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Commit d2bf98e6 authored by Steven J. Magnani's avatar Steven J. Magnani Committed by Michal Simek
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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: default avatarSteven J. Magnani <steve@digidescorp.com>
Signed-off-by: default avatarMichal Simek <monstr@monstr.eu>
parent 0fdf8675

arch/microblaze/kernel/ftrace.c

+3 −9
Original line number Diff line number Diff line
@@ -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();