[PATCH v5 3/5] powerpc/inst: Define ppc_inst_t as u32 on PPC32

Christophe Leroy
2021-11-29T17:56:09Z

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@csgroup.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 b3502f21e0f4..7ef5fd3bb167 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 378db980ded3..3b1c2236cbee 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
--
2.33.1