In-Reply-To: <[email protected]>
On Thu, 5 Jan 2006 at 02:51:30 -0800, Stephane Eranian wrote:
> I am trying to the user HW debug registers on i386
> and I am running into a problem with ptrace() not allowing access
> to EFLAGS_RF for POKEUSER (see FLAG_MASK).
>
> I am not sure I understand the motivation for denying access
> to this flag which can be used to resume after a code
> breakpoint has been reached. It avoids the need to remove the
> breakpoint, single step, and reinstall. The equivalent
> functionality exists on IA-64 and is allowed by ptrace().
I see no reason for denying this. This patch should fix it:
i386: PTRACE_POKEUSR: allow changing RF bit in EFLAGS register.
Setting RF (resume flag) allows a debugger to resume execution
after a code breakpoint without tripping the breakpoint again.
It is reset by the CPU after execution of one instruction.
Signed-off-by: Chuck Ebbert <[email protected]>
--- 2.6.15a.orig/arch/i386/kernel/ptrace.c
+++ 2.6.15a/arch/i386/kernel/ptrace.c
@@ -32,9 +32,12 @@
* in exit.c or in signal.c.
*/
-/* determines which flags the user has access to. */
-/* 1 = access 0 = no access */
-#define FLAG_MASK 0x00044dd5
+/*
+ * 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 0x00054dd5
/* set's the trap flag. */
#define TRAP_FLAG 0x100
--
Chuck
Currently reading: _Thud!_ by Terry Pratchett
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
