
-	}
-#endif /* CONFIG_MODULES */
-
-	return no_free_ptr(page);
+	return page;
 }
 
 static void *its_allocate_thunk(int reg)
@@ -268,7 +295,9 @@ u8 *its_static_thunk(int reg)
 	return thunk;
 }
 
-#endif
+#else
+static inline void its_fini_core(void) {}
+#endif /* CONFIG_MITIGATION_ITS */
 
 /*
  * Nomenclature for variable names to simplify and clarify this code and ease
@@ -2338,6 +2367,8 @@ void __init alternative_instructions(void)
 	apply_retpolines(__retpoline_sites, __retpoline_sites_end);
 	apply_returns(__return_sites, __return_sites_end);
 
+	its_fini_core();
+
 	/*
 	 * Adjust all CALL instructions to point to func()-10, including
 	 * those in .altinstr_replacement.