Commit 96e8fc58 authored by Juergen Gross's avatar Juergen Gross Committed by Borislav Petkov
Browse files

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



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: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220630071441.28576-2-jgross@suse.com
parent 03c765b0

arch/x86/include/asm/setup.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/head64.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/xen/enlighten_pv.c

+6 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/xen/xen-head.S

+1 −9
Original line number Diff line number Diff line
@@ -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