From 6f464e76cf5dd2c3fbb6b7ea84d00e21ee88cdbf Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Mon, 26 Aug 2013 16:18:24 +0300
Subject: [PATCH] mmu: don't pass really bad faults to the application
Trying to execute the null pointer, or faults within the kernel code, are
a really bad sign and it's better to abort early with them.
---
arch/x64/loader.ld | 2 ++
core/mmu.cc | 8 ++++++++
2 files changed, 10 insertions(+)
diff --git a/arch/x64/loader.ld b/arch/x64/loader.ld
index 78b25279a..121edec27 100644
--- a/arch/x64/loader.ld
+++ b/arch/x64/loader.ld
@@ -11,11 +11,13 @@ SECTIONS
. = 0x201000;
.dynamic : { *(.dynamic) } :dynamic :text
.text : {
+ text_start = .;
*(.text.hot .text.hot.*)
*(.text.unlikely .text.*_unlikely)
*(.text.fixup)
*(.text.startup .text.startup.*)
*(.text .text.*)
+ text_end = .;
} :text
. = ALIGN(8);
.fixup : {
diff --git a/core/mmu.cc b/core/mmu.cc
index 465caca25..97378b03c 100644
--- a/core/mmu.cc
+++ b/core/mmu.cc
@@ -868,10 +868,18 @@ void switch_to_runtime_page_table()
void page_fault(exception_frame *ef)
{
+ extern const char text_start[], text_end[];
sched::exception_guard g;
auto addr = processor::read_cr2();
if (fixup_fault(ef)) {
return;
}
+ auto pc = reinterpret_cast<void*>(ef->rip);
+ if (!pc) {
+ abort("trying to execute null pointer");
+ }
+ if (pc >= text_start && pc < text_end) {
+ abort("page fault outside application");
+ }
osv::handle_segmentation_fault(addr, ef);
}
--
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