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: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

4 files changed, 12 insertions, 1 deletions

diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index 8c7d137e4871..90f9d3399b2a 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -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
diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index 88e1673524e1..c00e1512d4fa 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -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);
diff --git a/arch/loongarch/include/asm/module.h b/arch/loongarch/include/asm/module.h
index 60dc62a1146e..12a0f1e66916 100644
--- a/arch/loongarch/include/asm/module.h
+++ b/arch/loongarch/include/asm/module.h
@@ -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));
diff --git a/arch/loongarch/include/asm/module.lds.h b/arch/loongarch/include/asm/module.lds.h
index a3d1bc0fcc72..438f09d4ccf4 100644
--- a/arch/loongarch/include/asm/module.lds.h
+++ b/arch/loongarch/include/asm/module.lds.h
@@ -5,4 +5,5 @@ SECTIONS {
 	.got : { BYTE(0) }
 	.plt : { BYTE(0) }
 	.plt.idx : { BYTE(0) }
+	.ftrace_trampoline : { BYTE(0) }
 }