summaryrefslogtreecommitdiff
path: root/arch/x86/include/asm/alternative.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/include/asm/alternative.h')
-rw-r--r--arch/x86/include/asm/alternative.h386
1 files changed, 274 insertions, 112 deletions
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 58ed6d96a6ac..03364510d5fe 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -1,10 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ALTERNATIVE_H
#define _ASM_X86_ALTERNATIVE_H
#include <linux/types.h>
-#include <linux/stddef.h>
#include <linux/stringify.h>
+#include <linux/objtool.h>
#include <asm/asm.h>
+#include <asm/bug.h>
+
+#define ALT_FLAGS_SHIFT 16
+
+#define ALT_FLAG_NOT (1 << 0)
+#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
+#define ALT_FLAG_DIRECT_CALL (1 << 1)
+#define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
+#define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)
+
+#ifndef __ASSEMBLER__
+
+#include <linux/stddef.h>
/*
* Alternative inline assembly for SMP.
@@ -35,26 +49,119 @@
".popsection\n" \
"671:"
-#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
+#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock "
#else /* ! CONFIG_SMP */
#define LOCK_PREFIX_HERE ""
#define LOCK_PREFIX ""
#endif
+/*
+ * The patching flags are part of the upper bits of the @ft_flags parameter when
+ * specifying them. The split is currently like this:
+ *
+ * [31... flags ...16][15... CPUID feature bit ...0]
+ *
+ * but since this is all hidden in the macros argument being split, those fields can be
+ * extended in the future to fit in a u64 or however the need arises.
+ */
struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */
- u16 cpuid; /* cpuid bit set for replacement */
+
+ union {
+ struct {
+ u32 cpuid: 16; /* CPUID bit set for replacement */
+ u32 flags: 16; /* patching control flags */
+ };
+ u32 ft_flags;
+ };
+
u8 instrlen; /* length of original instruction */
- u8 replacementlen; /* length of new instruction, <= instrlen */
-};
+ u8 replacementlen; /* length of new instruction */
+} __packed;
+
+extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
+
+extern s32 __retpoline_sites[], __retpoline_sites_end[];
+extern s32 __return_sites[], __return_sites_end[];
+extern s32 __cfi_sites[], __cfi_sites_end[];
+extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[];
+extern s32 __smp_locks[], __smp_locks_end[];
+
+/*
+ * Debug flag that can be tested to see whether alternative
+ * instructions were patched in already:
+ */
+extern int alternatives_patched;
extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+extern void apply_retpolines(s32 *start, s32 *end);
+extern void apply_returns(s32 *start, s32 *end);
+extern void apply_seal_endbr(s32 *start, s32 *end);
+extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
+ s32 *start_cfi, s32 *end_cfi);
struct module;
+struct callthunk_sites {
+ s32 *call_start, *call_end;
+};
+
+#ifdef CONFIG_CALL_THUNKS
+extern void callthunks_patch_builtin_calls(void);
+extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
+ struct module *mod);
+extern void *callthunks_translate_call_dest(void *dest);
+extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
+#else
+static __always_inline void callthunks_patch_builtin_calls(void) {}
+static __always_inline void
+callthunks_patch_module_calls(struct callthunk_sites *sites,
+ struct module *mod) {}
+static __always_inline void *callthunks_translate_call_dest(void *dest)
+{
+ return dest;
+}
+static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
+ void *func, void *ip)
+{
+ return 0;
+}
+#endif
+
+#ifdef CONFIG_MITIGATION_ITS
+extern void its_init_mod(struct module *mod);
+extern void its_fini_mod(struct module *mod);
+extern void its_free_mod(struct module *mod);
+extern u8 *its_static_thunk(int reg);
+#else /* CONFIG_MITIGATION_ITS */
+static inline void its_init_mod(struct module *mod) { }
+static inline void its_fini_mod(struct module *mod) { }
+static inline void its_free_mod(struct module *mod) { }
+static inline u8 *its_static_thunk(int reg)
+{
+ WARN_ONCE(1, "ITS not compiled in");
+
+ return NULL;
+}
+#endif
+
+#if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL)
+extern bool cpu_wants_rethunk(void);
+extern bool cpu_wants_rethunk_at(void *addr);
+#else
+static __always_inline bool cpu_wants_rethunk(void)
+{
+ return false;
+}
+static __always_inline bool cpu_wants_rethunk_at(void *addr)
+{
+ return false;
+}
+#endif
+
#ifdef CONFIG_SMP
extern void alternatives_smp_module_add(struct module *mod, char *name,
void *locks, void *locks_end,
@@ -75,60 +182,54 @@ static inline int alternatives_text_reserved(void *start, void *end)
}
#endif /* CONFIG_SMP */
-#define OLDINSTR(oldinstr) "661:\n\t" oldinstr "\n662:\n"
-
-#define b_replacement(number) "663"#number
-#define e_replacement(number) "664"#number
+#define ALT_CALL_INSTR "call BUG_func"
-#define alt_slen "662b-661b"
-#define alt_rlen(number) e_replacement(number)"f-"b_replacement(number)"f"
+#define alt_slen "772b-771b"
+#define alt_total_slen "773b-771b"
+#define alt_rlen "775f-774f"
-#define ALTINSTR_ENTRY(feature, number) \
- " .long 661b - .\n" /* label */ \
- " .long " b_replacement(number)"f - .\n" /* new instruction */ \
- " .word " __stringify(feature) "\n" /* feature bit */ \
- " .byte " alt_slen "\n" /* source len */ \
- " .byte " alt_rlen(number) "\n" /* replacement len */
+#define OLDINSTR(oldinstr) \
+ "# ALT: oldinstr\n" \
+ "771:\n\t" oldinstr "\n772:\n" \
+ "# ALT: padding\n" \
+ ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \
+ "((" alt_rlen ")-(" alt_slen ")),0x90\n" \
+ "773:\n"
-#define DISCARD_ENTRY(number) /* rlen <= slen */ \
- " .byte 0xff + (" alt_rlen(number) ") - (" alt_slen ")\n"
+#define ALTINSTR_ENTRY(ft_flags) \
+ ".pushsection .altinstructions, \"aM\", @progbits, " \
+ __stringify(ALT_INSTR_SIZE) "\n" \
+ " .long 771b - .\n" /* label */ \
+ " .long 774f - .\n" /* new instruction */ \
+ " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
+ " .byte " alt_total_slen "\n" /* source len */ \
+ " .byte " alt_rlen "\n" /* replacement len */ \
+ ".popsection\n"
-#define ALTINSTR_REPLACEMENT(newinstr, feature, number) /* replacement */ \
- b_replacement(number)":\n\t" newinstr "\n" e_replacement(number) ":\n\t"
+#define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \
+ ".pushsection .altinstr_replacement, \"ax\"\n" \
+ ANNOTATE_DATA_SPECIAL "\n" \
+ "# ALT: replacement\n" \
+ "774:\n\t" newinstr "\n775:\n" \
+ ".popsection\n"
/* alternative assembly primitive: */
-#define ALTERNATIVE(oldinstr, newinstr, feature) \
+#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
OLDINSTR(oldinstr) \
- ".pushsection .altinstructions,\"a\"\n" \
- ALTINSTR_ENTRY(feature, 1) \
- ".popsection\n" \
- ".pushsection .discard,\"aw\",@progbits\n" \
- DISCARD_ENTRY(1) \
- ".popsection\n" \
- ".pushsection .altinstr_replacement, \"ax\"\n" \
- ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
- ".popsection"
+ ALTINSTR_ENTRY(ft_flags) \
+ ALTINSTR_REPLACEMENT(newinstr)
-#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
- OLDINSTR(oldinstr) \
- ".pushsection .altinstructions,\"a\"\n" \
- ALTINSTR_ENTRY(feature1, 1) \
- ALTINSTR_ENTRY(feature2, 2) \
- ".popsection\n" \
- ".pushsection .discard,\"aw\",@progbits\n" \
- DISCARD_ENTRY(1) \
- DISCARD_ENTRY(2) \
- ".popsection\n" \
- ".pushsection .altinstr_replacement, \"ax\"\n" \
- ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
- ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
- ".popsection"
+#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
+ ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)
-/*
- * This must be included *after* the definition of ALTERNATIVE due to
- * <asm/arch_hweight.h>
- */
-#include <asm/cpufeature.h>
+/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
+#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
+ ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags)
+
+#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
+ newinstr3, ft_flags3) \
+ ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
+ newinstr3, ft_flags3)
/*
* Alternative instructions for different CPU types or capabilities.
@@ -142,33 +243,45 @@ static inline int alternatives_text_reserved(void *start, void *end)
* For non barrier like inlines please define new variants
* without volatile and memory clobber.
*/
-#define alternative(oldinstr, newinstr, feature) \
- asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
+#define alternative(oldinstr, newinstr, ft_flags) \
+ asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
+
+#define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
+ asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
/*
* Alternative inline assembly with input.
*
- * Pecularities:
+ * Peculiarities:
* No memory clobber here.
* Argument numbers start with 1.
- * Best is to use constraints that are fixed size (like (%1) ... "r")
- * If you use variable sized constraints like "m" or "g" in the
- * replacement make sure to pad to the worst case length.
* Leaving an unused argument 0 to keep API compatibility.
*/
-#define alternative_input(oldinstr, newinstr, feature, input...) \
- asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
+#define alternative_input(oldinstr, newinstr, ft_flags, input...) \
+ asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
: : "i" (0), ## input)
/* Like alternative_input, but with a single output argument */
-#define alternative_io(oldinstr, newinstr, feature, output, input...) \
- asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
+#define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \
+ asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
: output : "i" (0), ## input)
-/* Like alternative_io, but for replacing a direct call with another one. */
-#define alternative_call(oldfunc, newfunc, feature, output, input...) \
- asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
- : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
+/*
+ * Like alternative_io, but for replacing a direct call with another one.
+ *
+ * Use the %c operand modifier which is the generic way to print a bare
+ * constant expression with all syntax-specific punctuation omitted. %P
+ * is the x86-specific variant which can handle constants too, for
+ * historical reasons, but it should be used primarily for PIC
+ * references: i.e., if used for a function, it would add the PLT
+ * suffix.
+ */
+#define alternative_call(oldfunc, newfunc, ft_flags, output, input, clobbers...) \
+ asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
+ : ALT_OUTPUT_SP(output) \
+ : [old] "i" (oldfunc), [new] "i" (newfunc) \
+ COMMA(input) \
+ : clobbers)
/*
* Like alternative_call, but there are two features and respective functions.
@@ -176,64 +289,113 @@ static inline int alternatives_text_reserved(void *start, void *end)
* Otherwise, if CPU has feature1, function1 is used.
* Otherwise, old function is used.
*/
-#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
- output, input...) \
- asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
- "call %P[new2]", feature2) \
- : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
- [new2] "i" (newfunc2), ## input)
+#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
+ output, input, clobbers...) \
+ asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
+ "call %c[new2]", ft_flags2) \
+ : ALT_OUTPUT_SP(output) \
+ : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
+ [new2] "i" (newfunc2) \
+ COMMA(input) \
+ : clobbers)
+
+#define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__
+
+/* Macro for creating assembler functions avoiding any C magic. */
+#define DEFINE_ASM_FUNC(func, instr, sec) \
+ asm (".pushsection " #sec ", \"ax\"\n" \
+ ".global " #func "\n\t" \
+ ".type " #func ", @function\n\t" \
+ ASM_FUNC_ALIGN "\n" \
+ #func ":\n\t" \
+ ASM_ENDBR \
+ instr "\n\t" \
+ ASM_RET \
+ ".size " #func ", . - " #func "\n\t" \
+ ".popsection")
+
+void BUG_func(void);
+void nop_func(void);
+
+#else /* __ASSEMBLER__ */
+
+#ifdef CONFIG_SMP
+ .macro LOCK_PREFIX
+672: lock
+ .pushsection .smp_locks,"a"
+ .balign 4
+ .long 672b - .
+ .popsection
+ .endm
+#else
+ .macro LOCK_PREFIX
+ .endm
+#endif
/*
- * use this macro(s) if you need more than one output parameter
- * in alternative_io
+ * Issue one struct alt_instr descriptor entry (need to put it into
+ * the section .altinstructions, see below). This entry contains
+ * enough information for the alternatives patching code to patch an
+ * instruction. See apply_alternatives().
*/
-#define ASM_OUTPUT2(a...) a
+.macro altinstr_entry orig alt ft_flags orig_len alt_len
+ .long \orig - .
+ .long \alt - .
+ .4byte \ft_flags
+ .byte \orig_len
+ .byte \alt_len
+.endm
+
+.macro ALT_CALL_INSTR
+ call BUG_func
+.endm
/*
- * use this macro if you need clobbers but no inputs in
- * alternative_{input,io,call}()
+ * Define an alternative between two instructions. If @feature is
+ * present, early code in apply_alternatives() replaces @oldinstr with
+ * @newinstr. ".skip" directive takes care of proper instruction padding
+ * in case @newinstr is longer than @oldinstr.
*/
-#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
-
-struct paravirt_patch_site;
-#ifdef CONFIG_PARAVIRT
-void apply_paravirt(struct paravirt_patch_site *start,
- struct paravirt_patch_site *end);
-#else
-static inline void apply_paravirt(struct paravirt_patch_site *start,
- struct paravirt_patch_site *end)
-{}
-#define __parainstructions NULL
-#define __parainstructions_end NULL
-#endif
+#define __ALTERNATIVE(oldinst, newinst, flag) \
+740: \
+ oldinst ; \
+741: \
+ .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\
+742: \
+ .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE ;\
+ altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \
+ .popsection ; \
+ .pushsection .altinstr_replacement,"ax" ; \
+743: \
+ ANNOTATE_DATA_SPECIAL ; \
+ newinst ; \
+744: \
+ .popsection ;
-extern void *text_poke_early(void *addr, const void *opcode, size_t len);
+.macro ALTERNATIVE oldinstr, newinstr, ft_flags
+ __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
+.endm
/*
- * Clear and restore the kernel write-protection flag on the local CPU.
- * Allows the kernel to edit read-only pages.
- * Side-effect: any interrupt handler running between save and restore will have
- * the ability to write to read-only pages.
- *
- * Warning:
- * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
- * no thread can be preempted in the instructions being modified (no iret to an
- * invalid instruction possible) or if the instructions are changed from a
- * consistent state to another consistent state atomically.
- * More care must be taken when modifying code in the SMP case because of
- * Intel's errata. text_poke_smp() takes care that errata, but still
- * doesn't support NMI/MCE handler code modifying.
- * On the local CPU you need to be protected again NMI or MCE handlers seeing an
- * inconsistent instruction while you patch.
+ * Same as ALTERNATIVE macro above but for two alternatives. If CPU
+ * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
+ * @feature2, it replaces @oldinstr with @feature2.
*/
-struct text_poke_param {
- void *addr;
- const void *opcode;
- size_t len;
-};
+.macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
+ __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
+ \newinstr2, \ft_flags2)
+.endm
+
+.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
+ __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
+ \newinstr3, \ft_flags3)
+.endm
+
+/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
+#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
+ ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
+ newinstr_yes, ft_flags
-extern void *text_poke(void *addr, const void *opcode, size_t len);
-extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
-extern void text_poke_smp_batch(struct text_poke_param *params, int n);
+#endif /* __ASSEMBLER__ */
#endif /* _ASM_X86_ALTERNATIVE_H */
generated by cgit (git 2.34.1) at 2025-12-25 08:07:02 +0000