[PATCH 04/12] __wr_after_init: debug writes

[Igor Stoppa]

After each write operation, confirm that it was successful, otherwise
generate a warning.

Signed-off-by: Igor Stoppa <igor.stoppa@xxxxxxxxxx>

CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Nadav Amit <nadav.amit@xxxxxxxxx>
CC: Matthew Wilcox <willy@xxxxxxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CC: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
CC: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
CC: Ahmed Soliman <ahmedsoliman@xxxxxxxxxxx>
CC: linux-integrity@xxxxxxxxxxxxxxx
CC: kernel-hardening@xxxxxxxxxxxxxxxxxx
CC: linux-mm@xxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---
 mm/Kconfig.debug | 8 ++++++++
 mm/prmem.c       | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 9a7b8b049d04..b10305cfac3c 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -94,3 +94,11 @@ config DEBUG_RODATA_TEST
     depends on STRICT_KERNEL_RWX
     ---help---
       This option enables a testcase for the setting rodata read-only.
+
+config DEBUG_PRMEM
+    bool "Verify each write rare operation."
+    depends on PRMEM
+    default n
+    help
+      After any write rare operation, compares the data written with the
+      value provided by the caller.
diff --git a/mm/prmem.c b/mm/prmem.c
index e1c1be3a1171..51f6776e2515 100644
--- a/mm/prmem.c
+++ b/mm/prmem.c
@@ -61,6 +61,9 @@ void *wr_memcpy(void *p, const void *q, __kernel_size_t size)
 	__wr_enable(&wr_state);
 	__wr_memcpy(wr_poking_addr, q, size);
 	__wr_disable(&wr_state);
+#ifdef CONFIG_DEBUG_PRMEM
+	VM_WARN_ONCE(memcmp(p, q, size), "Failed %s()", __func__);
+#endif
 	local_irq_enable();
 	return p;
 }
@@ -92,6 +95,9 @@ void *wr_memset(void *p, int c, __kernel_size_t len)
 	__wr_enable(&wr_state);
 	__wr_memset(wr_poking_addr, c, len);
 	__wr_disable(&wr_state);
+#ifdef CONFIG_DEBUG_PRMEM
+	VM_WARN_ONCE(memtst(p, c, len), "Failed %s()", __func__);
+#endif
 	local_irq_enable();
 	return p;
 }
-- 
2.19.1