From: Zachary Amsden 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 Cc: "Seth, Rohit" Cc: Stephen Rothwell Signed-off-by: Andrew Morton --- arch/i386/kernel/process.c | 4 +--- include/asm-i386/system.h | 13 +++++++++++++ 2 files changed, 14 insertions(+), 3 deletions(-) diff -puN arch/i386/kernel/process.c~x86-cr4-is-valid-on-some-486s arch/i386/kernel/process.c --- devel/arch/i386/kernel/process.c~x86-cr4-is-valid-on-some-486s 2005-11-10 00:23:44.000000000 -0800 +++ devel-akpm/arch/i386/kernel/process.c 2005-11-10 00:23:44.000000000 -0800 @@ -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, ®s->esp); } diff -puN include/asm-i386/system.h~x86-cr4-is-valid-on-some-486s include/asm-i386/system.h --- devel/include/asm-i386/system.h~x86-cr4-is-valid-on-some-486s 2005-11-10 00:23:44.000000000 -0800 +++ devel-akpm/include/asm-i386/system.h 2005-11-10 00:23:44.000000000 -0800 @@ -140,6 +140,19 @@ static inline unsigned long _get_base(ch :"=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()) _