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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