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Subject[patch 21/38] No execute support cleanup.
From: Martin Schwidefsky <schwidefsky@de.ibm.com>

Simplify the signal_return function that checks for the two special
system calls sigreturn and rt_sigreturn. No need to do a page table
walk, a call to copy_from_user while disabled page faults will work
as well.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---
arch/s390/mm/fault.c | 72 ++++++++++++++-------------------------------------
1 files changed, 21 insertions(+), 51 deletions(-)
Index: quilt-2.6/arch/s390/mm/fault.c
===================================================================
--- quilt-2.6.orig/arch/s390/mm/fault.c 2007-04-27 16:04:57.000000000 +0200
+++ quilt-2.6/arch/s390/mm/fault.c 2007-04-27 16:04:57.000000000 +0200
@@ -26,9 +26,9 @@
#include <linux/module.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
+#include <linux/uaccess.h>

#include <asm/system.h>
-#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/kdebug.h>
#include <asm/s390_ext.h>
@@ -263,68 +263,38 @@
extern long sys32_sigreturn(struct pt_regs *regs);
extern long sys32_rt_sigreturn(struct pt_regs *regs);

-static inline void do_sigreturn(struct mm_struct *mm, struct pt_regs *regs,
- int rt)
+static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
+ unsigned long address, unsigned long error_code)
{
+ u16 instruction;
+ int rc, compat;
+
+ pagefault_disable();
+ rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
+ pagefault_enable();
+ if (rc)
+ return -EFAULT;
+
up_read(&mm->mmap_sem);
clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
#ifdef CONFIG_COMPAT
- if (test_tsk_thread_flag(current, TIF_31BIT)) {
- if (rt)
- sys32_rt_sigreturn(regs);
- else
- sys32_sigreturn(regs);
- return;
- }
-#endif /* CONFIG_COMPAT */
- if (rt)
- sys_rt_sigreturn(regs);
+ compat = test_tsk_thread_flag(current, TIF_31BIT);
+ if (compat && instruction == 0x0a77)
+ sys32_sigreturn(regs);
+ else if (compat && instruction == 0x0aad)
+ sys32_rt_sigreturn(regs);
else
+#endif
+ if (instruction == 0x0a77)
sys_sigreturn(regs);
- return;
-}
-
-static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
- unsigned long address, unsigned long error_code)
-{
- pgd_t *pgd;
- pmd_t *pmd;
- pte_t *pte;
- u16 *instruction;
- unsigned long pfn, uaddr = regs->psw.addr;
-
- spin_lock(&mm->page_table_lock);
- pgd = pgd_offset(mm, uaddr);
- if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
- goto out_fault;
- pmd = pmd_offset(pgd, uaddr);
- if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
- goto out_fault;
- pte = pte_offset_map(pmd_offset(pgd_offset(mm, uaddr), uaddr), uaddr);
- if (!pte || !pte_present(*pte))
- goto out_fault;
- pfn = pte_pfn(*pte);
- if (!pfn_valid(pfn))
- goto out_fault;
- spin_unlock(&mm->page_table_lock);
-
- instruction = (u16 *) ((pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE-1)));
- if (*instruction == 0x0a77)
- do_sigreturn(mm, regs, 0);
- else if (*instruction == 0x0aad)
- do_sigreturn(mm, regs, 1);
+ else if (instruction == 0x0aad)
+ sys_rt_sigreturn(regs);
else {
- printk("- XXX - do_exception: task = %s, primary, NO EXEC "
- "-> SIGSEGV\n", current->comm);
- up_read(&mm->mmap_sem);
current->thread.prot_addr = address;
current->thread.trap_no = error_code;
do_sigsegv(regs, error_code, SEGV_MAPERR, address);
}
return 0;
-out_fault:
- spin_unlock(&mm->page_table_lock);
- return -EFAULT;
}
#endif /* CONFIG_S390_EXEC_PROTECT */

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.

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