linux-kernel - [PATCH 4/6] x86/kvm/vmx: Simplify segment

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <5259c65665760cc0755cbb2ae6875954f437d3ec.1487609329.git.luto@kernel.org>
Date:   Mon, 20 Feb 2017 08:56:12 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>, X86 ML <x86@...nel.org>
Cc:     kvm list <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Thomas Garnier <thgarnie@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH 4/6] x86/kvm/vmx: Simplify segment_base()

Use actual pointer types for pointers (instead of unsigned long) and
replace hardcoded constants with the appropriate self-documenting
macros.

The function is still a bit messy, but this seems a lot better than
before to me.

This is mostly borrowed from a patch by Thomas Garnier.

Cc: Thomas Garnier <thgarnie@...gle.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kvm/vmx.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b1810a0edec3..17ef11c64702 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2069,24 +2069,23 @@ static unsigned long segment_base(u16 selector)
 {
 	struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
 	struct desc_struct *d;
-	unsigned long table_base;
+	struct desc_struct *table;
 	unsigned long v;
 
-	if (!(selector & ~3))
+	if (!(selector & ~SEGMENT_RPL_MASK))
 		return 0;
 
-	table_base = gdt->address;
+	table = (struct desc_struct *)gdt->address;
 
-	if (selector & 4) {           /* from ldt */
+	if ((selector & SEGMENT_TI_MASK) == SEGMENT_LDT) {
 		u16 ldt_selector = kvm_read_ldt();
 
-		if (!(ldt_selector & ~3))
+		if (!(ldt_selector & ~SEGMENT_RPL_MASK))
 			return 0;
 
-		table_base = segment_base(ldt_selector);
+		table = (struct desc_struct *)segment_base(ldt_selector);
 	}
-	d = (struct desc_struct *)(table_base + (selector & ~7));
-	v = get_desc_base(d);
+	v = get_desc_base(&table[selector >> 3]);
 	return v;
 }
 #endif
-- 
2.9.3