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Commit 87051ec1 authored by Marcin Nowakowski's avatar Marcin Nowakowski Committed by Ralf Baechle
Browse files

MIPS: ftrace: fix init functions tracing 



Since introduction of tracing for init functions the in_kernel_space()
check is no longer correct, as it ignores the init sections. As a
result, when probes are inserted (and disabled) in the init functions,
a branch instruction is inserted instead of a nop, which is likely to
result in random crashes during boot.

Remove the MIPS-specific in_kernel_space() method and replace it with a
generic core_kernel_text() that also checks for init sections during
system boot stage.

Fixes: 42c269c8 ("ftrace: Allow for function tracing to record init functions on boot up")
Signed-off-by: default avatarMarcin Nowakowski <marcin.nowakowski@imgtec.com>
Tested-by: default avatarMatt Redfearn <matt.redfearn@imgtec.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16092/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent c56e7a4c

arch/mips/kernel/ftrace.c

+5 −19
Original line number Diff line number Diff line
@@ -38,20 +38,6 @@ void arch_ftrace_update_code(int command) 


#endif



/*

 * Check if the address is in kernel space

 *

 * Clone core_kernel_text() from kernel/extable.c, but doesn't call

 * init_kernel_text() for Ftrace doesn't trace functions in init sections.

 */

static inline int in_kernel_space(unsigned long ip)

{

	if (ip >= (unsigned long)_stext &&

	    ip <= (unsigned long)_etext)

		return 1;

	return 0;

}



#ifdef CONFIG_DYNAMIC_FTRACE



#define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */
@@ -198,7 +184,7 @@ int ftrace_make_nop(struct module *mod, 
	 * If ip is in kernel space, no long call, otherwise, long call is

	 * needed.

	 */

	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;

	new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;

#ifdef CONFIG_64BIT

	return ftrace_modify_code(ip, new);

#else
@@ -218,12 +204,12 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	unsigned int new;

	unsigned long ip = rec->ip;



	new = in_kernel_space(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];

	new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];



#ifdef CONFIG_64BIT

	return ftrace_modify_code(ip, new);

#else

	return ftrace_modify_code_2r(ip, new, in_kernel_space(ip) ?

	return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?

						INSN_NOP : insn_la_mcount[1]);

#endif

}
@@ -289,7 +275,7 @@ unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long 
	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for

	 * kernel, move after the instruction "move ra, at"(offset is 16)

	 */

	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);

	ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);



	/*

	 * search the text until finding the non-store instruction or "s{d,w}
@@ -394,7 +380,7 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, 
	 * entries configured through the tracing/set_graph_function interface.

	 */



	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;

	insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;

	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);



	/* Only trace if the calling function expects to */