linux-kernel - [PATCH] x86_64: ia32 ptrace THREAD

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Message-Id: <20071106233038.3C41D4D0560@magilla.localdomain>
Date:	Tue,  6 Nov 2007 15:30:38 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] x86_64: ia32 ptrace THREAD_AREA fix


The addr argument to PTRACE_GET_THREAD_AREA and PTRACE_SET_THREAD_AREA is
not a magic constant.  It's derived from the segment register values being
used, which are computed originally from the index used with set_thread_area.
The value does not need to match what a native i386 kernel would accept.
It needs to match the segment selectors that can actually be in use in this
32-bit process.  The 64-bit ptrace support for PTRACE_GET_THREAD_AREA
(normally used only on 32-bit processes) is correct, but the 32-bit emulation
of ptrace is broken.

Signed-off-by: Roland McGrath <roland@...hat.com>
---
 arch/x86/ia32/ptrace32.c |   11 ++---------
 1 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/ia32/ptrace32.c b/arch/x86/ia32/ptrace32.c
index f52770e..fc4673d 100644
--- a/arch/x86/ia32/ptrace32.c
+++ b/arch/x86/ia32/ptrace32.c
@@ -228,8 +228,6 @@ static long ptrace32_siginfo(unsigned request, u32 pid, u32 addr, u32 data)
 	return ret;
 }
 
-#define COMPAT_GDT_ENTRY_TLS_MIN 6
-
 asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
 {
 	struct task_struct *child;
@@ -248,6 +246,8 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
 	case PTRACE_SYSCALL:
 	case PTRACE_OLDSETOPTIONS:
 	case PTRACE_SETOPTIONS:
+	case PTRACE_SET_THREAD_AREA:
+	case PTRACE_GET_THREAD_AREA:
 		return sys_ptrace(request, pid, addr, data); 
 
 	default:
@@ -271,12 +271,6 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
 	case PTRACE_SETSIGINFO:
 	case PTRACE_GETSIGINFO:
 		return ptrace32_siginfo(request, pid, addr, data);
-
-	case PTRACE_SET_THREAD_AREA:
-	case PTRACE_GET_THREAD_AREA:
-		return sys_ptrace(request, pid,
-			addr + GDT_ENTRY_TLS_MIN - COMPAT_GDT_ENTRY_TLS_MIN,
-			data);
 	}
 
 	child = ptrace_get_task_struct(pid);
-
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