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[PATCH] x86: Cr4 is valid on some 486s

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So some 486 processors do have CR4 register.  Allow them to present it in
register dumps by using the old fault technique rather than testing processor
family.

Thanks to Maciej for noticing this.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Cc: "Seth, Rohit" <rohit.seth@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Zachary Amsden 2006-01-06 00:11:50 -08:00 committed by Linus Torvalds
parent eb05c3249a
commit ff6e8c0d5e
2 changed files with 14 additions and 3 deletions
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4
arch/i386/kernel/process.c
View file

@ -308,9 +308,7 @@ void show_regs(struct pt_regs * regs)
cr0 = read_cr0();
cr2 = read_cr2();
cr3 = read_cr3();
if (current_cpu_data.x86 > 4) {
cr4 = read_cr4();
}
cr4 = read_cr4_safe();
printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
show_trace(NULL, &regs->esp);
}

13
include/asm-i386/system.h
View file

@ -140,6 +140,19 @@ static inline unsigned long _get_base(char * addr)
:"=r" (__dummy)); \
__dummy; \
})
#define read_cr4_safe() ({ \
unsigned int __dummy; \
/* This could fault if %cr4 does not exist */ \
__asm__("1: movl %%cr4, %0 \n" \
"2: \n" \
".section __ex_table,\"a\" \n" \
".long 1b,2b \n" \
".previous \n" \
: "=r" (__dummy): "0" (0)); \
__dummy; \
})
#define write_cr4(x) \
__asm__ __volatile__("movl %0,%%cr4": :"r" (x));
#define stts() write_cr0(8 | read_cr0())