diff options
author | Matt Fleming <mjf@gentoo.org> | 2008-11-12 20:11:47 +0900 |
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committer | Paul Mundt <lethal@linux-sh.org> | 2008-12-22 18:42:52 +0900 |
commit | fad57feba77d2e5b183e068cb6b90693e4567b40 (patch) | |
tree | 478788d5a05a30f638540d345e9d09c5733687da /arch/sh/kernel/ftrace.c | |
parent | ef6aff6884408db95ceb0f678f583536e0bd48f8 (diff) |
sh: dynamic ftrace support.
First cut at dynamic ftrace support.
Signed-off-by: Matt Fleming <mjf@gentoo.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'arch/sh/kernel/ftrace.c')
-rw-r--r-- | arch/sh/kernel/ftrace.c | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c new file mode 100644 index 00000000000..6c193d56c2e --- /dev/null +++ b/arch/sh/kernel/ftrace.c @@ -0,0 +1,109 @@ +/* + * Copyright (C) 2008 Matt Fleming <mjf@gentoo.org> + * + * Code for replacing ftrace calls with jumps. + * + * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> + * + * Thanks goes to Ingo Molnar, for suggesting the idea. + * Mathieu Desnoyers, for suggesting postponing the modifications. + * Arjan van de Ven, for keeping me straight, and explaining to me + * the dangers of modifying code on the run. + */ +#include <linux/uaccess.h> +#include <linux/ftrace.h> +#include <linux/string.h> +#include <linux/init.h> +#include <linux/io.h> +#include <asm/ftrace.h> +#include <asm/cacheflush.h> + +static unsigned char ftrace_nop[] = { + 0x09, 0x00, /* nop */ + 0x09, 0x00, /* nop */ +}; + +static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE]; + +unsigned char *ftrace_nop_replace(void) +{ + return ftrace_nop; +} + +static int is_sh_nop(unsigned char *ip) +{ + return strncmp(ip, ftrace_nop, sizeof(ftrace_nop)); +} + +unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) +{ + /* Place the address in the memory table. */ + if (addr == CALLER_ADDR) + __raw_writel(addr + MCOUNT_INSN_OFFSET, ftrace_replaced_code); + else + __raw_writel(addr, ftrace_replaced_code); + + /* + * No locking needed, this must be called via kstop_machine + * which in essence is like running on a uniprocessor machine. + */ + return ftrace_replaced_code; +} + +int ftrace_modify_code(unsigned long ip, unsigned char *old_code, + unsigned char *new_code) +{ + unsigned char replaced[MCOUNT_INSN_SIZE]; + + /* + * Note: Due to modules and __init, code can + * disappear and change, we need to protect against faulting + * as well as code changing. We do this by using the + * probe_kernel_* functions. + * + * No real locking needed, this code is run through + * kstop_machine, or before SMP starts. + */ + + /* + * If we're trying to nop out a call to a function, we instead + * place a call to the address after the memory table. + */ + if (is_sh_nop(new_code) == 0) + __raw_writel(ip + MCOUNT_INSN_SIZE, (unsigned long)new_code); + + /* read the text we want to modify */ + if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; + + /* Make sure it is what we expect it to be */ + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) + return -EINVAL; + + /* replace the text with the new text */ + if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE)) + return -EPERM; + + flush_icache_range(ip, ip + MCOUNT_INSN_SIZE); + + return 0; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long ip = (unsigned long)(&ftrace_call); + unsigned char old[MCOUNT_INSN_SIZE], *new; + + memcpy(old, (unsigned char *)(ip + MCOUNT_INSN_OFFSET), MCOUNT_INSN_SIZE); + new = ftrace_call_replace(ip, (unsigned long)func); + + return ftrace_modify_code(ip + MCOUNT_INSN_OFFSET, old, new); +} + +int __init ftrace_dyn_arch_init(void *data) +{ + /* The return code is retured via data */ + __raw_writel(0, (unsigned long)data); + + return 0; +} |