linux-kernel - [PATCH v3 04/25] powerpc/ftrace: Use is_offset_in_branch

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Date:   Mon,  9 May 2022 07:36:02 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        naveen.n.rao@...ux.vnet.ibm.com
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v3 04/25] powerpc/ftrace: Use is_offset_in_branch_range()

Use is_offset_in_branch_range() instead of create_branch()
to check if a target is within branch range.

This patch together with the previous one improves
ftrace activation time by 7%

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/trace/ftrace.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 3ce3697e8a7c..41c45b9c7f39 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -89,11 +89,9 @@ ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
  */
 static int test_24bit_addr(unsigned long ip, unsigned long addr)
 {
-	ppc_inst_t op;
 	addr = ppc_function_entry((void *)addr);
 
-	/* use the create_branch to verify that this offset can be branched */
-	return create_branch(&op, (u32 *)ip, addr, 0) == 0;
+	return is_offset_in_branch_range(addr - ip);
 }
 
 static int is_bl_op(ppc_inst_t op)
@@ -261,7 +259,6 @@ __ftrace_make_nop(struct module *mod,
 static unsigned long find_ftrace_tramp(unsigned long ip)
 {
 	int i;
-	ppc_inst_t instr;
 
 	/*
 	 * We have the compiler generated long_branch tramps at the end
@@ -270,8 +267,7 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
 	for (i = NUM_FTRACE_TRAMPS - 1; i >= 0; i--)
 		if (!ftrace_tramps[i])
 			continue;
-		else if (create_branch(&instr, (void *)ip,
-				       ftrace_tramps[i], 0) == 0)
+		else if (is_offset_in_branch_range(ftrace_tramps[i] - ip))
 			return ftrace_tramps[i];
 
 	return 0;
-- 
2.35.1