0029ff8752
Impact: clean up Paul Mackerras pointed out that the code to determine if the branch can reach the destination is incorrect. Michael Ellerman suggested to pull out the code from create_branch and use that. Simply using create_branch is probably the best. Reported-by: Michael Ellerman <michael@ellerman.id.au> Reported-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
519 lines
12 KiB
C
519 lines
12 KiB
C
/*
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* Code for replacing ftrace calls with jumps.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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*
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* Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
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*
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*/
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#include <linux/spinlock.h>
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#include <linux/hardirq.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/percpu.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <asm/cacheflush.h>
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#include <asm/code-patching.h>
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#include <asm/ftrace.h>
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(fmt , ...) do { } while (0)
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#endif
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static unsigned int ftrace_nop = PPC_NOP_INSTR;
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#ifdef CONFIG_PPC32
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# define GET_ADDR(addr) addr
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#else
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/* PowerPC64's functions are data that points to the functions */
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# define GET_ADDR(addr) (*(unsigned long *)addr)
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#endif
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static unsigned int ftrace_calc_offset(long ip, long addr)
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{
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return (int)(addr - ip);
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}
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static unsigned char *ftrace_nop_replace(void)
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{
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return (char *)&ftrace_nop;
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}
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static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
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{
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static unsigned int op;
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/*
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* It would be nice to just use create_function_call, but that will
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* update the code itself. Here we need to just return the
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* instruction that is going to be modified, without modifying the
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* code.
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*/
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addr = GET_ADDR(addr);
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/* Set to "bl addr" */
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op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
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/*
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* No locking needed, this must be called via kstop_machine
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* which in essence is like running on a uniprocessor machine.
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*/
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return (unsigned char *)&op;
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}
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#ifdef CONFIG_PPC64
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# define _ASM_ALIGN " .align 3 "
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# define _ASM_PTR " .llong "
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#else
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# define _ASM_ALIGN " .align 2 "
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# define _ASM_PTR " .long "
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#endif
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static int
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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 char replaced[MCOUNT_INSN_SIZE];
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/*
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* Note: Due to modules and __init, code can
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* disappear and change, we need to protect against faulting
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* as well as code changing. We do this by using the
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* probe_kernel_* functions.
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*
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* No real locking needed, this code is run through
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* kstop_machine, or before SMP starts.
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*/
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/* read the text we want to modify */
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if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* Make sure it is what we expect it to be */
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if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
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return -EINVAL;
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/* replace the text with the new text */
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if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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/*
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* Helper functions that are the same for both PPC64 and PPC32.
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*/
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static int test_24bit_addr(unsigned long ip, unsigned long addr)
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{
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/* use the create_branch to verify that this offset can be branched */
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return create_branch((unsigned int *)ip, addr, 0);
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}
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static int is_bl_op(unsigned int op)
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{
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return (op & 0xfc000003) == 0x48000001;
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}
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static unsigned long find_bl_target(unsigned long ip, unsigned int op)
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{
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static int offset;
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offset = (op & 0x03fffffc);
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/* make it signed */
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if (offset & 0x02000000)
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offset |= 0xfe000000;
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return ip + (long)offset;
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}
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#ifdef CONFIG_PPC64
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static int
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__ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int op;
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unsigned int jmp[5];
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unsigned long ptr;
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unsigned long ip = rec->ip;
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unsigned long tramp;
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int offset;
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/* read where this goes */
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if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
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return -EFAULT;
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/* Make sure that that this is still a 24bit jump */
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if (!is_bl_op(op)) {
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printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
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return -EINVAL;
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}
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/* lets find where the pointer goes */
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tramp = find_bl_target(ip, op);
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/*
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* On PPC64 the trampoline looks like:
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* 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
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* 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
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* Where the bytes 2,3,6 and 7 make up the 32bit offset
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* to the TOC that holds the pointer.
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* to jump to.
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* 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
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* 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
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* The actually address is 32 bytes from the offset
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* into the TOC.
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* 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
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*/
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DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
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/* Find where the trampoline jumps to */
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if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
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printk(KERN_ERR "Failed to read %lx\n", tramp);
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return -EFAULT;
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}
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DEBUGP(" %08x %08x", jmp[0], jmp[1]);
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/* verify that this is what we expect it to be */
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if (((jmp[0] & 0xffff0000) != 0x3d820000) ||
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((jmp[1] & 0xffff0000) != 0x398c0000) ||
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(jmp[2] != 0xf8410028) ||
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(jmp[3] != 0xe96c0020) ||
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(jmp[4] != 0xe84c0028)) {
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printk(KERN_ERR "Not a trampoline\n");
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return -EINVAL;
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}
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offset = (unsigned)((unsigned short)jmp[0]) << 16 |
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(unsigned)((unsigned short)jmp[1]);
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DEBUGP(" %x ", offset);
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/* get the address this jumps too */
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tramp = mod->arch.toc + offset + 32;
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DEBUGP("toc: %lx", tramp);
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if (probe_kernel_read(jmp, (void *)tramp, 8)) {
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printk(KERN_ERR "Failed to read %lx\n", tramp);
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return -EFAULT;
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}
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DEBUGP(" %08x %08x\n", jmp[0], jmp[1]);
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ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
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/* This should match what was called */
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if (ptr != GET_ADDR(addr)) {
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printk(KERN_ERR "addr does not match %lx\n", ptr);
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return -EINVAL;
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}
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/*
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* We want to nop the line, but the next line is
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* 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
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* This needs to be turned to a nop too.
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*/
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if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
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return -EFAULT;
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if (op != 0xe8410028) {
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printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
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return -EINVAL;
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}
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/*
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* Milton Miller pointed out that we can not blindly do nops.
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* If a task was preempted when calling a trace function,
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* the nops will remove the way to restore the TOC in r2
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* and the r2 TOC will get corrupted.
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*/
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/*
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* Replace:
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* bl <tramp> <==== will be replaced with "b 1f"
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* ld r2,40(r1)
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* 1:
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*/
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op = 0x48000008; /* b +8 */
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if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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#else /* !PPC64 */
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static int
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__ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int op;
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unsigned int jmp[4];
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unsigned long ip = rec->ip;
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unsigned long tramp;
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if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* Make sure that that this is still a 24bit jump */
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if (!is_bl_op(op)) {
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printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
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return -EINVAL;
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}
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/* lets find where the pointer goes */
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tramp = find_bl_target(ip, op);
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/*
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* On PPC32 the trampoline looks like:
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* 0x3d, 0x60, 0x00, 0x00 lis r11,sym@ha
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* 0x39, 0x6b, 0x00, 0x00 addi r11,r11,sym@l
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* 0x7d, 0x69, 0x03, 0xa6 mtctr r11
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* 0x4e, 0x80, 0x04, 0x20 bctr
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*/
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DEBUGP("ip:%lx jumps to %lx", ip, tramp);
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/* Find where the trampoline jumps to */
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if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
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printk(KERN_ERR "Failed to read %lx\n", tramp);
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return -EFAULT;
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}
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DEBUGP(" %08x %08x ", jmp[0], jmp[1]);
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/* verify that this is what we expect it to be */
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if (((jmp[0] & 0xffff0000) != 0x3d600000) ||
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((jmp[1] & 0xffff0000) != 0x396b0000) ||
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(jmp[2] != 0x7d6903a6) ||
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(jmp[3] != 0x4e800420)) {
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printk(KERN_ERR "Not a trampoline\n");
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return -EINVAL;
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}
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tramp = (jmp[1] & 0xffff) |
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((jmp[0] & 0xffff) << 16);
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if (tramp & 0x8000)
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tramp -= 0x10000;
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DEBUGP(" %x ", tramp);
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if (tramp != addr) {
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printk(KERN_ERR
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"Trampoline location %08lx does not match addr\n",
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tramp);
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return -EINVAL;
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}
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op = PPC_NOP_INSTR;
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if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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#endif /* PPC64 */
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned char *old, *new;
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unsigned long ip = rec->ip;
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/*
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* If the calling address is more that 24 bits away,
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* then we had to use a trampoline to make the call.
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* Otherwise just update the call site.
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*/
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if (test_24bit_addr(ip, addr)) {
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/* within range */
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old = ftrace_call_replace(ip, addr);
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new = ftrace_nop_replace();
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return ftrace_modify_code(ip, old, new);
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}
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/*
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* Out of range jumps are called from modules.
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* We should either already have a pointer to the module
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* or it has been passed in.
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*/
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if (!rec->arch.mod) {
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if (!mod) {
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printk(KERN_ERR "No module loaded addr=%lx\n",
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addr);
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return -EFAULT;
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}
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rec->arch.mod = mod;
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} else if (mod) {
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if (mod != rec->arch.mod) {
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printk(KERN_ERR
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"Record mod %p not equal to passed in mod %p\n",
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rec->arch.mod, mod);
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return -EINVAL;
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}
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/* nothing to do if mod == rec->arch.mod */
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} else
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mod = rec->arch.mod;
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return __ftrace_make_nop(mod, rec, addr);
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}
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#ifdef CONFIG_PPC64
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static int
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__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int op[2];
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unsigned long ip = rec->ip;
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/* read where this goes */
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if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
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return -EFAULT;
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/*
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* It should be pointing to two nops or
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* b +8; ld r2,40(r1)
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*/
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if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
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((op[0] != PPC_NOP_INSTR) || (op[1] != PPC_NOP_INSTR))) {
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printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
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return -EINVAL;
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}
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/* If we never set up a trampoline to ftrace_caller, then bail */
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if (!rec->arch.mod->arch.tramp) {
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printk(KERN_ERR "No ftrace trampoline\n");
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return -EINVAL;
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}
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/* create the branch to the trampoline */
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op[0] = create_branch((unsigned int *)ip,
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rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
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if (!op[0]) {
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printk(KERN_ERR "REL24 out of range!\n");
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return -EINVAL;
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}
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/* ld r2,40(r1) */
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op[1] = 0xe8410028;
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DEBUGP("write to %lx\n", rec->ip);
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if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
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return -EPERM;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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#else
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static int
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__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int op;
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unsigned long ip = rec->ip;
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/* read where this goes */
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if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* It should be pointing to a nop */
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if (op != PPC_NOP_INSTR) {
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printk(KERN_ERR "Expected NOP but have %x\n", op);
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return -EINVAL;
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}
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/* If we never set up a trampoline to ftrace_caller, then bail */
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if (!rec->arch.mod->arch.tramp) {
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printk(KERN_ERR "No ftrace trampoline\n");
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return -EINVAL;
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}
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/* create the branch to the trampoline */
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op = create_branch((unsigned int *)ip,
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rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
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if (!op) {
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printk(KERN_ERR "REL24 out of range!\n");
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return -EINVAL;
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}
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DEBUGP("write to %lx\n", rec->ip);
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if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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#endif /* CONFIG_PPC64 */
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned char *old, *new;
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unsigned long ip = rec->ip;
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/*
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* If the calling address is more that 24 bits away,
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* then we had to use a trampoline to make the call.
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* Otherwise just update the call site.
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*/
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if (test_24bit_addr(ip, addr)) {
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/* within range */
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old = ftrace_nop_replace();
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new = ftrace_call_replace(ip, addr);
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return ftrace_modify_code(ip, old, new);
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}
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/*
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* Out of range jumps are called from modules.
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* Being that we are converting from nop, it had better
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* already have a module defined.
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*/
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if (!rec->arch.mod) {
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printk(KERN_ERR "No module loaded\n");
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return -EINVAL;
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}
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return __ftrace_make_call(rec, addr);
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned long ip = (unsigned long)(&ftrace_call);
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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int ret;
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memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = ftrace_modify_code(ip, old, new);
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return ret;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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/* caller expects data to be zero */
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unsigned long *p = data;
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*p = 0;
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return 0;
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}
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