Commit 1f2aaed2 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/module_64: Simplify check for -mprofile-kernel ftrace relocations 



For -mprofile-kernel, we need special handling when generating stubs for
ftrace calls such as _mcount(). To faciliate this, we check if a
R_PPC64_REL24 relocation is for a symbol named "_mcount()" along with
also checking the instruction sequence. The latter is not really
required since "_mcount()" is an exported symbol and kernel modules
cannot use it. As such, drop the additional checking and simplify the
code. This helps unify stub creation for ftrace stubs with
-mprofile-kernel and aids in code reuse.

Also rename is_mprofile_mcount_callsite() to is_mprofile_ftrace_call()
to reflect the checking being done.

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7d9c316adfa1fb787ad268bb4691e7e4059ff2d5.1587488954.git.naveen.n.rao@linux.vnet.ibm.com
parent 03b51416

arch/powerpc/kernel/module_64.c

+4 −14
Original line number Diff line number Diff line
@@ -400,19 +400,9 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs, 
}



#ifdef CONFIG_MPROFILE_KERNEL

static bool is_mprofile_mcount_callsite(const char *name, u32 *instruction)

static bool is_mprofile_ftrace_call(const char *name)

{

	if (strcmp("_mcount", name))

		return false;



	/*

	 * Check if this is one of the -mprofile-kernel sequences.

	 */

	if (instruction[-1] == PPC_INST_STD_LR &&

	    instruction[-2] == PPC_INST_MFLR)

		return true;



	if (instruction[-1] == PPC_INST_MFLR)

	if (!strcmp("_mcount", name))

		return true;



	return false;
@@ -436,7 +426,7 @@ static void squash_toc_save_inst(const char *name, unsigned long addr) 
#else

static void squash_toc_save_inst(const char *name, unsigned long addr) { }



static bool is_mprofile_mcount_callsite(const char *name, u32 *instruction)

static bool is_mprofile_ftrace_call(const char *name)

{

	return false;

}
@@ -448,7 +438,7 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me) 
{

	u32 *prev_insn = instruction - 1;



	if (is_mprofile_mcount_callsite(name, prev_insn))

	if (is_mprofile_ftrace_call(name))

		return 1;



	/*