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From: Jordan Niethe <jniethe5@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: christophe.leroy@c-s.fr, ajd@linux.ibm.com, npiggin@gmail.com,
	naveen.n.rao@linux.ibm.com, Jordan Niethe <jniethe5@gmail.com>,
	dja@axtens.net
Subject: [PATCH v9 3/8] powerpc/kprobes: Mark newly allocated probes as RO
Date: Tue, 16 Mar 2021 14:17:36 +1100	[thread overview]
Message-ID: <20210316031741.1004850-3-jniethe5@gmail.com> (raw)
In-Reply-To: <20210316031741.1004850-1-jniethe5@gmail.com>

From: Russell Currey <ruscur@russell.cc>

With CONFIG_STRICT_KERNEL_RWX=y and CONFIG_KPROBES=y, there will be one
W+X page at boot by default.  This can be tested with
CONFIG_PPC_PTDUMP=y and CONFIG_PPC_DEBUG_WX=y set, and checking the
kernel log during boot.

Add an arch specific insn page allocator which returns RO pages if
STRICT_KERNEL_RWX is enabled. This page is only written to with
patch_instruction() which is able to write RO pages.

Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[jpn: Reword commit message, switch from vmalloc_exec(), add
      free_insn_page()]
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v9: - vmalloc_exec() no longer exists
    - Set the page to RW before freeing it
---
 arch/powerpc/kernel/kprobes.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 01ab2163659e..bb7e4d321988 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -25,6 +25,8 @@
 #include <asm/sections.h>
 #include <asm/inst.h>
 #include <linux/uaccess.h>
+#include <linux/set_memory.h>
+#include <linux/vmalloc.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -103,6 +105,26 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 	return addr;
 }
 
+void *alloc_insn_page(void)
+{
+	void *page = vmalloc(PAGE_SIZE);
+
+	if (!page)
+		return NULL;
+
+	set_memory_ro((unsigned long)page, 1);
+	set_memory_x((unsigned long)page, 1);
+
+	return page;
+}
+
+void free_insn_page(void *page)
+{
+	set_memory_nx((unsigned long)page, 1);
+	set_memory_rw((unsigned long)page, 1);
+	vfree(page);
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
-- 
2.25.1


  parent reply	other threads:[~2021-03-16  3:19 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-16  3:17 [PATCH v9 1/8] powerpc/mm: Implement set_memory() routines Jordan Niethe
2021-03-16  3:17 ` [PATCH v9 2/8] powerpc/lib/code-patching: Set up Strict RWX patching earlier Jordan Niethe
2021-03-16  3:36   ` Russell Currey
2021-03-16  6:32   ` Christophe Leroy
2021-03-17  0:38     ` Jordan Niethe
2021-03-17 12:04       ` Michael Ellerman
2021-03-16  3:17 ` Jordan Niethe [this message]
2021-03-16  6:44   ` [PATCH v9 3/8] powerpc/kprobes: Mark newly allocated probes as RO Christophe Leroy
2021-03-17  0:50     ` Jordan Niethe
2021-03-17  0:52     ` Jordan Niethe
2021-03-17  6:12   ` Christophe Leroy
2021-03-18  2:42     ` Jordan Niethe
2021-03-16  3:17 ` [PATCH v9 4/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Jordan Niethe
2021-03-16  6:47   ` Christophe Leroy
2021-03-16  3:17 ` [PATCH v9 5/8] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX Jordan Niethe
2021-03-16  6:51   ` Christophe Leroy
2021-03-17  2:15     ` Jordan Niethe
2021-03-17  5:43       ` Christophe Leroy
2021-03-16  3:17 ` [PATCH v9 6/8] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig Jordan Niethe
2021-03-16  3:17 ` [PATCH v9 7/8] powerpc/mm: implement set_memory_attr() Jordan Niethe
2021-03-16  7:25   ` Christophe Leroy
2021-03-17  0:54     ` Jordan Niethe
2021-03-16  3:17 ` [PATCH v9 8/8] powerpc/32: use set_memory_attr() Jordan Niethe
2021-03-19  1:19 ` [PATCH v9 1/8] powerpc/mm: Implement set_memory() routines Michael Ellerman

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