On 04/30/2018 12:57 PM, Roger Pau Monné wrote: > On Mon, Apr 30, 2018 at 12:23:36PM -0400, Boris Ostrovsky wrote: >> Latest binutils release (2.29.1) will no longer allow proper computation >> of GDT entries on 32-bits, with warning: >> >> arch/x86/xen/xen-pvh.S: Assembler messages: >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (40 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (40 is not between 0 and 31) >> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31) >> >> Use explicit value of the entry instead of using GDT_ENTRY() macro. >> >> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> >> Cc: stable@xxxxxxxxxxxxxxx >> --- >> arch/x86/xen/xen-pvh.S | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S >> index e1a5fbe..934f7d4 100644 >> --- a/arch/x86/xen/xen-pvh.S >> +++ b/arch/x86/xen/xen-pvh.S >> @@ -145,11 +145,11 @@ gdt_start: >> .quad 0x0000000000000000 /* NULL descriptor */ >> .quad 0x0000000000000000 /* reserved */ >> #ifdef CONFIG_X86_64 >> - .quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* __KERNEL_CS */ >> + .quad 0x00af9a000000ffff /* __BOOT_CS */ >> #else >> - .quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* __KERNEL_CS */ >> + .quad 0x00cf9a000000ffff /* __BOOT_CS */ > Maybe it would be cleaner to use something like: I actually considered all of these and ended up with a raw number because it seems to be a convention in kernel (and Xen too, apparently) to use raw values in .S files. Kernel is using now GDT_ENTRY_INIT() which is a C macro. There is one other location where GDT_INIT() is used (arch/x86/boot/pm.c) and, incidentally, it also generates this warning IIRC. I really don't want to move definition to C code just to use a macro --- I don't think C code needs to be exposed to this GDT. > > .word 0xffff /* limit */ > .word 0 /* base */ > .byte 0 /* base */ > .byte 0x9a /* access */ > #ifdef CONFIG_X86_64 > .byte 0xaf /* flags plus limit */ > #else > .byte 0xcf /* flags plus limit */ > #endif > .byte 0 /* base */ I, in fact, started with something like this. But if you repeat this 4 times you will probably see why I decided against it ;-) -boris > > Or try to fix the GDT_ENTRY macro, maybe if you prepend extra 0's to > make the values 64bit that would prevent the warnings? > > Or declare the GDT in enlighten_pvh in C and use it here? > > Also, IIRC the base/limit values are ignored in long mode. > > Thanks, Roger.
