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bn/asm/x86[_64]-mont*.pl: complement alloca with page-walking.

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Some OSes, *cough*-dows, insist on stack being "wired" to
physical memory in strictly sequential manner, i.e. if stack
allocation spans two pages, then reference to farmost one can
be punishable by SEGV. But page walking can do good even on
other OSes, because it guarantees that villain thread hits
the guard page before it can make damage to innocent one...

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit adc4f1fc25b2cac90076f1e1695b05b7aeeae501)

Resolved conflicts:
	crypto/bn/asm/x86_64-mont.pl
	crypto/bn/asm/x86_64-mont5.pl

Reviewed-by: Richard Levitte <levitte@openssl.org>
This commit is contained in:
Andy Polyakov 2016-03-04 11:39:11 +01:00
parent 6e7a1f35b7
commit a159719440
3 changed files with 74 additions and 3 deletions
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15
crypto/bn/asm/x86-mont.pl
View File

@ -85,6 +85,21 @@ $frame=32; # size of above frame rounded up to 16n
&and ("esp",-64); # align to cache line
# Some OSes, *cough*-dows, insist on stack being "wired" to
# physical memory in strictly sequential manner, i.e. if stack
# allocation spans two pages, then reference to farmost one can
# be punishable by SEGV. But page walking can do good even on
# other OSes, because it guarantees that villain thread hits
# the guard page before it can make damage to innocent one...
&mov ("eax","ebp");
&sub ("eax","esp");
&and ("eax",-4096);
&set_label("page_walk");
&mov ("edx",&DWP(0,"esp","eax"));
&sub ("eax",4096);
&data_byte(0x2e);
&jnc (&label("page_walk"));
################################# load argument block...
&mov ("eax",&DWP(0*4,"esi"));# BN_ULONG *rp
&mov ("ebx",&DWP(1*4,"esi"));# const BN_ULONG *ap

40
crypto/bn/asm/x86_64-mont.pl
View File

@ -91,6 +91,20 @@ bn_mul_mont:
mov %r11,8(%rsp,$num,8) # tp[num+1]=%rsp
.Lmul_body:
# Some OSes, *cough*-dows, insist on stack being "wired" to
# physical memory in strictly sequential manner, i.e. if stack
# allocation spans two pages, then reference to farmost one can
# be punishable by SEGV. But page walking can do good even on
# other OSes, because it guarantees that villain thread hits
# the guard page before it can make damage to innocent one...
sub %rsp,%r11
and \$-4096,%r11
.Lmul_page_walk:
mov (%rsp,%r11),%r10
sub \$4096,%r11
.byte 0x66,0x2e # predict non-taken
jnc .Lmul_page_walk
mov $bp,%r12 # reassign $bp
___
$bp="%r12";
@ -296,6 +310,14 @@ bn_mul4x_mont:
mov %r11,8(%rsp,$num,8) # tp[num+1]=%rsp
.Lmul4x_body:
sub %rsp,%r11
and \$-4096,%r11
.Lmul4x_page_walk:
mov (%rsp,%r11),%r10
sub \$4096,%r11
.byte 0x2e # predict non-taken
jnc .Lmul4x_page_walk
mov $rp,16(%rsp,$num,8) # tp[num+2]=$rp
mov %rdx,%r12 # reassign $bp
___
@ -707,6 +729,7 @@ $code.=<<___;
.align 16
bn_sqr4x_mont:
.Lsqr4x_enter:
mov %rsp,%rax
push %rbx
push %rbp
push %r12
@ -715,12 +738,23 @@ bn_sqr4x_mont:
push %r15
shl \$3,${num}d # convert $num to bytes
xor %r10,%r10
mov %rsp,%r11 # put aside %rsp
sub $num,%r10 # -$num
neg $num # -$num
mov ($n0),$n0 # *n0
lea -72(%rsp,%r10,2),%rsp # alloca(frame+2*$num)
lea -72(%rsp,$num,2),%rsp # alloca(frame+2*$num)
and \$-1024,%rsp # minimize TLB usage
sub %rsp,%r11
and \$-4096,%r11
.Lsqr4x_page_walk:
mov (%rsp,%r11),%r10
sub \$4096,%r11
.byte 0x2e # predict non-taken
jnc .Lsqr4x_page_walk
mov $num,%r10
neg $num # restore $num
lea -48(%rax),%r11 # restore saved %rsp
##############################################################
# Stack layout
#

22
crypto/bn/asm/x86_64-mont5.pl
View File

@ -84,6 +84,20 @@ bn_mul_mont_gather5:
mov %rax,8(%rsp,$num,8) # tp[num+1]=%rsp
.Lmul_body:
# Some OSes, *cough*-dows, insist on stack being "wired" to
# physical memory in strictly sequential manner, i.e. if stack
# allocation spans two pages, then reference to farmost one can
# be punishable by SEGV. But page walking can do good even on
# other OSes, because it guarantees that villain thread hits
# the guard page before it can make damage to innocent one...
sub %rsp,%rax
and \$-4096,%rax
.Lmul_page_walk:
mov (%rsp,%rax),%r11
sub \$4096,%rax
.byte 0x2e # predict non-taken
jnc .Lmul_page_walk
lea 128($bp),%r12 # reassign $bp (+size optimization)
___
$bp="%r12";
@ -407,6 +421,14 @@ bn_mul4x_mont_gather5:
mov %rax,8(%rsp,$num,8) # tp[num+1]=%rsp
.Lmul4x_body:
sub %rsp,%rax
and \$-4096,%rax
.Lmul4x_page_walk:
mov (%rsp,%rax),%r11
sub \$4096,%rax
.byte 0x2e # predict non-taken
jnc .Lmul4x_page_walk
mov $rp,16(%rsp,$num,8) # tp[num+2]=$rp
lea 128(%rdx),%r12 # reassign $bp (+size optimization)
___