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microblaze: Fix ftrace_update_ftrace_func panic 

The Microblaze dynamic ftrace code assumes a call ordering that is not met
in all scenarios. Specifically, executing a command similar to:

  echo 105 > /sys/kernel/debug/tracing/set_ftrace_pid

before any other tracing-related commands results in a kernel panic:

  BUG: failure at arch/microblaze/kernel/ftrace.c:198/ftrace_update_ftrace_func()!

Recoding ftrace_update_ftrace_func() to use &ftrace_caller directly eliminates
the need to capture its address elsewhere (and thus rely on a particular call
sequence).

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>
This commit is contained in:
Steven J. Magnani 2010-04-02 13:29:39 -05:00 committed by Michal Simek
parent 0fdf86754f
commit d2bf98e6fc
1 changed files with 3 additions and 9 deletions
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12
arch/microblaze/kernel/ftrace.c
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@ -151,13 +151,10 @@ int ftrace_make_nop(struct module *mod,
return ret;
}
static int ret_addr; /* initialized as 0 by default */
/* I believe that first is called ftrace_make_nop before this function */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
int ret;
ret_addr = addr; /* saving where the barrier jump is */
pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
ret = ftrace_modify_code(rec->ip, imm);
@ -194,12 +191,9 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
ret = ftrace_modify_code(ip, upper);
ret += ftrace_modify_code(ip + 4, lower);
/* We just need to remove the rtsd r15, 8 by NOP */
BUG_ON(!ret_addr);
if (ret_addr)
ret += ftrace_modify_code(ret_addr, MICROBLAZE_NOP);
else
ret = 1; /* fault */
/* We just need to replace the rtsd r15, 8 with NOP */
ret += ftrace_modify_code((unsigned long)&ftrace_caller,
MICROBLAZE_NOP);
/* All changes are done - lets do caches consistent */
flush_icache();