From: Ingo Molnar <mingo@kernel.org>
To: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, Brian Gerst <brgerst@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linuxfoundation.org>
Subject: Re: [PATCH 1/5] x86: provide new infrastructure for GDT descriptors
Date: Wed, 20 Dec 2023 10:51:11 +0100 [thread overview]
Message-ID: <ZYK5D/KfzpEjQr+8@gmail.com> (raw)
In-Reply-To: <20231219151200.2878271-2-vegard.nossum@oracle.com>
* Vegard Nossum <vegard.nossum@oracle.com> wrote:
> @@ -27,14 +77,14 @@ struct desc_struct {
> .base0 = (u16) (base), \
> .base1 = ((base) >> 16) & 0xFF, \
> .base2 = ((base) >> 24) & 0xFF, \
> - .type = (flags & 0x0f), \
> - .s = (flags >> 4) & 0x01, \
> - .dpl = (flags >> 5) & 0x03, \
> - .p = (flags >> 7) & 0x01, \
> - .avl = (flags >> 12) & 0x01, \
> - .l = (flags >> 13) & 0x01, \
> - .d = (flags >> 14) & 0x01, \
> - .g = (flags >> 15) & 0x01, \
> + .type = ((flags) & 0x0f), \
> + .s = ((flags) >> 4) & 0x01, \
> + .dpl = ((flags) >> 5) & 0x03, \
> + .p = ((flags) >> 7) & 0x01, \
> + .avl = ((flags) >> 12) & 0x01, \
> + .l = ((flags) >> 13) & 0x01, \
> + .d = ((flags) >> 14) & 0x01, \
> + .g = ((flags) >> 15) & 0x01, \
Yeah, so how about writing it like this:
#define GDT_ENTRY_INIT(flags, base, limit) \
{ \
.limit0 = ((limit) >> 0) & 0xFFFF, \
.limit1 = ((limit) >> 16) & 0x000F, \
.base0 = ((base) >> 0) & 0xFFFF, \
.base1 = ((base) >> 16) & 0x00FF, \
.base2 = ((base) >> 24) & 0x00FF, \
.type = ((flags) >> 0) & 0x000F, \
.s = ((flags) >> 4) & 0x0001, \
.dpl = ((flags) >> 5) & 0x0003, \
.p = ((flags) >> 7) & 0x0001, \
.avl = ((flags) >> 12) & 0x0001, \
.l = ((flags) >> 13) & 0x0001, \
.d = ((flags) >> 14) & 0x0001, \
.g = ((flags) >> 15) & 0x0001, \
}
This encodes it all in a very simple format, without C syntactic
variations: bit position and mask.
Thanks,
Ingo
next prev parent reply other threads:[~2023-12-20 9:51 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-19 15:11 [PATCH 0/5] replace magic numbers in GDT descriptors Vegard Nossum
2023-12-19 15:11 ` [PATCH 1/5] x86: provide new infrastructure for " Vegard Nossum
2023-12-20 9:51 ` Ingo Molnar [this message]
2023-12-20 10:04 ` [tip: x86/asm] x86/asm: Provide " tip-bot2 for Vegard Nossum
2023-12-19 15:11 ` [PATCH 2/5] x86: replace magic numbers in GDT descriptors, part 1 Vegard Nossum
2023-12-20 10:04 ` [tip: x86/asm] x86/asm: Replace magic numbers in GDT descriptors, preparations tip-bot2 for Vegard Nossum
2023-12-19 15:11 ` [PATCH 3/5] x86: replace magic numbers in GDT descriptors, part 2 Vegard Nossum
2023-12-20 10:04 ` [tip: x86/asm] x86/asm: Replace magic numbers in GDT descriptors, script-generated change tip-bot2 for Vegard Nossum
2023-12-19 15:11 ` [PATCH 4/5] x86: always set A (accessed) flag in GDT descriptors Vegard Nossum
2023-12-20 10:04 ` [tip: x86/asm] x86/asm: Always " tip-bot2 for Vegard Nossum
2023-12-19 15:12 ` [PATCH 5/5] x86: add DB flag to 32-bit percpu GDT entry Vegard Nossum
2023-12-20 10:03 ` [tip: x86/asm] x86/asm: Add " tip-bot2 for Vegard Nossum
2023-12-19 17:33 ` [PATCH 0/5] replace magic numbers in GDT descriptors Linus Torvalds
2023-12-20 9:59 ` Ingo Molnar
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