linux-kernel - [RFC PATCH 05/12] powerpc: Don't negate error in syscall_set_return

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Date:	Wed, 15 Jul 2015 17:37:07 +1000
From:	Michael Ellerman <mpe@...erman.id.au>
To:	<linuxppc-dev@...abs.org>
Cc:	<linux-kernel@...r.kernel.org>, keescook@...omium.org,
	luto@...capital.net, wad@...omium.org, strosake@...ux.vnet.ibm.com,
	bogdan.purcareata@...escale.com
Subject: [RFC PATCH 05/12] powerpc: Don't negate error in syscall_set_return_value()

Currently the only caller of syscall_set_return_value() is seccomp
filter, which is not enabled on powerpc.

This means we have not noticed that our implementation of
syscall_set_return_value() negates error, even though the value passed
in is already negative.

So remove the negation in syscall_set_return_value(), and expect the
caller to do it like all other implementations do.

Also add a comment about the ccr handling.

Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
---
 arch/powerpc/include/asm/syscall.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index c6239dabcfb1..cabe90133e69 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -44,9 +44,15 @@ static inline void syscall_set_return_value(struct task_struct *task,
 					    struct pt_regs *regs,
 					    int error, long val)
 {
+	/*
+	 * In the general case it's not obvious that we must deal with CCR
+	 * here, as the syscall exit path will also do that for us. However
+	 * there are some places, eg. the signal code, which check ccr to
+	 * decide if the value in r3 is actually an error.
+	 */
 	if (error) {
 		regs->ccr |= 0x10000000L;
-		regs->gpr[3] = -error;
+		regs->gpr[3] = error;
 	} else {
 		regs->ccr &= ~0x10000000L;
 		regs->gpr[3] = val;
-- 
2.1.0

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