linux-kernel - [PATCH 5.4 03/16] powerpc/ftrace: Remove ftrace init tramp once kernel init is complete

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Date:   Thu, 30 Jun 2022 15:46:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.4 03/16] powerpc/ftrace: Remove ftrace init tramp once kernel init is complete

From: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

commit 84ade0a6655bee803d176525ef457175cbf4df22 upstream.

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

Fixes: 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs")
Cc: stable@...r.kernel.org # v4.20+
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20220516071422.463738-1-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/include/asm/ftrace.h  |    5 ++++-
 arch/powerpc/kernel/trace/ftrace.c |   15 ++++++++++++---
 arch/powerpc/mm/mem.c              |    2 ++
 3 files changed, 18 insertions(+), 4 deletions(-)

--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -96,7 +96,7 @@ static inline bool arch_syscall_match_sy
 #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)
@@ -108,9 +108,12 @@ static inline void this_cpu_enable_ftrac
 {
 	get_paca()->ftrace_enabled = 1;
 }
+
+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 ftrace_free_init_tramp(void) { }
 #endif /* CONFIG_PPC64 */
 #endif /* !__ASSEMBLY__ */
 
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -328,9 +328,7 @@ static int setup_mcount_compiler_tramp(u
 
 	/* 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? */
@@ -868,6 +866,17 @@ 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;
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -48,6 +48,7 @@
 #include <asm/fixmap.h>
 #include <asm/swiotlb.h>
 #include <asm/rtas.h>
+#include <asm/ftrace.h>
 
 #include <mm/mmu_decl.h>
 
@@ -346,6 +347,7 @@ void free_initmem(void)
 	mark_initmem_nx();
 	init_mem_is_free = true;
 	free_initmem_default(POISON_FREE_INITMEM);
+	ftrace_free_init_tramp();
 }
 
 /**