linux-kernel - [PATCH v2 3/3] powerpc/inst: Define ppc_inst

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Date:   Mon, 20 Sep 2021 08:22:44 +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>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 3/3] powerpc/inst: Define ppc_inst_t as u32 on PPC32

Unlike PPC64 ABI, PPC32 uses the stack to pass a parameter defined
as a struct, even when the struct has a single simple element.

To avoid that, define ppc_inst_t as u32 on PPC32.

Keep it as 'struct ppc_inst' when __CHECKER__ is defined so that
sparse can perform type checking.

Also revert commit 511eea5e2ccd ("powerpc/kprobes: Fix Oops by passing
ppc_inst as a pointer to emulate_step() on ppc32") as now the
instruction to be emulated is passed as a register to emulate_step().

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v2: Make it work with kprobes
---
 arch/powerpc/include/asm/inst.h | 15 +++++++++++++--
 arch/powerpc/kernel/optprobes.c |  8 ++------
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index 055de1fa5d46..5c503816ebc0 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -34,6 +34,7 @@
  * Instruction data type for POWER
  */
 
+#if defined(CONFIG_PPC64) || defined(__CHECKER__)
 typedef struct {
 	u32 val;
 #ifdef CONFIG_PPC64
@@ -46,13 +47,23 @@ static inline u32 ppc_inst_val(ppc_inst_t x)
 	return x.val;
 }
 
+#define ppc_inst(x) ((ppc_inst_t){ .val = (x) })
+
+#else
+typedef u32 ppc_inst_t;
+
+static inline u32 ppc_inst_val(ppc_inst_t x)
+{
+	return x;
+}
+#define ppc_inst(x) (x)
+#endif
+
 static inline int ppc_inst_primary_opcode(ppc_inst_t x)
 {
 	return ppc_inst_val(x) >> 26;
 }
 
-#define ppc_inst(x) ((ppc_inst_t){ .val = (x) })
-
 #ifdef CONFIG_PPC64
 #define ppc_inst_prefix(x, y) ((ppc_inst_t){ .val = (x), .suffix = (y) })
 
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index 04b540c12800..7ab7f65fa6c6 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -228,12 +228,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	/*
 	 * 3. load instruction to be emulated into relevant register, and
 	 */
-	if (IS_ENABLED(CONFIG_PPC64)) {
-		temp = ppc_inst_read(p->ainsn.insn);
-		patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
-	} else {
-		patch_imm_load_insns((unsigned long)p->ainsn.insn, 4, buff + TMPL_INSN_IDX);
-	}
+	temp = ppc_inst_read(p->ainsn.insn);
+	patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
 
 	/*
 	 * 4. branch back from trampoline
-- 
2.31.1