| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <35ae5c17e8cc88506b5ae8f3b06d9491f7ef319c.1744098446.git.jpoimboe@kernel.org>
Date: Tue, 8 Apr 2025 01:21:17 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH RFC 4/5] x86/alternative: Improve code generation readability
Improve the readability and compactness of alternatives code.
---------------------
ALTERNATIVE() before:
---------------------
# ALT: oldinstr
771:
rep movsb
772:
# ALT: padding
.skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
.pushsection .altinstructions,"a"
.long 771b - .
.long 774f - .
.4byte (((1 << 0) << 16) | ((18*32+ 4)))
.byte 773b-771b
.byte 775f-774f
.popsection
.pushsection .altinstr_replacement, "ax"
# ALT: replacement
774:
call rep_movs_alternative
775:
.popsection
--------------------
ALTERNATIVE() after:
--------------------
# <ALTERNATIVE>
771: rep movsb
772: .skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
# ALT ENTRY:
.pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4byte (((1 << 0) << 16) | ((18*32+ 4))); .byte 773b-771b; .byte 775f-774f; .popsection
# ALT REPLACEMENT:
.pushsection .altinstr_replacement, "ax"
774: call rep_movs_alternative
775:
.popsection
# </ALTERNATIVE>
-----------------------
ALTERNATIVE_2() before:
-----------------------
# ALT: oldinstr
771:
# ALT: oldinstr
771:
jmp 6f
772:
# ALT: padding
.skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
.pushsection .altinstructions,"a"
.long 771b - .
.long 774f - .
.4byte ( 3*32+21)
.byte 773b-771b
.byte 775f-774f
.popsection
.pushsection .altinstr_replacement, "ax"
# ALT: replacement
774:
jmp .L4 #
775:
.popsection
772:
# ALT: padding
.skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
.pushsection .altinstructions,"a"
.long 771b - .
.long 774f - .
.4byte 297 #
.byte 773b-771b
.byte 775f-774f
.popsection
.pushsection .altinstr_replacement, "ax"
# ALT: replacement
774:
775:
.popsection
----------------------
ALTERNATIVE_2() after:
----------------------
# <ALTERNATIVE_2>
771:
771: jmp 6f
772: .skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
# ALT ENTRY:
.pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4byte ( 3*32+21); .byte 773b-771b; .byte 775f-774f; .popsection
# ALT REPLACEMENT:
.pushsection .altinstr_replacement, "ax"
774: jmp .L4 #
775:
.popsection
772: .skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90
773:
# ALT ENTRY:
.pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4byte 297; .byte 773b-771b; .byte 775f-774f; .popsection #
# ALT REPLACEMENT:
.pushsection .altinstr_replacement, "ax"
774:
775:
.popsection
# </ALTERNATIVE_2>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
arch/x86/include/asm/alternative.h | 88 +++++++++++++++++++++---------
1 file changed, 63 insertions(+), 25 deletions(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 4a37a8bd87fd..6472d53625dc 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -151,46 +151,84 @@ static inline int alternatives_text_reserved(void *start, void *end)
#define alt_rlen "775f-774f"
#define OLDINSTR(oldinstr) \
- "# ALT: oldinstr\n" \
- "771:\n\t" oldinstr "\n772:\n" \
- "# ALT: padding\n" \
- ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \
- "((" alt_rlen ")-(" alt_slen ")),0x90\n" \
+ "771:" oldinstr "\n" \
+ "772:\t.skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \
+ "((" alt_rlen ")-(" alt_slen ")),0x90\n" \
"773:\n"
-#define ALTINSTR_ENTRY(ft_flags) \
- ".pushsection .altinstructions,\"a\"\n" \
- " .long 771b - .\n" /* label */ \
- " .long 774f - .\n" /* new instruction */ \
- " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
- " .byte " alt_total_slen "\n" /* source len */ \
- " .byte " alt_rlen "\n" /* replacement len */ \
+#define ALTINSTR_ENTRY(ft_flags) \
+ "# ALT ENTRY:\n" \
+ ".pushsection .altinstructions,\"a\"; " \
+ " .long 771b - .; " /* label */ \
+ " .long 774f - .; " /* new instruction */ \
+ " .4byte " __stringify(ft_flags) "; " /* feature + flags */ \
+ " .byte " alt_total_slen "; " /* source len */ \
+ " .byte " alt_rlen "; " /* replacement len */ \
".popsection\n"
-#define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \
+#define ALTINSTR_REPLACEMENT(newinstr) \
+ "# ALT REPLACEMENT:\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
- "# ALT: replacement\n" \
- "774:\n\t" newinstr "\n775:\n" \
- ".popsection\n"
+ "774:\t" newinstr "\n" \
+ "775:\n" \
+ ".popsection"
-/* alternative assembly primitive: */
-#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
+
+#define __ALTERNATIVE(oldinstr, newinstr, ft_flags) \
OLDINSTR(oldinstr) \
ALTINSTR_ENTRY(ft_flags) \
ALTINSTR_REPLACEMENT(newinstr)
-#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
- ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)
+#define __ALTERNATIVE_2(oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2) \
+ __ALTERNATIVE("\n" \
+ __ALTERNATIVE(oldinstr, \
+ newinstr1, ft_flags1), \
+ newinstr2, ft_flags2)
+
+#define __ALTERNATIVE_3(oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2, \
+ newinstr3, ft_flags3) \
+ __ALTERNATIVE("\n" \
+ __ALTERNATIVE_2(oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2), \
+ newinstr3, ft_flags3)
+
+
+#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
+ "\n# <ALTERNATIVE>\n" \
+ __ALTERNATIVE("\t" oldinstr, newinstr, ft_flags) \
+ "\n# </ALTERNATIVE>\n"
+
+#define ALTERNATIVE_2(oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2) \
+ "\n# <ALTERNATIVE_2>\n" \
+ __ALTERNATIVE_2("\t" \
+ oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2) \
+ "\n# </ALTERNATIVE_2>\n"
+
+#define ALTERNATIVE_3(oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2, \
+ newinstr3, ft_flags3) \
+ "\n# <ALTERNATIVE_3>\n" \
+ __ALTERNATIVE_3("\t" \
+ oldinstr, \
+ newinstr1, ft_flags1, \
+ newinstr2, ft_flags2, \
+ newinstr3, ft_flags3) \
+ "\n# </ALTERNATIVE_3>\n"
/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags)
-#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
- newinstr3, ft_flags3) \
- ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
- newinstr3, ft_flags3)
-
/*
* Alternative instructions for different CPU types or capabilities.
*
--
2.49.0
Powered by blists - more mailing lists