Mailing List Archive

i386 mpih-add1.S and mpih-sub1.S use a trick to implment jump tables
with LEA. We can't use conditional branches nor normal jump tables
since jump table entries use EFLAGS set by jump table index. This
patch adds _CET_ENDBR to indirect jump targets and adjust destination
for _CET_ENDBR.

* mpi/i386/mpih-add1.S (_gcry_mpih_add_n): Save and restore
%ebx if IBT is enabed. Add _CET_ENDBR to indirect jump targets
and adjust jump destination for _CET_ENDBR.
* mpi/i386/mpih-sub1.S (_gcry_mpih_sub_n): Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
---
mpi/i386/mpih-add1.S | 35 +++++++++++++++++++++++++++++++++++
mpi/i386/mpih-sub1.S | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 70 insertions(+)

diff --git a/mpi/i386/mpih-add1.S b/mpi/i386/mpih-add1.S
index 32091f34..ef6423d9 100644
--- a/mpi/i386/mpih-add1.S
+++ b/mpi/i386/mpih-add1.S
@@ -55,6 +55,10 @@ C_SYMBOL_NAME(_gcry_mpih_add_n:)
movl 20(%esp),%edx /* s2_ptr */
movl 24(%esp),%ecx /* size */

+#if defined __CET__ && (__CET__ & 1) != 0
+ pushl %ebx
+#endif
+
movl %ecx,%eax
shrl $3,%ecx /* compute count for unrolled loop */
negl %eax
@@ -66,6 +70,9 @@ C_SYMBOL_NAME(_gcry_mpih_add_n:)
subl %eax,%esi /* ... by a constant when we ... */
subl %eax,%edx /* ... enter the loop */
shrl $2,%eax /* restore previous value */
+#if defined __CET__ && (__CET__ & 1) != 0
+ leal -4(,%eax,4),%ebx /* Count for 4-byte endbr32 */
+#endif
#ifdef PIC
/* Calculate start address in loop for PIC. Due to limitations in some
assemblers, Loop-L0-3 cannot be put into the leal */
@@ -77,30 +84,54 @@ L0: leal (%eax,%eax,8),%eax
#else
/* Calculate start address in loop for non-PIC. */
leal (Loop - 3)(%eax,%eax,8),%eax
+#endif
+#if defined __CET__ && (__CET__ & 1) != 0
+ addl %ebx,%eax /* Adjust for endbr32 */
#endif
jmp *%eax /* jump into loop */
ALIGN (3)
Loop: movl (%esi),%eax
adcl (%edx),%eax
movl %eax,(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 4(%esi),%eax
adcl 4(%edx),%eax
movl %eax,4(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 8(%esi),%eax
adcl 8(%edx),%eax
movl %eax,8(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 12(%esi),%eax
adcl 12(%edx),%eax
movl %eax,12(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 16(%esi),%eax
adcl 16(%edx),%eax
movl %eax,16(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 20(%esi),%eax
adcl 20(%edx),%eax
movl %eax,20(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 24(%esi),%eax
adcl 24(%edx),%eax
movl %eax,24(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 28(%esi),%eax
adcl 28(%edx),%eax
movl %eax,28(%edi)
@@ -113,6 +144,10 @@ Loop: movl (%esi),%eax
sbbl %eax,%eax
negl %eax

+#if defined __CET__ && (__CET__ & 1) != 0
+ popl %ebx
+#endif
+
popl %esi
CFI_POP(%esi)
popl %edi
diff --git a/mpi/i386/mpih-sub1.S b/mpi/i386/mpih-sub1.S
index 501c4a9f..86ab6725 100644
--- a/mpi/i386/mpih-sub1.S
+++ b/mpi/i386/mpih-sub1.S
@@ -56,6 +56,10 @@ C_SYMBOL_NAME(_gcry_mpih_sub_n:)
movl 20(%esp),%edx /* s2_ptr */
movl 24(%esp),%ecx /* size */

+#if defined __CET__ && (__CET__ & 1) != 0
+ pushl %ebx
+#endif
+
movl %ecx,%eax
shrl $3,%ecx /* compute count for unrolled loop */
negl %eax
@@ -67,6 +71,9 @@ C_SYMBOL_NAME(_gcry_mpih_sub_n:)
subl %eax,%esi /* ... by a constant when we ... */
subl %eax,%edx /* ... enter the loop */
shrl $2,%eax /* restore previous value */
+#if defined __CET__ && (__CET__ & 1) != 0
+ leal -4(,%eax,4),%ebx /* Count for 4-byte endbr32 */
+#endif
#ifdef PIC
/* Calculate start address in loop for PIC. Due to limitations in some
assemblers, Loop-L0-3 cannot be put into the leal */
@@ -78,30 +85,54 @@ L0: leal (%eax,%eax,8),%eax
#else
/* Calculate start address in loop for non-PIC. */
leal (Loop - 3)(%eax,%eax,8),%eax
+#endif
+#if defined __CET__ && (__CET__ & 1) != 0
+ addl %ebx,%eax /* Adjust for endbr32 */
#endif
jmp *%eax /* jump into loop */
ALIGN (3)
Loop: movl (%esi),%eax
sbbl (%edx),%eax
movl %eax,(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 4(%esi),%eax
sbbl 4(%edx),%eax
movl %eax,4(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 8(%esi),%eax
sbbl 8(%edx),%eax
movl %eax,8(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 12(%esi),%eax
sbbl 12(%edx),%eax
movl %eax,12(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 16(%esi),%eax
sbbl 16(%edx),%eax
movl %eax,16(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 20(%esi),%eax
sbbl 20(%edx),%eax
movl %eax,20(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 24(%esi),%eax
sbbl 24(%edx),%eax
movl %eax,24(%edi)
+#ifdef _CET_ENDBR
+ _CET_ENDBR
+#endif
movl 28(%esi),%eax
sbbl 28(%edx),%eax
movl %eax,28(%edi)
@@ -114,6 +145,10 @@ Loop: movl (%esi),%eax
sbbl %eax,%eax
negl %eax

+#if defined __CET__ && (__CET__ & 1) != 0
+ popl %ebx
+#endif
+
popl %esi
CFI_POP(%esi)
popl %edi
--
2.24.1


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