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Re: [PATCH] RISC-V: enable have_nonsteppable_watchpoint by default
- From: Craig Blackmore <craig dot blackmore at embecosm dot com>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: Andrew Burgess <andrew dot burgess at embecosm dot com>, gdb-patches at sourceware dot org
- Date: Thu, 4 Oct 2018 17:25:54 +0100
- Subject: Re: [PATCH] RISC-V: enable have_nonsteppable_watchpoint by default
- References: <c83e39fb-b1e8-cc67-85b5-c7cc66197078@embecosm.com> <20180917103409.GJ5952@embecosm.com> <77978648-c391-0011-6c03-c7fd38429914@embecosm.com> <20181003223703.GA22933@adacore.com>
On 03/10/18 23:37, Joel Brobecker wrote:
> I assume this patch is waiting for review from Andrew?
>
> I took a look, since I am interested in it as well. Here are my
> comments.
>
> You forgot to document the introduction of riscv_have_nonsteppable_watchpoint
> in your ChangeLog above; eg:
>
> * riscv-tdep.c (riscv_have_nonsteppable_watchpoint): New static
> global.
>
> You also forgot to document that you're adding new subcommands.
>
> The rest looks good to me.
Hi Joel,
Thanks for the review. I have updated the ChangeLog in the patch below.
Craig
---
The RISC-V debug spec 0.13 recommends that write triggers fire before the
write is committed. If the target follows this behaviour, then
have_nonsteppable_watchpoint needs to be set to 'on' so that GDB will step
over the watchpoint before checking if the value has changed.
This patch adds a setshow for have_nonsteppable_watchpoint which defaults
to 'on' to match the recommended behaviour. If a target does not follow
this timing, then 'set riscv have_nonsteppable_watchpoint off' will need
to be issued on the command line.
gdb/ChangeLog:
* riscv-tdep.c (riscv_have_nonsteppable_watchpoint): New static
global.
(set_have_nonsteppable_watchpoint): Add callback for
'set riscv have_nonsteppable_watchpoint'.
(show_have_nonsteppable_watchpoint): Add callback for
'show riscv have_nonsteppable_watchpoint'.
(riscv_gdbarch_init): Initialise gdbarch setting for
have_nonesteppable_watchpoint.
(_initialize_riscv_tdep): Add 'set/show riscv
have_nonsteppable_watchpoint' subcommands.
---
diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index 254914c..857c5d1 100644
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -226,6 +226,36 @@ show_use_compressed_breakpoints (struct ui_file *file, int from_tty,
"to %s%s.\n"), value, additional_info);
}
+/* Controls whether the debugger should step over hardware watchpoints before
+ checking if the watched variable has changed. If true, then the debugger
+ will step over the watchpoint. */
+
+static int riscv_have_nonsteppable_watchpoint = 1;
+
+/* The set callback for 'set riscv have-nonsteppable-watchpoint'. */
+
+static void
+set_have_nonsteppable_watchpoint (const char *args, int from_tty,
+ struct cmd_list_element *c)
+{
+ struct gdbarch *gdbarch = target_gdbarch ();
+
+ set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
+ riscv_have_nonsteppable_watchpoint);
+}
+
+/* The show callback for 'show riscv have-nonsteppable-watchpoint'. */
+
+static void
+show_have_nonsteppable_watchpoint (struct ui_file *file, int from_tty,
+ struct cmd_list_element *c,
+ const char *value)
+{
+ fprintf_filtered (file,
+ _("Debugger must step over hardware watchpoints is set to "
+ "%s.\n"), value);
+}
+
/* The set and show lists for 'set riscv' and 'show riscv' prefixes. */
static struct cmd_list_element *setriscvcmdlist = NULL;
@@ -2736,6 +2766,8 @@ riscv_gdbarch_init (struct gdbarch_info info,
set_gdbarch_return_value (gdbarch, riscv_return_value);
set_gdbarch_breakpoint_kind_from_pc (gdbarch, riscv_breakpoint_kind_from_pc);
set_gdbarch_sw_breakpoint_from_kind (gdbarch, riscv_sw_breakpoint_from_kind);
+ set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
+ riscv_have_nonsteppable_watchpoint);
/* Register architecture. */
set_gdbarch_num_regs (gdbarch, RISCV_LAST_REGNUM + 1);
@@ -2980,4 +3012,20 @@ can be used."),
show_use_compressed_breakpoints,
&setriscvcmdlist,
&showriscvcmdlist);
+
+ add_setshow_boolean_cmd ("have-nonsteppable-watchpoint", no_class,
+ &riscv_have_nonsteppable_watchpoint,
+ _("\
+Set whether debugger must step over hardware watchpoints"),
+ _("\
+Show whether debugger must step over hardware watchpoints"),
+ _("\
+The RISC-V debug spec recommends that hardware write watchpoints fire before\n\
+the write is committed, in which case, GDB must step over the watchpoint\n\
+before checking the old and new values. Set this option to 'on' (default)\n\
+for targets that follow this behaviour, otherwise set to 'off'."),
+ set_have_nonsteppable_watchpoint,
+ show_have_nonsteppable_watchpoint,
+ &setriscvcmdlist,
+ &showriscvcmdlist);
}