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authorAnton Blanchard <anton@samba.org>2011-01-11 19:50:51 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-01-21 14:08:38 +1100
commitd368514c3097a48a109b6ba64e12047106c7473d (patch)
treebdd892bec071fc042f70c1875642175cbcc782cb /arch/powerpc
parentd47d1d8af52e37bcf9059dd86878474e5ccc9c2a (diff)
downloadop-kernel-dev-d368514c3097a48a109b6ba64e12047106c7473d.zip
op-kernel-dev-d368514c3097a48a109b6ba64e12047106c7473d.tar.gz
powerpc: Fix corruption when grabbing FWNMI data
The FWNMI code uses a global buffer without any locks to read the RTAS error information. If two CPUs take a machine check at once then we will corrupt this buffer. Since most FWNMI rtas messages are not of the extended type, we can create a 64bit percpu buffer and use it where possible. If we do receive an extended RTAS log then we fall back to the old behaviour of using the global buffer. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/platforms/pseries/ras.c52
1 files changed, 38 insertions, 14 deletions
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index d194150..c55d7ad 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -54,7 +54,8 @@
static unsigned char ras_log_buf[RTAS_ERROR_LOG_MAX];
static DEFINE_SPINLOCK(ras_log_buf_lock);
-static char mce_data_buf[RTAS_ERROR_LOG_MAX];
+static char global_mce_data_buf[RTAS_ERROR_LOG_MAX];
+static DEFINE_PER_CPU(__u64, mce_data_buf);
static int ras_get_sensor_state_token;
static int ras_check_exception_token;
@@ -196,12 +197,24 @@ static irqreturn_t ras_error_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}
-/* Get the error information for errors coming through the
+/*
+ * Some versions of FWNMI place the buffer inside the 4kB page starting at
+ * 0x7000. Other versions place it inside the rtas buffer. We check both.
+ */
+#define VALID_FWNMI_BUFFER(A) \
+ ((((A) >= 0x7000) && ((A) < 0x7ff0)) || \
+ (((A) >= rtas.base) && ((A) < (rtas.base + rtas.size - 16))))
+
+/*
+ * Get the error information for errors coming through the
* FWNMI vectors. The pt_regs' r3 will be updated to reflect
* the actual r3 if possible, and a ptr to the error log entry
* will be returned if found.
*
- * The mce_data_buf does not have any locks or protection around it,
+ * If the RTAS error is not of the extended type, then we put it in a per
+ * cpu 64bit buffer. If it is the extended type we use global_mce_data_buf.
+ *
+ * The global_mce_data_buf does not have any locks or protection around it,
* if a second machine check comes in, or a system reset is done
* before we have logged the error, then we will get corruption in the
* error log. This is preferable over holding off on calling
@@ -210,20 +223,31 @@ static irqreturn_t ras_error_interrupt(int irq, void *dev_id)
*/
static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs)
{
- unsigned long errdata = regs->gpr[3];
- struct rtas_error_log *errhdr = NULL;
unsigned long *savep;
+ struct rtas_error_log *h, *errhdr = NULL;
- if ((errdata >= 0x7000 && errdata < 0x7fff0) ||
- (errdata >= rtas.base && errdata < rtas.base + rtas.size - 16)) {
- savep = __va(errdata);
- regs->gpr[3] = savep[0]; /* restore original r3 */
- memset(mce_data_buf, 0, RTAS_ERROR_LOG_MAX);
- memcpy(mce_data_buf, (char *)(savep + 1), RTAS_ERROR_LOG_MAX);
- errhdr = (struct rtas_error_log *)mce_data_buf;
+ if (!VALID_FWNMI_BUFFER(regs->gpr[3])) {
+ printk(KERN_ERR "FWNMI: corrupt r3\n");
+ return NULL;
+ }
+
+ savep = __va(regs->gpr[3]);
+ regs->gpr[3] = savep[0]; /* restore original r3 */
+
+ /* If it isn't an extended log we can use the per cpu 64bit buffer */
+ h = (struct rtas_error_log *)&savep[1];
+ if (!h->extended) {
+ memcpy(&__get_cpu_var(mce_data_buf), h, sizeof(__u64));
+ errhdr = (struct rtas_error_log *)&__get_cpu_var(mce_data_buf);
} else {
- printk("FWNMI: corrupt r3\n");
+ int len;
+
+ len = max_t(int, 8+h->extended_log_length, RTAS_ERROR_LOG_MAX);
+ memset(global_mce_data_buf, 0, RTAS_ERROR_LOG_MAX);
+ memcpy(global_mce_data_buf, h, len);
+ errhdr = (struct rtas_error_log *)global_mce_data_buf;
}
+
return errhdr;
}
@@ -235,7 +259,7 @@ static void fwnmi_release_errinfo(void)
{
int ret = rtas_call(rtas_token("ibm,nmi-interlock"), 0, 1, NULL);
if (ret != 0)
- printk("FWNMI: nmi-interlock failed: %d\n", ret);
+ printk(KERN_ERR "FWNMI: nmi-interlock failed: %d\n", ret);
}
int pSeries_system_reset_exception(struct pt_regs *regs)
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