Merge branch 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 jumplabel changes from Peter Anvin: "One more x86 tree for this merge window. This tree improves the handling of jump labels, so that most of the time we don't have to do a massive initial patching run. Furthermore, we will error out of the jump label is not what is expected, eg if it has been corrupted or tampered with" * 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/jump-label: Show where and what was wrong on errors x86/jump-label: Add safety checks to jump label conversions x86/jump-label: Do not bother updating nops if they are correct x86/jump-label: Use best default nops for inital jump label calls
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commit
442e0973e9
2 changed files with 73 additions and 6 deletions
arch/x86
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@ -3,18 +3,23 @@
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#ifdef __KERNEL__
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#ifdef __KERNEL__
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#include <linux/stringify.h>
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#include <linux/types.h>
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#include <linux/types.h>
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#include <asm/nops.h>
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#include <asm/nops.h>
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#include <asm/asm.h>
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#include <asm/asm.h>
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#define JUMP_LABEL_NOP_SIZE 5
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#define JUMP_LABEL_NOP_SIZE 5
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#define STATIC_KEY_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
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#ifdef CONFIG_X86_64
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# define STATIC_KEY_INIT_NOP P6_NOP5_ATOMIC
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#else
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# define STATIC_KEY_INIT_NOP GENERIC_NOP5_ATOMIC
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#endif
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static __always_inline bool arch_static_branch(struct static_key *key)
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static __always_inline bool arch_static_branch(struct static_key *key)
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{
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{
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asm goto("1:"
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asm goto("1:"
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STATIC_KEY_INITIAL_NOP
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".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
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".pushsection __jump_table, \"aw\" \n\t"
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".pushsection __jump_table, \"aw\" \n\t"
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_ASM_ALIGN "\n\t"
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_ASM_ALIGN "\n\t"
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_ASM_PTR "1b, %l[l_yes], %c0 \n\t"
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_ASM_PTR "1b, %l[l_yes], %c0 \n\t"
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@ -24,18 +24,57 @@ union jump_code_union {
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} __attribute__((packed));
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} __attribute__((packed));
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};
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};
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static void bug_at(unsigned char *ip, int line)
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{
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/*
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* The location is not an op that we were expecting.
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* Something went wrong. Crash the box, as something could be
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* corrupting the kernel.
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*/
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pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
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ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
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BUG();
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}
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static void __jump_label_transform(struct jump_entry *entry,
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static void __jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type,
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enum jump_label_type type,
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void *(*poker)(void *, const void *, size_t))
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void *(*poker)(void *, const void *, size_t),
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int init)
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{
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{
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union jump_code_union code;
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union jump_code_union code;
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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if (type == JUMP_LABEL_ENABLE) {
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if (type == JUMP_LABEL_ENABLE) {
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/*
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* We are enabling this jump label. If it is not a nop
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* then something must have gone wrong.
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*/
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if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
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bug_at((void *)entry->code, __LINE__);
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code.jump = 0xe9;
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code.jump = 0xe9;
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code.offset = entry->target -
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code.offset = entry->target -
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(entry->code + JUMP_LABEL_NOP_SIZE);
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(entry->code + JUMP_LABEL_NOP_SIZE);
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} else
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} else {
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/*
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* We are disabling this jump label. If it is not what
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* we think it is, then something must have gone wrong.
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* If this is the first initialization call, then we
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* are converting the default nop to the ideal nop.
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*/
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if (init) {
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
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bug_at((void *)entry->code, __LINE__);
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} else {
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code.jump = 0xe9;
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code.offset = entry->target -
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(entry->code + JUMP_LABEL_NOP_SIZE);
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if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
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bug_at((void *)entry->code, __LINE__);
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}
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memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
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memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
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}
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/*
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/*
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* Make text_poke_bp() a default fallback poker.
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* Make text_poke_bp() a default fallback poker.
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@ -57,15 +96,38 @@ void arch_jump_label_transform(struct jump_entry *entry,
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{
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{
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get_online_cpus();
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get_online_cpus();
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mutex_lock(&text_mutex);
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mutex_lock(&text_mutex);
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__jump_label_transform(entry, type, NULL);
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__jump_label_transform(entry, type, NULL, 0);
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mutex_unlock(&text_mutex);
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mutex_unlock(&text_mutex);
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put_online_cpus();
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put_online_cpus();
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}
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}
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static enum {
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JL_STATE_START,
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JL_STATE_NO_UPDATE,
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JL_STATE_UPDATE,
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} jlstate __initdata_or_module = JL_STATE_START;
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__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
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__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
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enum jump_label_type type)
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enum jump_label_type type)
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{
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{
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__jump_label_transform(entry, type, text_poke_early);
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/*
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* This function is called at boot up and when modules are
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* first loaded. Check if the default nop, the one that is
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* inserted at compile time, is the ideal nop. If it is, then
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* we do not need to update the nop, and we can leave it as is.
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* If it is not, then we need to update the nop to the ideal nop.
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*/
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if (jlstate == JL_STATE_START) {
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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if (memcmp(ideal_nop, default_nop, 5) != 0)
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jlstate = JL_STATE_UPDATE;
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else
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jlstate = JL_STATE_NO_UPDATE;
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}
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if (jlstate == JL_STATE_UPDATE)
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__jump_label_transform(entry, type, text_poke_early, 1);
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}
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}
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#endif
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#endif
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