arch/powerpc/platforms/powernv/opal-msglog.c

Source file repositories/reference/linux-study-clean/arch/powerpc/platforms/powernv/opal-msglog.c

File Facts

System
Linux kernel
Corpus path
arch/powerpc/platforms/powernv/opal-msglog.c
Extension
.c
Size
3593 bytes
Lines
162
Domain
Architecture Layer
Bucket
arch/powerpc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct memcons {
	__be64 magic;
#define MEMCONS_MAGIC	0x6630696567726173L
	__be64 obuf_phys;
	__be64 ibuf_phys;
	__be32 obuf_size;
	__be32 ibuf_size;
	__be32 out_pos;
#define MEMCONS_OUT_POS_WRAP	0x80000000u
#define MEMCONS_OUT_POS_MASK	0x00ffffffu
	__be32 in_prod;
	__be32 in_cons;
};

static struct memcons *opal_memcons = NULL;

ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count)
{
	const char *conbuf;
	ssize_t ret;
	size_t first_read = 0;
	uint32_t out_pos, avail;

	if (!mc)
		return -ENODEV;

	out_pos = be32_to_cpu(READ_ONCE(mc->out_pos));

	/* Now we've read out_pos, put a barrier in before reading the new
	 * data it points to in conbuf. */
	smp_rmb();

	conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));

	/* When the buffer has wrapped, read from the out_pos marker to the end
	 * of the buffer, and then read the remaining data as in the un-wrapped
	 * case. */
	if (out_pos & MEMCONS_OUT_POS_WRAP) {

		out_pos &= MEMCONS_OUT_POS_MASK;
		avail = be32_to_cpu(mc->obuf_size) - out_pos;

		ret = memory_read_from_buffer(to, count, &pos,
				conbuf + out_pos, avail);

		if (ret < 0)
			goto out;

		first_read = ret;
		to += first_read;
		count -= first_read;
		pos -= avail;

		if (count <= 0)
			goto out;
	}

	/* Sanity check. The firmware should not do this to us. */
	if (out_pos > be32_to_cpu(mc->obuf_size)) {
		pr_err("OPAL: memory console corruption. Aborting read.\n");
		return -EINVAL;
	}

	ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);

	if (ret < 0)
		goto out;

	ret += first_read;
out:
	return ret;
}

ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
{
	return memcons_copy(opal_memcons, to, pos, count);
}

static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
				const struct bin_attribute *bin_attr, char *to,
				loff_t pos, size_t count)
{
	return opal_msglog_copy(to, pos, count);
}

static struct bin_attribute opal_msglog_attr __ro_after_init = {
	.attr = {.name = "msglog", .mode = 0400},
	.read = opal_msglog_read
};

Annotation

Implementation Notes