[PATCH stable 5.4 0/3] ARM: ftrace MODULE_PLTS warning fixes

@@ -19,6 +19,15 @@ enum {
 };
 #endif
 
+#define PLT_ENT_STRIDE		L1_CACHE_BYTES
+#define PLT_ENT_COUNT		(PLT_ENT_STRIDE / sizeof(u32))
+#define PLT_ENT_SIZE		(sizeof(struct plt_entries) / PLT_ENT_COUNT)
+
+struct plt_entries {
+	u32	ldr[PLT_ENT_COUNT];
+	u32	lit[PLT_ENT_COUNT];
+};
+
 struct mod_plt_sec {
 	struct elf32_shdr	*plt;
 	int			plt_count;

@@ -11,10 +11,6 @@
 #include <asm/cache.h>
 #include <asm/opcodes.h>
 
-#define PLT_ENT_STRIDE		L1_CACHE_BYTES
-#define PLT_ENT_COUNT		(PLT_ENT_STRIDE / sizeof(u32))
-#define PLT_ENT_SIZE		(sizeof(struct plt_entries) / PLT_ENT_COUNT)
-
 #ifdef CONFIG_THUMB2_KERNEL
 #define PLT_ENT_LDR		__opcode_to_mem_thumb32(0xf8dff000 | \
 							(PLT_ENT_STRIDE - 4))

@@ -23,11 +19,6 @@
 						    (PLT_ENT_STRIDE - 8))
 #endif
 
-struct plt_entries {
-	u32	ldr[PLT_ENT_COUNT];
-	u32	lit[PLT_ENT_COUNT];
-};
-
 static bool in_init(const struct module *mod, unsigned long loc)
 {
 	return loc - (u32)mod->init_layout.base < mod->init_layout.size;

@@ -13,18 +13,18 @@ arm_gen_nop(void)
 }
 
 unsigned long
-__arm_gen_branch(unsigned long pc, unsigned long addr, bool link);
+__arm_gen_branch(unsigned long pc, unsigned long addr, bool link, bool warn);
 
 static inline unsigned long
 arm_gen_branch(unsigned long pc, unsigned long addr)
 {
-	return __arm_gen_branch(pc, addr, false);
+	return __arm_gen_branch(pc, addr, false, true);
 }
 
 static inline unsigned long
-arm_gen_branch_link(unsigned long pc, unsigned long addr)
+arm_gen_branch_link(unsigned long pc, unsigned long addr, bool warn)
 {
-	return __arm_gen_branch(pc, addr, true);
+	return __arm_gen_branch(pc, addr, true, warn);
 }
 
 #endif

@@ -73,7 +73,7 @@ int ftrace_arch_code_modify_post_process(void)
 
 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
-	return arm_gen_branch_link(pc, addr);
+	return arm_gen_branch_link(pc, addr, true);
 }
 
 static int ftrace_modify_code(unsigned long pc, unsigned long old,

@@ -3,8 +3,9 @@
 #include <linux/kernel.h>
 #include <asm/opcodes.h>
 
-static unsigned long
-__arm_gen_branch_thumb2(unsigned long pc, unsigned long addr, bool link)
+static unsigned long __arm_gen_branch_thumb2(unsigned long pc,
+					     unsigned long addr, bool link,
+					     bool warn)
 {
 	unsigned long s, j1, j2, i1, i2, imm10, imm11;
 	unsigned long first, second;

@@ -12,7 +13,7 @@ __arm_gen_branch_thumb2(unsigned long pc, unsigned long addr, bool link)
 
 	offset = (long)addr - (long)(pc + 4);
 	if (offset < -16777216 || offset > 16777214) {
-		WARN_ON_ONCE(1);
+		WARN_ON_ONCE(warn);
 		return 0;
 	}
 

@@ -33,8 +34,8 @@ __arm_gen_branch_thumb2(unsigned long pc, unsigned long addr, bool link)
 	return __opcode_thumb32_compose(first, second);
 }
 
-static unsigned long
-__arm_gen_branch_arm(unsigned long pc, unsigned long addr, bool link)
+static unsigned long __arm_gen_branch_arm(unsigned long pc, unsigned long addr,
+					  bool link, bool warn)
 {
 	unsigned long opcode = 0xea000000;
 	long offset;

@@ -44,7 +45,7 @@ __arm_gen_branch_arm(unsigned long pc, unsigned long addr, bool link)
 
 	offset = (long)addr - (long)(pc + 8);
 	if (unlikely(offset < -33554432 || offset > 33554428)) {
-		WARN_ON_ONCE(1);
+		WARN_ON_ONCE(warn);
 		return 0;
 	}
 

@@ -54,10 +55,10 @@ __arm_gen_branch_arm(unsigned long pc, unsigned long addr, bool link)
 }
 
 unsigned long
-__arm_gen_branch(unsigned long pc, unsigned long addr, bool link)
+__arm_gen_branch(unsigned long pc, unsigned long addr, bool link, bool warn)
 {
 	if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
-		return __arm_gen_branch_thumb2(pc, addr, link);
+		return __arm_gen_branch_thumb2(pc, addr, link, warn);
 	else
-		return __arm_gen_branch_arm(pc, addr, link);
+		return __arm_gen_branch_arm(pc, addr, link, warn);
 }

@@ -16,6 +16,9 @@ extern void __gnu_mcount_nc(void);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 struct dyn_arch_ftrace {
+#ifdef CONFIG_ARM_MODULE_PLTS
+	struct module *mod;
+#endif
 };
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)

@@ -30,6 +30,7 @@ struct plt_entries {
 
 struct mod_plt_sec {
 	struct elf32_shdr	*plt;
+	struct plt_entries	*plt_ent;
 	int			plt_count;
 };
 

@@ -71,9 +71,10 @@ int ftrace_arch_code_modify_post_process(void)
 	return 0;
 }
 
-static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
+static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
+					 bool warn)
 {
-	return arm_gen_branch_link(pc, addr, true);
+	return arm_gen_branch_link(pc, addr, warn);
 }
 
 static int ftrace_modify_code(unsigned long pc, unsigned long old,

@@ -112,14 +113,14 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	int ret;
 
 	pc = (unsigned long)&ftrace_call;
-	new = ftrace_call_replace(pc, (unsigned long)func);
+	new = ftrace_call_replace(pc, (unsigned long)func, true);
 
 	ret = ftrace_modify_code(pc, 0, new, false);
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 	if (!ret) {
 		pc = (unsigned long)&ftrace_regs_call;
-		new = ftrace_call_replace(pc, (unsigned long)func);
+		new = ftrace_call_replace(pc, (unsigned long)func, true);
 
 		ret = ftrace_modify_code(pc, 0, new, false);
 	}

@@ -132,10 +133,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long new, old;
 	unsigned long ip = rec->ip;
+	unsigned long aaddr = adjust_address(rec, addr);
+	struct module *mod = NULL;
+
+#ifdef CONFIG_ARM_MODULE_PLTS
+	mod = rec->arch.mod;
+#endif
 
 	old = ftrace_nop_replace(rec);
 
-	new = ftrace_call_replace(ip, adjust_address(rec, addr));
+	new = ftrace_call_replace(ip, aaddr, !mod);
+#ifdef CONFIG_ARM_MODULE_PLTS
+	if (!new && mod) {
+		aaddr = get_module_plt(mod, ip, aaddr);
+		new = ftrace_call_replace(ip, aaddr, true);
+	}
+#endif
 
 	return ftrace_modify_code(rec->ip, old, new, true);
 }

@@ -148,9 +161,9 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	unsigned long new, old;
 	unsigned long ip = rec->ip;
 
-	old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
+	old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
 
-	new = ftrace_call_replace(ip, adjust_address(rec, addr));
+	new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
 
 	return ftrace_modify_code(rec->ip, old, new, true);
 }

@@ -160,12 +173,29 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 int ftrace_make_nop(struct module *mod,
 		    struct dyn_ftrace *rec, unsigned long addr)
 {
+	unsigned long aaddr = adjust_address(rec, addr);
 	unsigned long ip = rec->ip;
 	unsigned long old;
 	unsigned long new;
 	int ret;
 
-	old = ftrace_call_replace(ip, adjust_address(rec, addr));
+#ifdef CONFIG_ARM_MODULE_PLTS
+	/* mod is only supplied during module loading */
+	if (!mod)
+		mod = rec->arch.mod;
+	else
+		rec->arch.mod = mod;
+#endif
+
+	old = ftrace_call_replace(ip, aaddr,
+				  !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
+#ifdef CONFIG_ARM_MODULE_PLTS
+	if (!old && mod) {
+		aaddr = get_module_plt(mod, ip, aaddr);
+		old = ftrace_call_replace(ip, aaddr, true);
+	}
+#endif
+
 	new = ftrace_nop_replace(rec);
 	ret = ftrace_modify_code(ip, old, new, true);
 

@@ -4,6 +4,7 @@
  */
 
 #include <linux/elf.h>
+#include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/sort.h>

@@ -19,19 +20,52 @@
 						    (PLT_ENT_STRIDE - 8))
 #endif
 
+static const u32 fixed_plts[] = {
+#ifdef CONFIG_FUNCTION_TRACER
+	FTRACE_ADDR,
+	MCOUNT_ADDR,
+#endif
+};
+
 static bool in_init(const struct module *mod, unsigned long loc)
 {
 	return loc - (u32)mod->init_layout.base < mod->init_layout.size;
 }
 
+static void prealloc_fixed(struct mod_plt_sec *pltsec, struct plt_entries *plt)
+{
+	int i;
+
+	if (!ARRAY_SIZE(fixed_plts) || pltsec->plt_count)
+		return;
+	pltsec->plt_count = ARRAY_SIZE(fixed_plts);
+
+	for (i = 0; i < ARRAY_SIZE(plt->ldr); ++i)
+		plt->ldr[i] = PLT_ENT_LDR;
+
+	BUILD_BUG_ON(sizeof(fixed_plts) > sizeof(plt->lit));
+	memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
+}
+
 u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
 {
 	struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core :
 							  &mod->arch.init;
+	struct plt_entries *plt;
+	int idx;
+
+	/* cache the address, ELF header is available only during module load */
+	if (!pltsec->plt_ent)
+		pltsec->plt_ent = (struct plt_entries *)pltsec->plt->sh_addr;
+	plt = pltsec->plt_ent;
 
-	struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
-	int idx = 0;
+	prealloc_fixed(pltsec, plt);
+
+	for (idx = 0; idx < ARRAY_SIZE(fixed_plts); ++idx)
+		if (plt->lit[idx] == val)
+			return (u32)&plt->ldr[idx];
 
+	idx = 0;
 	/*
 	 * Look for an existing entry pointing to 'val'. Given that the
 	 * relocations are sorted, this will be the last entry we allocated.

@@ -179,8 +213,8 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 			      char *secstrings, struct module *mod)
 {
-	unsigned long core_plts = 0;
-	unsigned long init_plts = 0;
+	unsigned long core_plts = ARRAY_SIZE(fixed_plts);
+	unsigned long init_plts = ARRAY_SIZE(fixed_plts);
 	Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
 	Elf32_Sym *syms = NULL;
 

@@ -235,6 +269,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 	mod->arch.core.plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
 					       sizeof(struct plt_entries));
 	mod->arch.core.plt_count = 0;
+	mod->arch.core.plt_ent = NULL;
 
 	mod->arch.init.plt->sh_type = SHT_NOBITS;
 	mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;

@@ -242,6 +277,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 	mod->arch.init.plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
 					       sizeof(struct plt_entries));
 	mod->arch.init.plt_count = 0;
+	mod->arch.init.plt_ent = NULL;
 
 	pr_debug("%s: plt=%x, init.plt=%x\n", __func__,
 		 mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size);