From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Triplett Subject: [PATCH v3 2/3] x86: tss: Eliminate fragile calculation of TSS segment limit Date: Wed, 29 Oct 2014 09:03:07 -0700 Message-ID: <8982dc6cc6beadae9488830d566fb1c8cf42d4ee.1414598511.git.josh@joshtriplett.org> References: <7159269982aac3b732af2c33a2e3d04e2048bdfb.1414598511.git.josh@joshtriplett.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <7159269982aac3b732af2c33a2e3d04e2048bdfb.1414598511.git.josh@joshtriplett.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "H. Peter Anvin" , Ingo Molnar , Kees Cook , Thomas Gleixner , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, x86@kernel.org, xen-devel@lists.xenproject.org List-Id: virtualization@lists.linuxfoundation.org __set_tss_desc has a complex calculation of the TSS segment limit, duplicating the quirky details of the I/O bitmap array length, and requiring a complex comment to explain. Replace that calculation with a simpler one based on the offsetof the "stack" field that follows the array. That then removes the last use of IO_BITMAP_OFFSET, so delete it. Signed-off-by: Josh Triplett Acked-by: Alexander van Heukelum --- v3: No changes in this patch, only in patch 3/3. arch/x86/include/asm/desc.h | 11 +---------- arch/x86/include/asm/processor.h | 4 +++- 2 files changed, 4 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index 50d033a..f8dc455 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -177,16 +177,7 @@ static inline void __set_tss_desc(unsigned cpu, unsigned int entry, void *addr) struct desc_struct *d = get_cpu_gdt_table(cpu); tss_desc tss; - /* - * sizeof(unsigned long) coming from an extra "long" at the end - * of the iobitmap. See tss_struct definition in processor.h - * - * -1? seg base+limit should be pointing to the address of the - * last valid byte - */ - set_tssldt_descriptor(&tss, (unsigned long)addr, DESC_TSS, - IO_BITMAP_OFFSET + IO_BITMAP_BYTES + - sizeof(unsigned long) - 1); + set_tssldt_descriptor(&tss, (unsigned long)addr, DESC_TSS, TSS_LIMIT); write_gdt_entry(d, entry, &tss, DESC_TSS); } diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index eb71ec7..76751cd 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -258,9 +258,11 @@ struct x86_hw_tss { #define IO_BITMAP_BITS 65536 #define IO_BITMAP_BYTES (IO_BITMAP_BITS/8) #define IO_BITMAP_LONGS (IO_BITMAP_BYTES/sizeof(long)) -#define IO_BITMAP_OFFSET offsetof(struct tss_struct, io_bitmap) #define INVALID_IO_BITMAP_OFFSET 0x8000 +/* Segment limits point to the last valid byte, hence the -1 */ +#define TSS_LIMIT (offsetof(struct tss_struct, stack) - 1) + struct tss_struct { /* * The hardware state: -- 2.1.1