x86/asm changes for v6.8:

- Replace magic numbers in GDT descriptor definitions & handling: - Introduce symbolic names via macros for descriptor types/fields/flags, and then use these symbolic names. - Clean up definitions a bit, such as GDT_ENTRY_INIT() - Fix/clean up details that became visibly inconsistent after the symbol-based code was introduced: - Unify accessed flag handling - Set the D/B size flag consistently & according to the HW specification Signed-off-by: Ingo Molnar <mingo@kernel.org> -----BEGIN PGP SIGNATURE----- iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmWb1hQRHG1pbmdvQGtl cm5lbC5vcmcACgkQEnMQ0APhK1j7/xAAk2L36n4ZpWqm4oWxMyRDTd713qT+Jzg5 txVr7i8el5RZ8D9WQejzOWemJ/XgirkWuRSFfY+UzZZ+7lmioXWDFLz6PFpyMOwM OG2yyAAZIQzFhe1LxhurN5G7F+q9Nl/CcDnRWv+FUKs829GOGlaqirKfKwgIFzgw GUT0eT5gPfIfEFnzMUrix9+KNIZU6s6Lgg5tVpavNw6bKEimg8Mtn4J45voFbg98 l/PU0RaC28vePTMdoBLv/ZZUHS9K/UdGUq600guzk/Zh2plqxGtqjXtaM5/8giPO JbgQCTP0LaCC0oZf0SAbUW7+TiKD03CP6QzleYyLdhTjLz1CCOswgz0upPjfa/5j nhgsMCk/CEhr6nMwhJiRNhOrFFFJWX00bpcQ2tyyVO156Q+CfhJxuk1XafeQ5MSs K4l97IVc/vPQSEZy5Nh6GdGmWljYxP3Ku4eHRkyVGVYf8YyaD2l6CimaRcdPNqqL w9GLwczLfEzkomfdxsyppwu364O91Lpv6gi6AY4Tj7Hgo1ZMm9ucUO3AsTUz5EJJ aiqX6o7puIJJkU2O3hKviTzNwTojjjicD/Az66re3lHZBND+luP7LjVY2wIomH5i bFPVdSCDmCdTrsTkO3f87FHbCVrbNllKLGChvJ66vyC2nJeIM8UHJ/MxYJsGRhqk 87vU1DWYPrQ= =Y0pg -----END PGP SIGNATURE----- Merge tag 'x86-asm-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 asm updates from Ingo Molnar: "Replace magic numbers in GDT descriptor definitions & handling: - Introduce symbolic names via macros for descriptor types/fields/flags, and then use these symbolic names. - Clean up definitions a bit, such as GDT_ENTRY_INIT() - Fix/clean up details that became visibly inconsistent after the symbol-based code was introduced: - Unify accessed flag handling - Set the D/B size flag consistently & according to the HW specification" * tag 'x86-asm-2024-01-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/asm: Add DB flag to 32-bit percpu GDT entry x86/asm: Always set A (accessed) flag in GDT descriptors x86/asm: Replace magic numbers in GDT descriptors, script-generated change x86/asm: Replace magic numbers in GDT descriptors, preparations x86/asm: Provide new infrastructure for GDT descriptors
2025-01-11 08:18:47 +00:00 · 2024-01-08 17:02:57 -08:00 · 2024-01-08 17:02:57 -08:00 · 106b88d7a9
commit 106b88d7a9
parent 33034c4f94 bc90aefa99
10 changed files with 104 additions and 57 deletions
--- a/arch/x86/boot/pm.c
+++ b/arch/x86/boot/pm.c
@ -11,6 +11,7 @@
 */

 #include "boot.h"
+#include <asm/desc_defs.h>
 #include <asm/segment.h>

 /*
@ -67,13 +68,13 @@ static void setup_gdt(void)
 	   being 8-byte unaligned.  Intel recommends 16 byte alignment. */
 	static const u64 boot_gdt[] __attribute__((aligned(16))) = {
 		/* CS: code, read/execute, 4 GB, base 0 */
-		[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
+		[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(DESC_CODE32, 0, 0xfffff),
 		/* DS: data, read/write, 4 GB, base 0 */
-		[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
+		[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(DESC_DATA32, 0, 0xfffff),
 		/* TSS: 32-bit tss, 104 bytes, base 4096 */
 		/* We only have a TSS here to keep Intel VT happy;
 		   we don't actually use it for anything. */
-		[GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(0x0089, 4096, 103),
+		[GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(DESC_TSS32, 4096, 103),
 	};
 	/* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead
 	   of the gdt_ptr contents.  Thus, make it static so it will
--- a/arch/x86/include/asm/desc_defs.h
+++ b/arch/x86/include/asm/desc_defs.h
@ -8,6 +8,56 @@
 * archs.
 */

+/*
+ * Low-level interface mapping flags/field names to bits
+ */
+
+/* Flags for _DESC_S (non-system) descriptors */
+#define _DESC_ACCESSED		0x0001
+#define _DESC_DATA_WRITABLE	0x0002
+#define _DESC_CODE_READABLE	0x0002
+#define _DESC_DATA_EXPAND_DOWN	0x0004
+#define _DESC_CODE_CONFORMING	0x0004
+#define _DESC_CODE_EXECUTABLE	0x0008
+
+/* Common flags */
+#define _DESC_S			0x0010
+#define _DESC_DPL(dpl)		((dpl) << 5)
+#define _DESC_PRESENT		0x0080
+
+#define _DESC_LONG_CODE		0x2000
+#define _DESC_DB		0x4000
+#define _DESC_GRANULARITY_4K	0x8000
+
+/* System descriptors have a numeric "type" field instead of flags */
+#define _DESC_SYSTEM(code)	(code)
+
+/*
+ * High-level interface mapping intended usage to low-level combinations
+ * of flags
+ */
+
+#define _DESC_DATA		(_DESC_S | _DESC_PRESENT | _DESC_ACCESSED | \
+				 _DESC_DATA_WRITABLE)
+#define _DESC_CODE		(_DESC_S | _DESC_PRESENT | _DESC_ACCESSED | \
+				 _DESC_CODE_READABLE | _DESC_CODE_EXECUTABLE)
+
+#define DESC_DATA16		(_DESC_DATA)
+#define DESC_CODE16		(_DESC_CODE)
+
+#define DESC_DATA32		(_DESC_DATA | _DESC_GRANULARITY_4K | _DESC_DB)
+#define DESC_DATA32_BIOS	(_DESC_DATA | _DESC_DB)
+
+#define DESC_CODE32		(_DESC_CODE | _DESC_GRANULARITY_4K | _DESC_DB)
+#define DESC_CODE32_BIOS	(_DESC_CODE | _DESC_DB)
+
+#define DESC_TSS32		(_DESC_SYSTEM(9) | _DESC_PRESENT)
+
+#define DESC_DATA64		(_DESC_DATA | _DESC_GRANULARITY_4K | _DESC_DB)
+#define DESC_CODE64		(_DESC_CODE | _DESC_GRANULARITY_4K | _DESC_LONG_CODE)
+
+#define DESC_USER		(_DESC_DPL(3))
+
 #ifndef __ASSEMBLY__

 #include <linux/types.h>
@ -22,19 +72,19 @@ struct desc_struct {

 #define GDT_ENTRY_INIT(flags, base, limit)			\
 	{							\
-		.limit0		= (u16) (limit),		\
-		.limit1		= ((limit) >> 16) & 0x0F,	\
-		.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,		\
+		.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,	\
 	}

 enum {
@ -94,6 +144,7 @@ struct gate_struct {

 typedef struct gate_struct gate_desc;

+#ifndef _SETUP
 static inline unsigned long gate_offset(const gate_desc *g)
 {
 #ifdef CONFIG_X86_64
@ -108,6 +159,7 @@ static inline unsigned long gate_segment(const gate_desc *g)
 {
 	return g->segment;
 }
+#endif

 struct desc_ptr {
 	unsigned short size;
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@ -420,7 +420,7 @@ static DEFINE_MUTEX(apm_mutex);
 * This is for buggy BIOS's that refer to (real mode) segment 0x40
 * even though they are called in protected mode.
 */
-static struct desc_struct bad_bios_desc = GDT_ENTRY_INIT(0x4092,
+static struct desc_struct bad_bios_desc = GDT_ENTRY_INIT(DESC_DATA32_BIOS,
 			(unsigned long)__va(0x400UL), PAGE_SIZE - 0x400 - 1);

 static const char driver_version[] = "1.16ac";	/* no spaces */
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@ -188,45 +188,37 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
 	 * TLS descriptors are currently at a different place compared to i386.
 	 * Hopefully nobody expects them at a fixed place (Wine?)
 	 */
-	[GDT_ENTRY_KERNEL32_CS]		= GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_CS]		= GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_DS]		= GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
-	[GDT_ENTRY_DEFAULT_USER32_CS]	= GDT_ENTRY_INIT(0xc0fb, 0, 0xfffff),
-	[GDT_ENTRY_DEFAULT_USER_DS]	= GDT_ENTRY_INIT(0xc0f3, 0, 0xfffff),
-	[GDT_ENTRY_DEFAULT_USER_CS]	= GDT_ENTRY_INIT(0xa0fb, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL32_CS]		= GDT_ENTRY_INIT(DESC_CODE32, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_CS]		= GDT_ENTRY_INIT(DESC_CODE64, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_DS]		= GDT_ENTRY_INIT(DESC_DATA64, 0, 0xfffff),
+	[GDT_ENTRY_DEFAULT_USER32_CS]	= GDT_ENTRY_INIT(DESC_CODE32 | DESC_USER, 0, 0xfffff),
+	[GDT_ENTRY_DEFAULT_USER_DS]	= GDT_ENTRY_INIT(DESC_DATA64 | DESC_USER, 0, 0xfffff),
+	[GDT_ENTRY_DEFAULT_USER_CS]	= GDT_ENTRY_INIT(DESC_CODE64 | DESC_USER, 0, 0xfffff),
 #else
-	[GDT_ENTRY_KERNEL_CS]		= GDT_ENTRY_INIT(0xc09a, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_DS]		= GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
-	[GDT_ENTRY_DEFAULT_USER_CS]	= GDT_ENTRY_INIT(0xc0fa, 0, 0xfffff),
-	[GDT_ENTRY_DEFAULT_USER_DS]	= GDT_ENTRY_INIT(0xc0f2, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_CS]		= GDT_ENTRY_INIT(DESC_CODE32, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_DS]		= GDT_ENTRY_INIT(DESC_DATA32, 0, 0xfffff),
+	[GDT_ENTRY_DEFAULT_USER_CS]	= GDT_ENTRY_INIT(DESC_CODE32 | DESC_USER, 0, 0xfffff),
+	[GDT_ENTRY_DEFAULT_USER_DS]	= GDT_ENTRY_INIT(DESC_DATA32 | DESC_USER, 0, 0xfffff),
 	/*
 	 * Segments used for calling PnP BIOS have byte granularity.
 	 * They code segments and data segments have fixed 64k limits,
 	 * the transfer segment sizes are set at run time.
 	 */
-	/* 32-bit code */
-	[GDT_ENTRY_PNPBIOS_CS32]	= GDT_ENTRY_INIT(0x409a, 0, 0xffff),
-	/* 16-bit code */
-	[GDT_ENTRY_PNPBIOS_CS16]	= GDT_ENTRY_INIT(0x009a, 0, 0xffff),
-	/* 16-bit data */
-	[GDT_ENTRY_PNPBIOS_DS]		= GDT_ENTRY_INIT(0x0092, 0, 0xffff),
-	/* 16-bit data */
-	[GDT_ENTRY_PNPBIOS_TS1]		= GDT_ENTRY_INIT(0x0092, 0, 0),
-	/* 16-bit data */
-	[GDT_ENTRY_PNPBIOS_TS2]		= GDT_ENTRY_INIT(0x0092, 0, 0),
+	[GDT_ENTRY_PNPBIOS_CS32]	= GDT_ENTRY_INIT(DESC_CODE32_BIOS, 0, 0xffff),
+	[GDT_ENTRY_PNPBIOS_CS16]	= GDT_ENTRY_INIT(DESC_CODE16, 0, 0xffff),
+	[GDT_ENTRY_PNPBIOS_DS]		= GDT_ENTRY_INIT(DESC_DATA16, 0, 0xffff),
+	[GDT_ENTRY_PNPBIOS_TS1]		= GDT_ENTRY_INIT(DESC_DATA16, 0, 0),
+	[GDT_ENTRY_PNPBIOS_TS2]		= GDT_ENTRY_INIT(DESC_DATA16, 0, 0),
 	/*
 	 * The APM segments have byte granularity and their bases
 	 * are set at run time.  All have 64k limits.
 	 */
-	/* 32-bit code */
-	[GDT_ENTRY_APMBIOS_BASE]	= GDT_ENTRY_INIT(0x409a, 0, 0xffff),
-	/* 16-bit code */
-	[GDT_ENTRY_APMBIOS_BASE+1]	= GDT_ENTRY_INIT(0x009a, 0, 0xffff),
-	/* data */
-	[GDT_ENTRY_APMBIOS_BASE+2]	= GDT_ENTRY_INIT(0x4092, 0, 0xffff),
+	[GDT_ENTRY_APMBIOS_BASE]	= GDT_ENTRY_INIT(DESC_CODE32_BIOS, 0, 0xffff),
+	[GDT_ENTRY_APMBIOS_BASE+1]	= GDT_ENTRY_INIT(DESC_CODE16, 0, 0xffff),
+	[GDT_ENTRY_APMBIOS_BASE+2]	= GDT_ENTRY_INIT(DESC_DATA32_BIOS, 0, 0xffff),

-	[GDT_ENTRY_ESPFIX_SS]		= GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
-	[GDT_ENTRY_PERCPU]		= GDT_ENTRY_INIT(0xc092, 0, 0xfffff),
+	[GDT_ENTRY_ESPFIX_SS]		= GDT_ENTRY_INIT(DESC_DATA32, 0, 0xfffff),
+	[GDT_ENTRY_PERCPU]		= GDT_ENTRY_INIT(DESC_DATA32, 0, 0xfffff),
 #endif
 } };
 EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@ -71,9 +71,9 @@ EXPORT_SYMBOL(vmemmap_base);
 * GDT used on the boot CPU before switching to virtual addresses.
 */
 static struct desc_struct startup_gdt[GDT_ENTRIES] __initdata = {
-	[GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(DESC_CODE32, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(DESC_CODE64, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(DESC_DATA64, 0, 0xfffff),
 };

 /*
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@ -106,8 +106,8 @@ void __init pcpu_populate_pte(unsigned long addr)
 static inline void setup_percpu_segment(int cpu)
 {
 #ifdef CONFIG_X86_32
-	struct desc_struct d = GDT_ENTRY_INIT(0x8092, per_cpu_offset(cpu),
-					      0xFFFFF);
+	struct desc_struct d = GDT_ENTRY_INIT(DESC_DATA32,
+					      per_cpu_offset(cpu), 0xFFFFF);

 	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_PERCPU, &d, DESCTYPE_S);
 #endif
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@ -11,6 +11,7 @@
 #include <linux/elfnote.h>
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <asm/desc_defs.h>
 #include <asm/segment.h>
 #include <asm/asm.h>
 #include <asm/boot.h>
@ -148,11 +149,11 @@ SYM_DATA_END(gdt)
 SYM_DATA_START_LOCAL(gdt_start)
 	.quad 0x0000000000000000            /* NULL descriptor */
 #ifdef CONFIG_X86_64
-	.quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* PVH_CS_SEL */
+	.quad GDT_ENTRY(DESC_CODE64, 0, 0xfffff) /* PVH_CS_SEL */
 #else
-	.quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* PVH_CS_SEL */
+	.quad GDT_ENTRY(DESC_CODE32, 0, 0xfffff) /* PVH_CS_SEL */
 #endif
-	.quad GDT_ENTRY(0xc092, 0, 0xfffff) /* PVH_DS_SEL */
+	.quad GDT_ENTRY(DESC_DATA32, 0, 0xfffff) /* PVH_DS_SEL */
 SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)

 	.balign 16
--- a/arch/x86/realmode/rm/reboot.S
+++ b/arch/x86/realmode/rm/reboot.S
@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <linux/linkage.h>
+#include <asm/desc_defs.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
 #include <asm/processor-flags.h>
@ -153,5 +154,5 @@ SYM_DATA_START(machine_real_restart_gdt)
 	 * base value 0x100; since this is consistent with real mode
 	 * semantics we don't have to reload the segments once CR0.PE = 0.
 	 */
-	.quad	GDT_ENTRY(0x0093, 0x100, 0xffff)
+	.quad	GDT_ENTRY(DESC_DATA16, 0x100, 0xffff)
 SYM_DATA_END(machine_real_restart_gdt)
--- a/drivers/firmware/efi/libstub/x86-5lvl.c
+++ b/drivers/firmware/efi/libstub/x86-5lvl.c
@ -13,8 +13,8 @@ bool efi_no5lvl;
 static void (*la57_toggle)(void *cr3);

 static const struct desc_struct gdt[] = {
-	[GDT_ENTRY_KERNEL32_CS] = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
-	[GDT_ENTRY_KERNEL_CS]   = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL32_CS] = GDT_ENTRY_INIT(DESC_CODE32, 0, 0xfffff),
+	[GDT_ENTRY_KERNEL_CS]   = GDT_ENTRY_INIT(DESC_CODE64, 0, 0xfffff),
 };

 /*
--- a/drivers/pnp/pnpbios/bioscalls.c
+++ b/drivers/pnp/pnpbios/bioscalls.c
@ -60,7 +60,7 @@ do { \
 	set_desc_limit(&gdt[(selname) >> 3], (size) - 1); \
 } while(0)

-static struct desc_struct bad_bios_desc = GDT_ENTRY_INIT(0x4092,
+static struct desc_struct bad_bios_desc = GDT_ENTRY_INIT(DESC_DATA32_BIOS,
 			(unsigned long)__va(0x400UL), PAGE_SIZE - 0x400 - 1);

 /*