From 9f155b9802bb7049cd0f216c3fe903b58620df11 Mon Sep 17 00:00:00 2001 From: Chuck Ebbert <76306.1226@compuserve.com> Date: Thu, 5 Jan 2006 23:11:29 -0500 Subject: [PATCH] [PATCH] 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. Requested by Stephane Eranian: "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). [ ... ] It avoids the need to remove the breakpoint, single step, and reinstall. The equivalent functionality exists on IA-64 and is allowed by ptrace()" Cc: Stephane Eranian Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Linus Torvalds --- arch/i386/kernel/ptrace.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c index 5ffbb4b7ad05..5c1fb6aada5b 100644 --- a/arch/i386/kernel/ptrace.c +++ b/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