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x86/xen: Use clear_bss() for Xen PV guests

Browse source 
Instead of clearing the bss area in assembly code, use the clear_bss()
function.

This requires to pass the start_info address as parameter to
xen_start_kernel() in order to avoid the xen_start_info being zeroed
again.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220630071441.28576-2-jgross@suse.com
This commit is contained in:
Juergen Gross 2022-06-30 09:14:39 +02:00 committed by Borislav Petkov
parent 03c765b0e3
commit 96e8fc5818
4 changed files with 11 additions and 12 deletions
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3
arch/x86/include/asm/setup.h
View file

@ -120,6 +120,9 @@ void *extend_brk(size_t size, size_t align);
static char __brk_##name[size]
extern void probe_roms(void);
void clear_bss(void);
#ifdef __i386__
asmlinkage void __init i386_start_kernel(void);

2
arch/x86/kernel/head64.c
View file

@ -426,7 +426,7 @@ void __init do_early_exception(struct pt_regs *regs, int trapnr)
/* Don't add a printk in there. printk relies on the PDA which is not initialized
yet. */
static void __init clear_bss(void)
void __init clear_bss(void)
{
memset(__bss_start, 0,
(unsigned long) __bss_stop - (unsigned long) __bss_start);

8
arch/x86/xen/enlighten_pv.c
View file

@ -1183,15 +1183,19 @@ static void __init xen_domu_set_legacy_features(void)
extern void early_xen_iret_patch(void);
/* First C function to be called on Xen boot */
asmlinkage __visible void __init xen_start_kernel(void)
asmlinkage __visible void __init xen_start_kernel(struct start_info *si)
{
struct physdev_set_iopl set_iopl;
unsigned long initrd_start = 0;
int rc;
if (!xen_start_info)
if (!si)
return;
clear_bss();
xen_start_info = si;
__text_gen_insn(&early_xen_iret_patch,
JMP32_INSN_OPCODE, &early_xen_iret_patch, &xen_iret,
JMP32_INSN_SIZE);

10
arch/x86/xen/xen-head.S
View file

@ -48,15 +48,6 @@ SYM_CODE_START(startup_xen)
ANNOTATE_NOENDBR
cld
/* Clear .bss */
xor %eax,%eax
mov $__bss_start, %rdi
mov $__bss_stop, %rcx
sub %rdi, %rcx
shr $3, %rcx
rep stosq
mov %rsi, xen_start_info
mov initial_stack(%rip), %rsp
/* Set up %gs.
@ -71,6 +62,7 @@ SYM_CODE_START(startup_xen)
cdq
wrmsr
mov %rsi, %rdi
call xen_start_kernel
SYM_CODE_END(startup_xen)
__FINIT