[PATCH v2] powerpc/ftrace: Remove ftrace init tramp once kernel init is complete

[Naveen N. Rao]

Stop using the ftrace trampoline for init section once kernel init is
complete.

Fixes: 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs")
Cc: stable at vger.kernel.org # v4.20+
Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
v2: Update #ifdef to also check for CONFIG_FUNCTION_TRACER to address a
build break seen with corenet64_smp_defconfig.


 arch/powerpc/include/asm/ftrace.h  |  4 +++-
 arch/powerpc/kernel/trace/ftrace.c | 15 ++++++++++++---
 arch/powerpc/mm/mem.c              |  2 ++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index d83758acd1c7c3..44a37a2b6a1cfa 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -86,7 +86,7 @@ static inline bool arch_syscall_match_sym_name(const char *sym, const char *name
 #endif /* PPC64_ELF_ABI_v1 */
 #endif /* CONFIG_FTRACE_SYSCALLS */
 
-#ifdef CONFIG_PPC64
+#if defined(CONFIG_PPC64) && defined(CONFIG_FUNCTION_TRACER)
 #include <asm/paca.h>
 
 static inline void this_cpu_disable_ftrace(void)
@@ -110,11 +110,13 @@ static inline u8 this_cpu_get_ftrace_enabled(void)
 	return get_paca()->ftrace_enabled;
 }
 
+void ftrace_free_init_tramp(void);
 #else /* CONFIG_PPC64 */
 static inline void this_cpu_disable_ftrace(void) { }
 static inline void this_cpu_enable_ftrace(void) { }
 static inline void this_cpu_set_ftrace_enabled(u8 ftrace_enabled) { }
 static inline u8 this_cpu_get_ftrace_enabled(void) { return 1; }
+static inline void ftrace_free_init_tramp(void) { }
 #endif /* CONFIG_PPC64 */
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 4ee04aacf9f13c..a778f2ae1f3f50 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -306,9 +306,7 @@ static int setup_mcount_compiler_tramp(unsigned long tramp)
 
 	/* Is this a known long jump tramp? */
 	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
-		if (!ftrace_tramps[i])
-			break;
-		else if (ftrace_tramps[i] == tramp)
+		if (ftrace_tramps[i] == tramp)
 			return 0;
 
 	/* Is this a known plt tramp? */
@@ -863,6 +861,17 @@ void arch_ftrace_update_code(int command)
 
 extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
 
+void ftrace_free_init_tramp(void)
+{
+	int i;
+
+	for (i = 0; i < NUM_FTRACE_TRAMPS && ftrace_tramps[i]; i++)
+		if (ftrace_tramps[i] == (unsigned long)ftrace_tramp_init) {
+			ftrace_tramps[i] = 0;
+			return;
+		}
+}
+
 int __init ftrace_dyn_arch_init(void)
 {
 	int i;
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 4d221d033804ef..149635e5c16534 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -22,6 +22,7 @@
 #include <asm/kasan.h>
 #include <asm/svm.h>
 #include <asm/mmzone.h>
+#include <asm/ftrace.h>
 
 #include <mm/mmu_decl.h>
 
@@ -312,6 +313,7 @@ void free_initmem(void)
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
 	free_initmem_default(POISON_FREE_INITMEM);
+	ftrace_free_init_tramp();
 }
 
 /*

base-commit: f5802608e604dbedd4e791a43dd7732b68fcacae
-- 
2.36.1