[ Sasha's backport helper bot ]
Hi,
Summary of potential issues: ℹ️ This is part 14/14 of a series ⚠️ Found follow-up fixes in mainline
The upstream commit SHA1 provided is correct: 872df34d7c51a79523820ea6a14860398c639b87
WARNING: Author mismatch between patch and upstream commit: Backport author: Pawan Guptapawan.kumar.gupta@linux.intel.com Commit author: Peter Zijlstrapeterz@infradead.org
Status in newer kernel trees: 6.14.y | Present (different SHA1: 0177d630dd90) 6.12.y | Present (different SHA1: e730bef9bebb) 6.6.y | Present (different SHA1: 101d064c5817) 6.1.y | Present (different SHA1: bc7ff7035f36)
Found fixes commits: 9f35e33144ae x86/its: Fix build errors when CONFIG_MODULES=n
Note: The patch differs from the upstream commit: --- 1: 872df34d7c51a ! 1: ef20c226851f4 x86/its: Use dynamic thunks for indirect branches @@ Metadata ## Commit message ## x86/its: Use dynamic thunks for indirect branches
+ commit 872df34d7c51a79523820ea6a14860398c639b87 upstream. + 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. @@ Commit message they are both more flexible (got to extend them later) and live in 2M TLBs, just like kernel code, avoiding undue TLB pressure.
+ [ pawan: CONFIG_EXECMEM and CONFIG_EXECMEM_ROX are not supported on + backport kernel, made changes to use module_alloc() and + set_memory_*() for dynamic thunks. ] + Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Reviewed-by: Alexandre Chartre alexandre.chartre@oracle.com
- ## arch/x86/Kconfig ## -@@ arch/x86/Kconfig: config MITIGATION_ITS - bool "Enable Indirect Target Selection mitigation" - depends on CPU_SUP_INTEL && X86_64 - depends on MITIGATION_RETPOLINE && MITIGATION_RETHUNK -+ select EXECMEM - default y - help - Enable Indirect Target Selection (ITS) mitigation. ITS is a bug in - ## arch/x86/include/asm/alternative.h ## -@@ arch/x86/include/asm/alternative.h: static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, - } - #endif +@@ arch/x86/include/asm/alternative.h: extern void apply_returns(s32 *start, s32 *end); + + struct module;
+#ifdef CONFIG_MITIGATION_ITS +extern void its_init_mod(struct module *mod); @@ arch/x86/include/asm/alternative.h: static __always_inline int x86_call_depth_em +static inline void its_free_mod(struct module *mod) { } +#endif + - #if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL) + #ifdef CONFIG_RETHUNK extern bool cpu_wants_rethunk(void); extern bool cpu_wants_rethunk_at(void *addr);
@@ arch/x86/kernel/alternative.c #include <linux/mmu_context.h> #include <linux/bsearch.h> #include <linux/sync_core.h> -+#include <linux/execmem.h> ++#include <linux/moduleloader.h> #include <asm/text-patching.h> #include <asm/alternative.h> #include <asm/sections.h> @@ + #include <asm/fixmap.h> + #include <asm/paravirt.h> #include <asm/asm-prototypes.h> - #include <asm/cfi.h> - #include <asm/ibt.h> +#include <asm/set_memory.h>
int __read_mostly alternatives_patched;
-@@ arch/x86/kernel/alternative.c: const unsigned char * const x86_nops[ASM_NOP_MAX+1] = - #endif - }; +@@ arch/x86/kernel/alternative.c: static int emit_indirect(int op, int reg, u8 *bytes) + + #ifdef CONFIG_MITIGATION_ITS
-+#ifdef CONFIG_MITIGATION_ITS -+ +static struct module *its_mod; +static void *its_page; +static unsigned int its_offset; @@ arch/x86/kernel/alternative.c: const unsigned char * const x86_nops[ASM_NOP_MAX+ + +void its_fini_mod(struct module *mod) +{ ++ int i; ++ + if (!cpu_feature_enabled(X86_FEATURE_INDIRECT_THUNK_ITS)) + return; + @@ arch/x86/kernel/alternative.c: const unsigned char * const x86_nops[ASM_NOP_MAX+ + its_page = NULL; + mutex_unlock(&text_mutex); + -+ for (int i = 0; i < mod->its_num_pages; i++) { ++ for (i = 0; i < mod->its_num_pages; i++) { + void *page = mod->its_page_array[i]; -+ execmem_restore_rox(page, PAGE_SIZE); ++ set_memory_ro((unsigned long)page, 1); ++ set_memory_x((unsigned long)page, 1); + } +} + +void its_free_mod(struct module *mod) +{ ++ int i; ++ + if (!cpu_feature_enabled(X86_FEATURE_INDIRECT_THUNK_ITS)) + return; + -+ for (int i = 0; i < mod->its_num_pages; i++) { ++ for (i = 0; i < mod->its_num_pages; i++) { + void *page = mod->its_page_array[i]; -+ execmem_free(page); ++ module_memfree(page); + } + kfree(mod->its_page_array); +} + +static void *its_alloc(void) +{ -+ void *page __free(execmem) = execmem_alloc(EXECMEM_MODULE_TEXT, PAGE_SIZE); ++ void *page = module_alloc(PAGE_SIZE); + + if (!page) + return NULL; @@ arch/x86/kernel/alternative.c: const unsigned char * const x86_nops[ASM_NOP_MAX+ + void *tmp = krealloc(its_mod->its_page_array, + (its_mod->its_num_pages+1) * sizeof(void *), + GFP_KERNEL); -+ if (!tmp) ++ if (!tmp) { ++ module_memfree(page); + 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); + } + -+ return no_free_ptr(page); ++ return page; +} + +static void *its_allocate_thunk(int reg) @@ arch/x86/kernel/alternative.c: const unsigned char * const x86_nops[ASM_NOP_MAX+ + thunk = its_page + its_offset; + its_offset += size; + -+ return its_init_thunk(thunk, reg); -+} ++ set_memory_rw((unsigned long)its_page, 1); ++ thunk = its_init_thunk(thunk, reg); ++ set_memory_ro((unsigned long)its_page, 1); ++ set_memory_x((unsigned long)its_page, 1); + -+#endif ++ return thunk; ++} + - /* - * Nomenclature for variable names to simplify and clarify this code and ease - * any potential staring at it: -@@ arch/x86/kernel/alternative.c: static int emit_call_track_retpoline(void *addr, struct insn *insn, int reg, u8 - #ifdef CONFIG_MITIGATION_ITS + static int __emit_trampoline(void *addr, struct insn *insn, u8 *bytes, + void *call_dest, void *jmp_dest) + { +@@ arch/x86/kernel/alternative.c: static int __emit_trampoline(void *addr, struct insn *insn, u8 *bytes, + static int emit_its_trampoline(void *addr, struct insn *insn, int reg, u8 *bytes) { - return __emit_trampoline(addr, insn, bytes, @@ arch/x86/kernel/alternative.c: static int emit_call_track_retpoline(void *addr,
## arch/x86/kernel/module.c ## @@ arch/x86/kernel/module.c: int module_finalize(const Elf_Ehdr *hdr, - ibt_endbr = s; + void *pseg = (void *)para->sh_addr; + apply_paravirt(pseg, pseg + para->sh_size); } - ++ + its_init_mod(me); + - if (retpolines || cfi) { - void *rseg = NULL, *cseg = NULL; - unsigned int rsize = 0, csize = 0; -@@ arch/x86/kernel/module.c: int module_finalize(const Elf_Ehdr *hdr, + if (retpolines) { void *rseg = (void *)retpolines->sh_addr; apply_retpolines(rseg, rseg + retpolines->sh_size); } @@ arch/x86/kernel/module.c: int module_finalize(const Elf_Ehdr *hdr, + its_free_mod(mod); }
- ## include/linux/execmem.h ## -@@ - - #include <linux/types.h> - #include <linux/moduleloader.h> -+#include <linux/cleanup.h> - - #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \ - !defined(CONFIG_KASAN_VMALLOC) -@@ include/linux/execmem.h: void *execmem_alloc(enum execmem_type type, size_t size); - */ - void execmem_free(void *ptr); - -+DEFINE_FREE(execmem, void *, if (_T) execmem_free(_T)); -+ - #ifdef CONFIG_MMU - /** - * execmem_vmap - create virtual mapping for EXECMEM_MODULE_DATA memory - ## include/linux/module.h ## @@ include/linux/module.h: struct module { atomic_t refcnt; ---
NOTE: These results are for this patch alone. Full series testing will be performed when all parts are received.
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-6.1.y | Success | Success |