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Re: [PATCH] Return zero in aarch64_linux_can_use_hw_breakpoint if target doesn't support HW watchpoint/breakpoint
- From: Yao Qi <qiyaoltc at gmail dot com>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: Yao Qi <qiyaoltc at gmail dot com>, gdb-patches at sourceware dot org
- Date: Wed, 08 Jul 2015 09:09:52 +0100
- Subject: Re: [PATCH] Return zero in aarch64_linux_can_use_hw_breakpoint if target doesn't support HW watchpoint/breakpoint
- Authentication-results: sourceware.org; auth=none
- References: <1436286618-23963-1-git-send-email-yao dot qi at linaro dot org> <20150707163636 dot GA4802 at adacore dot com>
Joel Brobecker <brobecker@adacore.com> writes:
>> + else
>> + gdb_assert (FALSE);
>
> Use gdb_assert_not_reached instead?
Good point. Patch is updated to fix this.
--
Yao (éå)
From 79122a045b43a844de70612bf45ad8dee7f218b1 Mon Sep 17 00:00:00 2001
From: Yao Qi <yao.qi@linaro.org>
Date: Fri, 19 Jun 2015 12:21:27 +0100
Subject: [PATCH] Return zero in aarch64_linux_can_use_hw_breakpoint if target doesn't support HW watchpoint/breakpoint
Nowadays aarch64_linux_can_use_hw_breakpoint always return one, but it
can be smarter, say, if GDB knows target doesn't support HW watchpoint
or breakpoint because HW watchpoint/breakpoint is disabled in linux
kernel, for example, it can safely return zero.
gdb:
2015-07-08 Yao Qi <yao.qi@linaro.org>
* aarch64-linux-nat.c (aarch64_linux_can_use_hw_breakpoint): If
TYPE is watchpoint, return zero if aarch64_num_wp_regs is zero.
If TYPE is breakpoint, return zero if arch64_num_bp_regs is zero.
diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index cafd824..d5d0038 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -1051,19 +1051,32 @@ aarch64_align_watchpoint (CORE_ADDR addr, int len, CORE_ADDR *aligned_addr_p,
bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
CNT is the number of such watchpoints used so far (including this
one). OTHERTYPE is non-zero if other types of watchpoints are
- currently enabled.
-
- We always return 1 here because we don't have enough information
- about possible overlap of addresses that they want to watch. As an
- extreme example, consider the case where all the watchpoints watch
- the same address and the same region length: then we can handle a
- virtually unlimited number of watchpoints, due to debug register
- sharing implemented via reference counts. */
+ currently enabled. */
static int
aarch64_linux_can_use_hw_breakpoint (struct target_ops *self,
int type, int cnt, int othertype)
{
+ if (type == bp_hardware_watchpoint || type == bp_read_watchpoint
+ || type == bp_access_watchpoint || type == bp_watchpoint)
+ {
+ if (aarch64_num_wp_regs == 0)
+ return 0;
+ }
+ else if (type == bp_hardware_breakpoint)
+ {
+ if (aarch64_num_bp_regs == 0)
+ return 0;
+ }
+ else
+ gdb_assert_not_reached ("unexpected breakpoint type");
+
+ /* We always return 1 here because we don't have enough information
+ about possible overlap of addresses that they want to watch. As an
+ extreme example, consider the case where all the watchpoints watch
+ the same address and the same region length: then we can handle a
+ virtually unlimited number of watchpoints, due to debug register
+ sharing implemented via reference counts. */
return 1;
}