tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm head: a0bf7fc24303a538396aa8d32450d05c1929b9f0 commit: d309ba034fac1a149d00cac79318973e9ba81848 [2/4] x86/asm: Pin sensitive CR0 bits config: um-x86_64_defconfig (attached as .config) compiler: gcc-8 (Debian 8.3.0-2) 8.3.0 reproduce: git checkout d309ba034fac1a149d00cac79318973e9ba81848 # save the attached .config to linux build tree make ARCH=um SUBARCH=x86_64
All errors (new ones prefixed by >>):
In file included from arch/x86/include/asm/cacheflush.h:7,
from include/linux/highmem.h:12,
from net//core/sock.c:117:
arch/x86/include/asm/special_insns.h: In function 'native_write_cr0':
>> arch/x86/include/asm/special_insns.h:31:9: error: 'X86_CR0_WP' undeclared
>> (first use in this function)
val |= X86_CR0_WP;
^~~~~~~~~~
arch/x86/include/asm/special_insns.h:31:9: note: each undeclared identifier
is reported only once for each function it appears in
--
In file included from arch/x86/include/asm/cacheflush.h:7,
from include/linux/highmem.h:12,
from net//ipv4/ip_output.c:52:
arch/x86/include/asm/special_insns.h: In function 'native_write_cr0':
>> arch/x86/include/asm/special_insns.h:31:9: error: 'X86_CR0_WP' undeclared
>> (first use in this function); did you mean 'X86_BUG_11AP'?
val |= X86_CR0_WP;
^~~~~~~~~~
X86_BUG_11AP
arch/x86/include/asm/special_insns.h:31:9: note: each undeclared identifier
is reported only once for each function it appears in
vim +/X86_CR0_WP +31 arch/x86/include/asm/special_insns.h
25
26 static inline void native_write_cr0(unsigned long val)
27 {
28 bool warn = false;
29
30 again:
> 31 val |= X86_CR0_WP;
32 /*
33 * In order to have the compiler not optimize away the check
34 * after the cr4 write, mark "val" as being also an output
("+r")
35 * by this asm() block so it will perform an explicit check, as
36 * if it were "volatile".
37 */
38 asm volatile("mov %0,%%cr0" : "+r" (val) : "m" (__force_order)
: );
39 /*
40 * If the MOV above was used directly as a ROP gadget we can
41 * notice the lack of pinned bits in "val" and start the
function
42 * from the beginning to gain the WP bit for sure. And do it
43 * without first taking the exception for a WARN().
44 */
45 if ((val & X86_CR0_WP) != X86_CR0_WP) {
46 warn = true;
47 goto again;
48 }
49 WARN_ONCE(warn, "Attempt to unpin X86_CR0_WP, cr0 bypass
attack?!\n");
50 }
51
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.config.gz
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