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

/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _ASM_POWERPC_CODE_PATCHING_H
#define _ASM_POWERPC_CODE_PATCHING_H

/*
 * Copyright 2008, Michael Ellerman, IBM Corporation.
 */

#include <asm/types.h>
#include <asm/ppc-opcode.h>
#include <linux/string.h>
#include <linux/kallsyms.h>
#include <asm/asm-compat.h>
#include <asm/inst.h>

/* Flags for create_branch:
 * "b"   == create_branch(addr, target, 0);
 * "ba"  == create_branch(addr, target, BRANCH_ABSOLUTE);
 * "bl"  == create_branch(addr, target, BRANCH_SET_LINK);
 * "bla" == create_branch(addr, target, BRANCH_ABSOLUTE | BRANCH_SET_LINK);
 */
#define BRANCH_SET_LINK	0x1
#define BRANCH_ABSOLUTE	0x2

/*
 * Powerpc branch instruction is :
 *
 *  0         6                 30   31
 *  +---------+----------------+---+---+
 *  | opcode  |     LI         |AA |LK |
 *  +---------+----------------+---+---+
 *  Where AA = 0 and LK = 0
 *
 * LI is a signed 24 bits integer. The real branch offset is computed
 * by: imm32 = SignExtend(LI:'0b00', 32);
 *
 * So the maximum forward branch should be:
 *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
 * The maximum backward branch should be:
 *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
 */
static inline bool is_offset_in_branch_range(long offset)
{
	return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
}

static inline bool is_offset_in_cond_branch_range(long offset)
{
	return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
}

static inline int create_branch(ppc_inst_t *instr, const u32 *addr,
				unsigned long target, int flags)
{
	long offset;

	*instr = ppc_inst(0);
	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
		offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (!is_offset_in_branch_range(offset))
		return 1;

	/* Mask out the flags and target, so they don't step on each other. */
	*instr = ppc_inst(0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC));

	return 0;
}

int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
		       unsigned long target, int flags);
int patch_branch(u32 *addr, unsigned long target, int flags);
int patch_instruction(u32 *addr, ppc_inst_t instr);
int raw_patch_instruction(u32 *addr, ppc_inst_t instr);

static inline unsigned long patch_site_addr(s32 *site)
{
	return (unsigned long)site + *site;
}

static inline int patch_instruction_site(s32 *site, ppc_inst_t instr)
{
	return patch_instruction((u32 *)patch_site_addr(site), instr);
}

static inline int patch_branch_site(s32 *site, unsigned long target, int flags)
{
	return patch_branch((u32 *)patch_site_addr(site), target, flags);
}

static inline int modify_instruction(unsigned int *addr, unsigned int clr,
				     unsigned int set)
{
	return patch_instruction(addr, ppc_inst((*addr & ~clr) | set));
}

static inline int modify_instruction_site(s32 *site, unsigned int clr, unsigned int set)
{
	return modify_instruction((unsigned int *)patch_site_addr(site), clr, set);
}

static inline unsigned int branch_opcode(ppc_inst_t instr)
{
	return ppc_inst_primary_opcode(instr) & 0x3F;
}

static inline int instr_is_branch_iform(ppc_inst_t instr)
{
	return branch_opcode(instr) == 18;
}

static inline int instr_is_branch_bform(ppc_inst_t instr)
{
	return branch_opcode(instr) == 16;
}

int instr_is_relative_branch(ppc_inst_t instr);
int instr_is_relative_link_branch(ppc_inst_t instr);
unsigned long branch_target(const u32 *instr);
int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src);
bool is_conditional_branch(ppc_inst_t instr);

#define OP_RT_RA_MASK	0xffff0000UL
#define LIS_R2		(PPC_RAW_LIS(_R2, 0))
#define ADDIS_R2_R12	(PPC_RAW_ADDIS(_R2, _R12, 0))
#define ADDI_R2_R2	(PPC_RAW_ADDI(_R2, _R2, 0))


static inline unsigned long ppc_function_entry(void *func)
{
#ifdef CONFIG_PPC64_ELF_ABI_V2
	u32 *insn = func;

	/*
	 * A PPC64 ABIv2 function may have a local and a global entry
	 * point. We need to use the local entry point when patching
	 * functions, so identify and step over the global entry point
	 * sequence.
	 *
	 * The global entry point sequence is always of the form:
	 *
	 * addis r2,r12,XXXX
	 * addi  r2,r2,XXXX
	 *
	 * A linker optimisation may convert the addis to lis:
	 *
	 * lis   r2,XXXX
	 * addi  r2,r2,XXXX
	 */
	if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
	     ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
	    ((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
		return (unsigned long)(insn + 2);
	else
		return (unsigned long)func;
#elif defined(CONFIG_PPC64_ELF_ABI_V1)
	/*
	 * On PPC64 ABIv1 the function pointer actually points to the
	 * function's descriptor. The first entry in the descriptor is the
	 * address of the function text.
	 */
	return ((struct func_desc *)func)->addr;
#else
	return (unsigned long)func;
#endif
}

static inline unsigned long ppc_global_function_entry(void *func)
{
#ifdef CONFIG_PPC64_ELF_ABI_V2
	/* PPC64 ABIv2 the global entry point is at the address */
	return (unsigned long)func;
#else
	/* All other cases there is no change vs ppc_function_entry() */
	return ppc_function_entry(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 CONFIG_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(CONFIG_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;
}

/*
 * Some instruction encodings commonly used in dynamic ftracing
 * and function live patching.
 */

/* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
#ifdef CONFIG_PPC64_ELF_ABI_V2
#define R2_STACK_OFFSET         24
#else
#define R2_STACK_OFFSET         40
#endif

#define PPC_INST_LD_TOC		PPC_RAW_LD(_R2, _R1, R2_STACK_OFFSET)

/* usually preceded by a mflr r0 */
#define PPC_INST_STD_LR		PPC_RAW_STD(_R0, _R1, PPC_LR_STKOFF)

#endif /* _ASM_POWERPC_CODE_PATCHING_H */