Add configurable simulation of bad memory writes
Add new interface to enable configuring regions of the simulated
memory to fail probabilistically. An entry is based on an offset,
length and rate of failure. This only applies to write operatios
and throws an error that can be caught in tests.
Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/sim/simflash/src/lib.rs b/sim/simflash/src/lib.rs
index 300802c..d4817c1 100644
--- a/sim/simflash/src/lib.rs
+++ b/sim/simflash/src/lib.rs
@@ -3,9 +3,12 @@
//! This module is capable of simulating the type of NOR flash commonly used in microcontrollers.
//! These generally can be written as individual bytes, but must be erased in larger units.
+#[macro_use] extern crate log;
#[macro_use] extern crate error_chain;
+extern crate rand;
mod pdump;
+use rand::distributions::{IndependentSample, Range};
use std::fs::File;
use std::io::Write;
use std::iter::Enumerate;
@@ -23,6 +26,10 @@
description("Invalid write")
display("Invalid write: {}", t)
}
+ SimulatedFail(t: String) {
+ description("Write failed by chance")
+ display("Failed write: {}", t)
+ }
}
}
@@ -31,6 +38,9 @@
fn write(&mut self, offset: usize, payload: &[u8]) -> Result<()>;
fn read(&self, offset: usize, data: &mut [u8]) -> Result<()>;
+ fn add_bad_region(&mut self, offset: usize, len: usize, rate: f32) -> Result<()>;
+ fn reset_bad_regions(&mut self);
+
fn sector_iter(&self) -> SectorIter;
fn device_size(&self) -> usize;
}
@@ -44,6 +54,11 @@
ErrorKind::Write(message.as_ref().to_owned())
}
+#[allow(dead_code)]
+fn esimulatedwrite<T: AsRef<str>>(message: T) -> ErrorKind {
+ ErrorKind::SimulatedFail(message.as_ref().to_owned())
+}
+
/// An emulated flash device. It is represented as a block of bytes, and a list of the sector
/// mapings.
#[derive(Clone)]
@@ -51,6 +66,7 @@
data: Vec<u8>,
write_safe: Vec<bool>,
sectors: Vec<usize>,
+ bad_region: Vec<(usize, usize, f32)>,
// Alignment required for writes.
align: usize,
}
@@ -67,6 +83,7 @@
data: vec![0xffu8; total],
write_safe: vec![true; total],
sectors: sectors,
+ bad_region: Vec::new(),
align: align,
}
}
@@ -134,6 +151,17 @@
/// added restriction that repeated writes to the same location
/// are disallowed, even if they would be safe to do.
fn write(&mut self, offset: usize, payload: &[u8]) -> Result<()> {
+ for &(off, len, rate) in &self.bad_region {
+ if offset >= off && (offset + payload.len()) <= (off + len) {
+ let mut rng = rand::thread_rng();
+ let between = Range::new(0., 1.);
+ if between.ind_sample(&mut rng) < rate {
+ bail!(esimulatedwrite(
+ format!("Ignoring write to {:#x}-{:#x}", off, off + len)));
+ }
+ }
+ }
+
if offset + payload.len() > self.data.len() {
panic!("Write outside of device");
}
@@ -170,6 +198,23 @@
Ok(())
}
+ /// Adds a new flash bad region. Writes to this area fail with a chance
+ /// given by `rate`.
+ fn add_bad_region(&mut self, offset: usize, len: usize, rate: f32) -> Result<()> {
+ if rate < 0.0 || rate > 1.0 {
+ bail!(ebounds("Invalid rate"));
+ }
+
+ info!("Adding new bad region {:#x}-{:#x}", offset, offset + len);
+ self.bad_region.push((offset, len, rate));
+
+ Ok(())
+ }
+
+ fn reset_bad_regions(&mut self) {
+ self.bad_region.clear();
+ }
+
/// An iterator over each sector in the device.
fn sector_iter(&self) -> SectorIter {
SectorIter {