From nobody Fri Dec 19 15:49:46 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EEDE926463C for ; Tue, 8 Apr 2025 08:21:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744100489; cv=none; b=JdSOiXveqEX/or1kfvPeXlAv9PoH1fZL7x9QC+vivlgEBHUd+uFxCHYyklyH6j3HUiHns8igyu34sU7UYRqhIzmCZvjJYcKlU35A7seMvS7GSRpoX5kjK4Elu85eu4EJXbXJF9TITSX/bA3DqpFQ9cbcOnSTQq0YdEjkNeXa70g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744100489; c=relaxed/simple; bh=DNXe2cltquMRMBaAJp3jzbgLWlgty9WIo+JVZVQJGRw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KKC8WFy5JRlljfbITSWjnhYIHLTb4xsH5ZiIkMEcIYjZMCut1jMRUPPBoxyyArezYX92vivyWb6MZou8r/oMsSzorFgb4yHcHq6qaVGhd0poUFPTyTIGuCZtLO4BcuCEWSU0IcwW5yYXz8upal5TOX+kVpA81GbqU1icjxcs+vs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GL8Itij/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GL8Itij/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F9D8C4CEE9; Tue, 8 Apr 2025 08:21:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744100488; bh=DNXe2cltquMRMBaAJp3jzbgLWlgty9WIo+JVZVQJGRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GL8Itij/tMPdirFnEzoi2iZQFWDbWE7hFWFboPu5By7aM7rYb6Uj4uhAPJ/F1zW6i f8fBPuNpvaPlg94Yq1516mJMbjcP002LVRU+CPevhx4KVclswWTFMXvLF9NR0KOqFg pYuiiB/A+qIQfRxzgD1kdskgTgHSU4ainhZ4sgtwnOrkERaAu/wjxOTgxcCAHDhVGP aZf8oDNYWDNfpzusHDaIsKUskBGTAw+6dNrsmHYwBc0GGgUPdYoJUjt54F1ruPhKlX BacHRKJgSJZBZmBtVDOM/HHf42ifzvCPaaw4eBPOYMIvGdfwkUY8m1JTpNGKgL7cjk YKaEG94Hwj4FA== From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Peter Zijlstra Subject: [PATCH RFC 4/5] x86/alternative: Improve code generation readability Date: Tue, 8 Apr 2025 01:21:17 -0700 Message-ID: <35ae5c17e8cc88506b5ae8f3b06d9491f7ef319c.1744098446.git.jpoimboe@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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: -------------------- # 771: rep movsb 772: .skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x= 90 773: # ALT ENTRY: .pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4by= te (((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_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: ---------------------- # 771: 771: jmp 6f 772: .skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x= 90 773: # ALT ENTRY: .pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4by= te ( 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)),0x= 90 773: # ALT ENTRY: .pushsection .altinstructions,"a"; .long 771b - .; .long 774f - .; .4by= te 297; .byte 773b-771b; .byte 775f-774f; .popsection # # ALT REPLACEMENT: .pushsection .altinstr_replacement, "ax" 774: 775: .popsection # Signed-off-by: Josh Poimboeuf --- 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/alte= rnative.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 *st= art, void *end) #define alt_rlen "775f-774f" =20 #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" =20 -#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" =20 -#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" =20 -/* alternative assembly primitive: */ -#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \ + +#define __ALTERNATIVE(oldinstr, newinstr, ft_flags) \ OLDINSTR(oldinstr) \ ALTINSTR_ENTRY(ft_flags) \ ALTINSTR_REPLACEMENT(newinstr) =20 -#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2= ) \ - ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_fl= ags2) +#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# \n" \ + __ALTERNATIVE("\t" oldinstr, newinstr, ft_flags) \ + "\n# \n" + +#define ALTERNATIVE_2(oldinstr, \ + newinstr1, ft_flags1, \ + newinstr2, ft_flags2) \ + "\n# \n" \ + __ALTERNATIVE_2("\t" \ + oldinstr, \ + newinstr1, ft_flags1, \ + newinstr2, ft_flags2) \ + "\n# \n" + +#define ALTERNATIVE_3(oldinstr, \ + newinstr1, ft_flags1, \ + newinstr2, ft_flags2, \ + newinstr3, ft_flags3) \ + "\n# \n" \ + __ALTERNATIVE_3("\t" \ + oldinstr, \ + newinstr1, ft_flags1, \ + newinstr2, ft_flags2, \ + newinstr3, ft_flags3) \ + "\n# \n" =20 /* 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) =20 -#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2= , \ - newinstr3, ft_flags3) \ - ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_f= lags2), \ - newinstr3, ft_flags3) - /* * Alternative instructions for different CPU types or capabilities. * --=20 2.49.0