Patchwork [U-Boot,v2,11/17] x86: Tweak IDT and GDT for alignment and readability

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Submitter Graeme Russ
Date Jan. 4, 2012, 7:59 p.m.
Message ID <1325707195-3218-11-git-send-email-graeme.russ@gmail.com>
Download mbox | patch
Permalink /patch/134347/
State Awaiting Upstream
Delegated to: Graeme Russ
Headers show

Comments

Graeme Russ - Jan. 4, 2012, 7:59 p.m.
Signed-off-by: Graeme Russ <graeme.russ@gmail.com>
---
Changes for v2:
 - Renamed to better reflect nature of changes

 arch/x86/cpu/interrupts.c |    2 +-
 arch/x86/cpu/start16.S    |   57 +++++++++++++++++++++++++++++++++++---------
 2 files changed, 46 insertions(+), 13 deletions(-)

--
1.7.5.2.317.g391b14
Simon Glass - Jan. 12, 2012, 5 a.m.
On Wed, Jan 4, 2012 at 11:59 AM, Graeme Russ <graeme.russ@gmail.com> wrote:
> Signed-off-by: Graeme Russ <graeme.russ@gmail.com>

Acked-by: Simon Glass <sjg@chromium.org>

> ---
> Changes for v2:
>  - Renamed to better reflect nature of changes
>
>  arch/x86/cpu/interrupts.c |    2 +-
>  arch/x86/cpu/start16.S    |   57 +++++++++++++++++++++++++++++++++++---------
>  2 files changed, 46 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/cpu/interrupts.c b/arch/x86/cpu/interrupts.c
> index e0958eb..43ec3f8 100644
> --- a/arch/x86/cpu/interrupts.c
> +++ b/arch/x86/cpu/interrupts.c
> @@ -174,7 +174,7 @@ struct desc_ptr {
>        unsigned short segment;
>  } __packed;
>
> -struct idt_entry idt[256] __attribute__((aligned(16)));
> +struct idt_entry idt[256] __aligned(16);
>
>  struct desc_ptr idt_ptr;
>
> diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S
> index 33e53cd..cc393ff 100644
> --- a/arch/x86/cpu/start16.S
> +++ b/arch/x86/cpu/start16.S
> @@ -86,7 +86,11 @@ gdt_ptr:
>        .word   0x20            /* limit (32 bytes = 4 GDT entries) */
>        .long   BOOT_SEG + gdt  /* base */
>
> -       /* The GDT table ...
> +/* Some CPUs are picky about GDT alignment... */
> +.align 16
> +gdt:
> +       /*
> +        * The GDT table ...
>         *
>         *       Selector       Type
>         *       0x00           NULL
> @@ -94,17 +98,46 @@ gdt_ptr:
>         *       0x10           32bit code
>         *       0x18           32bit data/stack
>         */
> +       /* The NULL Desciptor - Mandatory */
> +       .word   0x0000          /* limit_low */
> +       .word   0x0000          /* base_low */
> +       .byte   0x00            /* base_middle */
> +       .byte   0x00            /* access */
> +       .byte   0x00            /* flags + limit_high */
> +       .byte   0x00            /* base_high */
>
> -gdt:
> -       .word   0, 0, 0, 0      /* NULL  */
> -       .word   0, 0, 0, 0      /* unused */
> +       /* Unused Desciptor - (matches Linux) */
> +       .word   0x0000          /* limit_low */
> +       .word   0x0000          /* base_low */
> +       .byte   0x00            /* base_middle */
> +       .byte   0x00            /* access */
> +       .byte   0x00            /* flags + limit_high */
> +       .byte   0x00            /* base_high */
>
> -       .word   0xFFFF          /* 4Gb - (0x100000*0x1000 = 4Gb) */
> -       .word   0               /* base address = 0 */
> -       .word   0x9B00          /* code read/exec */
> -       .word   0x00CF          /* granularity = 4096, 386 (+5th nibble of limit) */
> +       /*
> +        * The Code Segment Descriptor:
> +        * - Base   = 0x00000000
> +        * - Size   = 4GB
> +        * - Access = Present, Ring 0, Exec (Code), Readable
> +        * - Flags  = 4kB Granularity, 32-bit
> +        */
> +       .word   0xffff          /* limit_low */
> +       .word   0x0000          /* base_low */
> +       .byte   0x00            /* base_middle */
> +       .byte   0x9b            /* access */
> +       .byte   0xcf            /* flags + limit_high */
> +       .byte   0x00            /* base_high */
>
> -       .word   0xFFFF          /* 4Gb - (0x100000*0x1000 = 4Gb) */
> -       .word   0x0             /* base address = 0 */
> -       .word   0x9300          /* data read/write */
> -       .word   0x00CF          /* granularity = 4096, 386 (+5th nibble of limit) */
> +       /*
> +        * The Data Segment Descriptor:
> +        * - Base   = 0x00000000
> +        * - Size   = 4GB
> +        * - Access = Present, Ring 0, Non-Exec (Data), Writable
> +        * - Flags  = 4kB Granularity, 32-bit
> +        */
> +       .word   0xffff          /* limit_low */
> +       .word   0x0000          /* base_low */
> +       .byte   0x00            /* base_middle */
> +       .byte   0x93            /* access */
> +       .byte   0xcf            /* flags + limit_high */
> +       .byte   0x00            /* base_high */
> --
> 1.7.5.2.317.g391b14
>
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> U-Boot mailing list
> U-Boot@lists.denx.de
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Patch

diff --git a/arch/x86/cpu/interrupts.c b/arch/x86/cpu/interrupts.c
index e0958eb..43ec3f8 100644
--- a/arch/x86/cpu/interrupts.c
+++ b/arch/x86/cpu/interrupts.c
@@ -174,7 +174,7 @@  struct desc_ptr {
 	unsigned short segment;
 } __packed;

-struct idt_entry idt[256] __attribute__((aligned(16)));
+struct idt_entry idt[256] __aligned(16);

 struct desc_ptr idt_ptr;

diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S
index 33e53cd..cc393ff 100644
--- a/arch/x86/cpu/start16.S
+++ b/arch/x86/cpu/start16.S
@@ -86,7 +86,11 @@  gdt_ptr:
 	.word	0x20		/* limit (32 bytes = 4 GDT entries) */
 	.long	BOOT_SEG + gdt	/* base */

-	/* The GDT table ...
+/* Some CPUs are picky about GDT alignment... */
+.align 16
+gdt:
+	/*
+	 * The GDT table ...
 	 *
 	 *	 Selector	Type
 	 *	 0x00		NULL
@@ -94,17 +98,46 @@  gdt_ptr:
 	 *	 0x10		32bit code
 	 *	 0x18		32bit data/stack
 	 */
+	/* The NULL Desciptor - Mandatory */
+	.word	0x0000		/* limit_low */
+	.word	0x0000		/* base_low */
+	.byte	0x00		/* base_middle */
+	.byte	0x00		/* access */
+	.byte	0x00		/* flags + limit_high */
+	.byte	0x00		/* base_high */

-gdt:
-	.word	0, 0, 0, 0	/* NULL  */
-	.word	0, 0, 0, 0	/* unused */
+	/* Unused Desciptor - (matches Linux) */
+	.word	0x0000		/* limit_low */
+	.word	0x0000		/* base_low */
+	.byte	0x00		/* base_middle */
+	.byte	0x00		/* access */
+	.byte	0x00		/* flags + limit_high */
+	.byte	0x00		/* base_high */

-	.word	0xFFFF		/* 4Gb - (0x100000*0x1000 = 4Gb) */
-	.word	0		/* base address = 0 */
-	.word	0x9B00		/* code read/exec */
-	.word	0x00CF		/* granularity = 4096, 386 (+5th nibble of limit) */
+	/*
+	 * The Code Segment Descriptor:
+	 * - Base   = 0x00000000
+	 * - Size   = 4GB
+	 * - Access = Present, Ring 0, Exec (Code), Readable
+	 * - Flags  = 4kB Granularity, 32-bit
+	 */
+	.word	0xffff		/* limit_low */
+	.word	0x0000		/* base_low */
+	.byte	0x00		/* base_middle */
+	.byte	0x9b		/* access */
+	.byte	0xcf		/* flags + limit_high */
+	.byte	0x00		/* base_high */

-	.word	0xFFFF		/* 4Gb - (0x100000*0x1000 = 4Gb) */
-	.word	0x0		/* base address = 0 */
-	.word	0x9300		/* data read/write */
-	.word	0x00CF		/* granularity = 4096, 386 (+5th nibble of limit) */
+	/*
+	 * The Data Segment Descriptor:
+	 * - Base   = 0x00000000
+	 * - Size   = 4GB
+	 * - Access = Present, Ring 0, Non-Exec (Data), Writable
+	 * - Flags  = 4kB Granularity, 32-bit
+	 */
+	.word	0xffff		/* limit_low */
+	.word	0x0000		/* base_low */
+	.byte	0x00		/* base_middle */
+	.byte	0x93		/* access */
+	.byte	0xcf		/* flags + limit_high */
+	.byte	0x00		/* base_high */