Subject: [PATCH v4 10/20] powerpc: Use common syscall handler type

From: Rohan McLure <[email-masked]>
Date: Wed, 24 Aug 2022 12:05:38 +1000

Cause syscall handlers to be typed as follows when called indirectly
throughout the kernel.

typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
                           unsigned long, unsigned long, unsigned long);

Since both 32 and 64-bit abis allow for at least the first six
machine-word length parameters to a function to be passed by registers,
even handlers which admit fewer than six parameters may be viewed as
having the above type.

Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce
explicit cast on systems with SPUs.

Signed-off-by: Rohan McLure <[email-masked]>
---
V1 -> V2: New patch.
V2 -> V3: Remove unnecessary cast from const syscall_fn to syscall_fn
---
 arch/powerpc/include/asm/syscall.h          | 7 +++++--
 arch/powerpc/include/asm/syscalls.h         | 1 +
 arch/powerpc/kernel/systbl.c                | 6 +++---
 arch/powerpc/kernel/vdso.c                  | 4 ++--
 arch/powerpc/platforms/cell/spu_callbacks.c | 6 +++---
 5 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 25fc8ad9a27a..d2a8dfd5de33 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -14,9 +14,12 @@
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 
+typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
+			   unsigned long, unsigned long, unsigned long);
+
 /* ftrace syscalls requires exporting the sys_call_table */
-extern const unsigned long sys_call_table[];
-extern const unsigned long compat_sys_call_table[];
+extern const syscall_fn sys_call_table[];
+extern const syscall_fn compat_sys_call_table[];
 
 static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 {
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 91417dee534e..e979b7593d2b 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -8,6 +8,7 @@
 #include <linux/types.h>
 #include <linux/compat.h>
 
+#include <asm/syscall.h>
 #ifdef CONFIG_PPC64
 #include <asm/syscalls_32.h>
 #endif
diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
index 99ffdfef6b9c..b88a9c2a1f50 100644
--- a/arch/powerpc/kernel/systbl.c
+++ b/arch/powerpc/kernel/systbl.c
@@ -21,10 +21,10 @@
 #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
 #define __powerpc_sys_ni_syscall	sys_ni_syscall
 #else
-#define __SYSCALL(nr, entry) [nr] = entry,
+#define __SYSCALL(nr, entry) [nr] = (void *) entry,
 #endif
 
-void *sys_call_table[] = {
+const syscall_fn sys_call_table[] = {
 #ifdef CONFIG_PPC64
 #include <asm/syscall_table_64.h>
 #else
@@ -35,7 +35,7 @@ void *sys_call_table[] = {
 #ifdef CONFIG_COMPAT
 #undef __SYSCALL_WITH_COMPAT
 #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
-void *compat_sys_call_table[] = {
+const syscall_fn compat_sys_call_table[] = {
 #include <asm/syscall_table_32.h>
 };
 #endif /* CONFIG_COMPAT */
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 0da287544054..080c9e7de0c0 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -313,10 +313,10 @@ static void __init vdso_setup_syscall_map(void)
 	unsigned int i;
 
 	for (i = 0; i < NR_syscalls; i++) {
-		if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
+		if (sys_call_table[i] != (void *)&sys_ni_syscall)
 			vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 		if (IS_ENABLED(CONFIG_COMPAT) &&
-		    compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
+		    compat_sys_call_table[i] != (void *)&sys_ni_syscall)
 			vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 	}
 }
diff --git a/arch/powerpc/platforms/cell/spu_callbacks.c b/arch/powerpc/platforms/cell/spu_callbacks.c
index fe0d8797a00a..e780c14c5733 100644
--- a/arch/powerpc/platforms/cell/spu_callbacks.c
+++ b/arch/powerpc/platforms/cell/spu_callbacks.c
@@ -34,15 +34,15 @@
  *	mbind, mq_open, ipc, ...
  */
 
-static void *spu_syscall_table[] = {
+static const syscall_fn spu_syscall_table[] = {
 #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
-#define __SYSCALL(nr, entry) [nr] = entry,
+#define __SYSCALL(nr, entry) [nr] = (void *) entry,
 #include <asm/syscall_table_spu.h>
 };
 
 long spu_sys_callback(struct spu_syscall_block *s)
 {
-	long (*syscall)(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
+	syscall_fn syscall;
 
 	if (s->nr_ret >= ARRAY_SIZE(spu_syscall_table)) {
 		pr_debug("%s: invalid syscall #%lld", __func__, s->nr_ret);
-- 
2.34.1