diff options
Diffstat (limited to 'arch/x86/include/asm/segment.h')
| -rw-r--r-- | arch/x86/include/asm/segment.h | 49 |
1 files changed, 39 insertions, 10 deletions
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index 7d5a1929d76b..1549caa098f0 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -2,6 +2,7 @@ #define _ASM_X86_SEGMENT_H #include <linux/const.h> +#include <asm/alternative.h> /* * Constructor for a conventional segment GDT (or LDT) entry. @@ -207,13 +208,6 @@ #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) #define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3) -/* TLS indexes for 64-bit - hardcoded in arch_prctl(): */ -#define FS_TLS 0 -#define GS_TLS 1 - -#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 @@ -249,10 +243,13 @@ extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDL #endif /* - * Load a segment. Fall back on loading the zero - * segment if something goes wrong.. + * Load a segment. Fall back on loading the zero segment if something goes + * wrong. This variant assumes that loading zero fully clears the segment. + * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any + * failure to fully clear the cached descriptor is only observable for + * FS and GS. */ -#define loadsegment(seg, value) \ +#define __loadsegment_simple(seg, value) \ do { \ unsigned short __val = (value); \ \ @@ -269,6 +266,38 @@ do { \ : "+r" (__val) : : "memory"); \ } while (0) +#define __loadsegment_ss(value) __loadsegment_simple(ss, (value)) +#define __loadsegment_ds(value) __loadsegment_simple(ds, (value)) +#define __loadsegment_es(value) __loadsegment_simple(es, (value)) + +#ifdef CONFIG_X86_32 + +/* + * On 32-bit systems, the hidden parts of FS and GS are unobservable if + * the selector is NULL, so there's no funny business here. + */ +#define __loadsegment_fs(value) __loadsegment_simple(fs, (value)) +#define __loadsegment_gs(value) __loadsegment_simple(gs, (value)) + +#else + +static inline void __loadsegment_fs(unsigned short value) +{ + asm volatile(" \n" + "1: movw %0, %%fs \n" + "2: \n" + + _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs) + + : : "rm" (value) : "memory"); +} + +/* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */ + +#endif + +#define loadsegment(seg, value) __loadsegment_ ## seg (value) + /* * Save a segment register away: */ |