Commit 1b32cd17 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc: Introduce a new helper to obtain function entry points 



kprobe_lookup_name() is specific to the kprobe subsystem and may not always
return the function entry point (in a subsequent patch for KPROBES_ON_FTRACE).
For looking up function entry points, introduce a separate helper and use it
in optprobes.c

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent ead514d5

arch/powerpc/include/asm/code-patching.h

+41 −0
Original line number Diff line number Diff line
@@ -12,6 +12,8 @@ 


#include <asm/types.h>

#include <asm/ppc-opcode.h>

#include <linux/string.h>

#include <linux/kallsyms.h>



/* Flags for create_branch:

 * "b"   == create_branch(addr, target, 0);
@@ -99,6 +101,45 @@ static inline unsigned long ppc_global_function_entry(void *func) 
#endif

}



/*

 * Wrapper around kallsyms_lookup() to return function entry address:

 * - For ABIv1, we lookup the dot variant.

 * - For ABIv2, we return the local entry point.

 */

static inline unsigned long ppc_kallsyms_lookup_name(const char *name)

{

	unsigned long addr;

#ifdef PPC64_ELF_ABI_v1

	/* check for dot variant */

	char dot_name[1 + KSYM_NAME_LEN];

	bool dot_appended = false;



	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)

		return 0;



	if (name[0] != '.') {

		dot_name[0] = '.';

		dot_name[1] = '\0';

		strlcat(dot_name, name, sizeof(dot_name));

		dot_appended = true;

	} else {

		dot_name[0] = '\0';

		strlcat(dot_name, name, sizeof(dot_name));

	}

	addr = kallsyms_lookup_name(dot_name);

	if (!addr && dot_appended)

		/* Let's try the original non-dot symbol lookup	*/

		addr = kallsyms_lookup_name(name);

#elif defined(PPC64_ELF_ABI_v2)

	addr = kallsyms_lookup_name(name);

	if (addr)

		addr = ppc_function_entry((void *)addr);

#else

	addr = kallsyms_lookup_name(name);

#endif

	return addr;

}



#ifdef CONFIG_PPC64

/*

 * Some instruction encodings commonly used in dynamic ftracing

arch/powerpc/kernel/optprobes.c

+3 −3
Original line number Diff line number Diff line
@@ -243,10 +243,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p) 
	/*

	 * 2. branch to optimized_callback() and emulate_step()

	 */

	op_callback_addr = kprobe_lookup_name("optimized_callback", 0);

	emulate_step_addr = kprobe_lookup_name("emulate_step", 0);

	op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");

	emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step");

	if (!op_callback_addr || !emulate_step_addr) {

		WARN(1, "kprobe_lookup_name() failed\n");

		WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");

		goto error;

	}

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