[PATCH v3 2/6] hurd: Implement longjmp for x86_64

[Sergey Bugaev <bugaevc@gmail.com>]

Checked on x86_64-gnu.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
I have checked that setjmp/longjmp actually works sucessfully, with both
__longjmp and ____longjmp_chk. I have not been able to check w/ sigaltstack
because we don't yet have the proc server and signals.

Changes since v1:
- drop the separate non-PIC version, we can always use %rip-relative access
  on x86_64, and that's what the compiler generates anyway even with -fno-pic;
- use "cmpb $0, __libc_tls_initialized(%rip)" over
  "movb __libc_tls_initialized(%rip), %r10b; testb %r10b, %r10b" -- the former
  is what the compiler generates, so better be consistent.

 sysdeps/mach/hurd/x86_64/____longjmp_chk.S | 118 +++++++++++++++++++++
 sysdeps/mach/hurd/x86_64/__longjmp.S       |  96 +++++++++++++++++
 2 files changed, 214 insertions(+)
 create mode 100644 sysdeps/mach/hurd/x86_64/____longjmp_chk.S
 create mode 100644 sysdeps/mach/hurd/x86_64/__longjmp.S

diff --git a/sysdeps/mach/hurd/x86_64/____longjmp_chk.S b/sysdeps/mach/hurd/x86_64/____longjmp_chk.S
new file mode 100644
index 00000000..935b8575
--- /dev/null
+++ b/sysdeps/mach/hurd/x86_64/____longjmp_chk.S
@@ -0,0 +1,118 @@
+/* Checked longjmp support.  x86_64 Hurd version.
+   Copyright (C) 2001-2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <pointer_guard.h>
+#include <jmpbuf-offsets.h>
+#include <asm-syntax.h>
+#include <tcb-offsets.h>
+#include <jmp_buf-ssp.h>
+#include <signal-defines.h>
+
+#define SS_ONSTACK 1
+
+/* 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
+longjmp_msg:
+	.string "longjmp causes uninitialized stack frame"
+	.size	longjmp_msg, .-longjmp_msg
+
+
+# define CALL_FAIL	sub	$8, %RSP_LP;				      \
+			cfi_remember_state;				      \
+			cfi_def_cfa_offset(16);				      \
+			lea	longjmp_msg(%rip), %RDI_LP;		      \
+			call	HIDDEN_JUMPTARGET(__fortify_fail);	      \
+			nop;						      \
+			cfi_restore_state
+
+/* 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).  */
+	.text
+ENTRY(____longjmp_chk)
+	/* Restore registers.  */
+	mov	(JB_RSP*8)(%rdi), %R8_LP
+	mov	(JB_RBP*8)(%rdi),%R9_LP
+	mov	(JB_PC*8)(%rdi), %RDX_LP
+#ifdef PTR_DEMANGLE
+	PTR_DEMANGLE (%R8_LP)
+	PTR_DEMANGLE (%R9_LP)
+	PTR_DEMANGLE (%RDX_LP)
+#endif
+
+#if !defined (SHARED) || IS_IN (rtld)
+	cmpb	$0, __libc_tls_initialized(%rip)
+	jz	.Lok		/* TLS not initialized yet */
+#endif
+
+	movq %fs:SIGSTATE_OFFSET, %R10_LP
+	testq %R10_LP, %R10_LP
+	jz	.Lok		/* sigstate not initialized yet */
+
+	testl	$SS_ONSTACK, (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
+	jnz	.Lonstack
+
+	/* We were on the main stack.  Jumping to a higher-address
+           frame is always allowed, otherwise it's not allowed.  */
+	cmp	%R8_LP, %RSP_LP
+	jbe	.Lok
+
+.Lfail:	CALL_FAIL
+
+.Lonstack:
+	cmpq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R8_LP
+	jb	.Loks		/* Jumping below the altstack, switch */
+
+	movq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R11_LP
+	addq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SIZE__OFFSET)(%R10_LP), %R11_LP
+	cmpq	%R11_LP, %R8_LP
+	jb	.Lok		/* Jumping inside the altstack, do not switch */
+
+	/* Jumping above the altstack, switch */
+
+.Loks:
+	andl	$~(SS_ONSTACK), (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
+
+.Lok:
+	/* We add unwind information for the target here.  */
+	cfi_def_cfa(%rdi, 0)
+	cfi_register(%rsp,%r8)
+	cfi_register(%rbp,%r9)
+	cfi_register(%rip,%rdx)
+	cfi_offset(%rbx,JB_RBX*8)
+	cfi_offset(%r12,JB_R12*8)
+	cfi_offset(%r13,JB_R13*8)
+	cfi_offset(%r14,JB_R14*8)
+	cfi_offset(%r15,JB_R15*8)
+	movq	(JB_RBX*8)(%rdi), %rbx
+	movq	(JB_R12*8)(%rdi), %r12
+	movq	(JB_R13*8)(%rdi), %r13
+	movq	(JB_R14*8)(%rdi), %r14
+	movq	(JB_R15*8)(%rdi), %r15
+	/* Set return value for setjmp.  */
+	movl	%esi, %eax
+	mov	%R8_LP, %RSP_LP
+	movq	%r9,%rbp
+	jmpq	*%rdx
+END (____longjmp_chk)
diff --git a/sysdeps/mach/hurd/x86_64/__longjmp.S b/sysdeps/mach/hurd/x86_64/__longjmp.S
new file mode 100644
index 00000000..389c1d16
--- /dev/null
+++ b/sysdeps/mach/hurd/x86_64/__longjmp.S
@@ -0,0 +1,96 @@
+/* longjmp support.  x86_64/Hurd version.
+   Copyright (C) 2001-2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <pointer_guard.h>
+#include <jmpbuf-offsets.h>
+#include <asm-syntax.h>
+#include <tcb-offsets.h>
+#include <jmp_buf-ssp.h>
+#include <signal-defines.h>
+
+#define SS_ONSTACK 1
+
+/* Don't restore shadow stack register if shadow stack isn't enabled.  */
+#if !SHSTK_ENABLED
+# 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).  */
+	.text
+ENTRY(__longjmp)
+	/* Restore registers.  */
+	mov	(JB_RSP*8)(%rdi), %R8_LP
+	mov	(JB_RBP*8)(%rdi),%R9_LP
+	mov	(JB_PC*8)(%rdi), %RDX_LP
+#ifdef PTR_DEMANGLE
+	PTR_DEMANGLE (%R8_LP)
+	PTR_DEMANGLE (%R9_LP)
+	PTR_DEMANGLE (%RDX_LP)
+#endif
+
+#if !defined (SHARED) || IS_IN (rtld)
+	cmpb	$0, __libc_tls_initialized(%rip)
+	jz	.Lok		/* TLS not initialized yet */
+#endif
+
+	movq %fs:SIGSTATE_OFFSET, %R10_LP
+	testq %R10_LP, %R10_LP
+	jz	.Lok		/* sigstate not initialized yet */
+
+	testl	$SS_ONSTACK, (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
+	jz	.Lok
+
+.Lonstack:
+	cmpq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R8_LP
+	jb	.Loks		/* Jumping below the altstack, switch */
+
+	movq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R11_LP
+	addq	(HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SIZE__OFFSET)(%R10_LP), %R11_LP
+	cmpq	%R11_LP, %R8_LP
+	jb	.Lok		/* Jumping inside the altstack, do not switch */
+
+	/* Jumping above the altstack, switch */
+
+.Loks:
+	andl	$~(SS_ONSTACK), (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
+
+.Lok:
+	/* We add unwind information for the target here.  */
+	cfi_def_cfa(%rdi, 0)
+	cfi_register(%rsp,%r8)
+	cfi_register(%rbp,%r9)
+	cfi_register(%rip,%rdx)
+	cfi_offset(%rbx,JB_RBX*8)
+	cfi_offset(%r12,JB_R12*8)
+	cfi_offset(%r13,JB_R13*8)
+	cfi_offset(%r14,JB_R14*8)
+	cfi_offset(%r15,JB_R15*8)
+	movq	(JB_RBX*8)(%rdi), %rbx
+	movq	(JB_R12*8)(%rdi), %r12
+	movq	(JB_R13*8)(%rdi), %r13
+	movq	(JB_R14*8)(%rdi), %r14
+	movq	(JB_R15*8)(%rdi), %r15
+	/* Set return value for setjmp.  */
+	movl	%esi, %eax
+	mov	%R8_LP, %RSP_LP
+	movq	%r9,%rbp
+	jmpq	*%rdx
+END (__longjmp)
-- 
2.40.1