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freebsd-dev/sys/amd64/include/asmacros.h
Konstantin Belousov 3e902b3d76 Make WRFSBASE and WRGSBASE instructions functional. 
Right now, we enable the CR4.FSGSBASE bit on CPUs which support the
facility (Ivy and later), to allow usermode to read fs and gs bases
without syscalls. This bit also controls the write access to bases
from userspace, but WRFSBASE and WRGSBASE instructions currently
cannot be used, because return path from both exceptions or interrupts
overrides bases with the values from pcb.

Supporting the instructions is useful because this means that usermode
can implement green-threads completely in userspace without issuing
syscalls to change all of the machine context.

Support is implemented by saving the fs base and user gs base when
PCB_FULL_IRET flag is set. The flag is set on the context switch,
which potentially causes clobber of the bases due to activation of
another context, and when explicit modification of the user context by
a syscall or exception handler is performed. In particular, the patch
moves setting of the flag before syscalls change context.

The changes to doreti_exit and PUSH_FRAME to clear PCB_FULL_IRET on
entry from userspace can be considered a bug fixes on its own.

Reviewed by:	jhb (previous version)
Tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	3 weeks
Differential revision:	https://reviews.freebsd.org/D12023
2017-08-21 17:38:02 +00:00

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/*-
* Copyright (c) 1993 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _MACHINE_ASMACROS_H_
#define _MACHINE_ASMACROS_H_
#include <sys/cdefs.h>
/* XXX too much duplication in various asm*.h's. */
/*
* CNAME is used to manage the relationship between symbol names in C
* and the equivalent assembly language names. CNAME is given a name as
* it would be used in a C program. It expands to the equivalent assembly
* language name.
*/
#define CNAME(csym) csym
#define ALIGN_DATA .p2align 3 /* 8 byte alignment, zero filled */
#ifdef GPROF
#define ALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */
#else
#define ALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */
#endif
#define SUPERALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */
#define GEN_ENTRY(name) ALIGN_TEXT; .globl CNAME(name); \
.type CNAME(name),@function; CNAME(name):
#define NON_GPROF_ENTRY(name) GEN_ENTRY(name)
#define NON_GPROF_RET .byte 0xc3 /* opcode for `ret' */
#define END(name) .size name, . - name
#ifdef GPROF
/*
* __mcount is like [.]mcount except that doesn't require its caller to set
* up a frame pointer. It must be called before pushing anything onto the
* stack. gcc should eventually generate code to call __mcount in most
* cases. This would make -pg in combination with -fomit-frame-pointer
* useful. gcc has a configuration variable PROFILE_BEFORE_PROLOGUE to
* allow profiling before setting up the frame pointer, but this is
* inadequate for good handling of special cases, e.g., -fpic works best
* with profiling after the prologue.
*
* [.]mexitcount is a new function to support non-statistical profiling if an
* accurate clock is available. For C sources, calls to it are generated
* by the FreeBSD extension `-mprofiler-epilogue' to gcc. It is best to
* call [.]mexitcount at the end of a function like the MEXITCOUNT macro does,
* but gcc currently generates calls to it at the start of the epilogue to
* avoid problems with -fpic.
*
* [.]mcount and __mcount may clobber the call-used registers and %ef.
* [.]mexitcount may clobber %ecx and %ef.
*
* Cross-jumping makes non-statistical profiling timing more complicated.
* It is handled in many cases by calling [.]mexitcount before jumping. It
* is handled for conditional jumps using CROSSJUMP() and CROSSJUMP_LABEL().
* It is handled for some fault-handling jumps by not sharing the exit
* routine.
*
* ALTENTRY() must be before a corresponding ENTRY() so that it can jump to
* the main entry point. Note that alt entries are counted twice. They
* have to be counted as ordinary entries for gprof to get the call times
* right for the ordinary entries.
*
* High local labels are used in macros to avoid clashes with local labels
* in functions.
*
* Ordinary `ret' is used instead of a macro `RET' because there are a lot
* of `ret's. 0xc3 is the opcode for `ret' (`#define ret ... ret' can't
* be used because this file is sometimes preprocessed in traditional mode).
* `ret' clobbers eflags but this doesn't matter.
*/
#define ALTENTRY(name) GEN_ENTRY(name) ; MCOUNT ; MEXITCOUNT ; jmp 9f
#define CROSSJUMP(jtrue, label, jfalse) \
jfalse 8f; MEXITCOUNT; jmp __CONCAT(to,label); 8:
#define CROSSJUMPTARGET(label) \
ALIGN_TEXT; __CONCAT(to,label): ; MCOUNT; jmp label
#define ENTRY(name) GEN_ENTRY(name) ; 9: ; MCOUNT
#define FAKE_MCOUNT(caller) pushq caller ; call __mcount ; popq %rcx
#define MCOUNT call __mcount
#define MCOUNT_LABEL(name) GEN_ENTRY(name) ; nop ; ALIGN_TEXT
#ifdef GUPROF
#define MEXITCOUNT call .mexitcount
#define ret MEXITCOUNT ; NON_GPROF_RET
#else
#define MEXITCOUNT
#endif
#else /* !GPROF */
/*
* ALTENTRY() has to align because it is before a corresponding ENTRY().
* ENTRY() has to align to because there may be no ALTENTRY() before it.
* If there is a previous ALTENTRY() then the alignment code for ENTRY()
* is empty.
*/
#define ALTENTRY(name) GEN_ENTRY(name)
#define CROSSJUMP(jtrue, label, jfalse) jtrue label
#define CROSSJUMPTARGET(label)
#define ENTRY(name) GEN_ENTRY(name)
#define FAKE_MCOUNT(caller)
#define MCOUNT
#define MCOUNT_LABEL(name)
#define MEXITCOUNT
#endif /* GPROF */
/*
* Convenience for adding frame pointers to hand-coded ASM. Useful for
* DTrace, HWPMC, and KDB.
*/
#define PUSH_FRAME_POINTER \
pushq %rbp ; \
movq %rsp, %rbp ;
#define POP_FRAME_POINTER \
popq %rbp
#ifdef LOCORE
/*
* Convenience macro for declaring interrupt entry points.
*/
#define IDTVEC(name) ALIGN_TEXT; .globl __CONCAT(X,name); \
.type __CONCAT(X,name),@function; __CONCAT(X,name):
/*
* Macros to create and destroy a trap frame.
*/
#define PUSH_FRAME \
subq $TF_RIP,%rsp ; /* skip dummy tf_err and tf_trapno */ \
testb $SEL_RPL_MASK,TF_CS(%rsp) ; /* come from kernel? */ \
jz 1f ; /* Yes, dont swapgs again */ \
swapgs ; \
1: movq %rdi,TF_RDI(%rsp) ; \
movq %rsi,TF_RSI(%rsp) ; \
movq %rdx,TF_RDX(%rsp) ; \
movq %rcx,TF_RCX(%rsp) ; \
movq %r8,TF_R8(%rsp) ; \
movq %r9,TF_R9(%rsp) ; \
movq %rax,TF_RAX(%rsp) ; \
movq %rbx,TF_RBX(%rsp) ; \
movq %rbp,TF_RBP(%rsp) ; \
movq %r10,TF_R10(%rsp) ; \
movq %r11,TF_R11(%rsp) ; \
movq %r12,TF_R12(%rsp) ; \
movq %r13,TF_R13(%rsp) ; \
movq %r14,TF_R14(%rsp) ; \
movq %r15,TF_R15(%rsp) ; \
movw %fs,TF_FS(%rsp) ; \
movw %gs,TF_GS(%rsp) ; \
movw %es,TF_ES(%rsp) ; \
movw %ds,TF_DS(%rsp) ; \
movl $TF_HASSEGS,TF_FLAGS(%rsp) ; \
cld ; \
testb $SEL_RPL_MASK,TF_CS(%rsp) ; /* come from kernel ? */ \
jz 2f ; /* yes, leave PCB_FULL_IRET alone */ \
movq PCPU(CURPCB),%r8 ; \
andl $~PCB_FULL_IRET,PCB_FLAGS(%r8) ; \
2:
#define POP_FRAME \
movq TF_RDI(%rsp),%rdi ; \
movq TF_RSI(%rsp),%rsi ; \
movq TF_RDX(%rsp),%rdx ; \
movq TF_RCX(%rsp),%rcx ; \
movq TF_R8(%rsp),%r8 ; \
movq TF_R9(%rsp),%r9 ; \
movq TF_RAX(%rsp),%rax ; \
movq TF_RBX(%rsp),%rbx ; \
movq TF_RBP(%rsp),%rbp ; \
movq TF_R10(%rsp),%r10 ; \
movq TF_R11(%rsp),%r11 ; \
movq TF_R12(%rsp),%r12 ; \
movq TF_R13(%rsp),%r13 ; \
movq TF_R14(%rsp),%r14 ; \
movq TF_R15(%rsp),%r15 ; \
testb $SEL_RPL_MASK,TF_CS(%rsp) ; /* come from kernel? */ \
jz 1f ; /* keep kernel GS.base */ \
cli ; \
swapgs ; \
1: addq $TF_RIP,%rsp /* skip over tf_err, tf_trapno */
/*
* Access per-CPU data.
*/
#define PCPU(member) %gs:PC_ ## member
#define PCPU_ADDR(member, reg) \
movq %gs:PC_PRVSPACE, reg ; \
addq $PC_ ## member, reg
#endif /* LOCORE */
#ifdef __STDC__
#define ELFNOTE(name, type, desctype, descdata...) \
.pushsection .note.name ; \
.align 4 ; \
.long 2f - 1f /* namesz */ ; \
.long 4f - 3f /* descsz */ ; \
.long type ; \
1:.asciz #name ; \
2:.align 4 ; \
3:desctype descdata ; \
4:.align 4 ; \
.popsection
#else /* !__STDC__, i.e. -traditional */
#define ELFNOTE(name, type, desctype, descdata) \
.pushsection .note.name ; \
.align 4 ; \
.long 2f - 1f /* namesz */ ; \
.long 4f - 3f /* descsz */ ; \
.long type ; \
1:.asciz "name" ; \
2:.align 4 ; \
3:desctype descdata ; \
4:.align 4 ; \
.popsection
#endif /* __STDC__ */
#endif /* !_MACHINE_ASMACROS_H_ */
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