From: Russell King > These stock GCC versions miscompile the kernel by incorrectly optimising > the function epilogue code - by first increasing the stack pointer, and > then loading entries from below the stack. This means that an opportune > interrupt or exception will corrupt the current function's saved state, > which may result in the parent function seeing different register > values. > > As this bug has been known to result in corrupted filesystems, and these > buggy compiler versions seem to be frequently used, we have little > option but to blacklist these compiler versions. > > Distributions may have fixed PR58854, but as their compilers are totally > indistinguishable from the buggy versions, it is unfortunate that this > also results in those also being blacklisted. Given the filesystem > corruption potential of the original, this is the lesser evil. People > who want to build with their fixed compiler versions will need to adjust > the kernel source. (Distros need to think about the implications of > fixing such a compiler bug, and consider how to ensure that their fixed > compiler versions can be detected if they wish to avoid this.) > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > --- > > This is what I came up with - this places the build check right at the > beginning of the kernel build, rather than at some point where > linux/compiler.h gets included. Note that this is where we have > previous ARM specific GCC version blacklisting. I'm blacklisting > GCC 4.8.0 to GCC 4.8.2 inclussive, which seems to be the right versions > for stock GCC. > > I was in two minds whether to include 4.8.3 as Linaro released a buggy > toolchain which identifies itself as 4.8.3, but I decided that's also > a distro problem. IMHO Linaro should really think about taking that > compiler down given the seriousness of this bug and it being > indistinguishable from the fixed stock version. > > arch/arm/kernel/asm-offsets.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c > index 713e807621d2..e14c1a12b414 100644 > --- a/arch/arm/kernel/asm-offsets.c > +++ b/arch/arm/kernel/asm-offsets.c > @@ -10,6 +10,7 @@ > * it under the terms of the GNU General Public License version 2 as > * published by the Free Software Foundation. > */ > +#include <linux/compiler.h> > #include <linux/sched.h> > #include <linux/mm.h> > #include <linux/dma-mapping.h> > @@ -39,10 +40,19 @@ > * GCC 3.2.x: miscompiles NEW_AUX_ENT in fs/binfmt_elf.c > * (http://gcc.gnu.org/PR8896) and incorrect structure > * initialisation in fs/jffs2/erase.c > + * GCC 4.8.0-4.8.2: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58854 > + * miscompiles find_get_entry(), and can result in EXT3 and EXT4 > + * filesystem corruption (possibly other FS too). > */ > +#ifdef __GNUC__ > #if (__GNUC__ == 3 && __GNUC_MINOR__ < 3) > #error Your compiler is too buggy; it is known to miscompile kernels. > -#error Known good compilers: 3.3 > +#error Known good compilers: 3.3, 4.x Except that isn't true since 4.8.0 isn't a good compiler. > +#endif > +#if GCC_VERSION >= 40800 || GCC_VERSION < 40803 > +#error Your compiler is too buggy; it is known to miscompile kernels > +#error and result in filesystem corruption and oopses. > +#endif > #endif You are mixing the style of the version check. Why not the single test: #if GCC_VERSION < 30300 || (GCC_VERSION >= 40800 && GCC_VERSION < 40803) #error Your compiler is too buggy; it is known to miscompile code. #error Known good compilers: 3.3 onwards excluding 4.8.0 through 4.8.2 #endif David > > int main(void) > -- > 1.8.3.1 ��.n��������+%������w��{.n�����{�������ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
