[RFC PATCH 0/5] Bump gcc minimum version to 3.4, 4.1 for x86

[RFC PATCH 0/5] Bump gcc minimum version to 3.4, 4.1 for x86

[H. Peter Anvin]

This patchset bumps the minimum supported gcc version to 3.4 for the
general kernel, and to 4.1 for x86.

We have had a rash of bug reports related to these really old
compilers and their associated binutils version lately, and it is
clear that the support burden of these older compilers is getting to
be excessive.  If you really want to build a kernel on a system that
old you can build or obtain an updated gcc/binutils as well.

 Documentation/Changes             |    2 +-
 arch/x86/include/asm/bitops.h     |    7 -------
 arch/x86/include/asm/cpufeature.h |    7 -------
 arch/x86/include/asm/string_32.h  |   21 ---------------------
 arch/x86/kernel/Makefile          |    3 ++-
 arch/x86/kernel/compiler.c        |    5 +++++
 include/linux/compiler-gcc3.h     |   15 +--------------
 7 files changed, 9 insertions(+), 51 deletions(-)

[PATCH 1/5] Disallow building with gcc < 3.4

[H. Peter Anvin]

Disallow building the generic kernel code with gcc < 3.4.  Earlier
versions of gcc have known problems, and it appears that anyone who
genuinely needs gcc 3.x can use gcc 3.4 at this point.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 Documentation/Changes         |    2 +-
 include/linux/compiler-gcc3.h |   15 +--------------
 2 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/Documentation/Changes b/Documentation/Changes
index 4fb88f1..0ea8040 100644
--- a/Documentation/Changes
+++ b/Documentation/Changes
@@ -28,7 +28,7 @@ necessary on all systems; obviously, if you don't have any ISDN
 hardware, for example, you probably needn't concern yourself with
 isdn4k-utils.
 
-o  Gnu C                  3.2                     # gcc --version
+o  Gnu C                  3.4                     # gcc --version
 o  Gnu make               3.80                    # make --version
 o  binutils               2.12                    # ld -v
 o  util-linux             2.10o                   # fdformat --version
diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
index b721129..c11d443 100644
--- a/include/linux/compiler-gcc3.h
+++ b/include/linux/compiler-gcc3.h
@@ -2,25 +2,12 @@
 #error "Please don't include <linux/compiler-gcc3.h> directly, include <linux/compiler.h> instead."
 #endif
 
-#if __GNUC_MINOR__ < 2
+#if __GNUC_MINOR__ < 4
 # error Sorry, your compiler is too old - please upgrade it.
 #endif
 
-#if __GNUC_MINOR__ >= 3
 # define __used			__attribute__((__used__))
-#else
-# define __used			__attribute__((__unused__))
-#endif
-
-#if __GNUC_MINOR__ >= 4
 #define __must_check		__attribute__((warn_unused_result))
-#endif
-
-#ifdef CONFIG_GCOV_KERNEL
-# if __GNUC_MINOR__ < 4
-#   error "GCOV profiling support for gcc versions below 3.4 not included"
-# endif /* __GNUC_MINOR__ */
-#endif /* CONFIG_GCOV_KERNEL */
 
 /*
  * A trick to suppress uninitialized variable warning without generating any
-- 
1.7.2.1

Re: [PATCH 1/5] Disallow building with gcc < 3.4

[Russell King - ARM Linux]

On Mon, Sep 13, 2010 at 01:14:36PM -0700, H. Peter Anvin wrote:
> Disallow building the generic kernel code with gcc < 3.4.  Earlier
> versions of gcc have known problems, and it appears that anyone who
> genuinely needs gcc 3.x can use gcc 3.4 at this point.
> 
> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

Reviewed-by: Russell King <rmk+kernel@arm.linux.org.uk>

[PATCH 2/5] x86, gcc: Disallow building Linux/x86 with gcc 3.x/4.0

[H. Peter Anvin]

We are starting to get "straggler problems" with people compiling
current Linux kernels with now-ancient versions of gcc.  All the
development is being done against gcc 4.x; this simply disallows gcc
4.0 or earlier.

We disallow 4.0 as well as 3.x because 4.0 had a fair share of bugs
especially around asm() statements; this allows us to remove those
workarounds.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/kernel/Makefile   |    3 ++-
 arch/x86/kernel/compiler.c |    5 +++++
 2 files changed, 7 insertions(+), 1 deletions(-)
 create mode 100644 arch/x86/kernel/compiler.c

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0925676..a6459b7 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -29,7 +29,8 @@ GCOV_PROFILE_hpet.o		:= n
 GCOV_PROFILE_tsc.o		:= n
 GCOV_PROFILE_paravirt.o		:= n
 
-obj-y			:= process_$(BITS).o signal.o entry_$(BITS).o
+obj-y			:= compiler.o
+obj-y			+= process_$(BITS).o signal.o entry_$(BITS).o
 obj-y			+= traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
 obj-y			+= time.o ioport.o ldt.o dumpstack.o
 obj-y			+= setup.o x86_init.o i8259.o irqinit.o
diff --git a/arch/x86/kernel/compiler.c b/arch/x86/kernel/compiler.c
new file mode 100644
index 0000000..8914974
--- /dev/null
+++ b/arch/x86/kernel/compiler.c
@@ -0,0 +1,5 @@
+#if __GNUC__ < 4
+#error "Compiling Linux/x86 with gcc 3.x is no longer supported"
+#elif __GNUC__ == 4 && __GNUC_MINOR__ < 1
+#error "Compiling Linux/x86 with gcc 4.0 is not supported"
+#endif
-- 
1.7.2.1

[PATCH 3/5] x86, cpu: Remove gcc 3.x workarounds in <asm/cpufeature.h>

[H. Peter Anvin]

We no longer support gcc 3.x, so remove the workaround for it.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/include/asm/cpufeature.h |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 781a50b..830a94f 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -345,7 +345,6 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
 #endif
 }
 
-#if __GNUC__ >= 4
 #define static_cpu_has(bit)					\
 (								\
 	__builtin_constant_p(boot_cpu_has(bit)) ?		\
@@ -354,12 +353,6 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
 		__static_cpu_has(bit) :				\
 		boot_cpu_has(bit)				\
 )
-#else
-/*
- * gcc 3.x is too stupid to do the static test; fall back to dynamic.
- */
-#define static_cpu_has(bit) boot_cpu_has(bit)
-#endif
 
 #endif /* defined(__KERNEL__) && !defined(__ASSEMBLY__) */
 
-- 
1.7.2.1

[PATCH 4/5] x86, mem: Remove gcc < 4.1 support code for memcpy()

[H. Peter Anvin]

We require gcc 4.1 or later, so remove support code for previous
versions of gcc.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/include/asm/string_32.h |   21 ---------------------
 1 files changed, 0 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index 3d3e835..fde4eb2 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -177,16 +177,8 @@ static inline void *__memcpy3d(void *to, const void *from, size_t len)
  */
 
 #ifndef CONFIG_KMEMCHECK
-
-#if (__GNUC__ >= 4)
 #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
 #else
-#define memcpy(t, f, n)				\
-	(__builtin_constant_p((n))		\
-	 ? __constant_memcpy((t), (f), (n))	\
-	 : __memcpy((t), (f), (n)))
-#endif
-#else
 /*
  * kmemcheck becomes very happy if we use the REP instructions unconditionally,
  * because it means that we know both memory operands in advance.
@@ -284,12 +276,7 @@ void *__constant_c_and_count_memset(void *s, unsigned long pattern,
 
 	{
 		int d0, d1;
-#if __GNUC__ == 4 && __GNUC_MINOR__ == 0
-		/* Workaround for broken gcc 4.0 */
-		register unsigned long eax asm("%eax") = pattern;
-#else
 		unsigned long eax = pattern;
-#endif
 
 		switch (count % 4) {
 		case 0:
@@ -321,15 +308,7 @@ void *__constant_c_and_count_memset(void *s, unsigned long pattern,
 	 : __memset_generic((s), (c), (count)))
 
 #define __HAVE_ARCH_MEMSET
-#if (__GNUC__ >= 4)
 #define memset(s, c, count) __builtin_memset(s, c, count)
-#else
-#define memset(s, c, count)						\
-	(__builtin_constant_p(c)					\
-	 ? __constant_c_x_memset((s), (0x01010101UL * (unsigned char)(c)), \
-				 (count))				\
-	 : __memset((s), (c), (count)))
-#endif
 
 /*
  * find the first occurrence of byte 'c', or 1 past the area if none
-- 
1.7.2.1

[PATCH 5/5] x86, bitops: Remove gcc < 4.1 workaround

[H. Peter Anvin]

Remove workaround for gcc older than 4.1.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/include/asm/bitops.h |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 545776e..1532109 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -22,14 +22,7 @@
  *
  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  */
-
-#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1)
-/* Technically wrong, but this avoids compilation errors on some gcc
-   versions. */
-#define BITOP_ADDR(x) "=m" (*(volatile long *) (x))
-#else
 #define BITOP_ADDR(x) "+m" (*(volatile long *) (x))
-#endif
 
 #define ADDR				BITOP_ADDR(addr)
 
-- 
1.7.2.1

Re: [RFC PATCH 0/5] Bump gcc minimum version to 3.4, 4.1 for x86

[Brian Gerst]

On Mon, Sep 13, 2010 at 4:14 PM, H. Peter Anvin <hpa@linux.intel.com> wrote:
> This patchset bumps the minimum supported gcc version to 3.4 for the
> general kernel, and to 4.1 for x86.
>
> We have had a rash of bug reports related to these really old
> compilers and their associated binutils version lately, and it is
> clear that the support burden of these older compilers is getting to
> be excessive.  If you really want to build a kernel on a system that
> old you can build or obtain an updated gcc/binutils as well.

What version of binutils does this correspond to?  It would be nice to
clean up some of the hacks for ancient binutils as well.

--
Brian Gerst

Re: [RFC PATCH 0/5] Bump gcc minimum version to 3.4, 4.1 for x86

[H. Peter Anvin]

On 09/13/2010 05:11 PM, Brian Gerst wrote:
> On Mon, Sep 13, 2010 at 4:14 PM, H. Peter Anvin <hpa@linux.intel.com> wrote:
>> This patchset bumps the minimum supported gcc version to 3.4 for the
>> general kernel, and to 4.1 for x86.
>>
>> We have had a rash of bug reports related to these really old
>> compilers and their associated binutils version lately, and it is
>> clear that the support burden of these older compilers is getting to
>> be excessive.  If you really want to build a kernel on a system that
>> old you can build or obtain an updated gcc/binutils as well.
> 
> What version of binutils does this correspond to?  It would be nice to
> clean up some of the hacks for ancient binutils as well.
> 

4.1 -> 2.16
3.4 -> 2.14/2.15 (gcc 3.4.0 beat binutils 2.15 by a mere 29 days)

This is somewhat unfortunate, since neither of these brackets eliminate
the Binutils Version From Hell, a.k.a. 2.16.

	-hpa