ftrace: use nops instead of jmp
This patch patches the call to mcount with nops instead of a jmp over the mcount call. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -143,7 +143,7 @@ static const unsigned char *const p6_nops[ASM_NOP_MAX+1] = {
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#ifdef CONFIG_X86_64
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extern char __vsyscall_0;
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static inline const unsigned char*const * find_nop_table(void)
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const unsigned char *const *find_nop_table(void)
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{
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return boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
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boot_cpu_data.x86 < 6 ? k8_nops : p6_nops;
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@ -162,7 +162,7 @@ static const struct nop {
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{ -1, NULL }
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};
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static const unsigned char*const * find_nop_table(void)
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const unsigned char *const *find_nop_table(void)
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{
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const unsigned char *const *noptable = intel_nops;
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int i;
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@ -16,11 +16,12 @@
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#include <linux/init.h>
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#include <linux/list.h>
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#include <asm/alternative.h>
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#define CALL_BACK 5
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#define JMPFWD 0x03eb
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static unsigned short ftrace_jmp = JMPFWD;
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/* Long is fine, even if it is only 4 bytes ;-) */
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static long *ftrace_nop;
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struct ftrace_record {
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struct dyn_ftrace rec;
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@ -55,13 +56,13 @@ static struct ftrace_page *ftrace_pages;
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notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
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{
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struct ftrace_record *rec;
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unsigned short save;
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unsigned long save;
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ip -= CALL_BACK;
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save = *(short *)ip;
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save = *(long *)ip;
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/* If this was already converted, skip it */
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if (save == JMPFWD)
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if (save == *ftrace_nop)
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return NULL;
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if (ftrace_pages->index == ENTRIES_PER_PAGE) {
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@ -79,9 +80,10 @@ static int notrace
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ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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unsigned char *new_code)
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{
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unsigned short old = *(unsigned short *)old_code;
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unsigned short new = *(unsigned short *)new_code;
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unsigned short replaced;
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unsigned replaced;
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unsigned old = *(unsigned *)old_code; /* 4 bytes */
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unsigned new = *(unsigned *)new_code; /* 4 bytes */
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unsigned char newch = new_code[4];
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int faulted = 0;
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/*
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@ -94,7 +96,9 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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*/
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asm volatile (
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"1: lock\n"
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" cmpxchg %w3, (%2)\n"
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" cmpxchg %3, (%2)\n"
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" jnz 2f\n"
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" movb %b4, 4(%2)\n"
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"2:\n"
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".section .fixup, \"ax\"\n"
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" movl $1, %0\n"
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@ -102,11 +106,12 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: "=r"(faulted), "=a"(replaced)
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: "r"(ip), "r"(new), "0"(faulted), "a"(old)
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: "r"(ip), "r"(new), "r"(newch),
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"0"(faulted), "a"(old)
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: "memory");
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sync_core();
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if (replaced != old)
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if (replaced != old && replaced != new)
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faulted = 2;
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return faulted;
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@ -132,7 +137,7 @@ notrace void ftrace_code_disable(struct dyn_ftrace *rec)
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/* move the IP back to the start of the call */
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ip -= CALL_BACK;
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r->failed = ftrace_modify_code(ip, save.code, (char *)&ftrace_jmp);
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r->failed = ftrace_modify_code(ip, save.code, (char *)ftrace_nop);
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}
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static void notrace ftrace_replace_code(int saved)
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@ -144,9 +149,9 @@ static void notrace ftrace_replace_code(int saved)
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int i;
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if (saved)
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old = (char *)&ftrace_jmp;
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old = (char *)ftrace_nop;
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else
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new = (char *)&ftrace_jmp;
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new = (char *)ftrace_nop;
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for (pg = ftrace_pages_start; pg; pg = pg->next) {
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for (i = 0; i < pg->index; i++) {
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@ -194,12 +199,15 @@ notrace void ftrace_shutdown_replenish(void)
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ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
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}
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notrace int ftrace_shutdown_arch_init(void)
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notrace int __init ftrace_shutdown_arch_init(void)
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{
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const unsigned char *const *noptable = find_nop_table();
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struct ftrace_page *pg;
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int cnt;
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int i;
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ftrace_nop = (unsigned long *)noptable[CALL_BACK];
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/* allocate a few pages */
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ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
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if (!ftrace_pages_start)
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@ -72,6 +72,8 @@ static inline void alternatives_smp_module_del(struct module *mod) {}
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static inline void alternatives_smp_switch(int smp) {}
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#endif /* CONFIG_SMP */
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const unsigned char *const *find_nop_table(void);
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/*
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* Alternative instructions for different CPU types or capabilities.
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*
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