linux-kernel - [PATCH v3 5/6] powerpc: Prepare arch_static_call_transform() for supporting inline static calls

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Date:   Thu,  1 Sep 2022 13:48:24 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>, sv@...ux.ibm.com,
        bgray@...ux.ibm.com, agust@...x.de, jpoimboe@...nel.org,
        peterz@...radead.org, jbaron@...mai.com, rostedt@...dmis.org,
        ardb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        x86@...nel.org, chenzhongjin@...wei.com
Subject: [PATCH v3 5/6] powerpc: Prepare arch_static_call_transform() for supporting inline static calls

Reorganise arch_static_call_transform() in order to ease the support
of inline static calls in following patch:
- remove 'target' to nhide whether it is a 'return 0' or not.
- Don't bail out if 'tramp' is NULL, just do nothing until next patch.

Note that 'target' was 'tramp + PPC_SCT_RET0', is_short was perforce
true. So in the 'if (func && !is_short)' leg, target was perforce
equal to 'func'.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v3: New. Split out of following patch.
---
 arch/powerpc/kernel/static_call.c | 36 ++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kernel/static_call.c b/arch/powerpc/kernel/static_call.c
index 863a7aa24650..97765b9e1c5b 100644
--- a/arch/powerpc/kernel/static_call.c
+++ b/arch/powerpc/kernel/static_call.c
@@ -8,26 +8,32 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 {
 	int err;
 	bool is_ret0 = (func == __static_call_return0);
-	unsigned long target = (unsigned long)(is_ret0 ? tramp + PPC_SCT_RET0 : func);
-	bool is_short = is_offset_in_branch_range((long)target - (long)tramp);
-
-	if (!tramp)
-		return;
+	unsigned long _tramp = (unsigned long)tramp;
+	unsigned long _func = (unsigned long)func;
+	unsigned long _ret0 = _tramp + PPC_SCT_RET0;
+	bool is_short = is_offset_in_branch_range((long)func - (long)(site ? : tramp));
 
 	mutex_lock(&text_mutex);
 
-	if (func && !is_short) {
-		err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(target));
-		if (err)
-			goto out;
+	if (tramp) {
+		if (func && !is_short) {
+			err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(_func));
+			if (err)
+				goto out;
+		}
+
+		if (!func)
+			err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR()));
+		else if (is_ret0)
+			err = patch_branch(tramp, _ret0, 0);
+		else if (is_short)
+			err = patch_branch(tramp, _func, 0);
+		else
+			err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP()));
+	} else {
+		err = 0;
 	}
 
-	if (!func)
-		err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR()));
-	else if (is_short)
-		err = patch_branch(tramp, target, 0);
-	else
-		err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP()));
 out:
 	mutex_unlock(&text_mutex);
 
-- 
2.37.1