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x86/headers: Clean up and better document uapi/asm/sigcontext.h 

Clean up sigcontext.h:

 - the explanations were full of typos and were hard to read in general
 - use consistent and readable vertical spacing
 - fix, harmonize and extend comments

No field name has been changed, user-space might be relying on
them.

Acked-by: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1441438363-9999-4-git-send-email-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-09-05 09:32:31 +02:00
parent c3f4986fb0
commit cbf5f4fbf4
1 changed files with 182 additions and 148 deletions
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134
arch/x86/include/uapi/asm/sigcontext.h
View File

@ -1,6 +1,19 @@
#ifndef _UAPI_ASM_X86_SIGCONTEXT_H
#define _UAPI_ASM_X86_SIGCONTEXT_H
/*
* Linux signal context definitions. The sigcontext includes a complex hierarchy of CPU
* and FPU state, available to user-space (on the stack) when a signal handler is
* executed.
*
* As over the years this ABI grew from its very simple roots towards supporting more and
* more CPU state organically, some of the details (which were rather clever hacks back
* in the days) became a bit quirky by today.
*
* The current ABI includes flexible provisions for future extensions, so we won't have
* to grow new quirks for quite some time. Promise!
*/
#include <linux/compiler.h>
#include <linux/types.h>
@ -9,67 +22,82 @@
#define FP_XSTATE_MAGIC2_SIZE sizeof(FP_XSTATE_MAGIC2)
/*
* bytes 464..511 in the current 512byte layout of fxsave/fxrstor frame
* are reserved for SW usage. On cpu's supporting xsave/xrstor, these bytes
* are used to extended the fpstate pointer in the sigcontext, which now
* Bytes 464..511 in the current 512-byte layout of the FXSAVE/FXRSTOR frame
* are reserved for SW usage. On CPUs supporting XSAVE/XRSTOR, these bytes
* are used to extend the fpstate pointer in the sigcontext, which now
* includes the extended state information along with fpstate information.
*
* Presence of FP_XSTATE_MAGIC1 at the beginning of this SW reserved
* area and FP_XSTATE_MAGIC2 at the end of memory layout
* (extended_size - FP_XSTATE_MAGIC2_SIZE) indicates the presence of the
* extended state information in the memory layout pointed by the fpstate
* pointer in sigcontext.
* If sw_reserved.magic1 == FP_XSTATE_MAGIC1 then there's a sw_reserved.extended_size
* bytes large extended context area present. (The last 32-bit word of this extended
* area (at the fpstate+extended_size-FP_XSTATE_MAGIC2_SIZE address) is set to
* FP_XSTATE_MAGIC2 so that you can sanity check your size calculations.)
*
* This extended area typically grows with newer CPUs that have larger and larger
* XSAVE areas.
*/
struct _fpx_sw_bytes {
__u32 magic1; /* FP_XSTATE_MAGIC1 */
__u32 extended_size; /* total size of the layout referred by
* fpstate pointer in the sigcontext.
/* If set to FP_XSTATE_MAGIC1 then this is an xstate context. 0 if a legacy frame. */
__u32 magic1;
/*
* Total size of the fpstate area:
*
* - if magic1 == 0 then it's sizeof(struct _fpstate)
* - if magic1 == FP_XSTATE_MAGIC1 then it's sizeof(struct _xstate) plus extensions (if any)
*/
__u32 extended_size;
/*
* Feature bit mask (including FP/SSE/extended state) that is present
* in the memory layout:
*/
__u64 xfeatures;
/* feature bit mask (including fp/sse/extended
* state) that is present in the memory
* layout.
/*
* Actual XSAVE state size, based on the xfeatures saved in the layout.
* 'extended_size' is greater than 'xstate_size':
*/
__u32 xstate_size; /* actual xsave state size, based on the
* features saved in the layout.
* 'extended_size' will be greater than
* 'xstate_size'.
*/
__u32 padding[7]; /* for future use. */
__u32 xstate_size;
/* For future use: */
__u32 padding[7];
};
#ifdef __i386__
/*
* As documented in the iBCS2 standard..
* As documented in the iBCS2 standard:
*
* The first part of "struct _fpstate" is just the normal i387
* hardware setup, the extra "status" word is used to save the
* coprocessor status word before entering the handler.
*
* Pentium III FXSR, SSE support
* Gareth Hughes <gareth@valinux.com>, May 2000
*
* The FPU state data structure has had to grow to accommodate the
* extended FPU state required by the Streaming SIMD Extensions.
* There is no documented standard to accomplish this at the moment.
*/
/* 10-byte legacy floating point register: */
struct _fpreg {
unsigned short significand[4];
unsigned short exponent;
};
/* 16-byte floating point register: */
struct _fpxreg {
unsigned short significand[4];
unsigned short exponent;
unsigned short padding[3];
};
/* 16-byte XMM register: */
struct _xmmreg {
unsigned long element[4];
};
#define X86_FXSR_MAGIC 0x0000
struct _fpstate {
/* Regular FPU environment */
/* Legacy FPU environment: */
unsigned long cw;
unsigned long sw;
unsigned long tag;
@ -79,25 +107,23 @@ struct _fpstate {
unsigned long datasel;
struct _fpreg _st[8];
unsigned short status;
unsigned short magic; /* 0xffff = regular FPU data only */
unsigned short magic; /* 0xffff: regular FPU data only */
/* 0x0000: FXSR FPU data */
/* FXSR FPU environment */
unsigned long _fxsr_env[6]; /* FXSR FPU env is ignored */
unsigned long mxcsr;
unsigned long reserved;
struct _fpxreg _fxsr_st[8]; /* FXSR FPU reg data is ignored */
struct _xmmreg _xmm[8];
unsigned long padding1[44];
struct _xmmreg _xmm[8]; /* First 8 XMM registers */
unsigned long padding1[44]; /* Second 8 XMM registers plus padding */
union {
unsigned long padding2[12];
struct _fpx_sw_bytes sw_reserved; /* represents the extended
* state info */
struct _fpx_sw_bytes sw_reserved; /* Potential extended state is encoded here */
};
};
#define X86_FXSR_MAGIC 0x0000
# ifndef __KERNEL__
/*
* User-space might still rely on the old definition:
@ -128,28 +154,35 @@ struct sigcontext {
};
# endif /* !__KERNEL__ */
#else /* __i386__ */
#else /* __x86_64__: */
/* FXSAVE frame */
/* Note: reserved1/2 may someday contain valuable data. Always save/restore
them when you change signal frames. */
/*
* The FXSAVE frame.
*
* Note1: If sw_reserved.magic1 == FP_XSTATE_MAGIC1 then the structure is
* larger: 'struct _xstate'. Note that 'struct _xstate' embedds
* 'struct _fpstate' so that you can always assume the _fpstate portion
* exists so that you can check the magic value.
*
* Note2: Reserved fields may someday contain valuable data. Always save/restore
* them when you change signal frames.
*/
struct _fpstate {
__u16 cwd;
__u16 swd;
__u16 twd; /* Note this is not the same as the
32bit/x87/FSAVE twd */
/* Note this is not the same as the 32-bit/x87/FSAVE twd: */
__u16 twd;
__u16 fop;
__u64 rip;
__u64 rdp;
__u32 mxcsr;
__u32 mxcsr_mask;
__u32 st_space[32]; /* 8*16 bytes for each FP-reg */
__u32 xmm_space[64]; /* 16*16 bytes for each XMM-reg */
__u32 st_space[32]; /* 8x FP registers, 16 bytes each */
__u32 xmm_space[64]; /* 16x XMM registers, 16 bytes each */
__u32 reserved2[12];
union {
__u32 reserved3[12];
struct _fpx_sw_bytes sw_reserved; /* represents the extended
* state information */
struct _fpx_sw_bytes sw_reserved; /* Potential extended state is encoded here */
};
};
@ -184,7 +217,7 @@ struct sigcontext {
__u64 trapno;
__u64 oldmask;
__u64 cr2;
struct _fpstate __user *fpstate; /* zero when no FPU context */
struct _fpstate __user *fpstate; /* Zero when no FPU context */
# ifdef __ILP32__
__u32 __fpstate_pad;
# endif
@ -192,7 +225,7 @@ struct sigcontext {
};
# endif /* !__KERNEL__ */
#endif /* !__i386__ */
#endif /* __x86_64__ */
struct _header {
__u64 xfeatures;
@ -201,21 +234,22 @@ struct _header {
};
struct _ymmh_state {
/* 16 * 16 bytes for each YMMH-reg */
/* 16x YMM registers, 16 bytes each: */
__u32 ymmh_space[64];
};
/*
* Extended state pointed by the fpstate pointer in the sigcontext.
* In addition to the fpstate, information encoded in the xstate_hdr
* indicates the presence of other extended state information
* supported by the processor and OS.
* Extended state pointed to by sigcontext::fpstate.
*
* In addition to the fpstate, information encoded in _xstate::xstate_hdr
* indicates the presence of other extended state information supported
* by the CPU and kernel:
*/
struct _xstate {
struct _fpstate fpstate;
struct _header xstate_hdr;
struct _ymmh_state ymmh;
/* new processor state extensions go here */
/* New processor state extensions go here: */
};
#endif /* _UAPI_ASM_X86_SIGCONTEXT_H */