Re: Add private syscalls to support NPTL

[Maxim Kuvyrkov <maxim@codesourcery.com>]

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Maxim Kuvyrkov wrote:

> Here is the updated patch.

Hm, I've attached the patch without the unistd.h hunk.  Here is the 
proper one.

--
Maxim K.
CodeSourcery

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From 828160ab5d329e15543a50d0b50ce50f2975966b Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim@codesourcery.com>
Date: Tue, 25 Aug 2009 23:37:26 +0400
Subject: [PATCH] Add syscalls to support m68k NPTL.

This patch adds several syscalls, private to M68K, that provide necessary
functionality to support NPTL.
The syscalls are read_tp, write_tp, atomic_cmpxchg_32 and atomic_barrier.
The cmpxchg syscall is required for ColdFire as it doesn't support 'cas'
instruction.

Signed-off-by: Maxim Kuvyrkov <maxim@codesourcery.com>
---
 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/sys_m68k.c            |   82 ++++++++++++++++++++++++++++++++
 4 files changed, 92 insertions(+), 1 deletions(-)

diff --git a/arch/m68k/include/asm/thread_info_mm.h b/arch/m68k/include/asm/thread_info_mm.h
index af0fda4..a240244 100644
--- a/arch/m68k/include/asm/thread_info_mm.h
+++ b/arch/m68k/include/asm/thread_info_mm.h
@@ -10,6 +10,7 @@ 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;
 	struct restart_block    restart_block;
 };
 
diff --git a/arch/m68k/include/asm/unistd.h b/arch/m68k/include/asm/unistd.h
index 946d869..c035c8b 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_counter_open	332
+#define __NR_read_tp		333
+#define __NR_write_tp		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 c3735cd..e2a245f 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -757,4 +757,8 @@ sys_call_table:
 	.long sys_pwritev		/* 330 */
 	.long sys_rt_tgsigqueueinfo
 	.long sys_perf_counter_open
+ 	.long sys_read_tp
+ 	.long sys_write_tp
+ 	.long sys_atomic_cmpxchg_32	/* 335 */
+ 	.long sys_atomic_barrier
 
diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 7f54efa..03651e5 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -29,6 +29,11 @@
 #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(
@@ -663,3 +668,80 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[])
 			: "d" (__a), "d" (__b), "d" (__c));
 	return __res;
 }
+
+asmlinkage unsigned long
+sys_read_tp(void)
+{
+	return current_thread_info()->tp_value;
+}
+
+asmlinkage int
+sys_write_tp(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)
+{
+	struct mm_struct *mm = current->mm;
+
+	/* This was borrowed from ARM's implementation.  */
+	for(;;) {
+		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_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;
+}
-- 
1.6.4