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authorIngo van Lil <inguin@gmx.de>2011-09-14 16:21:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-09-14 18:09:37 -0700
commitfbfe9c847edf57ac8232aeafb290f272289893a3 (patch)
treeda25f3f4ece74b9fa328ce3884f19ff18eff516d /arch/um/os-Linux/skas
parentb40997b872cdb70140f127af6069f00a86b6cf81 (diff)
um: Save FPU registers between task switches
Some time ago Jeff prepared 42daba316557 ("uml: stop saving process FP state") 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 reintroduces the saving and restoring of the FP context between task switches. [richard@nod.at: Ingo posted this patch in 2009, sadly it was never applied and got lost. Now in 2011 the problem was reported by Gunnar.] Signed-off-by: Ingo van Lil <inguin@gmx.de> Signed-off-by: Richard Weinberger <richard@nod.at> Reported-by: <gunnarlindroth@hotmail.com> Tested-by: <gunnarlindroth@hotmail.com> Cc: Stanislav Meduna <stano@meduna.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um/os-Linux/skas')
-rw-r--r--arch/um/os-Linux/skas/mem.c2
-rw-r--r--arch/um/os-Linux/skas/process.c19
2 files changed, 19 insertions, 2 deletions
diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index d261f170d120..e771398be5f3 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 d6e0a2234b86..dee0e8cf8ad0 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;

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