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x86/restorer/tls: simplify restoring of TLS

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We can live here without 32-bit CS - this syscall doesn't depend on
descriptor type.
No functional changes expected, cleanup.

travis-ci: success for Rectify 32-bit compatible C/R on x86
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
This commit is contained in:
Dmitry Safonov 2016-12-09 21:19:44 +03:00 • committed by Andrei Vagin
parent b7c4ca512f
commit fa2e8f76be
1 changed files with 18 additions and 18 deletions
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36
criu/arch/x86/restorer.c
View file

@ -33,22 +33,18 @@ int restore_nonsigframe_gpregs(UserX86RegsEntry *r)
}
#ifdef CONFIG_COMPAT
asm ( " .pushsection .text \n"
" .global restore_set_thread_area \n"
" .code32 \n"
"restore_set_thread_area: \n"
" movl $"__stringify(__NR32_set_thread_area)",%eax\n"
" int $0x80 \n"
" ret \n"
" .popsection \n"
" .code64");
extern char restore_set_thread_area;
/*
* We need here compatible stack, because 32-bit syscalls get
* 4-byte pointer and _usally_ restorer is also under 4Gb, but
* it can be upper and then pointers are messed up.
* (we lose high 4 bytes and... BUNG!)
* Nothing serious, but syscall will return -EFAULT - or if we're
* lucky and lower 4 bytes points on some writeable VMA - corruption).
*/
static void *stack32;
static int prepare_stack32(void)
{
if (stack32)
return 0;
@ -63,7 +59,7 @@ static int prepare_stack32(void)
void restore_tls(tls_t *ptls)
{
int i;
unsigned i;
for (i = 0; i < GDT_ENTRY_TLS_NUM; i++) {
user_desc_t *desc = &ptls->desc[i];
@ -76,13 +72,17 @@ void restore_tls(tls_t *ptls)
return;
builtin_memcpy(stack32, desc, sizeof(user_desc_t));
asm volatile (
" mov %1,%%eax \n"
" mov %2,%%ebx \n"
" int $0x80 \n"
" mov %%eax,%0 \n"
: "=g"(ret)
: "r"(__NR32_set_thread_area), "r"((uint32_t)(uintptr_t)stack32)
: "eax", "ebx", "memory");
/* user_desc parameter for set_thread_area syscall */
asm volatile ("\t movl %%ebx,%%ebx\n" : :"b"(stack32));
call32_from_64(stack32 + PAGE_SIZE, &restore_set_thread_area);
asm volatile ("\t movl %%eax,%0\n" : "=r"(ret));
if (ret)
pr_err("Failed to restore TLS descriptor %d in GDT ret %d\n",
pr_err("Failed to restore TLS descriptor %u in GDT: %d\n",
desc->entry_number, ret);
}