Eric Lee / linux-smarc-t335x-v3.2

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Commit 9f155b9802bb7049cd0f216c3fe903b58620df11

Authored by Chuck Ebbert
Committed by Linus Torvalds
1 parent 29552b1462
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

[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 <eranian@hpl.hp.com>
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Showing 1 changed file with 6 additions and 3 deletions Side-by-side Diff

arch/i386/kernel/ptrace.c
Diff comments   View file @ 9f155b9
... ... @@ -32,9 +32,12 @@
32 32 * in exit.c or in signal.c.
33 33 */
34 34  
35   -/* determines which flags the user has access to. */
36   -/* 1 = access 0 = no access */
37   -#define FLAG_MASK 0x00044dd5
  35 +/*
  36 + * Determines which flags the user has access to [1 = access, 0 = no access].
  37 + * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
  38 + * Also masks reserved bits (31-22, 15, 5, 3, 1).
  39 + */
  40 +#define FLAG_MASK 0x00054dd5
38 41  
39 42 /* set's the trap flag. */
40 43 #define TRAP_FLAG 0x100