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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>
This commit is contained in:
Anton Blanchard 2011-01-11 19:50:51 +00:00 committed by Benjamin Herrenschmidt
parent d47d1d8af5
commit d368514c30
1 changed files with 39 additions and 15 deletions
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54
arch/powerpc/platforms/pseries/ras.c
View File

@ -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;
} else {
printk("FWNMI: corrupt r3\n");
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 {
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)