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

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>

diff --git a/crypto/bn/asm/x86-mont.pl b/crypto/bn/asm/x86-mont.pl
index e8f6b050842e361df1b28d6e90f0e4a400b91dfb..89f4de61e8964fce2793804a78c313fde9e27a3c 100755 (executable)
--- a/crypto/bn/asm/x86-mont.pl
+++ b/crypto/bn/asm/x86-mont.pl
@@ -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

diff --git a/crypto/bn/asm/x86_64-mont.pl b/crypto/bn/asm/x86_64-mont.pl
index 29ba1224e36b5e2bece27a2c89ff4ef31603d38d..8fb6c994e1efb5322bdc59cd2c1d665546fe4212 100755 (executable)
--- a/crypto/bn/asm/x86_64-mont.pl
+++ b/crypto/bn/asm/x86_64-mont.pl
@@ -130,6 +130,20 @@ $code.=<<___;
 
        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";
@@ -342,6 +356,14 @@ $code.=<<___;
 
        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
 ___
@@ -795,6 +817,15 @@ bn_sqr8x_mont:
        sub     %r11,%rsp
 .Lsqr8x_sp_done:
        and     \$-64,%rsp
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lsqr8x_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x2e                    # predict non-taken
+       jnc     .Lsqr8x_page_walk
+
        mov     $num,%r10
        neg     $num
 
@@ -932,8 +963,17 @@ bn_mulx4x_mont:
        sub     $num,%r10               # -$num
        mov     ($n0),$n0               # *n0
        lea     -72(%rsp,%r10),%rsp     # alloca(frame+$num+8)
-       lea     ($bp,$num),%r10
        and     \$-128,%rsp
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lmulx4x_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x66,0x2e               # predict non-taken
+       jnc     .Lmulx4x_page_walk
+
+       lea     ($bp,$num),%r10
        ##############################################################
        # Stack layout
        # +0    num

diff --git a/crypto/bn/asm/x86_64-mont5.pl b/crypto/bn/asm/x86_64-mont5.pl
index 2e8c9db32cbc13d93e497f5485e9382dd0295663..938e170818036447b923f791b55eee3efc36a7dc 100755 (executable)
--- a/crypto/bn/asm/x86_64-mont5.pl
+++ b/crypto/bn/asm/x86_64-mont5.pl
@@ -115,6 +115,20 @@ $code.=<<___;
 
        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";
@@ -469,6 +483,15 @@ $code.=<<___;
        sub     %r11,%rsp
 .Lmul4xsp_done:
        and     \$-64,%rsp
+       mov     %rax,%r11
+       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
+
        neg     $num
 
        mov     %rax,40(%rsp)
@@ -1058,6 +1081,15 @@ $code.=<<___;
        sub     %r11,%rsp
 .Lpwr_sp_done:
        and     \$-64,%rsp
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lpwr_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x2e                    # predict non-taken
+       jnc     .Lpwr_page_walk
+
        mov     $num,%r10       
        neg     $num
 
@@ -2028,7 +2060,16 @@ bn_from_mont8x:
        sub     %r11,%rsp
 .Lfrom_sp_done:
        and     \$-64,%rsp
-       mov     $num,%r10       
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lfrom_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x2e                    # predict non-taken
+       jnc     .Lfrom_page_walk
+
+       mov     $num,%r10
        neg     $num
 
        ##############################################################
@@ -2173,6 +2214,15 @@ bn_mulx4x_mont_gather5:
        sub     %r11,%rsp
 .Lmulx4xsp_done:       
        and     \$-64,%rsp              # ensure alignment
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lmulx4x_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x2e                    # predict non-taken
+       jnc     .Lmulx4x_page_walk
+
        ##############################################################
        # Stack layout
        # +0    -num
@@ -2619,6 +2669,15 @@ bn_powerx5:
        sub     %r11,%rsp
 .Lpwrx_sp_done:
        and     \$-64,%rsp
+       mov     %rax,%r11
+       sub     %rsp,%r11
+       and     \$-4096,%r11
+.Lpwrx_page_walk:
+       mov     (%rsp,%r11),%r10
+       sub     \$4096,%r11
+       .byte   0x2e                    # predict non-taken
+       jnc     .Lpwrx_page_walk
+
        mov     $num,%r10       
        neg     $num