From 5db475f0b987bfa7935a117aac81e14a98de34fb Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Wed, 11 Mar 2020 19:02:52 -0400
Subject: [PATCH] work around negated error code bug on some mips kernels
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on all mips variants, Linux did (and maybe still does) have some
syscall return paths that wrongly return both the error flag in r7 and
a negated error code in r2. in particular this happened for at least
some causes of ENOSYS.

add an extra check to only negate the error code if it's positive to
begin with.

bug report and concept for patch by Andreas Dröscher.
---
 arch/mips/syscall_arch.h    | 16 ++++++++--------
 arch/mips64/syscall_arch.h  | 14 +++++++-------
 arch/mipsn32/syscall_arch.h | 14 +++++++-------
 3 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h
index 4286f00a..380a94b3 100644
--- a/arch/mips/syscall_arch.h
+++ b/arch/mips/syscall_arch.h
@@ -24,7 +24,7 @@ static inline long __syscall0(long n)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2)
 		: SYSCALL_CLOBBERLIST, "$8", "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall1(long n, long a)
@@ -37,7 +37,7 @@ static inline long __syscall1(long n, long a)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4)
 		: SYSCALL_CLOBBERLIST, "$8", "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall2(long n, long a, long b)
@@ -51,7 +51,7 @@ static inline long __syscall2(long n, long a, long b)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5)
 		: SYSCALL_CLOBBERLIST, "$8", "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall3(long n, long a, long b, long c)
@@ -66,7 +66,7 @@ static inline long __syscall3(long n, long a, long b, long c)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST, "$8", "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall4(long n, long a, long b, long c, long d)
@@ -81,7 +81,7 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST, "$8", "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
@@ -99,7 +99,7 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 		: "=&r"(r2), "+r"(r7), "+r"(r8)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST, "$9", "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
@@ -118,7 +118,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
 		: "=&r"(r2), "+r"(r7), "+r"(r8), "+r"(r9)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST, "$10");
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall7(long n, long a, long b, long c, long d, long e, long f, long g)
@@ -138,7 +138,7 @@ static inline long __syscall7(long n, long a, long b, long c, long d, long e, lo
 		: "=&r"(r2), "+r"(r7), "+r"(r8), "+r"(r9), "+r"(r10)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 #define VDSO_USEFUL
diff --git a/arch/mips64/syscall_arch.h b/arch/mips64/syscall_arch.h
index d34efdc0..ae6532fc 100644
--- a/arch/mips64/syscall_arch.h
+++ b/arch/mips64/syscall_arch.h
@@ -22,7 +22,7 @@ static inline long __syscall0(long n)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall1(long n, long a)
@@ -35,7 +35,7 @@ static inline long __syscall1(long n, long a)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall2(long n, long a, long b)
@@ -50,7 +50,7 @@ static inline long __syscall2(long n, long a, long b)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall3(long n, long a, long b, long c)
@@ -66,7 +66,7 @@ static inline long __syscall3(long n, long a, long b, long c)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall4(long n, long a, long b, long c, long d)
@@ -82,7 +82,7 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
@@ -99,7 +99,7 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6), "r"(r8)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
@@ -117,7 +117,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6), "r"(r8), "r"(r9)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 #define VDSO_USEFUL
diff --git a/arch/mipsn32/syscall_arch.h b/arch/mipsn32/syscall_arch.h
index cbb4a055..c681905d 100644
--- a/arch/mipsn32/syscall_arch.h
+++ b/arch/mipsn32/syscall_arch.h
@@ -22,7 +22,7 @@ static inline long __syscall0(long n)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall1(long n, long a)
@@ -35,7 +35,7 @@ static inline long __syscall1(long n, long a)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall2(long n, long a, long b)
@@ -50,7 +50,7 @@ static inline long __syscall2(long n, long a, long b)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall3(long n, long a, long b, long c)
@@ -66,7 +66,7 @@ static inline long __syscall3(long n, long a, long b, long c)
 		: "=&r"(r2), "=r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall4(long n, long a, long b, long c, long d)
@@ -82,7 +82,7 @@ static inline long __syscall4(long n, long a, long b, long c, long d)
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
@@ -99,7 +99,7 @@ static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6), "r"(r8)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
@@ -117,7 +117,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
 		: "=&r"(r2), "+r"(r7)
 		: "ir"(n), "0"(r2), "r"(r4), "r"(r5), "r"(r6), "r"(r8), "r"(r9)
 		: SYSCALL_CLOBBERLIST);
-	return r7 ? -r2 : r2;
+	return r7 && r2>0 ? -r2 : r2;
 }
 
 #define VDSO_USEFUL
-- 
2.25.1