[PATCH] x86: Cr4 is valid on some 486s (ff6e8c0d) · Commits · 戴 / test

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>

arch/i386/kernel/process.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -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);
		}

include/asm-i386/system.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -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())

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