Re: ptrace denies access to EFLAGS_RF

[Chuck Ebbert]

In-Reply-To: <20060106140217.GD7676@xxxxxxxxxxxxxxxxx>

On Fri, 6 Jan 2006 at 06:02:17 -0800, Stephane Eranian wrote:


> To my surprise, applying the same fix to the x86_64 does not
> solve the problem on my Opteron box. I verified that the
> offset (144) matches with what the kernel is expecting.
> Somehow the RF is lost or not set in the proper location.
> I cannot make forward progress once I reach the breakpoint.


I sent this to Andi this morning.  Does it work for you?

Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>

 arch/x86_64/ia32/ptrace32.c |    9 ++++++---
 arch/x86_64/kernel/ptrace.c |    9 ++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

--- 2.6.15-64a.orig/arch/x86_64/ia32/ptrace32.c
+++ 2.6.15-64a/arch/x86_64/ia32/ptrace32.c
@@ -28,9 +28,12 @@
 #include <asm/i387.h>
 #include <asm/fpu32.h>
 
-/* determines which flags the user has access to. */
-/* 1 = access 0 = no access */
-#define FLAG_MASK 0x44dd5UL
+/*
+ * Determines which flags the user has access to [1 = access, 0 = no access].
+ * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
+ * Also masks reserved bits (31-22, 15, 5, 3, 1).
+ */
+#define FLAG_MASK 0x54dd5UL
 
 #define R32(l,q) \
 	case offsetof(struct user32, regs.l): stack[offsetof(struct pt_regs, q)/8] = val; break
--- 2.6.15-64a.orig/arch/x86_64/kernel/ptrace.c
+++ 2.6.15-64a/arch/x86_64/kernel/ptrace.c
@@ -36,9 +36,12 @@
  * in exit.c or in signal.c.
  */
 
-/* determines which flags the user has access to. */
-/* 1 = access 0 = no access */
-#define FLAG_MASK 0x44dd5UL
+/*
+ * Determines which flags the user has access to [1 = access, 0 = no access].
+ * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
+ * Also masks reserved bits (63-22, 15, 5, 3, 1).
+ */
+#define FLAG_MASK 0x54dd5UL
 
 /* set's the trap flag. */
 #define TRAP_FLAG 0x100UL
-- 
Chuck
Currently reading: _Thud!_ by Terry Pratchett
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