svn commit: r297613 - in head/sys: amd64/cloudabi64 arm64/cloudabi64 compat/cloudabi64 contrib/cloudabi
Ed Schouten
ed at FreeBSD.org
Wed Apr 6 11:11:32 UTC 2016
Author: ed
Date: Wed Apr 6 11:11:31 2016
New Revision: 297613
URL: https://svnweb.freebsd.org/changeset/base/297613
Log:
Make CloudABI's way of doing TLS more friendly to userspace emulators.
We're currently seeing how hard it would be to run CloudABI binaries on
operating systems cannot be modified easily (Windows, Mac OS X). The
idea is that we want to just run them without any sandboxing. Now
that CloudABI executables are PIE, this is already a bit easier, but TLS
is still problematic:
- CloudABI executables want to write to the %fs, which typically
requires extra system calls by the emulator every time it needs to
switch between CloudABI's and its own TLS.
- If CloudABI executables overwrite the %fs base unconditionally, it
also becomes harder for the emulator to store a backup of the old
value of %fs. To solve this, let's no longer overwrite %fs, but just
%fs:0.
As CloudABI's C library does not use a TCB, this space can now be used
by an emulator to keep track of its internal state. The executable can
now safely overwrite %fs:0, as long as it makes sure that the TCB is
copied over to the new TLS area.
Ensure that there is an initial TLS area set up when the process starts,
only containing a bogus TCB. We don't really care about its contents on
FreeBSD.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D5836
Modified:
head/sys/amd64/cloudabi64/cloudabi64_sysvec.c
head/sys/arm64/cloudabi64/cloudabi64_sysvec.c
head/sys/compat/cloudabi64/cloudabi64_module.c
head/sys/compat/cloudabi64/cloudabi64_thread.c
head/sys/compat/cloudabi64/cloudabi64_util.h
head/sys/contrib/cloudabi/cloudabi64_types.h
Modified: head/sys/amd64/cloudabi64/cloudabi64_sysvec.c
==============================================================================
--- head/sys/amd64/cloudabi64/cloudabi64_sysvec.c Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/amd64/cloudabi64/cloudabi64_sysvec.c Wed Apr 6 11:11:31 2016 (r297613)
@@ -27,6 +27,7 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
+#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/sysent.h>
@@ -47,6 +48,45 @@ extern const char *cloudabi64_syscallnam
extern struct sysent cloudabi64_sysent[];
static int
+cloudabi64_fixup_tcb(register_t **stack_base, struct image_params *imgp)
+{
+ int error;
+ register_t tcbptr;
+
+ /* Place auxiliary vector and TCB on the stack. */
+ error = cloudabi64_fixup(stack_base, imgp);
+ if (error != 0)
+ return (error);
+
+ /*
+ * On x86-64, the TCB is referred to by %fs:0. Take some space
+ * from the top of the stack to store a single element array,
+ * containing a pointer to the TCB. %fs base will point to this.
+ */
+ tcbptr = (register_t)*stack_base;
+ return (copyout(&tcbptr, --*stack_base, sizeof(tcbptr)));
+}
+
+static void
+cloudabi64_proc_setregs(struct thread *td, struct image_params *imgp,
+ unsigned long stack)
+{
+ struct trapframe *regs;
+
+ exec_setregs(td, imgp, stack);
+
+ /*
+ * The stack now contains a pointer to the TCB, the TCB itself,
+ * and the auxiliary vector. Let %rdx point to the auxiliary
+ * vector, and set %fs base to the address of the TCB.
+ */
+ regs = td->td_frame;
+ regs->tf_rdi = stack + sizeof(register_t) +
+ roundup(sizeof(cloudabi64_tcb_t), sizeof(register_t));
+ (void)cpu_set_user_tls(td, (void *)stack);
+}
+
+static int
cloudabi64_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
{
struct trapframe *frame = td->td_frame;
@@ -109,16 +149,29 @@ cloudabi64_schedtail(struct thread *td)
frame->tf_rdx = td->td_tid;
}
-void
+int
cloudabi64_thread_setregs(struct thread *td,
- const cloudabi64_threadattr_t *attr)
+ const cloudabi64_threadattr_t *attr, uint64_t tcb)
{
struct trapframe *frame;
stack_t stack;
+ uint64_t tcbptr;
+ int error;
+
+ /*
+ * On x86-64, the TCB is referred to by %fs:0. Take some space
+ * from the top of the stack to store a single element array,
+ * containing a pointer to the TCB. %fs base will point to this.
+ */
+ tcbptr = rounddown(attr->stack + attr->stack_size - sizeof(tcbptr),
+ _Alignof(tcbptr));
+ error = copyout(&tcb, (void *)tcbptr, sizeof(tcb));
+ if (error != 0)
+ return (error);
/* Perform standard register initialization. */
stack.ss_sp = (void *)attr->stack;
- stack.ss_size = attr->stack_size;
+ stack.ss_size = tcbptr - attr->stack;
cpu_set_upcall_kse(td, (void *)attr->entry_point, NULL, &stack);
/*
@@ -129,12 +182,14 @@ cloudabi64_thread_setregs(struct thread
frame = td->td_frame;
frame->tf_rdi = td->td_tid;
frame->tf_rsi = attr->argument;
+
+ return (cpu_set_user_tls(td, (void *)tcbptr));
}
static struct sysentvec cloudabi64_elf_sysvec = {
.sv_size = CLOUDABI64_SYS_MAXSYSCALL,
.sv_table = cloudabi64_sysent,
- .sv_fixup = cloudabi64_fixup,
+ .sv_fixup = cloudabi64_fixup_tcb,
.sv_name = "CloudABI ELF64",
.sv_coredump = elf64_coredump,
.sv_pagesize = PAGE_SIZE,
@@ -143,6 +198,7 @@ static struct sysentvec cloudabi64_elf_s
.sv_usrstack = USRSTACK,
.sv_stackprot = VM_PROT_READ | VM_PROT_WRITE,
.sv_copyout_strings = cloudabi64_copyout_strings,
+ .sv_setregs = cloudabi64_proc_setregs,
.sv_flags = SV_ABI_CLOUDABI | SV_CAPSICUM | SV_LP64,
.sv_set_syscall_retval = cloudabi64_set_syscall_retval,
.sv_fetch_syscall_args = cloudabi64_fetch_syscall_args,
Modified: head/sys/arm64/cloudabi64/cloudabi64_sysvec.c
==============================================================================
--- head/sys/arm64/cloudabi64/cloudabi64_sysvec.c Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/arm64/cloudabi64/cloudabi64_sysvec.c Wed Apr 6 11:11:31 2016 (r297613)
@@ -27,6 +27,7 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
+#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/sysent.h>
@@ -46,6 +47,25 @@ __FBSDID("$FreeBSD$");
extern const char *cloudabi64_syscallnames[];
extern struct sysent cloudabi64_sysent[];
+static void
+cloudabi64_proc_setregs(struct thread *td, struct image_params *imgp,
+ unsigned long stack)
+{
+ struct trapframe *regs;
+
+ exec_setregs(td, imgp, stack);
+
+ /*
+ * The stack now contains a pointer to the TCB and the auxiliary
+ * vector. Let x0 point to the auxiliary vector, and set
+ * tpidr_el0 to the TCB.
+ */
+ regs = td->td_frame;
+ regs->tf_x[0] = td->td_retval[0] =
+ stack + roundup(sizeof(cloudabi64_tcb_t), sizeof(register_t));
+ (void)cpu_set_user_tls(td, (void *)stack);
+}
+
static int
cloudabi64_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
{
@@ -110,9 +130,9 @@ cloudabi64_schedtail(struct thread *td)
}
}
-void
+int
cloudabi64_thread_setregs(struct thread *td,
- const cloudabi64_threadattr_t *attr)
+ const cloudabi64_threadattr_t *attr, uint64_t tcb)
{
struct trapframe *frame;
stack_t stack;
@@ -130,6 +150,9 @@ cloudabi64_thread_setregs(struct thread
frame = td->td_frame;
frame->tf_x[0] = td->td_tid;
frame->tf_x[1] = attr->argument;
+
+ /* Set up TLS. */
+ return (cpu_set_user_tls(td, (void *)tcb));
}
static struct sysentvec cloudabi64_elf_sysvec = {
@@ -144,6 +167,7 @@ static struct sysentvec cloudabi64_elf_s
.sv_usrstack = USRSTACK,
.sv_stackprot = VM_PROT_READ | VM_PROT_WRITE,
.sv_copyout_strings = cloudabi64_copyout_strings,
+ .sv_setregs = cloudabi64_proc_setregs,
.sv_flags = SV_ABI_CLOUDABI | SV_CAPSICUM | SV_LP64,
.sv_set_syscall_retval = cloudabi64_set_syscall_retval,
.sv_fetch_syscall_args = cloudabi64_fetch_syscall_args,
Modified: head/sys/compat/cloudabi64/cloudabi64_module.c
==============================================================================
--- head/sys/compat/cloudabi64/cloudabi64_module.c Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/compat/cloudabi64/cloudabi64_module.c Wed Apr 6 11:11:31 2016 (r297613)
@@ -112,7 +112,13 @@ cloudabi64_fixup(register_t **stack_base
{ .a_type = CLOUDABI_AT_NULL },
};
*stack_base -= howmany(sizeof(auxv), sizeof(register_t));
- return (copyout(auxv, *stack_base, sizeof(auxv)));
+ error = copyout(auxv, *stack_base, sizeof(auxv));
+ if (error != 0)
+ return (error);
+
+ /* Reserve space for storing the TCB. */
+ *stack_base -= howmany(sizeof(cloudabi64_tcb_t), sizeof(register_t));
+ return (0);
}
static int
Modified: head/sys/compat/cloudabi64/cloudabi64_thread.c
==============================================================================
--- head/sys/compat/cloudabi64/cloudabi64_thread.c Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/compat/cloudabi64/cloudabi64_thread.c Wed Apr 6 11:11:31 2016 (r297613)
@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
struct thread_create_args {
cloudabi64_threadattr_t attr;
+ uint64_t tcb;
lwpid_t tid;
};
@@ -49,8 +50,7 @@ initialize_thread(struct thread *td, voi
args->tid = td->td_tid;
/* Set up initial register contents. */
- cloudabi64_thread_setregs(td, &args->attr);
- return (0);
+ return (cloudabi64_thread_setregs(td, &args->attr, args->tcb));
}
int
@@ -63,6 +63,12 @@ cloudabi64_sys_thread_create(struct thre
error = copyin(uap->attr, &args.attr, sizeof(args.attr));
if (error != 0)
return (error);
+
+ /* Remove some space on the top of the stack for the TCB. */
+ args.tcb = rounddown(args.attr.stack + args.attr.stack_size -
+ sizeof(cloudabi64_tcb_t), _Alignof(cloudabi64_tcb_t));
+ args.attr.stack_size = args.tcb - args.attr.stack;
+
error = thread_create(td, NULL, initialize_thread, &args);
if (error != 0)
return (error);
Modified: head/sys/compat/cloudabi64/cloudabi64_util.h
==============================================================================
--- head/sys/compat/cloudabi64/cloudabi64_util.h Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/compat/cloudabi64/cloudabi64_util.h Wed Apr 6 11:11:31 2016 (r297613)
@@ -42,7 +42,7 @@ extern Elf64_Brandinfo cloudabi64_brand;
register_t *cloudabi64_copyout_strings(struct image_params *);
int cloudabi64_fixup(register_t **, struct image_params *);
-void cloudabi64_thread_setregs(struct thread *,
- const cloudabi64_threadattr_t *);
+int cloudabi64_thread_setregs(struct thread *,
+ const cloudabi64_threadattr_t *, uint64_t);
#endif
Modified: head/sys/contrib/cloudabi/cloudabi64_types.h
==============================================================================
--- head/sys/contrib/cloudabi/cloudabi64_types.h Wed Apr 6 06:37:36 2016 (r297612)
+++ head/sys/contrib/cloudabi/cloudabi64_types.h Wed Apr 6 11:11:31 2016 (r297613)
@@ -192,6 +192,13 @@ _Static_assert(offsetof(cloudabi64_subsc
_Static_assert(sizeof(cloudabi64_subscription_t) == 56, "Incorrect layout");
_Static_assert(_Alignof(cloudabi64_subscription_t) == 8, "Incorrect layout");
+typedef struct {
+ _Alignas(8) uint64_t parent;
+} cloudabi64_tcb_t;
+_Static_assert(offsetof(cloudabi64_tcb_t, parent) == 0, "Incorrect layout");
+_Static_assert(sizeof(cloudabi64_tcb_t) == 8, "Incorrect layout");
+_Static_assert(_Alignof(cloudabi64_tcb_t) == 8, "Incorrect layout");
+
typedef void cloudabi64_threadentry_t(cloudabi_tid_t tid, uint64_t aux);
typedef struct {
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