When an application reads the ETB buffer too often, it can be empty. In this case, it results in a "vmalloc: allocation failure: 0 bytes", a backtrace in dmesg and a vfree on an incorrect address.
This patch allocates and frees the trace buffer only when necessary. Signed-off-by: Adrien Vergé <[email protected]> --- arch/arm/kernel/etm.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c index 8ff0ecd..5192693 100644 --- a/arch/arm/kernel/etm.c +++ b/arch/arm/kernel/etm.c @@ -275,7 +275,7 @@ static ssize_t etb_read(struct file *file, char __user *data, long length; struct tracectx *t = file->private_data; u32 first = 0; - u32 *buf; + u32 *buf = NULL; mutex_lock(&t->mutex); @@ -293,12 +293,14 @@ static ssize_t etb_read(struct file *file, char __user *data, etb_writel(t, first, ETBR_READADDR); length = min(total * 4, (int)len); - buf = vmalloc(length); + if (length != 0) + buf = vmalloc(length); dev_dbg(t->dev, "ETB buffer length: %d\n", total); dev_dbg(t->dev, "ETB status reg: %x\n", etb_readl(t, ETBR_STATUS)); - for (i = 0; i < length / 4; i++) - buf[i] = etb_readl(t, ETBR_READMEM); + if (buf) + for (i = 0; i < length / 4; i++) + buf[i] = etb_readl(t, ETBR_READMEM); /* the only way to deassert overflow bit in ETB status is this */ etb_writel(t, 1, ETBR_CTRL); @@ -311,7 +313,8 @@ static ssize_t etb_read(struct file *file, char __user *data, etb_lock(t); length -= copy_to_user(data, buf, length); - vfree(buf); + if (buf) + vfree(buf); out: mutex_unlock(&t->mutex); -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
