Commit 28ac0a9e authored by Qing Zhang's avatar Qing Zhang Committed by Huacai Chen
Browse files

LoongArch: modules/ftrace: Initialize PLT at load time 



This patch implements ftrace trampolines through plt entry.

Tested by forcing ftrace_make_call() to use the module PLT, and then
loading up a module after setting up ftrace with:

| echo ":mod:<module-name>" > set_ftrace_filter;
| echo function > current_tracer;
| modprobe <module-name>

Since FTRACE_ADDR/FTRACE_REGS_ADDR is only defined when CONFIG_DYNAMIC_
FTRACE is selected, we wrap their usage in module_init_ftrace_plt() with
ifdeffery rather than using IS_ENABLED().

Signed-off-by: default avatarQing Zhang <zhangqing@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent a51ac524

arch/loongarch/include/asm/ftrace.h

+4 −0
Original line number Diff line number Diff line
@@ -6,6 +6,10 @@ 
#ifndef _ASM_LOONGARCH_FTRACE_H

#define _ASM_LOONGARCH_FTRACE_H



#define FTRACE_PLT_IDX		0

#define FTRACE_REGS_PLT_IDX	1

#define NR_FTRACE_PLTS		2



#define GRAPH_FAKE_OFFSET (sizeof(struct pt_regs) - offsetof(struct pt_regs, regs[1]))



#ifdef CONFIG_FUNCTION_TRACER

arch/loongarch/include/asm/inst.h

+3 −0
Original line number Diff line number Diff line
@@ -13,10 +13,12 @@ 


#define ADDR_IMMMASK_LU52ID	0xFFF0000000000000

#define ADDR_IMMMASK_LU32ID	0x000FFFFF00000000

#define ADDR_IMMMASK_LU12IW	0x00000000FFFFF000

#define ADDR_IMMMASK_ADDU16ID	0x00000000FFFF0000



#define ADDR_IMMSHIFT_LU52ID	52

#define ADDR_IMMSHIFT_LU32ID	32

#define ADDR_IMMSHIFT_LU12IW	12

#define ADDR_IMMSHIFT_ADDU16ID	16



#define ADDR_IMM(addr, INSN)	((addr & ADDR_IMMMASK_##INSN) >> ADDR_IMMSHIFT_##INSN)
@@ -360,6 +362,7 @@ u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest); 
u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj, enum loongarch_gpr rk);

u32 larch_insn_gen_move(enum loongarch_gpr rd, enum loongarch_gpr rj);



u32 larch_insn_gen_lu12iw(enum loongarch_gpr rd, int imm);

u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm);

u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);

u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest);

arch/loongarch/include/asm/module.h

+4 −1
Original line number Diff line number Diff line
@@ -20,6 +20,9 @@ struct mod_arch_specific { 
	struct mod_section got;

	struct mod_section plt;

	struct mod_section plt_idx;



	/* For CONFIG_DYNAMIC_FTRACE */

	struct plt_entry *ftrace_trampolines;

};



struct got_entry {
@@ -49,7 +52,7 @@ static inline struct plt_entry emit_plt_entry(unsigned long val) 
{

	u32 lu12iw, lu32id, lu52id, jirl;



	lu12iw = (lu12iw_op << 25 | (((val >> 12) & 0xfffff) << 5) | LOONGARCH_GPR_T1);

	lu12iw = larch_insn_gen_lu12iw(LOONGARCH_GPR_T1, ADDR_IMM(val, LU12IW));

	lu32id = larch_insn_gen_lu32id(LOONGARCH_GPR_T1, ADDR_IMM(val, LU32ID));

	lu52id = larch_insn_gen_lu52id(LOONGARCH_GPR_T1, LOONGARCH_GPR_T1, ADDR_IMM(val, LU52ID));

	jirl = larch_insn_gen_jirl(0, LOONGARCH_GPR_T1, 0, (val & 0xfff));

arch/loongarch/include/asm/module.lds.h

+1 −0
Original line number Diff line number Diff line
@@ -5,4 +5,5 @@ SECTIONS { 
	.got : { BYTE(0) }

	.plt : { BYTE(0) }

	.plt.idx : { BYTE(0) }

	.ftrace_trampoline : { BYTE(0) }

}

arch/loongarch/kernel/ftrace_dyn.c

+93 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <linux/uaccess.h>



#include <asm/inst.h>

#include <asm/module.h>



static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate)

{
@@ -29,18 +30,78 @@ static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate) 
}



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS



#ifdef CONFIG_MODULES

static inline int __get_mod(struct module **mod, unsigned long addr)

{

	preempt_disable();

	*mod = __module_text_address(addr);

	preempt_enable();



	if (WARN_ON(!(*mod)))

		return -EINVAL;



	return 0;

}



static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)

{

	struct plt_entry *plt = mod->arch.ftrace_trampolines;



	if (addr == FTRACE_ADDR)

		return &plt[FTRACE_PLT_IDX];

	if (addr == FTRACE_REGS_ADDR &&

			IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))

		return &plt[FTRACE_REGS_PLT_IDX];



	return NULL;

}



static unsigned long get_plt_addr(struct module *mod, unsigned long addr)

{

	struct plt_entry *plt;



	plt = get_ftrace_plt(mod, addr);

	if (!plt) {

		pr_err("ftrace: no module PLT for %ps\n", (void *)addr);

		return -EINVAL;

	}



	return (unsigned long)plt;

}

#endif



int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)

{

	u32 old, new;

	unsigned long pc;

	long offset __maybe_unused;



	pc = rec->ip + LOONGARCH_INSN_SIZE;



#ifdef CONFIG_MODULES

	offset = (long)pc - (long)addr;



	if (offset < -SZ_128M || offset >= SZ_128M) {

		int ret;

		struct module *mod;



		ret = __get_mod(&mod, pc);

		if (ret)

			return ret;



		addr = get_plt_addr(mod, addr);



		old_addr = get_plt_addr(mod, old_addr);

	}

#endif



	new = larch_insn_gen_bl(pc, addr);

	old = larch_insn_gen_bl(pc, old_addr);



	return ftrace_modify_code(pc, old, new, true);

}



#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */



int ftrace_update_ftrace_func(ftrace_func_t func)
@@ -91,9 +152,25 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
{

	u32 old, new;

	unsigned long pc;

	long offset __maybe_unused;



	pc = rec->ip + LOONGARCH_INSN_SIZE;



#ifdef CONFIG_MODULES

	offset = (long)pc - (long)addr;



	if (offset < -SZ_128M || offset >= SZ_128M) {

		int ret;

		struct module *mod;



		ret = __get_mod(&mod, pc);

		if (ret)

			return ret;



		addr = get_plt_addr(mod, addr);

	}

#endif



	old = larch_insn_gen_nop();

	new = larch_insn_gen_bl(pc, addr);
@@ -104,9 +181,25 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long ad 
{

	u32 old, new;

	unsigned long pc;

	long offset __maybe_unused;



	pc = rec->ip + LOONGARCH_INSN_SIZE;



#ifdef CONFIG_MODULES

	offset = (long)pc - (long)addr;



	if (offset < -SZ_128M || offset >= SZ_128M) {

		int ret;

		struct module *mod;



		ret = __get_mod(&mod, pc);

		if (ret)

			return ret;



		addr = get_plt_addr(mod, addr);

	}

#endif



	new = larch_insn_gen_nop();

	old = larch_insn_gen_bl(pc, addr);