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Message-ID: <20120910155033.GF27042@arm.com>
Date: Mon, 10 Sep 2012 16:50:33 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Al Viro <viro@...iv.linux.org.uk>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 17/31] arm64: System calls handling
On Mon, Sep 10, 2012 at 03:24:21PM +0100, Arnd Bergmann wrote:
> On Monday 10 September 2012, Catalin Marinas wrote:
> >
> > On Mon, Sep 10, 2012 at 02:51:52PM +0100, Arnd Bergmann wrote:
> > > On Monday 10 September 2012, Catalin Marinas wrote:
> > > > Yes, I've seen these but since Al's patches are not in mainline, I don't
> > > > want to add additional dependencies to the arm64 patches (currently
> > > > based on 3.6-rc4). Once they get into mainline, I'll add a patch that
> > > > converts arm64 to the generic functions above.
> > > >
> > > > For kernel_execve(), I think I can simplify it further and not rely on
> > > > Al's patches (similar to other architectures doing an SVC from kernel):
> > >
> > > Hmm, I thought one of the reasons for Al to do his series was to discourage
> > > people from doing syscalls from kernel space, but I may be misremembering
> > > things. Al?
> >
> > If that was the aim, I'm happy to change the code similar to the
> > arch/arm one. But as I said I would wait until Al's patches get into
> > mainline.
>
> Ok. Another point: I wouldn't be too worried about dependencies for new
> code, because it's not possible to bisect through your series anyway
> (one needs all the patches before anything starts working really),
> so from my point of view you could also write your code in a way that
> expects Al's patches to get merged first.
It's not about bisectability but rather a way to test the branch that I
publish. On its own, my branch wouldn't even compile. Anyway, here's the
update (tested on a local branch with Al's execve2 branch merged):
arm64: Switch to generic sys_execve/kernel_execve
This patch converts the arm64 port to use the generic sys_execve and
kernel_execve() functions. It introduces the ret_from_kernel_execve()
function for starting the new user context and removes the
(compat_)sys_execve_wrapper() functions.
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Cc: Al Viro <viro@...iv.linux.org.uk>
diff --git a/arch/arm64/include/asm/syscalls.h b/arch/arm64/include/asm/syscalls.h
index 09ff335..81680a0 100644
--- a/arch/arm64/include/asm/syscalls.h
+++ b/arch/arm64/include/asm/syscalls.h
@@ -23,9 +23,6 @@
/*
* System call wrappers implemented in kernel/entry.S.
*/
-asmlinkage long sys_execve_wrapper(const char __user *filename,
- const char __user *const __user *argv,
- const char __user *const __user *envp);
asmlinkage long sys_clone_wrapper(unsigned long clone_flags,
unsigned long newsp,
void __user *parent_tid,
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index fe18a68..948cfb1 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -24,4 +24,7 @@
#include <asm/unistd32.h>
#endif
+#define __ARCH_WANT_SYS_EXECVE
+#define __ARCH_WANT_KERNEL_EXECVE
+
#endif /* __ASM_UNISTD_H */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 38cf853..5e0b28c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -592,7 +592,7 @@ work_resched:
/*
* "slow" syscall return path.
*/
-ENTRY(ret_to_user)
+ret_to_user:
disable_irq // disable interrupts
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
@@ -614,6 +614,22 @@ ENTRY(ret_from_fork)
ENDPROC(ret_from_fork)
/*
+ * ret_from_kernel_execve(struct pt_regs *normal, struct pt_regs *new)
+ *
+ * Turn a kernel thread into a user process.
+ */
+ENTRY(ret_from_kernel_execve)
+ str xzr, [x1, #S_X0] // returning 0
+ mov x2, #-1
+ str x2, [x1, #S_SYSCALLNO] // not a syscall
+ mov x2, #S_FRAME_SIZE
+ bl memmove // copy regs to the normal location
+ get_thread_info tsk
+ mov sp, x0 // normal pt_regs
+ b ret_to_user
+ENDPROC(ret_from_kernel_execve)
+
+/*
* SVC handler.
*/
.align 6
@@ -671,11 +687,6 @@ __sys_trace_return:
/*
* Special system call wrappers.
*/
-ENTRY(sys_execve_wrapper)
- mov x3, sp
- b sys_execve
-ENDPROC(sys_execve_wrapper)
-
ENTRY(sys_clone_wrapper)
mov x5, sp
b sys_clone
diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index 905fcfb..9c77c0b 100644
--- a/arch/arm64/kernel/sys.c
+++ b/arch/arm64/kernel/sys.c
@@ -41,70 +41,6 @@ asmlinkage long sys_clone(unsigned long clone_flags, unsigned long newsp,
return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
}
-/*
- * sys_execve() executes a new program.
- */
-asmlinkage long sys_execve(const char __user *filenamei,
- const char __user *const __user *argv,
- const char __user *const __user *envp,
- struct pt_regs *regs)
-{
- long error;
- char * filename;
-
- filename = getname(filenamei);
- error = PTR_ERR(filename);
- if (IS_ERR(filename))
- goto out;
- error = do_execve(filename, argv, envp, regs);
- putname(filename);
-out:
- return error;
-}
-
-int kernel_execve(const char *filename,
- const char *const argv[],
- const char *const envp[])
-{
- struct pt_regs regs;
- int ret;
-
- memset(®s, 0, sizeof(struct pt_regs));
- ret = do_execve(filename,
- (const char __user *const __user *)argv,
- (const char __user *const __user *)envp, ®s);
- if (ret < 0)
- goto out;
-
- /*
- * Save argc to the register structure for userspace.
- */
- regs.regs[0] = ret;
-
- /*
- * We were successful. We won't be returning to our caller, but
- * instead to user space by manipulating the kernel stack.
- */
- asm( "add x0, %0, %1\n\t"
- "mov x1, %2\n\t"
- "mov x2, %3\n\t"
- "bl memmove\n\t" /* copy regs to top of stack */
- "mov x27, #0\n\t" /* not a syscall */
- "mov x28, %0\n\t" /* thread structure */
- "mov sp, x0\n\t" /* reposition stack pointer */
- "b ret_to_user"
- :
- : "r" (current_thread_info()),
- "Ir" (THREAD_START_SP - sizeof(regs)),
- "r" (®s),
- "Ir" (sizeof(regs))
- : "x0", "x1", "x2", "x27", "x28", "x30", "memory");
-
- out:
- return ret;
-}
-EXPORT_SYMBOL(kernel_execve);
-
asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
unsigned long fd, off_t off)
@@ -118,7 +54,6 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
/*
* Wrappers to pass the pt_regs argument.
*/
-#define sys_execve sys_execve_wrapper
#define sys_clone sys_clone_wrapper
#define sys_rt_sigreturn sys_rt_sigreturn_wrapper
#define sys_sigaltstack sys_sigaltstack_wrapper
diff --git a/arch/arm64/kernel/sys32.S b/arch/arm64/kernel/sys32.S
index 5e4dc93..903ba9d 100644
--- a/arch/arm64/kernel/sys32.S
+++ b/arch/arm64/kernel/sys32.S
@@ -36,11 +36,6 @@ compat_sys_vfork_wrapper:
b compat_sys_vfork
ENDPROC(compat_sys_vfork_wrapper)
-compat_sys_execve_wrapper:
- mov x3, sp
- b compat_sys_execve
-ENDPROC(compat_sys_execve_wrapper)
-
compat_sys_clone_wrapper:
mov x5, sp
b compat_sys_clone
@@ -152,7 +147,7 @@ ENDPROC(compat_sys_fanotify_mark_wrapper)
*/
#define sys_fork compat_sys_fork_wrapper
#define sys_open compat_sys_open
-#define sys_execve compat_sys_execve_wrapper
+#define sys_execve compat_sys_execve
#define sys_lseek compat_sys_lseek_wrapper
#define sys_mount compat_sys_mount
#define sys_ptrace compat_sys_ptrace
diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
index 967e92f..d77ba8e 100644
--- a/arch/arm64/kernel/sys_compat.c
+++ b/arch/arm64/kernel/sys_compat.c
@@ -51,24 +51,6 @@ asmlinkage int compat_sys_vfork(struct pt_regs *regs)
regs, 0, NULL, NULL);
}
-asmlinkage int compat_sys_execve(const char __user *filenamei,
- compat_uptr_t argv, compat_uptr_t envp,
- struct pt_regs *regs)
-{
- int error;
- char * filename;
-
- filename = getname(filenamei);
- error = PTR_ERR(filename);
- if (IS_ERR(filename))
- goto out;
- error = compat_do_execve(filename, compat_ptr(argv), compat_ptr(envp),
- regs);
- putname(filename);
-out:
- return error;
-}
-
asmlinkage int compat_sys_sched_rr_get_interval(compat_pid_t pid,
struct compat_timespec __user *interval)
{
--
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