linux-kernel - [PATCH v2 02/25] powerpc/ftrace: Remove redundant create

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Message-Id: <aa45fbad0b4b7493080835d8276c0cb4ce146503.1651905939.git.christophe.leroy@csgroup.eu>
Date:   Sat,  7 May 2022 08:46:04 +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 v2 02/25] powerpc/ftrace: Remove redundant create_branch() calls

Since commit d5937db114e4 ("powerpc/code-patching: Fix patch_branch()
return on out-of-range failure") patch_branch() fails with -ERANGE
when trying to branch out of range.

No need to perform the test twice. Remove redundant create_branch()
calls.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/trace/ftrace.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 7a266fd469b7..3ce3697e8a7c 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -301,7 +301,6 @@ static int setup_mcount_compiler_tramp(unsigned long tramp)
 	int i;
 	ppc_inst_t op;
 	unsigned long ptr;
-	ppc_inst_t instr;
 	static unsigned long ftrace_plt_tramps[NUM_FTRACE_TRAMPS];
 
 	/* Is this a known long jump tramp? */
@@ -344,12 +343,6 @@ static int setup_mcount_compiler_tramp(unsigned long tramp)
 #else
 	ptr = ppc_global_function_entry((void *)ftrace_caller);
 #endif
-	if (create_branch(&instr, (void *)tramp, ptr, 0)) {
-		pr_debug("%ps is not reachable from existing mcount tramp\n",
-				(void *)ptr);
-		return -1;
-	}
-
 	if (patch_branch((u32 *)tramp, ptr, 0)) {
 		pr_debug("REL24 out of range!\n");
 		return -1;
@@ -490,7 +483,6 @@ static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	ppc_inst_t op[2];
-	ppc_inst_t instr;
 	void *ip = (void *)rec->ip;
 	unsigned long entry, ptr, tramp;
 	struct module *mod = rec->arch.mod;
@@ -539,12 +531,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 		return -EINVAL;
 	}
 
-	/* Ensure branch is within 24 bits */
-	if (create_branch(&instr, ip, tramp, BRANCH_SET_LINK)) {
-		pr_err("Branch out of range\n");
-		return -EINVAL;
-	}
-
 	if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
 		pr_err("REL24 out of range!\n");
 		return -EINVAL;
@@ -770,12 +756,6 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 		return -EINVAL;
 	}
 
-	/* Ensure branch is within 24 bits */
-	if (create_branch(&op, (u32 *)ip, tramp, BRANCH_SET_LINK)) {
-		pr_err("Branch out of range\n");
-		return -EINVAL;
-	}
-
 	if (patch_branch((u32 *)ip, tramp, BRANCH_SET_LINK)) {
 		pr_err("REL24 out of range!\n");
 		return -EINVAL;
-- 
2.35.1