linux-kernel - [PATCH v2] powerpc/watchpoint/ptrace: Introduce PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH

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Message-Id: <20200723093330.306341-1-ravi.bangoria@linux.ibm.com>
Date:   Thu, 23 Jul 2020 15:03:30 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     mpe@...erman.id.au
Cc:     ravi.bangoria@...ux.ibm.com, mikey@...ling.org, paulus@...ba.org,
        christophe.leroy@....fr, naveen.n.rao@...ux.vnet.ibm.com,
        pedromfc@...ibm.com, rogealve@...ibm.com, jniethe5@...il.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] powerpc/watchpoint/ptrace: Introduce PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH_31

PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH_31 can be used to determine
whether we are running on an ISA 3.1 compliant machine. Which is
needed to determine DAR behaviour, 512 byte boundary limit etc.
This was requested by Pedro Miraglia Franco de Carvalho for
extending watchpoint features in gdb. Note that availability of
2nd DAWR is independent of this flag and should be checked using
ppc_debug_info->num_data_bps.

Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
v1->v2:
 - Mention new flag in Documentaion/ as well.

 Documentation/powerpc/ptrace.rst          | 1 +
 arch/powerpc/include/uapi/asm/ptrace.h    | 1 +
 arch/powerpc/kernel/ptrace/ptrace-noadv.c | 5 ++++-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/powerpc/ptrace.rst b/Documentation/powerpc/ptrace.rst
index 864d4b6dddd1..4d42290248cb 100644
--- a/Documentation/powerpc/ptrace.rst
+++ b/Documentation/powerpc/ptrace.rst
@@ -46,6 +46,7 @@ features will have bits indicating whether there is support for::
   #define PPC_DEBUG_FEATURE_DATA_BP_RANGE		0x4
   #define PPC_DEBUG_FEATURE_DATA_BP_MASK		0x8
   #define PPC_DEBUG_FEATURE_DATA_BP_DAWR		0x10
+  #define PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH_31	0x20
 
 2. PTRACE_SETHWDEBUG
 
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index f5f1ccc740fc..0a87bcd4300a 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -222,6 +222,7 @@ struct ppc_debug_info {
 #define PPC_DEBUG_FEATURE_DATA_BP_RANGE		0x0000000000000004
 #define PPC_DEBUG_FEATURE_DATA_BP_MASK		0x0000000000000008
 #define PPC_DEBUG_FEATURE_DATA_BP_DAWR		0x0000000000000010
+#define PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH_31	0x0000000000000020
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/powerpc/kernel/ptrace/ptrace-noadv.c b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
index 697c7e4b5877..b2de874d650b 100644
--- a/arch/powerpc/kernel/ptrace/ptrace-noadv.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
@@ -52,8 +52,11 @@ void ppc_gethwdinfo(struct ppc_debug_info *dbginfo)
 	dbginfo->sizeof_condition = 0;
 	if (IS_ENABLED(CONFIG_HAVE_HW_BREAKPOINT)) {
 		dbginfo->features = PPC_DEBUG_FEATURE_DATA_BP_RANGE;
-		if (dawr_enabled())
+		if (dawr_enabled()) {
 			dbginfo->features |= PPC_DEBUG_FEATURE_DATA_BP_DAWR;
+			if (cpu_has_feature(CPU_FTR_ARCH_31))
+				dbginfo->features |= PPC_DEBUG_FEATURE_DATA_BP_DAWR_ARCH_31;
+		}
 	} else {
 		dbginfo->features = 0;
 	}
-- 
2.26.2