x86: Support shadow stack pointer in setjmp/longjmp

Save and restore shadow stack pointer in setjmp and longjmp to support
shadow stack in Intel CET.  Use feature_1 in tcbhead_t to check if
shadow stack is enabled before saving and restoring shadow stack pointer.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* sysdeps/i386/__longjmp.S: Include <jmp_buf-ssp.h>.
	(__longjmp): Restore shadow stack pointer if shadow stack is
	enabled, SHADOW_STACK_POINTER_OFFSET is defined and __longjmp
	isn't defined for __longjmp_cancel.
	* sysdeps/i386/bsd-_setjmp.S: Include <jmp_buf-ssp.h>.
	(_setjmp): Save shadow stack pointer if shadow stack is enabled
	and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/i386/bsd-setjmp.S: Include <jmp_buf-ssp.h>.
	(setjmp): Save shadow stack pointer if shadow stack is enabled
	and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/i386/setjmp.S: Include <jmp_buf-ssp.h>.
	(__sigsetjmp): Save shadow stack pointer if shadow stack is
	enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/unix/sysv/linux/i386/____longjmp_chk.S: Include
	<jmp_buf-ssp.h>.
	(____longjmp_chk): Restore shadow stack pointer if shadow stack
	is enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/unix/sysv/linux/x86/Makefile (gen-as-const-headers):
	Remove jmp_buf-ssp.sym.
	* sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S: Include
	<jmp_buf-ssp.h>.
	(____longjmp_chk): Restore shadow stack pointer if shadow stack
	is enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/x86/Makefile (gen-as-const-headers): Add
	jmp_buf-ssp.sym.
	* sysdeps/x86/jmp_buf-ssp.sym: New dummy file.
	* sysdeps/x86_64/__longjmp.S: Include <jmp_buf-ssp.h>.
	(__longjmp): Restore shadow stack pointer if shadow stack is
	enabled, SHADOW_STACK_POINTER_OFFSET is defined and __longjmp
	isn't defined for __longjmp_cancel.
	* sysdeps/x86_64/setjmp.S: Include <jmp_buf-ssp.h>.
	(__sigsetjmp): Save shadow stack pointer if shadow stack is
	enabled and SHADOW_STACK_POINTER_OFFSET is defined.

11 files changed, 278 insertions, 1 deletions

diff --git a/sysdeps/i386/__longjmp.S b/sysdeps/i386/__longjmp.S
index b38333bead..6e98ed538d 100644
--- a/sysdeps/i386/__longjmp.S
+++ b/sysdeps/i386/__longjmp.S
@@ -18,14 +18,55 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't restore shadow stack register if
+   1. Shadow stack isn't enabled.  Or
+   2. __longjmp is defined for __longjmp_cancel.
+ */
+#if !SHSTK_ENABLED || defined __longjmp
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 	.text
 ENTRY (__longjmp)
 #ifdef PTR_DEMANGLE
 	movl 4(%esp), %eax	/* User's jmp_buf in %eax.  */
 
+# ifdef SHADOW_STACK_POINTER_OFFSET
+#  if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+#  else
+	xorl %edx, %edx
+#  endif
+	/* Check and adjust the Shadow-Stack-Pointer.  */
+	rdsspd %edx
+	/* And compare it with the saved ssp value.  */
+	subl SHADOW_STACK_POINTER_OFFSET(%eax), %edx
+	je L(skip_ssp)
+	/* Count the number of frames to adjust and adjust it
+	   with incssp instruction.  The instruction can adjust
+	   the ssp by [0..255] value only thus use a loop if
+	   the number of frames is bigger than 255.  */
+	negl %edx
+	shrl $2, %edx
+	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+	       restoring Shadow-Stack-Pointer of setjmp's caller, we
+	       need to unwind shadow stack by one more frame.  */
+	addl $1, %edx
+	movl	$255, %ebx
+L(loop):
+	cmpl	%ebx, %edx
+	cmovb	%edx, %ebx
+	incsspd	%ebx
+	subl	%ebx, %edx
+	ja	L(loop)
+L(skip_ssp):
+# endif
 	/* Save the return address now.  */
 	movl (JB_PC*4)(%eax), %edx
 	/* Get the stack pointer.  */
@@ -56,6 +97,38 @@ ENTRY (__longjmp)
 #else
 	movl 4(%esp), %ecx	/* User's jmp_buf in %ecx.  */
 	movl 8(%esp), %eax	/* Second argument is return value.  */
+# ifdef SHADOW_STACK_POINTER_OFFSET
+#  if IS_IN (libc) && defined SHARED
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+#  endif
+	/* Check and adjust the Shadow-Stack-Pointer.  */
+	xorl %edx, %edx
+	/* Get the current ssp.  */
+	rdsspd	%edx
+	/* And compare it with the saved ssp value.  */
+	subl SHADOW_STACK_POINTER_OFFSET(%ecx), %edx
+	je L(skip_ssp)
+	/* Count the number of frames to adjust and adjust it
+	   with incssp instruction.  The instruction can adjust
+	   the ssp by [0..255] value only thus use a loop if
+	   the number of frames is bigger than 255.  */
+	negl %edx
+	shrl $2, %edx
+	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+	       restoring Shadow-Stack-Pointer of setjmp's caller, we
+	       need to unwind shadow stack by one more frame.  */
+	addl $1, %edx
+	movl	$255, %ebx
+L(loop):
+	cmpl	%ebx, %edx
+	cmovb	%edx, %ebx
+	incsspd	%ebx
+	subl	%ebx, %edx
+	ja	L(loop)
+L(skip_ssp):
+# endif
 	/* Save the return address now.  */
 	movl (JB_PC*4)(%ecx), %edx
 	LIBC_PROBE (longjmp, 3, 4@%ecx, -4@%eax, 4@%edx)
diff --git a/sysdeps/i386/bsd-_setjmp.S b/sysdeps/i386/bsd-_setjmp.S
index a626cc6d22..db47df0ba1 100644
--- a/sysdeps/i386/bsd-_setjmp.S
+++ b/sysdeps/i386/bsd-_setjmp.S
@@ -22,12 +22,18 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <stap-probe.h>
 
 #define PARMS	4		/* no space for saved regs */
 #define JMPBUF	PARMS
 #define SIGMSK	JMPBUF+4
 
+/* Don't save shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 ENTRY (_setjmp)
 
 	xorl %eax, %eax
@@ -51,6 +57,21 @@ ENTRY (_setjmp)
 	movl %ebp, (JB_BP*4)(%edx) /* Save caller's frame pointer.  */
 
 	movl %eax, JB_SIZE(%edx) /* No signal mask set.  */
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+# else
+	xorl %ecx, %ecx
+# endif
+	/* Get the current Shadow-Stack-Pointer and save it.  */
+	rdsspd %ecx
+	movl %ecx, SHADOW_STACK_POINTER_OFFSET(%edx)
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+L(skip_ssp):
+# endif
+#endif
 	ret
 END (_setjmp)
 libc_hidden_def (_setjmp)
diff --git a/sysdeps/i386/bsd-setjmp.S b/sysdeps/i386/bsd-setjmp.S
index 2da8b73c49..1290d0d82b 100644
--- a/sysdeps/i386/bsd-setjmp.S
+++ b/sysdeps/i386/bsd-setjmp.S
@@ -22,12 +22,18 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <stap-probe.h>
 
 #define PARMS  4		/* no space for saved regs */
 #define JMPBUF PARMS
 #define SIGMSK JMPBUF+4
 
+/* Don't save shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 ENTRY (setjmp)
 	/* Note that we have to use a non-exported symbol in the next
 	   jump since otherwise gas will emit it as a jump through the
@@ -51,6 +57,21 @@ ENTRY (setjmp)
 #endif
 	movl %ecx, (JB_PC*4)(%eax)
 	movl %ebp, (JB_BP*4)(%eax) /* Save caller's frame pointer.  */
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+# else
+	xorl %ecx, %ecx
+# endif
+	/* Get the current Shadow-Stack-Pointer and save it.  */
+	rdsspd %ecx
+	movl %ecx, SHADOW_STACK_POINTER_OFFSET(%eax)
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+L(skip_ssp):
+# endif
+#endif
 
 	/* Call __sigjmp_save.  */
 	pushl $1
diff --git a/sysdeps/i386/setjmp.S b/sysdeps/i386/setjmp.S
index 6a08701717..889337b8ae 100644
--- a/sysdeps/i386/setjmp.S
+++ b/sysdeps/i386/setjmp.S
@@ -18,6 +18,7 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
@@ -25,6 +26,11 @@
 #define JMPBUF	PARMS
 #define SIGMSK	JMPBUF+4
 
+/* Don't save shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 ENTRY (__sigsetjmp)
 
 	movl JMPBUF(%esp), %eax
@@ -46,6 +52,21 @@ ENTRY (__sigsetjmp)
 	movl %ecx, (JB_PC*4)(%eax)
 	movl %ebp, (JB_BP*4)(%eax) /* Save caller's frame pointer.  */
 
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+# else
+	xorl %ecx, %ecx
+# endif
+	/* Get the current Shadow-Stack-Pointer and save it.  */
+	rdsspd %ecx
+	movl %ecx, SHADOW_STACK_POINTER_OFFSET(%eax)
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+L(skip_ssp):
+# endif
+#endif
 #if IS_IN (rtld)
 	/* In ld.so we never save the signal mask.  */
 	xorl %eax, %eax
diff --git a/sysdeps/unix/sysv/linux/i386/____longjmp_chk.S b/sysdeps/unix/sysv/linux/i386/____longjmp_chk.S
index 3452433112..a7640d9892 100644
--- a/sysdeps/unix/sysv/linux/i386/____longjmp_chk.S
+++ b/sysdeps/unix/sysv/linux/i386/____longjmp_chk.S
@@ -17,9 +17,14 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't restore shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
 
 	.section .rodata.str1.1,"aMS",@progbits,1
 	.type	longjmp_msg,@object
@@ -46,6 +51,38 @@ longjmp_msg:
 ENTRY (____longjmp_chk)
 	movl	4(%esp), %ecx	/* User's jmp_buf in %ecx.  */
 
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl	$X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
+	jz	L(skip_ssp)
+# else
+	xorl	%edx, %edx
+# endif
+	/* Check and adjust the Shadow-Stack-Pointer.  */
+	rdsspd	%edx
+	/* And compare it with the saved ssp value.  */
+	subl	SHADOW_STACK_POINTER_OFFSET(%ecx), %edx
+	je	L(skip_ssp)
+	/* Count the number of frames to adjust and adjust it
+	   with incssp instruction.  The instruction can adjust
+	   the ssp by [0..255] value only thus use a loop if
+	   the number of frames is bigger than 255.  */
+	negl	%edx
+	shrl	$2, %edx
+	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+	       restoring Shadow-Stack-Pointer of setjmp's caller, we
+	       need to unwind shadow stack by one more frame.  */
+	addl	$1, %edx
+	movl	$255, %ebx
+L(loop):
+	cmpl	%ebx, %edx
+	cmovb	%edx, %ebx
+	incsspd	%ebx
+	subl	%ebx, %edx
+	ja	L(loop)
+L(skip_ssp):
+#endif
 	/* Save the return address now.  */
 	movl	(JB_PC*4)(%ecx), %edx
 	/* Get the stack pointer.  */
diff --git a/sysdeps/unix/sysv/linux/x86/Makefile b/sysdeps/unix/sysv/linux/x86/Makefile
index c55a43e58d..111ff9ff58 100644
--- a/sysdeps/unix/sysv/linux/x86/Makefile
+++ b/sysdeps/unix/sysv/linux/x86/Makefile
@@ -21,6 +21,5 @@ sysdep_routines += dl-vdso
 endif
 
 ifeq ($(subdir),setjmp)
-gen-as-const-headers += jmp_buf-ssp.sym
 tests += tst-saved_mask-1
 endif
diff --git a/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S b/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
index 8a9f2e1a3c..7eb26fafca 100644
--- a/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
+++ b/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
@@ -20,7 +20,13 @@
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't restore shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 #include <sigaltstack-offsets.h>
+#include <jmp_buf-ssp.h>
 
 	.section .rodata.str1.1,"aMS",@progbits,1
 	.type	longjmp_msg,@object
@@ -105,6 +111,38 @@ ENTRY(____longjmp_chk)
 	cfi_restore (%rsi)
 
 .Lok:
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl	$X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
+	jz	L(skip_ssp)
+# else
+	xorl	%eax, %eax
+# endif
+	/* Check and adjust the Shadow-Stack-Pointer.  */
+	rdsspq	%rax
+	/* And compare it with the saved ssp value.  */
+	subq	SHADOW_STACK_POINTER_OFFSET(%rdi), %rax
+	je	L(skip_ssp)
+	/* Count the number of frames to adjust and adjust it
+	   with incssp instruction.  The instruction can adjust
+	   the ssp by [0..255] value only thus use a loop if
+	   the number of frames is bigger than 255.  */
+	negq	%rax
+	shrq	$3, %rax
+	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+	       restoring Shadow-Stack-Pointer of setjmp's caller, we
+	       need to unwind shadow stack by one more frame.  */
+	addq	$1, %rax
+	movl	$255, %ebx
+L(loop):
+	cmpq	%rbx, %rax
+	cmovb	%rax, %rbx
+	incsspq	%rbx
+	subq	%rbx, %rax
+	ja	L(loop)
+L(skip_ssp):
+#endif
 	LIBC_PROBE (longjmp, 3, LP_SIZE@%RDI_LP, -4@%esi, LP_SIZE@%RDX_LP)
 	/* We add unwind information for the target here.  */
 	cfi_def_cfa(%rdi, 0)
diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index d25d6f0ae4..65292f4032 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -10,5 +10,6 @@ tests-static += tst-get-cpu-features-static
 endif
 
 ifeq ($(subdir),setjmp)
+gen-as-const-headers += jmp_buf-ssp.sym
 sysdep_routines += __longjmp_cancel
 endif
diff --git a/sysdeps/x86/jmp_buf-ssp.sym b/sysdeps/x86/jmp_buf-ssp.sym
new file mode 100644
index 0000000000..1aaaedc9ec
--- /dev/null
+++ b/sysdeps/x86/jmp_buf-ssp.sym
@@ -0,0 +1 @@
+-- FIXME: Define SHADOW_STACK_POINTER_OFFSET to support shadow stack.
diff --git a/sysdeps/x86_64/__longjmp.S b/sysdeps/x86_64/__longjmp.S
index a487e0efd0..d7d123e4bc 100644
--- a/sysdeps/x86_64/__longjmp.S
+++ b/sysdeps/x86_64/__longjmp.S
@@ -17,9 +17,18 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't restore shadow stack register if
+   1. Shadow stack isn't enabled.  Or
+   2. __longjmp is defined for __longjmp_cancel.
+ */
+#if !SHSTK_ENABLED || defined __longjmp
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 /* Jump to the position specified by ENV, causing the
    setjmp call there to return VAL, or 1 if VAL is 0.
    void __longjmp (__jmp_buf env, int val).  */
@@ -42,6 +51,41 @@ ENTRY(__longjmp)
 	orq %rax, %r9
 # endif
 #endif
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+# else
+	xorl %eax, %eax
+# endif
+	/* Check and adjust the Shadow-Stack-Pointer.  */
+	/* Get the current ssp.  */
+	rdsspq %rax
+	/* And compare it with the saved ssp value.  */
+	subq SHADOW_STACK_POINTER_OFFSET(%rdi), %rax
+	je L(skip_ssp)
+	/* Count the number of frames to adjust and adjust it
+	   with incssp instruction.  The instruction can adjust
+	   the ssp by [0..255] value only thus use a loop if
+	   the number of frames is bigger than 255.  */
+	negq %rax
+	shrq $3, %rax
+	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
+	       restoring Shadow-Stack-Pointer of setjmp's caller, we
+	       need to unwind shadow stack by one more frame.  */
+	addq $1, %rax
+
+	movl $255, %ebx
+L(loop):
+	cmpq %rbx, %rax
+	cmovb %rax, %rbx
+	incsspq %rbx
+	subq %rbx, %rax
+	ja L(loop)
+
+L(skip_ssp):
+#endif
 	LIBC_PROBE (longjmp, 3, LP_SIZE@%RDI_LP, -4@%esi, LP_SIZE@%RDX_LP)
 	/* We add unwind information for the target here.  */
 	cfi_def_cfa(%rdi, 0)
diff --git a/sysdeps/x86_64/setjmp.S b/sysdeps/x86_64/setjmp.S
index e0a648e3e4..78a8bf4644 100644
--- a/sysdeps/x86_64/setjmp.S
+++ b/sysdeps/x86_64/setjmp.S
@@ -18,9 +18,15 @@
 
 #include <sysdep.h>
 #include <jmpbuf-offsets.h>
+#include <jmp_buf-ssp.h>
 #include <asm-syntax.h>
 #include <stap-probe.h>
 
+/* Don't save shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# undef SHADOW_STACK_POINTER_OFFSET
+#endif
+
 ENTRY (__sigsetjmp)
 	/* Save registers.  */
 	movq %rbx, (JB_RBX*8)(%rdi)
@@ -54,6 +60,21 @@ ENTRY (__sigsetjmp)
 #endif
 	movq %rax, (JB_PC*8)(%rdi)
 
+#ifdef SHADOW_STACK_POINTER_OFFSET
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+	/* Check if Shadow Stack is enabled.  */
+	testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
+	jz L(skip_ssp)
+# else
+	xorl %eax, %eax
+# endif
+	/* Get the current Shadow-Stack-Pointer and save it.  */
+	rdsspq %rax
+	movq %rax, SHADOW_STACK_POINTER_OFFSET(%rdi)
+# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
+L(skip_ssp):
+# endif
+#endif
 #if IS_IN (rtld)
 	/* In ld.so we never save the signal mask.  */
 	xorl %eax, %eax