ppc64le FTRACE_WITH_REGS implementation

index ef89b14..6eb9fbc 100644
@@ -46,6 +46,8 @@
 extern void _mcount(void);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
+# define FTRACE_ADDR ((unsigned long)ftrace_caller)
+# define FTRACE_REGS_ADDR FTRACE_ADDR
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
        /* reloction of mcount call site is the same as the address */

@@ -58,6 +60,9 @@ struct dyn_arch_ftrace {
 #endif /*  CONFIG_DYNAMIC_FTRACE */
 #endif /* __ASSEMBLY__ */
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+#define ARCH_SUPPORTS_FTRACE_OPS 1
+#endif
 #endif
 
 #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64) && !defined(__ASSEMBLY__)

120 lines not on this page · raw message

index 6838451..e62c41f 100644
@@ -138,12 +138,21 @@ static u32 ppc64_stub_insns[] = {
 	0x4e800420			/* bctr */
 };
 
+/* In case of _mcount calls or dynamic ftracing, Do not save the
+ * current callee's TOC (in R2) again into the original caller's stack
+ * frame during this trampoline hop. The stack frame already holds
+ * that of the original caller.  _mcount and ftrace_caller will take
+ * care of this TOC value themselves.
+ */
+#define SQUASH_TOC_SAVE_INSN(trampoline_addr) \
+	(((struct ppc64_stub_entry *)(trampoline_addr))->jump[2] = PPC_INST_NOP)
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 static u32 ppc64_stub_mask[] = {
 	0xffff0000,
 	0xffff0000,
-	0xffffffff,
+	0x00000000,
 	0xffffffff,
 #if !defined(_CALL_ELF) || _CALL_ELF != 2
 	0xffffffff,

@@ -170,6 +179,9 @@ bool is_module_trampoline(u32 *p)
 		if ((insna & mask) != (insnb & mask))
 			return false;
 	}
+	if (insns[2] != ppc64_stub_insns[2] &&
+	    insns[2] != PPC_INST_NOP)
+		return false;
 
 	return true;
 }

@@ -475,6 +487,19 @@ static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,
 static int restore_r2(u32 *instruction, struct module *me)
 {
 	if (*instruction != PPC_INST_NOP) {
+
+		/* -mprofile_kernel sequence starting with
+		 * mflr r0; std r0, LRSAVE(r1)
+		 */
+		if (instruction[-3] == 0x7c0802a6 &&
+		    instruction[-2] == 0xf8010010) {
+			/* Nothing to be done here, it's an _mcount
+			 * call location and r2 will have to be
+			 * restored in the _mcount function.
+			 */
+			return 2;
+		};
+
 		pr_err("%s: Expect noop after relocate, got %08x\n",
 		       me->name, *instruction);
 		return 0;

@@ -490,7 +515,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 		       unsigned int relsec,
 		       struct module *me)
 {
-	unsigned int i;
+	unsigned int i, r2;
 	Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 	Elf64_Sym *sym;
 	unsigned long *location;

@@ -603,8 +628,12 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 				value = stub_for_addr(sechdrs, value, me);
 				if (!value)
 					return -ENOENT;
-				if (!restore_r2((u32 *)location + 1, me))
+				r2 = restore_r2((u32 *)location + 1, me);
+				if (!r2)
 					return -ENOEXEC;
+				/* Squash the TOC saver for profiler calls */
+				if (!strcmp("_mcount", strtab+sym->st_name))
+					SQUASH_TOC_SAVE_INSN(value);
 			} else
 				value += local_entry_offset(sym);
 

@@ -665,6 +694,10 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 	me->arch.tramp = stub_for_addr(sechdrs,
 				       (unsigned long)ftrace_caller,
 				       me);
+	/* ftrace_caller will take care of the TOC;
+	 * do not clobber original caller's value.
+	 */
+	SQUASH_TOC_SAVE_INSN(me->arch.tramp);
 #endif
 
 	return 0;