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lib/csu/i386/reloc.c
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/*- | |||||
* Copyright (c) 2018 The FreeBSD Foundation | |||||
* | |||||
* This software was developed by Konstantin Belousov <kib@FreeBSD.org> | |||||
* under sponsorship from the FreeBSD Foundation. | |||||
* | |||||
* 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. | |||||
* | |||||
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. | |||||
*/ | |||||
#include <sys/cdefs.h> | |||||
__FBSDID("$FreeBSD$"); | |||||
#include <machine/specialreg.h> | |||||
#include <machine/cpufunc.h> | |||||
static void | |||||
crt1_handle_rel(const Elf_Rel *r) | |||||
{ | |||||
Elf_Addr *where, target; | |||||
u_int cpuid_supported, p[4]; | |||||
uint32_t cpu_feature, cpu_feature2; | |||||
uint32_t cpu_stdext_feature, cpu_stdext_feature2; | |||||
__asm __volatile( | |||||
" pushfl\n" | |||||
" popl %%eax\n" | |||||
" movl %%eax,%%ecx\n" | |||||
" xorl $0x200000,%%eax\n" | |||||
" pushl %%eax\n" | |||||
" popfl\n" | |||||
" pushfl\n" | |||||
" popl %%eax\n" | |||||
" xorl %%eax,%%ecx\n" | |||||
" je 1f\n" | |||||
" movl $1,%0\n" | |||||
" jmp 2f\n" | |||||
"1: movl $0,%0\n" | |||||
"2:\n" | |||||
: "=r" (cpuid_supported) : : "eax", "ecx", "cc"); | |||||
if (cpuid_supported) { | |||||
do_cpuid(1, p); | |||||
markj: If cpuid is supported, this has the side effect of leaving the ID bit inverted in EFLAGS. I… | |||||
Done Inline ActionsThe code is taken literally from the Intel App Note 485 CPU Identification. Code uses XOR, so any state of the EFLAGS.ID bit is fine for it. I do not believe that we need to care about anything else. The same code is present in x86/__vdso_tc.c and in i386/gen/getcontextx.c. kib: The code is taken literally from the Intel App Note 485 CPU Identification. Code uses XOR, so… | |||||
cpu_feature = p[3]; | |||||
cpu_feature2 = p[2]; | |||||
do_cpuid(0, p); | |||||
if (p[0] >= 7) { | |||||
cpuid_count(7, 0, p); | |||||
cpu_stdext_feature = p[1]; | |||||
cpu_stdext_feature2 = p[2]; | |||||
} else { | |||||
cpu_stdext_feature = 0; | |||||
cpu_stdext_feature2 = 0; | |||||
} | |||||
} else { | |||||
cpu_feature = 0; | |||||
cpu_feature2 = 0; | |||||
cpu_stdext_feature = 0; | |||||
cpu_stdext_feature2 = 0; | |||||
} | |||||
switch (ELF_R_TYPE(r->r_info)) { | |||||
case R_386_IRELATIVE: | |||||
where = (Elf_Addr *)r->r_offset; | |||||
target = ((Elf_Addr (*)(uint32_t, uint32_t, uint32_t, | |||||
uint32_t))*where)(cpu_feature, cpu_feature2, | |||||
cpu_stdext_feature, cpu_stdext_feature2); | |||||
*where = target; | |||||
break; | |||||
} | |||||
} |
If cpuid is supported, this has the side effect of leaving the ID bit inverted in EFLAGS. I guess that's not likely a problem in practice.