Messages in this thread Patch in this message | | | Date | Fri, 3 Apr 2015 19:06:25 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/xsave: Robustify and merge macros |
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On Fri, Apr 03, 2015 at 05:40:55PM +0200, Quentin Casasnovas wrote: > So yeah I still think we're not properly padding, if you take my earlier > example where repl2 = 5 bytes, repl1 = 4 bytes and orin_insn = 3. > > I'll let you re-read my original mail and come back to me to tell me what'd > I really miss! :)
Dammit, dammit, dammit!
And I thought this aspect was taken care of. I went into the old branches where I had done this and there I have:
+#define OLDINSTR_2(oldinstr, num1, num2) \ + __OLDINSTR(oldinstr, num1) \ + ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")) > 0) * " \ + "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")),0x90\n" \ + alt_end_marker ":\n" +
without the size of the orig_insn factored in into the padding.
And that would work for your example because it would add 1+1 bytes padding.
Basically, the idea was:
.skip len(repl1) - len(orig), 0x90 .skip len(repl2) - len(repl1), 0x90
BUT!, for some reason I changed it to what's there now and I can't remember why anymore.
IOW, this should fix your example but I need to think about it on a clear head first, to try to remember what was the problem with that original approach:
--- diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h index 524bddce0b76..708838260f7c 100644 --- a/arch/x86/include/asm/alternative-asm.h +++ b/arch/x86/include/asm/alternative-asm.h @@ -50,7 +50,7 @@ \oldinstr 141: .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 - .skip -(((145f-144f)-(144f-143f)-(141b-140b)) > 0) * ((145f-144f)-(144f-143f)-(141b-140b)),0x90 + .skip -(((145f-144f)-(144f-143f)) > 0) * ((145f-144f)-(144f-143f)),0x90 142: .pushsection .altinstructions,"a" diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 5aef6a97d80e..2b8cc1dd7dbf 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -101,8 +101,8 @@ static inline int alternatives_text_reserved(void *start, void *end) */ #define OLDINSTR_2(oldinstr, num1, num2) \ __OLDINSTR(oldinstr, num1) \ - ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)) > 0) * " \ - "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)),0x90\n" \ + ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")) > 0) * " \ + "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")),0x90\n" \ alt_end_marker ":\n" #define ALTINSTR_ENTRY(feature, num) \ --- -- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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