linux-kernel - [PATCH] arch-powerpc: Return false instead of -EFAULT

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Date:	Thu, 17 Sep 2015 11:18:56 +0200
From:	Peter Senna Tschudin <peter.senna@...il.com>
To:	benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
	anton@...ba.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Cc:	Peter Senna Tschudin <peter.senna@...il.com>
Subject: [PATCH] arch-powerpc: Return false instead of -EFAULT

Returning a negative value for a boolean function seem to have the
undesired effect of returning true. Replace -EINVAL by false in a
bool-returning function.

The diff of the .s file before and after the change (using cross
compilation) starts with:

440,441c440,441
< .L43:
< 	li 3,1	 # D.25775,
---
> .L42:
> 	li 3,0	 # D.25775,
...

while if -EFAULT is replaced by true, the diff is empty.

There is only one call site, and it expects a boolean value:
arch/powerpc/kernel/ftrace.c:129:
        if (!is_module_trampoline(tramp)) {
                pr_err("Not a trampoline\n");
                return -EINVAL;
        }

This issue was found by the following Coccinelle semantic patch:
<smpl>
@@
identifier f;
constant C;
typedef bool;
@@
bool f (...){
<+...
* return -C;
...+>
}
</smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@...il.com>
---
 arch/powerpc/kernel/module_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 6838451..a94a5f1 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -160,7 +160,7 @@ bool is_module_trampoline(u32 *p)
 	BUILD_BUG_ON(sizeof(ppc64_stub_insns) != sizeof(ppc64_stub_mask));
 
 	if (probe_kernel_read(insns, p, sizeof(insns)))
-		return -EFAULT;
+		return false;
 
 	for (i = 0; i < ARRAY_SIZE(ppc64_stub_insns); i++) {
 		u32 insna = insns[i];
-- 
2.1.0

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