[Qemu-devel] [PATCH v2 0/5] linux-user: safe_syscall updates

[Qemu-devel] [PATCH v2 0/5] linux-user: safe_syscall updates

[Richard Henderson]

Rebased on Riku's linux-user-for-upstream branch.
Fixed some nits that Peter pointed out.
Fixed the ppc64 version to properly return -errno.

Retested all except s390x, which is, at the moment, inconvenient.


r~


Richard Henderson (5):
  linux-user: Provide safe_syscall for i386
  linux-user: Provide safe_syscall for arm
  linux-user: Provide safe_syscall for aarch64
  linux-user: Provide safe_syscall for s390x
  linux-user: Provide safe_syscall for ppc64

 linux-user/host/aarch64/hostdep.h          |  23 ++++++
 linux-user/host/aarch64/safe-syscall.inc.S |  75 +++++++++++++++++++
 linux-user/host/arm/hostdep.h              |  23 ++++++
 linux-user/host/arm/safe-syscall.inc.S     |  90 +++++++++++++++++++++++
 linux-user/host/i386/hostdep.h             |  23 ++++++
 linux-user/host/i386/safe-syscall.inc.S    | 112 +++++++++++++++++++++++++++++
 linux-user/host/ppc64/hostdep.h            |  23 ++++++
 linux-user/host/ppc64/safe-syscall.inc.S   |  92 ++++++++++++++++++++++++
 linux-user/host/s390x/hostdep.h            |  23 ++++++
 linux-user/host/s390x/safe-syscall.inc.S   |  90 +++++++++++++++++++++++
 10 files changed, 574 insertions(+)
 create mode 100644 linux-user/host/aarch64/safe-syscall.inc.S
 create mode 100644 linux-user/host/arm/safe-syscall.inc.S
 create mode 100644 linux-user/host/i386/safe-syscall.inc.S
 create mode 100644 linux-user/host/ppc64/safe-syscall.inc.S
 create mode 100644 linux-user/host/s390x/safe-syscall.inc.S

-- 
2.5.5

[Qemu-devel] [PATCH v2 1/5] linux-user: Provide safe_syscall for i386

[Richard Henderson]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/host/i386/hostdep.h          |  23 +++++++
 linux-user/host/i386/safe-syscall.inc.S | 112 ++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 linux-user/host/i386/safe-syscall.inc.S

diff --git a/linux-user/host/i386/hostdep.h b/linux-user/host/i386/hostdep.h
index 7609bf5..5a12f4a 100644
--- a/linux-user/host/i386/hostdep.h
+++ b/linux-user/host/i386/hostdep.h
@@ -12,4 +12,27 @@
 #ifndef QEMU_HOSTDEP_H
 #define QEMU_HOSTDEP_H
 
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    struct ucontext *uc = puc;
+    greg_t *pcreg = &uc->uc_mcontext.gregs[REG_EIP];
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
 #endif
diff --git a/linux-user/host/i386/safe-syscall.inc.S b/linux-user/host/i386/safe-syscall.inc.S
new file mode 100644
index 0000000..766d0de
--- /dev/null
+++ b/linux-user/host/i386/safe-syscall.inc.S
@@ -0,0 +1,112 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, @function
+
+	/* This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+safe_syscall_base:
+	.cfi_startproc
+	push	%ebp
+	.cfi_adjust_cfa_offset 4
+	.cfi_rel_offset ebp, 0
+	push	%esi
+	.cfi_adjust_cfa_offset 4
+	.cfi_rel_offset esi, 0
+	push	%edi
+	.cfi_adjust_cfa_offset 4
+	.cfi_rel_offset edi, 0
+	push	%ebx
+	.cfi_adjust_cfa_offset 4
+	.cfi_rel_offset ebx, 0
+
+	/* The syscall calling convention isn't the same as the C one:
+	 * we enter with 0(%esp) == return address
+	 *               4(%esp) == *signal_pending
+	 *               8(%esp) == syscall number
+	 *               12(%esp) ... 32(%esp) == syscall arguments
+	 *               and return the result in eax
+	 * and the syscall instruction needs
+	 *               eax == syscall number
+	 *               ebx, ecx, edx, esi, edi, ebp == syscall arguments
+	 *               and returns the result in eax
+	 * Shuffle everything around appropriately.
+	 * Note the 16 bytes that we pushed to save registers.
+	 */
+	mov	12+16(%esp), %ebx	/* the syscall arguments */
+	mov	16+16(%esp), %ecx
+	mov	20+16(%esp), %edx
+	mov	24+16(%esp), %esi
+	mov	28+16(%esp), %edi
+	mov	32+16(%esp), %ebp
+
+	/* This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* if signal_pending is non-zero, don't do the call */
+	mov	4+16(%esp), %eax	/* signal_pending */
+	cmp	$0, (%eax)
+	jnz	1f
+	mov	8+16(%esp), %eax	/* syscall number */
+	int	$0x80
+safe_syscall_end:
+	/* code path for having successfully executed the syscall */
+	pop	%ebx
+	.cfi_remember_state
+	.cfi_def_cfa_offset -4
+	.cfi_restore ebx
+	pop	%edi
+	.cfi_def_cfa_offset -4
+	.cfi_restore edi
+	pop	%esi
+	.cfi_def_cfa_offset -4
+	.cfi_restore esi
+	pop	%ebp
+	.cfi_def_cfa_offset -4
+	.cfi_restore ebp
+	ret
+
+1:
+	/* code path when we didn't execute the syscall */
+	.cfi_restore_state
+	mov	$-TARGET_ERESTARTSYS, %eax
+	pop	%ebx
+	.cfi_def_cfa_offset -4
+	.cfi_restore ebx
+	pop	%edi
+	.cfi_def_cfa_offset -4
+	.cfi_restore edi
+	pop	%esi
+	.cfi_def_cfa_offset -4
+	.cfi_restore esi
+	pop	%ebp
+	.cfi_def_cfa_offset -4
+	.cfi_restore ebp
+	ret
+	.cfi_endproc
+
+	.size	safe_syscall_base, .-safe_syscall_base
-- 
2.5.5

[Qemu-devel] [PATCH v2 2/5] linux-user: Provide safe_syscall for arm

[Richard Henderson]

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/host/arm/hostdep.h          | 23 +++++++++
 linux-user/host/arm/safe-syscall.inc.S | 90 ++++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 linux-user/host/arm/safe-syscall.inc.S

diff --git a/linux-user/host/arm/hostdep.h b/linux-user/host/arm/hostdep.h
index 7609bf5..8e1ff2f 100644
--- a/linux-user/host/arm/hostdep.h
+++ b/linux-user/host/arm/hostdep.h
@@ -12,4 +12,27 @@
 #ifndef QEMU_HOSTDEP_H
 #define QEMU_HOSTDEP_H
 
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    struct ucontext *uc = puc;
+    unsigned long *pcreg = &uc->uc_mcontext.arm_pc;
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
 #endif
diff --git a/linux-user/host/arm/safe-syscall.inc.S b/linux-user/host/arm/safe-syscall.inc.S
new file mode 100644
index 0000000..88c4958
--- /dev/null
+++ b/linux-user/host/arm/safe-syscall.inc.S
@@ -0,0 +1,90 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, %function
+
+	.cfi_sections	.debug_frame
+
+	.text
+	.syntax unified
+	.arm
+	.align 2
+
+	/* This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+safe_syscall_base:
+	.fnstart
+	.cfi_startproc
+	mov	r12, sp			/* save entry stack */
+	push	{ r4, r5, r6, r7, r8, lr }
+	.save	{ r4, r5, r6, r7, r8, lr }
+	.cfi_adjust_cfa_offset 24
+	.cfi_rel_offset r4, 0
+	.cfi_rel_offset r5, 4
+	.cfi_rel_offset r6, 8
+	.cfi_rel_offset r7, 12
+	.cfi_rel_offset r8, 16
+	.cfi_rel_offset lr, 20
+
+	/* The syscall calling convention isn't the same as the C one:
+	 * we enter with r0 == *signal_pending
+	 *               r1 == syscall number
+	 *               r2, r3, [sp+0] ... [sp+12] == syscall arguments
+	 *               and return the result in r0
+	 * and the syscall instruction needs
+	 *               r7 == syscall number
+	 *               r0 ... r6 == syscall arguments
+	 *               and returns the result in r0
+	 * Shuffle everything around appropriately.
+	 * Note the 16 bytes that we pushed to save registers.
+	 */
+	mov	r8, r0			/* copy signal_pending */
+	mov	r7, r1			/* syscall number */
+	mov	r0, r2			/* syscall args */
+	mov	r1, r3
+	ldm	r12, { r2, r3, r4, r5, r6 }
+
+	/* This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* if signal_pending is non-zero, don't do the call */
+	ldr	r12, [r8]		/* signal_pending */
+	tst	r12, r12
+	bne	1f
+	swi	0
+safe_syscall_end:
+	/* code path for having successfully executed the syscall */
+	pop	{ r4, r5, r6, r7, r8, pc }
+
+1:
+	/* code path when we didn't execute the syscall */
+	ldr	r0, =-TARGET_ERESTARTSYS
+	pop	{ r4, r5, r6, r7, r8, pc }
+	.fnend
+	.cfi_endproc
+
+	.size	safe_syscall_base, .-safe_syscall_base
-- 
2.5.5

[Qemu-devel] [PATCH v2 3/5] linux-user: Provide safe_syscall for aarch64

[Richard Henderson]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/host/aarch64/hostdep.h          | 23 +++++++++
 linux-user/host/aarch64/safe-syscall.inc.S | 75 ++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 linux-user/host/aarch64/safe-syscall.inc.S

diff --git a/linux-user/host/aarch64/hostdep.h b/linux-user/host/aarch64/hostdep.h
index 7609bf5..b79eaf1 100644
--- a/linux-user/host/aarch64/hostdep.h
+++ b/linux-user/host/aarch64/hostdep.h
@@ -12,4 +12,27 @@
 #ifndef QEMU_HOSTDEP_H
 #define QEMU_HOSTDEP_H
 
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    struct ucontext *uc = puc;
+    __u64 *pcreg = &uc->uc_mcontext.pc;
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
 #endif
diff --git a/linux-user/host/aarch64/safe-syscall.inc.S b/linux-user/host/aarch64/safe-syscall.inc.S
new file mode 100644
index 0000000..e4058bb
--- /dev/null
+++ b/linux-user/host/aarch64/safe-syscall.inc.S
@@ -0,0 +1,75 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, #function
+	.type	safe_syscall_start, #function
+	.type	safe_syscall_end, #function
+
+	/* This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+safe_syscall_base:
+	.cfi_startproc
+	/* The syscall calling convention isn't the same as the
+	 * C one:
+	 * we enter with x0 == *signal_pending
+	 *               x1 == syscall number
+	 *               x2 ... x7, (stack) == syscall arguments
+	 *               and return the result in x0
+	 * and the syscall instruction needs
+	 *               x8 == syscall number
+	 *               x0 ... x6 == syscall arguments
+	 *               and returns the result in x0
+	 * Shuffle everything around appropriately.
+	 */
+	mov	x9, x0		/* signal_pending pointer */
+	mov	x8, x1		/* syscall number */
+	mov	x0, x2		/* syscall arguments */
+	mov	x1, x3
+	mov	x2, x4
+	mov	x3, x5
+	mov	x4, x6
+	mov	x6, x7
+	ldr	x7, [sp]
+
+	/* This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* if signal_pending is non-zero, don't do the call */
+	ldr	w10, [x9]
+	cbnz	w10, 0f 
+	svc	0x0
+safe_syscall_end:
+	/* code path for having successfully executed the syscall */
+	ret
+
+0:
+	/* code path when we didn't execute the syscall */
+	mov	x0, #-TARGET_ERESTARTSYS
+	ret
+	.cfi_endproc
+
+	.size	safe_syscall_base, .-safe_syscall_base
-- 
2.5.5

[Qemu-devel] [PATCH v2 4/5] linux-user: Provide safe_syscall for s390x

[Richard Henderson]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/host/s390x/hostdep.h          | 23 ++++++++
 linux-user/host/s390x/safe-syscall.inc.S | 90 ++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 linux-user/host/s390x/safe-syscall.inc.S

diff --git a/linux-user/host/s390x/hostdep.h b/linux-user/host/s390x/hostdep.h
index 7609bf5..e95871c 100644
--- a/linux-user/host/s390x/hostdep.h
+++ b/linux-user/host/s390x/hostdep.h
@@ -12,4 +12,27 @@
 #ifndef QEMU_HOSTDEP_H
 #define QEMU_HOSTDEP_H
 
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    struct ucontext *uc = puc;
+    unsigned long *pcreg = &uc->uc_mcontext.psw.addr;
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
 #endif
diff --git a/linux-user/host/s390x/safe-syscall.inc.S b/linux-user/host/s390x/safe-syscall.inc.S
new file mode 100644
index 0000000..f1b446a
--- /dev/null
+++ b/linux-user/host/s390x/safe-syscall.inc.S
@@ -0,0 +1,90 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, @function
+
+	/* This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+safe_syscall_base:
+	.cfi_startproc
+	stmg	%r6,%r15,48(%r15)	/* save all call-saved registers */
+	.cfi_offset %r15,-40
+	.cfi_offset %r14,-48
+	.cfi_offset %r13,-56
+	.cfi_offset %r12,-64
+	.cfi_offset %r11,-72
+	.cfi_offset %r10,-80
+	.cfi_offset %r9,-88
+	.cfi_offset %r8,-96
+	.cfi_offset %r7,-104
+	.cfi_offset %r6,-112
+	lgr	%r1,%r15
+	lg	%r0,8(%r15)		/* load eos */
+	aghi	%r15,-160
+	.cfi_adjust_cfa_offset 160
+	stg	%r1,0(%r15)		/* store back chain */
+	stg	%r0,8(%r15)		/* store eos */
+
+	/* The syscall calling convention isn't the same as the
+	 * C one:
+	 * we enter with r2 == *signal_pending
+	 *               r3 == syscall number
+	 *               r4, r5, r6, (stack) == syscall arguments
+	 *               and return the result in r2
+	 * and the syscall instruction needs
+	 *               r1 == syscall number
+	 *               r2 ... r7 == syscall arguments
+	 *               and returns the result in r2
+	 * Shuffle everything around appropriately.
+	 */
+	lgr	%r8,%r2			/* signal_pending pointer */
+	lgr	%r1,%r3			/* syscall number */
+	lgr	%r2,%r4			/* syscall args */
+	lgr	%r3,%r5
+	lgr	%r4,%r6
+	lmg	%r5,%r7,320(%r15)
+
+	/* This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* if signal_pending is non-zero, don't do the call */
+	lt	%r0,0(%r8)
+	jne	2f
+	svc	0
+safe_syscall_end:
+
+1:	lg	%r15,0(%r15)		/* load back chain */
+	.cfi_remember_state
+	.cfi_adjust_cfa_offset -160
+	lmg	%r6,%r15,48(%r15)	/* load saved registers */
+	br	%r14
+	.cfi_restore_state
+2:	lghi	%r2, -TARGET_ERESTARTSYS
+	j	1b
+	.cfi_endproc
+
+	.size	safe_syscall_base, .-safe_syscall_base
-- 
2.5.5

[Qemu-devel] [PATCH v2 5/5] linux-user: Provide safe_syscall for ppc64

[Richard Henderson]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 linux-user/host/ppc64/hostdep.h          | 23 ++++++++
 linux-user/host/ppc64/safe-syscall.inc.S | 92 ++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 linux-user/host/ppc64/safe-syscall.inc.S

diff --git a/linux-user/host/ppc64/hostdep.h b/linux-user/host/ppc64/hostdep.h
index 7609bf5..310e7d1 100644
--- a/linux-user/host/ppc64/hostdep.h
+++ b/linux-user/host/ppc64/hostdep.h
@@ -12,4 +12,27 @@
 #ifndef QEMU_HOSTDEP_H
 #define QEMU_HOSTDEP_H
 
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    struct ucontext *uc = puc;
+    unsigned long *pcreg = &uc->uc_mcontext.gp_regs[PT_NIP];
+
+    if (*pcreg > (uintptr_t)safe_syscall_start
+        && *pcreg < (uintptr_t)safe_syscall_end) {
+        *pcreg = (uintptr_t)safe_syscall_start;
+    }
+}
+
+#endif /* __ASSEMBLER__ */
+
 #endif
diff --git a/linux-user/host/ppc64/safe-syscall.inc.S b/linux-user/host/ppc64/safe-syscall.inc.S
new file mode 100644
index 0000000..d30050a
--- /dev/null
+++ b/linux-user/host/ppc64/safe-syscall.inc.S
@@ -0,0 +1,92 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by linux-user/safe-syscall.S
+ *
+ * Written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+	.global safe_syscall_base
+	.global safe_syscall_start
+	.global safe_syscall_end
+	.type	safe_syscall_base, @function
+
+	.text
+
+	/* This is the entry point for making a system call. The calling
+	 * convention here is that of a C varargs function with the
+	 * first argument an 'int *' to the signal_pending flag, the
+	 * second one the system call number (as a 'long'), and all further
+	 * arguments being syscall arguments (also 'long').
+	 * We return a long which is the syscall's return value, which
+	 * may be negative-errno on failure. Conversion to the
+	 * -1-and-errno-set convention is done by the calling wrapper.
+	 */
+#if _CALL_ELF == 2
+safe_syscall_base:
+	.cfi_startproc
+	.localentry safe_syscall_base,0
+#else
+	.section ".opd","aw"
+	.align	3
+safe_syscall_base:
+	.quad	.L.safe_syscall_base,.TOC.@tocbase,0
+	.previous
+.L.safe_syscall_base:
+	.cfi_startproc
+#endif
+	/* We enter with r3 == *signal_pending
+	 *               r4 == syscall number
+	 *               r5 ... r10 == syscall arguments
+	 *               and return the result in r3
+	 * and the syscall instruction needs
+	 *               r0 == syscall number
+	 *               r3 ... r8 == syscall arguments
+	 *               and returns the result in r3
+	 * Shuffle everything around appropriately.
+	 */
+	mr	11, 3	/* signal_pending */
+	mr	0, 4	/* syscall number */
+	mr	3, 5	/* syscall arguments */
+	mr	4, 6
+	mr	5, 7
+	mr	6, 8
+	mr	7, 9
+	mr	8, 10
+
+	/* This next sequence of code works in conjunction with the
+	 * rewind_if_safe_syscall_function(). If a signal is taken
+	 * and the interrupted PC is anywhere between 'safe_syscall_start'
+	 * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+	 * The code sequence must therefore be able to cope with this, and
+	 * the syscall instruction must be the final one in the sequence.
+	 */
+safe_syscall_start:
+	/* if signal_pending is non-zero, don't do the call */
+	lwz	12, 0(11)
+	cmpwi	0, 12, 0
+	bne-	0f
+	sc
+safe_syscall_end:
+	/* code path when we did execute the syscall */
+	bnslr+
+
+	/* syscall failed; return negative errno */
+	neg	3, 3
+	blr
+
+	/* code path when we didn't execute the syscall */
+0:	addi	3, 0, -TARGET_ERESTARTSYS
+	blr
+	.cfi_endproc
+
+#if _CALL_ELF == 2
+	.size	safe_syscall_base, .-safe_syscall_base
+#else
+	.size	safe_syscall_base, .-.L.safe_syscall_base
+	.size	.L.safe_syscall_base, .-.L.safe_syscall_base
+#endif
-- 
2.5.5

Re: [Qemu-devel] [PATCH v2 3/5] linux-user: Provide safe_syscall for aarch64

[Peter Maydell]

On 22 June 2016 at 01:32, Richard Henderson <rth@twiddle.net> wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  linux-user/host/aarch64/hostdep.h          | 23 +++++++++
>  linux-user/host/aarch64/safe-syscall.inc.S | 75 ++++++++++++++++++++++++++++++
>  2 files changed, 98 insertions(+)
>  create mode 100644 linux-user/host/aarch64/safe-syscall.inc.S

> +safe_syscall_base:
> +       .cfi_startproc
> +       /* The syscall calling convention isn't the same as the
> +        * C one:
> +        * we enter with x0 == *signal_pending
> +        *               x1 == syscall number
> +        *               x2 ... x7, (stack) == syscall arguments
> +        *               and return the result in x0
> +        * and the syscall instruction needs
> +        *               x8 == syscall number
> +        *               x0 ... x6 == syscall arguments
> +        *               and returns the result in x0
> +        * Shuffle everything around appropriately.
> +        */
> +       mov     x9, x0          /* signal_pending pointer */
> +       mov     x8, x1          /* syscall number */
> +       mov     x0, x2          /* syscall arguments */
> +       mov     x1, x3
> +       mov     x2, x4
> +       mov     x3, x5
> +       mov     x4, x6
> +       mov     x6, x7
> +       ldr     x7, [sp]

Comment says "x0 ... x6 == syscall arguments" but the code loads x7 too.

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2 1/5] linux-user: Provide safe_syscall for i386

[Peter Maydell]

On 22 June 2016 at 01:32, Richard Henderson <rth@twiddle.net> wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  linux-user/host/i386/hostdep.h          |  23 +++++++
>  linux-user/host/i386/safe-syscall.inc.S | 112 ++++++++++++++++++++++++++++++++
>  2 files changed, 135 insertions(+)
>  create mode 100644 linux-user/host/i386/safe-syscall.inc.S

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2 0/5] linux-user: safe_syscall updates

[Peter Maydell]

On 22 June 2016 at 01:32, Richard Henderson <rth@twiddle.net> wrote:
> Rebased on Riku's linux-user-for-upstream branch.
> Fixed some nits that Peter pointed out.
> Fixed the ppc64 version to properly return -errno.
>
> Retested all except s390x, which is, at the moment, inconvenient.

I don't know enough s390/ppc to really review those two patches
but they look right to me.

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2 0/5] linux-user: safe_syscall updates

[Riku Voipio]

On Thu, Jun 23, 2016 at 01:10:40PM +0100, Peter Maydell wrote:
> On 22 June 2016 at 01:32, Richard Henderson <rth@twiddle.net> wrote:
> > Rebased on Riku's linux-user-for-upstream branch.
> > Fixed some nits that Peter pointed out.
> > Fixed the ppc64 version to properly return -errno.
> >
> > Retested all except s390x, which is, at the moment, inconvenient.
 
> I don't know enough s390/ppc to really review those two patches
> but they look right to me.

All pushed to linux-user, thanks!

https://git.linaro.org/people/riku.voipio/qemu.git/shortlog/refs/heads/linux-user-for-upstream

I'll craft a pull req to get these in well before soft freeze.

Riku