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Date: Wed, 5 Dec 2012 17:01:39 +0000
From: James Hogan <james.hogan@...tec.com>
To: <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
Al Viro <viro@...IV.linux.org.uk>
CC: James Hogan <james.hogan@...tec.com>
Subject: [PATCH 1/1] metag: Switch to generic kernel_{thread,execve}
Since commit 2aa3a7f8660355c3dddead17e224545c1a3d5a5f
"preparation for generic kernel_thread()"
and commit a74fb73c12398b250fdc5e333a11e15a9e3a84fc
"infrastructure for saner ret_from_kernel_thread semantics"
introduced in v3.7-rc1, arches are advised to migrate to the new generic
implementation of the kernel_thread() and kernel_execve() functions. The
generic implementation of kernel_thread() does not fill the the pt_regs
anymore, but it passes the 'fn' and 'arg' arguments to do_fork() which
then blindly passes them to copy_thread(). As a result of which,
copy_thread() needs to check whether a kernel thread did a do_fork()
call, and if it did, it need to prepare the stack like the arch-specific
kernel_thread() used to do. Later on, when the kernel thread is
returning from the do_fork() call, it will execute fn(arg) which never
returns.
Signed-off-by: James Hogan <james.hogan@...tec.com>
---
This patch is based on v2 of the core metag patchset, which can be found
at git://github.com/jahogan/metag-linux.git, branch metag-core (tag
metag-core-v2).
arch/metag/Kconfig | 2 +
arch/metag/kernel/process.c | 77 ++++++++++++++++-------------------------
arch/metag/kernel/sys_metag.c | 20 -----------
arch/metag/kernel/traps.c | 8 ++++
4 files changed, 40 insertions(+), 67 deletions(-)
diff --git a/arch/metag/Kconfig b/arch/metag/Kconfig
index 29787c8..d53606d 100644
--- a/arch/metag/Kconfig
+++ b/arch/metag/Kconfig
@@ -33,6 +33,8 @@ config METAG
select MODULES_USE_ELF_RELA
select OF
select OF_EARLY_FLATTREE
+ select GENERIC_KERNEL_EXECVE
+ select GENERIC_KERNEL_THREAD
config ARCH_NO_VIRT_TO_BUS
def_bool y
diff --git a/arch/metag/kernel/process.c b/arch/metag/kernel/process.c
index 379b52e..8522750 100644
--- a/arch/metag/kernel/process.c
+++ b/arch/metag/kernel/process.c
@@ -154,73 +154,56 @@ void show_regs(struct pt_regs *regs)
show_trace(NULL, (unsigned long *)regs->ctx.AX[0].U0, regs);
}
-extern void kernel_thread_helper(void);
-__asm__(".pushsection .text\n\t"
- ".type _kernel_thread_helper,function\n\t"
- "_kernel_thread_helper:\n\t"
- "SWAP PC,D1RtP\n\t"
- "MOV D1Ar1,D0Re0\n\t"
- "MOVT D1RtP,#HI(_do_exit)\n\t"
- "CALL D1RtP,#LO(_do_exit)\n\t"
- ".size _kernel_thread_helper,.-_kernel_thread_helper\n\t"
- ".popsection");
-
-/*
- * Create a kernel thread
- */
-int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
- struct pt_regs regs;
- unsigned long global_base;
-
- memset(®s, 0, sizeof(regs));
- regs.ctx.DX[3].U1 = (unsigned long)arg;
- regs.ctx.DX[4].U1 = (unsigned long)fn;
-
- asm volatile("MOV %0,A1GbP\n" : "=r" (global_base));
- regs.ctx.AX[0].U1 = (unsigned long)global_base;
-
- regs.ctx.CurrPC = (unsigned long)kernel_thread_helper;
-
- /* Ok, create the new process.. */
- return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0,
- ®s, 0, NULL, NULL);
-}
-
int copy_thread(unsigned long clone_flags, unsigned long usp,
- unsigned long unused, struct task_struct *tsk,
+ unsigned long arg, struct task_struct *tsk,
struct pt_regs *regs)
{
struct pt_regs *childregs = task_pt_regs(tsk);
void *kernel_context = ((void *) childregs +
sizeof(struct pt_regs));
+ unsigned long global_base;
BUG_ON(((unsigned long)childregs) & 0x7);
BUG_ON(((unsigned long)kernel_context) & 0x7);
- /* Get a pointer to where the new child's register block should have
+ memset(&tsk->thread.kernel_context, 0,
+ sizeof(tsk->thread.kernel_context));
+
+ tsk->thread.kernel_context = __TBISwitchInit(kernel_context,
+ ret_from_fork,
+ 0, 0);
+
+ /* generic kernel_thread() passes a NULL pointer for *regs */
+ if (unlikely(tsk->flags & PF_KTHREAD)) {
+ /*
+ * Make sure we don't leak any kernel data to child's regs
+ * if kernel thread becomes a userspace thread in the future
+ */
+ memset(childregs, 0 , sizeof(struct pt_regs));
+
+ asm volatile("MOV %0,A1GbP\n" : "=r" (global_base));
+ childregs->ctx.AX[0].U1 = (unsigned long) global_base;
+ childregs->ctx.AX[0].U0 = (unsigned long) kernel_context;
+ /* Set D1Ar1=arg and D1RtP=usp (fn) */
+ childregs->ctx.DX[4].U1 = usp;
+ childregs->ctx.DX[3].U1 = arg;
+ tsk->thread.int_depth = 2;
+ return 0;
+ }
+ /*
+ * Get a pointer to where the new child's register block should have
* been pushed.
* The Meta's stack grows upwards, and the context is the the first
* thing to be pushed by TBX (phew)
*/
*childregs = *regs;
-
/* Set the correct stack for the clone mode */
- if (user_mode(childregs)) {
- childregs->ctx.AX[0].U0 = ALIGN(usp, 8);
- tsk->thread.int_depth = 1;
- } else {
- childregs->ctx.AX[0].U0 = (unsigned long) kernel_context;
- tsk->thread.int_depth = 2;
- }
+ childregs->ctx.AX[0].U0 = ALIGN(usp, 8);
+ tsk->thread.int_depth = 1;
/* set return value for child process */
childregs->ctx.DX[0].U0 = 0;
- tsk->thread.kernel_context = __TBISwitchInit(kernel_context,
- ret_from_fork,
- 0, 0);
-
/* The TLS pointer is passed as an argument to sys_clone. */
if (clone_flags & CLONE_SETTLS)
tsk->thread.tls_ptr = (__force void __user *)regs->ctx.DX[1].U1;
diff --git a/arch/metag/kernel/sys_metag.c b/arch/metag/kernel/sys_metag.c
index 7d8f389..b21f1fe 100644
--- a/arch/metag/kernel/sys_metag.c
+++ b/arch/metag/kernel/sys_metag.c
@@ -74,26 +74,6 @@ out:
return ret;
}
-/*
- * Do a system call from kernel instead of calling sys_execve so we
- * end up with proper pt_regs.
- */
-int kernel_execve(const char *filename, const char *const argv[],
- const char *const envp[])
-{
- register long __call __asm__("D1Re0") = __NR_execve;
- register long __res __asm__("D0Re0");
- register long __a __asm__("D1Ar1") = (long)(filename);
- register long __b __asm__("D0Ar2") = (long)(argv);
- register long __c __asm__("D1Ar3") = (long)(envp);
- __asm__ __volatile__("SWITCH #%c1"
- : "=d" (__res)
- : "i" (__METAG_SW_SYS), "d" (__call),
- "d" (__a), "d" (__b), "d" (__c)
- : "memory");
- return __res;
-}
-
#define TXDEFR_FPU_MASK ((0x1f << 16) | 0x1f)
asmlinkage void sys_metag_set_fpu_flags(unsigned int flags)
diff --git a/arch/metag/kernel/traps.c b/arch/metag/kernel/traps.c
index e476a4d..c3cff52 100644
--- a/arch/metag/kernel/traps.c
+++ b/arch/metag/kernel/traps.c
@@ -861,10 +861,18 @@ int ret_from_fork(TBIRES arg)
struct task_struct *prev = arg.Switch.pPara;
struct task_struct *tsk = current;
struct pt_regs *regs = task_pt_regs(tsk);
+ int (*fn)(void *);
TBIRES Next;
schedule_tail(prev);
+ if (tsk->flags & PF_KTHREAD) {
+ fn = (void *)regs->ctx.DX[4].U1;
+ BUG_ON(!fn);
+
+ fn((void *)regs->ctx.DX[3].U1);
+ }
+
if (test_syscall_work())
syscall_trace_leave(regs);
--
1.7.7.6
--
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