From 84f53788458c95309b88948b69ff95921e9c74a8 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Sun, 22 Mar 2015 22:01:12 +0100 Subject: x86/asm: Deobfuscate segment.h This file just defines a number of constants, and a few macros and inline functions. It is particularly badly written. For example, it is not trivial to see how descriptors are numbered (you'd expect that should be easy, right?). This change deobfuscates it via the following changes: Group all GDT_ENTRY_foo together (move intervening stuff away). Number them explicitly: use a number, not PREV_DEFINE+1, +2, +3: I want to immediately see that GDT_ENTRY_PNPBIOS_CS32 is 18. Seeing (GDT_ENTRY_KERNEL_BASE+6) instead is not useful. The above change allows to remove GDT_ENTRY_KERNEL_BASE and GDT_ENTRY_PNPBIOS_BASE, which weren't used anywhere else. After a group of GDT_ENTRY_foo, define all selector values. Remove or improve some comments. In particular: Comment deleted as stating the obvious: /* * The GDT has 32 entries */ #define GDT_ENTRIES 32 "The segment offset needs to contain a RPL. Grr. -AK" changed to "Selectors need to also have a correct RPL (+3 thingy)" "GDT layout to get 64bit syscall right (sysret hardcodes gdt offsets)" expanded into a description *how exactly* sysret hardcodes them. Patch was tested to compile and not change vmlinux.o on 32-bit and 64-bit builds (verified with objdump). Signed-off-by: Denys Vlasenko Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Signed-off-by: Ingo Molnar --- arch/x86/include/asm/segment.h | 125 ++++++++++++++++++----------------------- 1 file changed, 54 insertions(+), 71 deletions(-) (limited to 'arch/x86/include/asm/segment.h') diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index db257a58571f..117028f58882 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -15,12 +15,10 @@ /* Simple and small GDT entries for booting only */ #define GDT_ENTRY_BOOT_CS 2 +#define GDT_ENTRY_BOOT_DS 3 +#define GDT_ENTRY_BOOT_TSS 4 #define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8) - -#define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1) #define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8) - -#define GDT_ENTRY_BOOT_TSS (GDT_ENTRY_BOOT_CS + 2) #define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8) #define SEGMENT_RPL_MASK 0x3 /* @@ -80,97 +78,86 @@ #define GDT_ENTRY_TLS_MIN 6 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1) +#define GDT_ENTRY_KERNEL_CS 12 +#define GDT_ENTRY_KERNEL_DS 13 #define GDT_ENTRY_DEFAULT_USER_CS 14 - #define GDT_ENTRY_DEFAULT_USER_DS 15 +#define GDT_ENTRY_TSS 16 +#define GDT_ENTRY_LDT 17 +#define GDT_ENTRY_PNPBIOS_CS32 18 +#define GDT_ENTRY_PNPBIOS_CS16 19 +#define GDT_ENTRY_PNPBIOS_DS 20 +#define GDT_ENTRY_PNPBIOS_TS1 21 +#define GDT_ENTRY_PNPBIOS_TS2 22 +#define GDT_ENTRY_APMBIOS_BASE 23 + +#define GDT_ENTRY_ESPFIX_SS 26 +#define GDT_ENTRY_PERCPU 27 +#define GDT_ENTRY_STACK_CANARY 28 -#define GDT_ENTRY_KERNEL_BASE (12) - -#define GDT_ENTRY_KERNEL_CS (GDT_ENTRY_KERNEL_BASE+0) - -#define GDT_ENTRY_KERNEL_DS (GDT_ENTRY_KERNEL_BASE+1) - -#define GDT_ENTRY_TSS (GDT_ENTRY_KERNEL_BASE+4) -#define GDT_ENTRY_LDT (GDT_ENTRY_KERNEL_BASE+5) - -#define GDT_ENTRY_PNPBIOS_BASE (GDT_ENTRY_KERNEL_BASE+6) -#define GDT_ENTRY_APMBIOS_BASE (GDT_ENTRY_KERNEL_BASE+11) +#define GDT_ENTRY_DOUBLEFAULT_TSS 31 -#define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE+14) +#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) +#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) +#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3) +#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3) #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8) - -#define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE+15) +#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */ +#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */ +/* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */ +#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32) +#define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */ +#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */ +#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */ #ifdef CONFIG_SMP -#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8) +#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8) #else -#define __KERNEL_PERCPU 0 +#define __KERNEL_PERCPU 0 #endif - -#define GDT_ENTRY_STACK_CANARY (GDT_ENTRY_KERNEL_BASE+16) #ifdef CONFIG_CC_STACKPROTECTOR #define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8) #else #define __KERNEL_STACK_CANARY 0 #endif -#define GDT_ENTRY_DOUBLEFAULT_TSS 31 - -/* - * The GDT has 32 entries - */ #define GDT_ENTRIES 32 -/* The PnP BIOS entries in the GDT */ -#define GDT_ENTRY_PNPBIOS_CS32 (GDT_ENTRY_PNPBIOS_BASE + 0) -#define GDT_ENTRY_PNPBIOS_CS16 (GDT_ENTRY_PNPBIOS_BASE + 1) -#define GDT_ENTRY_PNPBIOS_DS (GDT_ENTRY_PNPBIOS_BASE + 2) -#define GDT_ENTRY_PNPBIOS_TS1 (GDT_ENTRY_PNPBIOS_BASE + 3) -#define GDT_ENTRY_PNPBIOS_TS2 (GDT_ENTRY_PNPBIOS_BASE + 4) - -/* The PnP BIOS selectors */ -#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */ -#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */ -#define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */ -#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */ -#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */ +#else /* 64-bit: */ - -/* - * Matching rules for certain types of segments. - */ - -/* Matches PNP_CS32 and PNP_CS16 (they must be consecutive) */ -#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == GDT_ENTRY_PNPBIOS_BASE * 8) - - -#else #include -#define GDT_ENTRY_KERNEL32_CS 1 -#define GDT_ENTRY_KERNEL_CS 2 -#define GDT_ENTRY_KERNEL_DS 3 - -#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS * 8) - +#define GDT_ENTRY_KERNEL32_CS 1 +#define GDT_ENTRY_KERNEL_CS 2 +#define GDT_ENTRY_KERNEL_DS 3 /* * we cannot use the same code segment descriptor for user and kernel * -- not even in the long flat mode, because of different DPL /kkeil - * The segment offset needs to contain a RPL. Grr. -AK - * GDT layout to get 64bit syscall right (sysret hardcodes gdt offsets) + * GDT layout to get 64bit syscall/sysret right. sysret hardcodes selectors: + * if returning to 32-bit userspace: cs = STAR.SYSRET_CS, + * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16, + * ss = STAR.SYSRET_CS+8 (in either case) + * thus USER_DS should be between 32-bit and 64-bit code selectors: */ #define GDT_ENTRY_DEFAULT_USER32_CS 4 #define GDT_ENTRY_DEFAULT_USER_DS 5 #define GDT_ENTRY_DEFAULT_USER_CS 6 -#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8+3) -#define __USER32_DS __USER_DS -#define GDT_ENTRY_TSS 8 /* needs two entries */ -#define GDT_ENTRY_LDT 10 /* needs two entries */ -#define GDT_ENTRY_TLS_MIN 12 -#define GDT_ENTRY_TLS_MAX 14 +#define GDT_ENTRY_TSS 8 /* needs two entries */ +#define GDT_ENTRY_LDT 10 /* needs two entries */ +#define GDT_ENTRY_TLS_MIN 12 +#define GDT_ENTRY_TLS_MAX 14 -#define GDT_ENTRY_PER_CPU 15 /* Abused to load per CPU data from limit */ -#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU * 8 + 3) +#define GDT_ENTRY_PER_CPU 15 /* abused to load per CPU data from limit */ + +/* Selectors need to also have a correct RPL (+3 thingy) */ +#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) +#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) +#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3) +#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3) +#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8) +#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8+3) +#define __USER32_DS __USER_DS +#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8+3) /* TLS indexes for 64bit - hardcoded in arch_prctl */ #define FS_TLS 0 @@ -183,10 +170,6 @@ #endif -#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) -#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) -#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3) -#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3) #ifndef CONFIG_PARAVIRT #define get_kernel_rpl() 0 #endif -- cgit v1.2.3 From 72d64cc76941cde45e65e2a5b9fb81d527963645 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 24 Mar 2015 20:45:42 +0100 Subject: x86/asm: Further improve segment.h readability - extend/clarify explanations where necessary - move comments from macro values to before the macro, to make them more consistent, and to reduce preprocessor overhead - sort GDT index and selector values likewise by number - use consistent, modern kernel coding style across the file - capitalize consistently - use consistent vertical spacing - remove the unused get_limit() method (noticed by Andy Lutomirski) No change in code (verified with objdump -d): 64-bit defconfig+kvmconfig: 815a129bc1f80de6445c1d8ca5b97cad vmlinux.o.before.asm 815a129bc1f80de6445c1d8ca5b97cad vmlinux.o.after.asm 32-bit defconfig+kvmconfig: e659ef045159ddf41a0771b33a34aae5 vmlinux.o.before.asm e659ef045159ddf41a0771b33a34aae5 vmlinux.o.after.asm Acked-by: Andy Lutomirski Cc: Alexei Starovoitov Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Signed-off-by: Ingo Molnar --- arch/x86/include/asm/segment.h | 242 ++++++++++++++++++++++++----------------- 1 file changed, 141 insertions(+), 101 deletions(-) (limited to 'arch/x86/include/asm/segment.h') diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index 117028f58882..d394899e055c 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -3,8 +3,10 @@ #include -/* Constructor for a conventional segment GDT (or LDT) entry */ -/* This is a macro so it can be used in initializers */ +/* + * Constructor for a conventional segment GDT (or LDT) entry. + * This is a macro so it can be used in initializers. + */ #define GDT_ENTRY(flags, base, limit) \ ((((base) & _AC(0xff000000,ULL)) << (56-24)) | \ (((flags) & _AC(0x0000f0ff,ULL)) << 40) | \ @@ -12,71 +14,78 @@ (((base) & _AC(0x00ffffff,ULL)) << 16) | \ (((limit) & _AC(0x0000ffff,ULL)))) -/* Simple and small GDT entries for booting only */ +/* Simple and small GDT entries for booting only: */ #define GDT_ENTRY_BOOT_CS 2 #define GDT_ENTRY_BOOT_DS 3 #define GDT_ENTRY_BOOT_TSS 4 -#define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8) -#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8) -#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8) - -#define SEGMENT_RPL_MASK 0x3 /* - * Bottom two bits of selector give the ring - * privilege level - */ -#define SEGMENT_TI_MASK 0x4 /* Bit 2 is table indicator (LDT/GDT) */ -#define USER_RPL 0x3 /* User mode is privilege level 3 */ -#define SEGMENT_LDT 0x4 /* LDT segment has TI set... */ -#define SEGMENT_GDT 0x0 /* ... GDT has it cleared */ +#define __BOOT_CS (GDT_ENTRY_BOOT_CS*8) +#define __BOOT_DS (GDT_ENTRY_BOOT_DS*8) +#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS*8) + +/* + * Bottom two bits of selector give the ring + * privilege level + */ +#define SEGMENT_RPL_MASK 0x3 + +/* User mode is privilege level 3: */ +#define USER_RPL 0x3 + +/* Bit 2 is Table Indicator (TI): selects between LDT or GDT */ +#define SEGMENT_TI_MASK 0x4 +/* LDT segment has TI set ... */ +#define SEGMENT_LDT 0x4 +/* ... GDT has it cleared */ +#define SEGMENT_GDT 0x0 #ifdef CONFIG_X86_32 /* * The layout of the per-CPU GDT under Linux: * - * 0 - null + * 0 - null <=== cacheline #1 * 1 - reserved * 2 - reserved * 3 - reserved * - * 4 - unused <==== new cacheline + * 4 - unused <=== cacheline #2 * 5 - unused * * ------- start of TLS (Thread-Local Storage) segments: * * 6 - TLS segment #1 [ glibc's TLS segment ] * 7 - TLS segment #2 [ Wine's %fs Win32 segment ] - * 8 - TLS segment #3 + * 8 - TLS segment #3 <=== cacheline #3 * 9 - reserved * 10 - reserved * 11 - reserved * * ------- start of kernel segments: * - * 12 - kernel code segment <==== new cacheline + * 12 - kernel code segment <=== cacheline #4 * 13 - kernel data segment * 14 - default user CS * 15 - default user DS - * 16 - TSS + * 16 - TSS <=== cacheline #5 * 17 - LDT * 18 - PNPBIOS support (16->32 gate) * 19 - PNPBIOS support - * 20 - PNPBIOS support + * 20 - PNPBIOS support <=== cacheline #6 * 21 - PNPBIOS support * 22 - PNPBIOS support * 23 - APM BIOS support - * 24 - APM BIOS support + * 24 - APM BIOS support <=== cacheline #7 * 25 - APM BIOS support * * 26 - ESPFIX small SS * 27 - per-cpu [ offset to per-cpu data area ] - * 28 - stack_canary-20 [ for stack protector ] + * 28 - stack_canary-20 [ for stack protector ] <=== cacheline #8 * 29 - unused * 30 - unused * 31 - TSS for double fault handler */ -#define GDT_ENTRY_TLS_MIN 6 -#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1) +#define GDT_ENTRY_TLS_MIN 6 +#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1) #define GDT_ENTRY_KERNEL_CS 12 #define GDT_ENTRY_KERNEL_DS 13 @@ -97,96 +106,134 @@ #define GDT_ENTRY_DOUBLEFAULT_TSS 31 +/* + * Number of entries in the GDT table: + */ +#define GDT_ENTRIES 32 + +/* + * Segment selector values corresponding to the above entries: + */ + #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) -#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3) -#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3) +#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) +#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8) -#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */ -#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */ + +/* segment for calling fn: */ +#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8) +/* code segment for BIOS: */ +#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8) + /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */ -#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32) -#define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */ -#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */ -#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */ +#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32) + +/* data segment for BIOS: */ +#define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8) +/* transfer data segment: */ +#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8) +/* another data segment: */ +#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8) + #ifdef CONFIG_SMP -#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8) +# define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8) #else -#define __KERNEL_PERCPU 0 +# define __KERNEL_PERCPU 0 #endif + #ifdef CONFIG_CC_STACKPROTECTOR -#define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8) +# define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8) #else -#define __KERNEL_STACK_CANARY 0 +# define __KERNEL_STACK_CANARY 0 #endif -#define GDT_ENTRIES 32 - #else /* 64-bit: */ #include -#define GDT_ENTRY_KERNEL32_CS 1 -#define GDT_ENTRY_KERNEL_CS 2 -#define GDT_ENTRY_KERNEL_DS 3 +#define GDT_ENTRY_KERNEL32_CS 1 +#define GDT_ENTRY_KERNEL_CS 2 +#define GDT_ENTRY_KERNEL_DS 3 + /* - * we cannot use the same code segment descriptor for user and kernel - * -- not even in the long flat mode, because of different DPL /kkeil - * GDT layout to get 64bit syscall/sysret right. sysret hardcodes selectors: - * if returning to 32-bit userspace: cs = STAR.SYSRET_CS, - * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16, + * We cannot use the same code segment descriptor for user and kernel mode, + * not even in long flat mode, because of different DPL. + * + * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes + * selectors: + * + * if returning to 32-bit userspace: cs = STAR.SYSRET_CS, + * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16, + * * ss = STAR.SYSRET_CS+8 (in either case) + * * thus USER_DS should be between 32-bit and 64-bit code selectors: */ -#define GDT_ENTRY_DEFAULT_USER32_CS 4 -#define GDT_ENTRY_DEFAULT_USER_DS 5 -#define GDT_ENTRY_DEFAULT_USER_CS 6 +#define GDT_ENTRY_DEFAULT_USER32_CS 4 +#define GDT_ENTRY_DEFAULT_USER_DS 5 +#define GDT_ENTRY_DEFAULT_USER_CS 6 + +/* Needs two entries */ +#define GDT_ENTRY_TSS 8 +/* Needs two entries */ +#define GDT_ENTRY_LDT 10 -#define GDT_ENTRY_TSS 8 /* needs two entries */ -#define GDT_ENTRY_LDT 10 /* needs two entries */ -#define GDT_ENTRY_TLS_MIN 12 -#define GDT_ENTRY_TLS_MAX 14 +#define GDT_ENTRY_TLS_MIN 12 +#define GDT_ENTRY_TLS_MAX 14 -#define GDT_ENTRY_PER_CPU 15 /* abused to load per CPU data from limit */ +/* Abused to load per CPU data from limit */ +#define GDT_ENTRY_PER_CPU 15 -/* Selectors need to also have a correct RPL (+3 thingy) */ -#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) -#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) -#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3) -#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3) -#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8) -#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8+3) -#define __USER32_DS __USER_DS -#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8+3) +/* + * Number of entries in the GDT table: + */ +#define GDT_ENTRIES 16 -/* TLS indexes for 64bit - hardcoded in arch_prctl */ -#define FS_TLS 0 -#define GS_TLS 1 +/* + * Segment selector values corresponding to the above entries: + * + * Note, selectors also need to have a correct RPL, + * expressed with the +3 value for user-space selectors: + */ +#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8) +#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) +#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) +#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3) +#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) +#define __USER32_DS __USER_DS +#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) +#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3) -#define GS_TLS_SEL ((GDT_ENTRY_TLS_MIN+GS_TLS)*8 + 3) -#define FS_TLS_SEL ((GDT_ENTRY_TLS_MIN+FS_TLS)*8 + 3) +/* TLS indexes for 64-bit - hardcoded in arch_prctl(): */ +#define FS_TLS 0 +#define GS_TLS 1 -#define GDT_ENTRIES 16 +#define GS_TLS_SEL ((GDT_ENTRY_TLS_MIN+GS_TLS)*8 + 3) +#define FS_TLS_SEL ((GDT_ENTRY_TLS_MIN+FS_TLS)*8 + 3) #endif #ifndef CONFIG_PARAVIRT -#define get_kernel_rpl() 0 +# define get_kernel_rpl() 0 #endif -#define IDT_ENTRIES 256 -#define NUM_EXCEPTION_VECTORS 32 -/* Bitmask of exception vectors which push an error code on the stack */ -#define EXCEPTION_ERRCODE_MASK 0x00027d00 -#define GDT_SIZE (GDT_ENTRIES * 8) -#define GDT_ENTRY_TLS_ENTRIES 3 -#define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8) +#define IDT_ENTRIES 256 +#define NUM_EXCEPTION_VECTORS 32 + +/* Bitmask of exception vectors which push an error code on the stack: */ +#define EXCEPTION_ERRCODE_MASK 0x00027d00 + +#define GDT_SIZE (GDT_ENTRIES*8) +#define GDT_ENTRY_TLS_ENTRIES 3 +#define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8) #ifdef __KERNEL__ #ifndef __ASSEMBLY__ + extern const char early_idt_handlers[NUM_EXCEPTION_VECTORS][2+2+5]; #ifdef CONFIG_TRACING -#define trace_early_idt_handlers early_idt_handlers +# define trace_early_idt_handlers early_idt_handlers #endif /* @@ -211,37 +258,30 @@ do { \ } while (0) /* - * Save a segment register away + * Save a segment register away: */ #define savesegment(seg, value) \ asm("mov %%" #seg ",%0":"=r" (value) : : "memory") /* - * x86_32 user gs accessors. + * x86-32 user GS accessors: */ #ifdef CONFIG_X86_32 -#ifdef CONFIG_X86_32_LAZY_GS -#define get_user_gs(regs) (u16)({unsigned long v; savesegment(gs, v); v;}) -#define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v)) -#define task_user_gs(tsk) ((tsk)->thread.gs) -#define lazy_save_gs(v) savesegment(gs, (v)) -#define lazy_load_gs(v) loadsegment(gs, (v)) -#else /* X86_32_LAZY_GS */ -#define get_user_gs(regs) (u16)((regs)->gs) -#define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0) -#define task_user_gs(tsk) (task_pt_regs(tsk)->gs) -#define lazy_save_gs(v) do { } while (0) -#define lazy_load_gs(v) do { } while (0) -#endif /* X86_32_LAZY_GS */ +# ifdef CONFIG_X86_32_LAZY_GS +# define get_user_gs(regs) (u16)({ unsigned long v; savesegment(gs, v); v; }) +# define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v)) +# define task_user_gs(tsk) ((tsk)->thread.gs) +# define lazy_save_gs(v) savesegment(gs, (v)) +# define lazy_load_gs(v) loadsegment(gs, (v)) +# else /* X86_32_LAZY_GS */ +# define get_user_gs(regs) (u16)((regs)->gs) +# define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0) +# define task_user_gs(tsk) (task_pt_regs(tsk)->gs) +# define lazy_save_gs(v) do { } while (0) +# define lazy_load_gs(v) do { } while (0) +# endif /* X86_32_LAZY_GS */ #endif /* X86_32 */ -static inline unsigned long get_limit(unsigned long segment) -{ - unsigned long __limit; - asm("lsll %1,%0" : "=r" (__limit) : "r" (segment)); - return __limit + 1; -} - #endif /* !__ASSEMBLY__ */ #endif /* __KERNEL__ */ -- cgit v1.2.3 From 6b51311c976593fb7311322b1647a912cd456ec4 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Fri, 3 Apr 2015 14:25:28 +0200 Subject: x86/asm/entry/64: Use a define for an invalid segment selector ... instead of a naked number, for better readability. Signed-off-by: Borislav Petkov Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1428054130-25847-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar --- arch/x86/include/asm/segment.h | 2 ++ arch/x86/kernel/cpu/common.c | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/x86/include/asm/segment.h') diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index d394899e055c..5a9856eb12ba 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -39,6 +39,8 @@ /* ... GDT has it cleared */ #define SEGMENT_GDT 0x0 +#define GDT_ENTRY_INVALID_SEG 0 + #ifdef CONFIG_X86_32 /* * The layout of the per-CPU GDT under Linux: diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d56d30714d43..3f70538012e2 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1184,7 +1184,7 @@ void syscall_init(void) wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target); #else wrmsrl(MSR_CSTAR, ignore_sysret); - wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0ULL); + wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); #endif -- cgit v1.2.3