From 38e9e81f4c81c75799b002d5811de7241b307676 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 28 Aug 2017 08:47:41 +0200 Subject: [PATCH] x86/gdt: Use bitfields for initialization The GDT entry related code uses two ways to access entries via union fields: - bitfields - macros which initialize the two 16-bit parts of the entry by magic shift and mask operations. Clean it up and only use the bitfields to initialize and access entries. ( The old access patterns were partly done due to GCC optimizing bitfield accesses in a horrible way - that's mostly fixed these days and clarity of code in such low level accessors is very important. ) Signed-off-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20170828064958.197673367@linutronix.de Signed-off-by: Ingo Molnar --- arch/x86/entry/vdso/vma.c | 2 +- arch/x86/include/asm/desc.h | 26 +++++++++++-------- arch/x86/include/asm/desc_defs.h | 44 +++++++++++++++----------------- arch/x86/math-emu/fpu_system.h | 2 +- 4 files changed, 38 insertions(+), 36 deletions(-) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 726355ce8497..1911310959f8 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -351,7 +351,7 @@ static void vgetcpu_cpu_init(void *arg) * and 8 bits for the node) */ d.limit0 = cpu | ((node & 0xf) << 12); - d.limit = node >> 4; + d.limit1 = node >> 4; d.type = 5; /* RO data, expand down, accessed */ d.dpl = 3; /* Visible to user code */ d.s = 1; /* Not a system segment */ diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index 0731064c633b..2090cd223505 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -23,7 +23,7 @@ static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *in desc->s = 1; desc->dpl = 0x3; desc->p = info->seg_not_present ^ 1; - desc->limit = (info->limit & 0xf0000) >> 16; + desc->limit1 = (info->limit & 0xf0000) >> 16; desc->avl = info->useable; desc->d = info->seg_32bit; desc->g = info->limit_in_pages; @@ -170,14 +170,20 @@ static inline void pack_descriptor(struct desc_struct *desc, unsigned long base, unsigned long limit, unsigned char type, unsigned char flags) { - desc->a = ((base & 0xffff) << 16) | (limit & 0xffff); - desc->b = (base & 0xff000000) | ((base & 0xff0000) >> 16) | - (limit & 0x000f0000) | ((type & 0xff) << 8) | - ((flags & 0xf) << 20); - desc->p = 1; + desc->limit0 = (u16) limit; + desc->base0 = (u16) base; + desc->base1 = (base >> 16) & 0xFF; + desc->type = type & 0x0F; + desc->s = 0; + desc->dpl = 0; + desc->p = 1; + desc->limit1 = (limit >> 16) & 0xF; + desc->avl = (flags >> 0) & 0x01; + desc->l = (flags >> 1) & 0x01; + desc->d = (flags >> 2) & 0x01; + desc->g = (flags >> 3) & 0x01; } - static inline void set_tssldt_descriptor(void *d, unsigned long addr, unsigned type, unsigned size) { @@ -195,7 +201,7 @@ static inline void set_tssldt_descriptor(void *d, unsigned long addr, desc->base2 = (addr >> 24) & 0xFF; desc->base3 = (u32) (addr >> 32); #else - pack_descriptor((struct desc_struct *)d, addr, size, 0x80 | type, 0); + pack_descriptor((struct desc_struct *)d, addr, size, type, 0); #endif } @@ -395,13 +401,13 @@ static inline void set_desc_base(struct desc_struct *desc, unsigned long base) static inline unsigned long get_desc_limit(const struct desc_struct *desc) { - return desc->limit0 | (desc->limit << 16); + return desc->limit0 | (desc->limit1 << 16); } static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit) { desc->limit0 = limit & 0xffff; - desc->limit = (limit >> 16) & 0xf; + desc->limit1 = (limit >> 16) & 0xf; } #ifdef CONFIG_X86_64 diff --git a/arch/x86/include/asm/desc_defs.h b/arch/x86/include/asm/desc_defs.h index d684bee8a59a..1b9494e006a1 100644 --- a/arch/x86/include/asm/desc_defs.h +++ b/arch/x86/include/asm/desc_defs.h @@ -11,34 +11,30 @@ #include -/* - * FIXME: Accessing the desc_struct through its fields is more elegant, - * and should be the one valid thing to do. However, a lot of open code - * still touches the a and b accessors, and doing this allow us to do it - * incrementally. We keep the signature as a struct, rather than a union, - * so we can get rid of it transparently in the future -- glommer - */ /* 8 byte segment descriptor */ struct desc_struct { - union { - struct { - unsigned int a; - unsigned int b; - }; - struct { - u16 limit0; - u16 base0; - unsigned base1: 8, type: 4, s: 1, dpl: 2, p: 1; - unsigned limit: 4, avl: 1, l: 1, d: 1, g: 1, base2: 8; - }; - }; + u16 limit0; + u16 base0; + u16 base1: 8, type: 4, s: 1, dpl: 2, p: 1; + u16 limit1: 4, avl: 1, l: 1, d: 1, g: 1, base2: 8; } __attribute__((packed)); -#define GDT_ENTRY_INIT(flags, base, limit) { { { \ - .a = ((limit) & 0xffff) | (((base) & 0xffff) << 16), \ - .b = (((base) & 0xff0000) >> 16) | (((flags) & 0xf0ff) << 8) | \ - ((limit) & 0xf0000) | ((base) & 0xff000000), \ - } } } +#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, \ + } enum { GATE_INTERRUPT = 0xE, diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h index 2319a257ec32..699f329f1d40 100644 --- a/arch/x86/math-emu/fpu_system.h +++ b/arch/x86/math-emu/fpu_system.h @@ -49,7 +49,7 @@ static inline unsigned long seg_get_base(struct desc_struct *d) static inline unsigned long seg_get_limit(struct desc_struct *d) { - return ((unsigned long)d->limit << 16) | d->limit0; + return ((unsigned long)d->limit1 << 16) | d->limit0; } static inline unsigned long seg_get_granularity(struct desc_struct *d) -- 2.20.1