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[uml-devel] [PATCH 3/9] um: Save FPU registers between task switches
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From: Richard W. <ri...@no...> - 2011-08-29 16:04:27
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From: Ingo van Lil <in...@gm...>
Some time ago Jeff prepared a patch (42daba3) for UML to stop saving the
process FP state between task switches. The assumption was that since
with SKAS0 every guest process runs inside a host process context the
host OS will take care of keeping the proper FP state. Unfortunately
this is not true for multi-threaded applications, where all guest
threads share a single host process context yet all may use the FPU on
their own. Although I haven't verified it I suspect things to be even
worse in SKAS3 mode where all guest processes run inside a single host
process.
The patch below reintroduces the saving and restoring of the FP context
between task switches.
Signed-off-by: Ingo van Lil <in...@gm...>
Signed-off-by: Richard Weinberger <ri...@no...>
Reported-by: gun...@ho...
Tested-by: gun...@ho...
CC: Stanislav Meduna <st...@me...>
[ri...@no...: Ingo posted this patch in 2009, sadly it was never applied
and got lost. Now in 2011 the problem was reported by Gunnar.]
---
arch/um/include/shared/registers.h | 2 +-
arch/um/kernel/process.c | 2 +-
arch/um/os-Linux/registers.c | 9 ++++++++-
arch/um/os-Linux/skas/mem.c | 2 +-
arch/um/os-Linux/skas/process.c | 19 ++++++++++++++++++-
arch/um/sys-i386/shared/sysdep/ptrace.h | 1 +
arch/um/sys-x86_64/shared/sysdep/ptrace.h | 1 +
7 files changed, 31 insertions(+), 5 deletions(-)
diff --git a/arch/um/include/shared/registers.h b/arch/um/include/shared/registers.h
index b0b4589..f1e0aa5 100644
--- a/arch/um/include/shared/registers.h
+++ b/arch/um/include/shared/registers.h
@@ -16,7 +16,7 @@ extern int restore_fpx_registers(int pid, unsigned long *fp_regs);
extern int save_registers(int pid, struct uml_pt_regs *regs);
extern int restore_registers(int pid, struct uml_pt_regs *regs);
extern int init_registers(int pid);
-extern void get_safe_registers(unsigned long *regs);
+extern void get_safe_registers(unsigned long *regs, unsigned long *fp_regs);
extern unsigned long get_thread_reg(int reg, jmp_buf *buf);
extern int get_fp_registers(int pid, unsigned long *regs);
extern int put_fp_registers(int pid, unsigned long *regs);
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index fab4371..21c1ae7 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -202,7 +202,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
arch_copy_thread(¤t->thread.arch, &p->thread.arch);
}
else {
- get_safe_registers(p->thread.regs.regs.gp);
+ get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
p->thread.request.u.thread = current->thread.request.u.thread;
handler = new_thread_handler;
}
diff --git a/arch/um/os-Linux/registers.c b/arch/um/os-Linux/registers.c
index 830fe6a..b866b9e 100644
--- a/arch/um/os-Linux/registers.c
+++ b/arch/um/os-Linux/registers.c
@@ -8,6 +8,8 @@
#include <string.h>
#include <sys/ptrace.h>
#include "sysdep/ptrace.h"
+#include "sysdep/ptrace_user.h"
+#include "registers.h"
int save_registers(int pid, struct uml_pt_regs *regs)
{
@@ -32,6 +34,7 @@ int restore_registers(int pid, struct uml_pt_regs *regs)
/* This is set once at boot time and not changed thereafter */
static unsigned long exec_regs[MAX_REG_NR];
+static unsigned long exec_fp_regs[FP_SIZE];
int init_registers(int pid)
{
@@ -42,10 +45,14 @@ int init_registers(int pid)
return -errno;
arch_init_registers(pid);
+ get_fp_registers(pid, exec_fp_regs);
return 0;
}
-void get_safe_registers(unsigned long *regs)
+void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
{
memcpy(regs, exec_regs, sizeof(exec_regs));
+
+ if (fp_regs)
+ memcpy(fp_regs, exec_fp_regs, sizeof(exec_fp_regs));
}
diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index d261f17..e771398 100644
--- a/arch/um/os-Linux/skas/mem.c
+++ b/arch/um/os-Linux/skas/mem.c
@@ -39,7 +39,7 @@ static unsigned long syscall_regs[MAX_REG_NR];
static int __init init_syscall_regs(void)
{
- get_safe_registers(syscall_regs);
+ get_safe_registers(syscall_regs, NULL);
syscall_regs[REGS_IP_INDEX] = STUB_CODE +
((unsigned long) &batch_syscall_stub -
(unsigned long) &__syscall_stub_start);
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index d6e0a22..dee0e8c 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -373,6 +373,9 @@ void userspace(struct uml_pt_regs *regs)
if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
fatal_sigsegv();
+ if (put_fp_registers(pid, regs->fp))
+ fatal_sigsegv();
+
/* Now we set local_using_sysemu to be used for one loop */
local_using_sysemu = get_using_sysemu();
@@ -399,6 +402,12 @@ void userspace(struct uml_pt_regs *regs)
fatal_sigsegv();
}
+ if (get_fp_registers(pid, regs->fp)) {
+ printk(UM_KERN_ERR "userspace - get_fp_registers failed, "
+ "errno = %d\n", errno);
+ fatal_sigsegv();
+ }
+
UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
if (WIFSTOPPED(status)) {
@@ -457,10 +466,11 @@ void userspace(struct uml_pt_regs *regs)
}
static unsigned long thread_regs[MAX_REG_NR];
+static unsigned long thread_fp_regs[FP_SIZE];
static int __init init_thread_regs(void)
{
- get_safe_registers(thread_regs);
+ get_safe_registers(thread_regs, thread_fp_regs);
/* Set parent's instruction pointer to start of clone-stub */
thread_regs[REGS_IP_INDEX] = STUB_CODE +
(unsigned long) stub_clone_handler -
@@ -503,6 +513,13 @@ int copy_context_skas0(unsigned long new_stack, int pid)
return err;
}
+ err = put_fp_registers(pid, thread_fp_regs);
+ if (err < 0) {
+ printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
+ "failed, pid = %d, err = %d\n", pid, err);
+ return err;
+ }
+
/* set a well known return code for detection of child write failure */
child_data->err = 12345678;
diff --git a/arch/um/sys-i386/shared/sysdep/ptrace.h b/arch/um/sys-i386/shared/sysdep/ptrace.h
index d50e62e..c398a50 100644
--- a/arch/um/sys-i386/shared/sysdep/ptrace.h
+++ b/arch/um/sys-i386/shared/sysdep/ptrace.h
@@ -53,6 +53,7 @@ extern int sysemu_supported;
struct uml_pt_regs {
unsigned long gp[MAX_REG_NR];
+ unsigned long fp[HOST_FPX_SIZE];
struct faultinfo faultinfo;
long syscall;
int is_user;
diff --git a/arch/um/sys-x86_64/shared/sysdep/ptrace.h b/arch/um/sys-x86_64/shared/sysdep/ptrace.h
index fdba545..8ee8f8e 100644
--- a/arch/um/sys-x86_64/shared/sysdep/ptrace.h
+++ b/arch/um/sys-x86_64/shared/sysdep/ptrace.h
@@ -85,6 +85,7 @@
struct uml_pt_regs {
unsigned long gp[MAX_REG_NR];
+ unsigned long fp[HOST_FP_SIZE];
struct faultinfo faultinfo;
long syscall;
int is_user;
--
1.7.6.1
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