Messages in this thread Patch in this message | | | From | "Luck, Tony" <> | Subject | Re: [PATCH v13] x86, mce: Add memcpy_trap() | Date | Thu, 25 Feb 2016 11:33:49 -0800 |
| |
For reference below is what I'd hoped to be able to do with copy_from_user() [obviously needs to not just replace that ALTERNATIVE_2 setup in _copy_from_user ... would have to invent an ALTERNATIVE_3 to pick the new function for people willing to sacrifice speed for recoverability]
BUT ... there are a maze of twisty little other places that also need to be fixed:
1) There is iov_iter_fault_in_readable() that uses fault_in_pages_readable() to pre-fault the first (and last) page using a raw __get_user() call. 2) I tried to avoid that by injecting my error to the middle of a page, but still ended up in a "rep mov" copy function instead of mine. Not sure which one because no output from the core that died. :-(
-Tony
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S index 982ce34f4a9b..e31d8964ac09 100644 --- a/arch/x86/lib/copy_user_64.S +++ b/arch/x86/lib/copy_user_64.S @@ -38,11 +38,15 @@ ENTRY(_copy_from_user) jc bad_from_user cmpq TI_addr_limit(%rax),%rcx ja bad_from_user +#if 1 + jmp copy_from_user_with_mce_check +#else ALTERNATIVE_2 "jmp copy_user_generic_unrolled", \ "jmp copy_user_generic_string", \ X86_FEATURE_REP_GOOD, \ "jmp copy_user_enhanced_fast_string", \ X86_FEATURE_ERMS +#endif ENDPROC(_copy_from_user) .section .fixup,"ax" diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c index 0a42327a59d7..c377a70474e0 100644 --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -6,6 +6,8 @@ * Copyright 2002 Andi Kleen <ak@suse.de> */ #include <linux/module.h> +#include <linux/mm.h> +#include <asm/traps.h> #include <asm/uaccess.h> /* @@ -86,3 +88,25 @@ copy_user_handle_tail(char *to, char *from, unsigned len) memset(to, 0, len); return len; } + +__visible unsigned long +copy_from_user_with_mce_check(void *to, const void __user *from, unsigned n) +{ + struct memcpy_trap_ret r; + + stac(); + r = memcpy_trap(to, (__force void *)from, n); + clac(); + + if (likely(r.bytes_left == 0)) + return 0; + + if (r.trap_nr == X86_TRAP_MC) { + volatile void *fault_addr = (volatile void *)from + n - r.bytes_left; + phys_addr_t p = virt_to_phys(fault_addr); + + memory_failure(p >> PAGE_SHIFT, MCE_VECTOR, 0); + } + + return r.bytes_left; +}
| |