Re: Add private syscalls to support NPTL

Maxim Kuvyrkov
2009-12-17T17:53:38Z

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On 12/11/09 7:23 PM, Maxim Kuvyrkov wrote:
> On 12/11/09 5:01 PM, Geert Uytterhoeven wrote:
>> On Mon, Dec 7, 2009 at 09:38, Maxim Kuvyrkov<maxim@codesourcery.com>
>> wrote:
...
>> BTW, other architectures seem to call these __NR_[gs]et_thread_area
>> instead of __NR_{read,write}_tp?
>> Shouldn't we follow for consistency?
>
> Yes, we may. As long as the syscall numbers stay the same. I'll send the
> updated patch once the memory handling issue is resolved.

Here is the updated patch. I renamed {read,write}_tp syscalls to
[gs]et_thread_area. Regarding the memory access issue in cmpxchg
syscall, I looked through the mm/ files and it seems that checking for
!pte_write() is the right way to fix the problem; so the patch fixes
that too.

As I understand, this patch fixes all outstanding issues and is ready
for merge.

Regards,

--
Maxim Kuvyrkov
CodeSourcery
maxim@codesourcery.com
(650) 331-3385 x724

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From f1e2bdaa191f08d33938bd42cf090f3d9466866e Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim@codesourcery.com>
Date: Mon, 7 Dec 2009 00:24:27 -0800
Subject: [PATCH 1/2] Add NPTL support for m68k

This patch adds several syscalls, that provide necessary
functionality to support NPTL on m68k/ColdFire.
The syscalls are get_thread_area, set_thread_area, atomic_cmpxchg_32 and
atomic_barrier.
The cmpxchg syscall is required for ColdFire as it doesn't support 'cas'
instruction.

Also a ptrace call PTRACE_GET_THREAD_AREA is added to allow debugger to
inspect the TLS storage.

Signed-off-by: Maxim Kuvyrkov <maxim@codesourcery.com>
---
arch/m68k/include/asm/ptrace.h | 2 +
arch/m68k/include/asm/swab.h | 2 +-
arch/m68k/include/asm/thread_info_mm.h | 1 +
arch/m68k/include/asm/unistd.h | 6 ++-
arch/m68k/kernel/entry.S | 4 ++
arch/m68k/kernel/process.c | 4 ++
arch/m68k/kernel/ptrace.c | 5 ++
arch/m68k/kernel/sys_m68k.c | 81 ++++++++++++++++++++++++++++++++
8 files changed, 103 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/include/asm/ptrace.h b/arch/m68k/include/asm/ptrace.h
index a6ab663..43ab86a 100644
--- a/arch/m68k/include/asm/ptrace.h
+++ b/arch/m68k/include/asm/ptrace.h
@@ -71,6 +71,8 @@ struct switch_stack {
#define PTRACE_GETFPREGS 14
#define PTRACE_SETFPREGS 15

+#define PTRACE_GET_THREAD_AREA 25
+
#define PTRACE_SINGLEBLOCK 33 /* resume execution until next branch */

#ifdef __KERNEL__
diff --git a/arch/m68k/include/asm/swab.h b/arch/m68k/include/asm/swab.h
index 5b754aa..b7b37a4 100644
--- a/arch/m68k/include/asm/thread_info_mm.h
+++ b/arch/m68k/include/asm/thread_info_mm.h
@@ -16,6 +16,7 @@ struct thread_info {
struct exec_domain *exec_domain; /* execution domain */
int preempt_count; /* 0 => preemptable, <0 => BUG */
__u32 cpu; /* should always be 0 on m68k */
+ unsigned long tp_value; /* thread pointer */
struct restart_block restart_block;
};
#endif /* __ASSEMBLY__ */
diff --git a/arch/m68k/include/asm/unistd.h b/arch/m68k/include/asm/unistd.h
index 48b87f5..d72a71d 100644
--- a/arch/m68k/include/asm/unistd.h
+++ b/arch/m68k/include/asm/unistd.h
@@ -336,10 +336,14 @@
#define __NR_pwritev 330
#define __NR_rt_tgsigqueueinfo 331
#define __NR_perf_event_open 332
+#define __NR_get_thread_area 333
+#define __NR_set_thread_area 334
+#define __NR_atomic_cmpxchg_32 335
+#define __NR_atomic_barrier 336

#ifdef __KERNEL__

-#define NR_syscalls 333
+#define NR_syscalls 337

#define __ARCH_WANT_IPC_PARSE_VERSION
#define __ARCH_WANT_OLD_READDIR
diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index 77fc7c1..e136b8c 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -761,4 +761,8 @@ sys_call_table:
.long sys_pwritev /* 330 */
.long sys_rt_tgsigqueueinfo
.long sys_perf_event_open
+ .long sys_get_thread_area
+ .long sys_set_thread_area
+ .long sys_atomic_cmpxchg_32 /* 335 */
+ .long sys_atomic_barrier

diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index 0529659..17c3f32 100644
--- a/arch/m68k/kernel/process.c
+++ b/arch/m68k/kernel/process.c
@@ -251,6 +251,10 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,

p->thread.usp = usp;
p->thread.ksp = (unsigned long)childstack;
+
+ if (clone_flags & CLONE_SETTLS)
+ task_thread_info(p)->tp_value = regs->d5;
+
/*
* Must save the current SFC/DFC value, NOT the value when
* the parent was last descheduled - RGH 10-08-96
diff --git a/arch/m68k/kernel/ptrace.c b/arch/m68k/kernel/ptrace.c
index 1fc217e..616e597 100644
--- a/arch/m68k/kernel/ptrace.c
+++ b/arch/m68k/kernel/ptrace.c
@@ -245,6 +245,11 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
ret = -EFAULT;
break;

+ case PTRACE_GET_THREAD_AREA:
+ ret = put_user(task_thread_info(child)->tp_value,
+ (unsigned long __user *)data);
+ break;
+
default:
ret = ptrace_request(child, request, addr, data);
break;
diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 7deb402..1f0db88 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -28,6 +28,11 @@
#include <asm/traps.h>
#include <asm/page.h>
#include <asm/unistd.h>
+#include <linux/elf.h>
+#include <asm/tlb.h>
+
+asmlinkage int do_page_fault(struct pt_regs *regs, unsigned long address,
+ unsigned long error_code);

/* common code for old and new mmaps */
static inline long do_mmap2(
@@ -662,3 +667,79 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[])
: "d" (__a), "d" (__b), "d" (__c));
return __res;
}
+
+asmlinkage unsigned long sys_get_thread_area(void)
+{
+ return current_thread_info()->tp_value;
+}
+
+asmlinkage int sys_set_thread_area(unsigned long tp)
+{
+ current_thread_info()->tp_value = tp;
+ return 0;
+}
+
+/* This syscall gets its arguments in A0 (mem), D2 (oldval) and
+ D1 (newval). */
+asmlinkage int
+sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
+ unsigned long __user * mem)
+{
+ /* This was borrowed from ARM's implementation. */
+ for (;;) {
+ struct mm_struct *mm = current->mm;
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+ spinlock_t *ptl;
+ unsigned long mem_value;
+
+ down_read(&mm->mmap_sem);
+ pgd = pgd_offset(mm, (unsigned long)mem);
+ if (!pgd_present(*pgd))
+ goto bad_access;
+ pmd = pmd_offset(pgd, (unsigned long)mem);
+ if (!pmd_present(*pmd))
+ goto bad_access;
+ pte = pte_offset_map_lock(mm, pmd, (unsigned long)mem, &ptl);
+ if (!pte_present(*pte) || !pte_dirty(*pte)
+ || !pte_write(*pte)) {
+ pte_unmap_unlock(pte, ptl);
+ goto bad_access;
+ }
+
+ mem_value = *mem;
+ if (mem_value == oldval)
+ *mem = newval;
+
+ pte_unmap_unlock(pte, ptl);
+ up_read(&mm->mmap_sem);
+ return mem_value;
+
+ bad_access:
+ up_read(&mm->mmap_sem);
+ /* This is not necessarily a bad access, we can get here if
+ a memory we're trying to write to should be copied-on-write.
+ Make the kernel do the necessary page stuff, then re-iterate.
+ Simulate a write access fault to do that. */
+ {
+ /* The first argument of the function corresponds to
+ D1, which is the first field of struct pt_regs. */
+ struct pt_regs *fp = (struct pt_regs *)&newval;
+
+ /* '3' is an RMW flag. */
+ if (do_page_fault(fp, (unsigned long)mem, 3))
+ /* If the do_page_fault() failed, we don't
+ have anything meaningful to return.
+ There should be a SIGSEGV pending for
+ the process. */
+ return 0xdeadbeef;
+ }
+ }
+}
+
+asmlinkage int sys_atomic_barrier(void)
+{
+ /* no code needed for uniprocs */
+ return 0;
+}
--
1.6.2.4