Messages in this thread Patch in this message | | | Date | Wed, 9 Nov 2005 16:32:42 -0800 | Subject | [PATCH 1/10] Cr4 is valid on some 486s | From | Zachary Amsden <> |
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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> Index: linux-2.6.14/arch/i386/kernel/process.c =================================================================== --- linux-2.6.14.orig/arch/i386/kernel/process.c 2005-11-08 03:25:24.000000000 -0800 +++ linux-2.6.14/arch/i386/kernel/process.c 2005-11-08 03:26:03.000000000 -0800 @@ -314,9 +314,7 @@ 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, ®s->esp); } Index: linux-2.6.14/include/asm-i386/system.h =================================================================== --- linux-2.6.14.orig/include/asm-i386/system.h 2005-11-08 03:25:29.000000000 -0800 +++ linux-2.6.14/include/asm-i386/system.h 2005-11-08 03:26:03.000000000 -0800 @@ -140,6 +140,19 @@ :"=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()) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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