* [PATCH 1/2] firmware: google: memconsole: Make memconsole interface more flexible
2017-05-02 22:16 [PATCH v3 0/2] Memconsole changes for new coreboot format Julius Werner
@ 2017-05-02 22:16 ` Julius Werner
2017-05-02 22:16 ` [PATCH 2/2] firmware: google: memconsole: Adapt to new coreboot ring buffer format Julius Werner
1 sibling, 0 replies; 3+ messages in thread
From: Julius Werner @ 2017-05-02 22:16 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: linux-kernel, Thierry Escande, Dmitry Torokhov, Aaron Durbin,
Julius Werner
This patch redesigns the interface between the generic memconsole driver
and its implementations to become more flexible than a flat memory
buffer with unchanging bounds. This allows memconsoles like coreboot's
to include lines that were added by runtime firmware after the driver
was initialized. Since the console log size is thus no longer static,
this means that the /sys/firmware/log file has to become unseekable.
Signed-off-by: Julius Werner <jwerner@chromium.org>
---
drivers/firmware/google/memconsole-coreboot.c | 12 +++++++++---
drivers/firmware/google/memconsole-x86-legacy.c | 18 +++++++++++++++---
drivers/firmware/google/memconsole.c | 14 ++++++--------
drivers/firmware/google/memconsole.h | 7 ++++---
4 files changed, 34 insertions(+), 17 deletions(-)
diff --git a/drivers/firmware/google/memconsole-coreboot.c b/drivers/firmware/google/memconsole-coreboot.c
index 21210144def7..b6234e61004d 100644
--- a/drivers/firmware/google/memconsole-coreboot.c
+++ b/drivers/firmware/google/memconsole-coreboot.c
@@ -33,6 +33,14 @@ struct cbmem_cons {
static struct cbmem_cons __iomem *cbmem_console;
+static ssize_t memconsole_coreboot_read(char *buf, loff_t pos, size_t count)
+{
+ return memory_read_from_buffer(buf, count, &pos,
+ cbmem_console->buffer_body,
+ min(cbmem_console->buffer_cursor,
+ cbmem_console->buffer_size));
+}
+
static int memconsole_coreboot_init(phys_addr_t physaddr)
{
struct cbmem_cons __iomem *tmp_cbmc;
@@ -50,9 +58,7 @@ static int memconsole_coreboot_init(phys_addr_t physaddr)
if (!cbmem_console)
return -ENOMEM;
- memconsole_setup(cbmem_console->buffer_body,
- min(cbmem_console->buffer_cursor, cbmem_console->buffer_size));
-
+ memconsole_setup(memconsole_coreboot_read);
return 0;
}
diff --git a/drivers/firmware/google/memconsole-x86-legacy.c b/drivers/firmware/google/memconsole-x86-legacy.c
index 529078c62488..1b556e944599 100644
--- a/drivers/firmware/google/memconsole-x86-legacy.c
+++ b/drivers/firmware/google/memconsole-x86-legacy.c
@@ -49,6 +49,15 @@ struct biosmemcon_ebda {
};
} __packed;
+static char *memconsole_baseaddr;
+static size_t memconsole_length;
+
+static ssize_t memconsole_read(char *buf, loff_t pos, size_t count)
+{
+ return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
+ memconsole_length);
+}
+
static void found_v1_header(struct biosmemcon_ebda *hdr)
{
pr_info("memconsole: BIOS console v1 EBDA structure found at %p\n",
@@ -57,7 +66,9 @@ static void found_v1_header(struct biosmemcon_ebda *hdr)
hdr->v1.buffer_addr, hdr->v1.start,
hdr->v1.end, hdr->v1.num_chars);
- memconsole_setup(phys_to_virt(hdr->v1.buffer_addr), hdr->v1.num_chars);
+ memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
+ memconsole_length = hdr->v1.num_chars;
+ memconsole_setup(memconsole_read);
}
static void found_v2_header(struct biosmemcon_ebda *hdr)
@@ -68,8 +79,9 @@ static void found_v2_header(struct biosmemcon_ebda *hdr)
hdr->v2.buffer_addr, hdr->v2.start,
hdr->v2.end, hdr->v2.num_bytes);
- memconsole_setup(phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start),
- hdr->v2.end - hdr->v2.start);
+ memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start);
+ memconsole_length = hdr->v2.end - hdr->v2.start;
+ memconsole_setup(memconsole_read);
}
/*
diff --git a/drivers/firmware/google/memconsole.c b/drivers/firmware/google/memconsole.c
index 94e200ddb4fa..166f07c68c02 100644
--- a/drivers/firmware/google/memconsole.c
+++ b/drivers/firmware/google/memconsole.c
@@ -22,15 +22,15 @@
#include "memconsole.h"
-static char *memconsole_baseaddr;
-static size_t memconsole_length;
+static ssize_t (*memconsole_read_func)(char *, loff_t, size_t);
static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
struct bin_attribute *bin_attr, char *buf,
loff_t pos, size_t count)
{
- return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
- memconsole_length);
+ if (WARN_ON_ONCE(!memconsole_read_func))
+ return -EIO;
+ return memconsole_read_func(buf, pos, count);
}
static struct bin_attribute memconsole_bin_attr = {
@@ -38,16 +38,14 @@ static struct bin_attribute memconsole_bin_attr = {
.read = memconsole_read,
};
-void memconsole_setup(void *baseaddr, size_t length)
+void memconsole_setup(ssize_t (*read_func)(char *, loff_t, size_t))
{
- memconsole_baseaddr = baseaddr;
- memconsole_length = length;
+ memconsole_read_func = read_func;
}
EXPORT_SYMBOL(memconsole_setup);
int memconsole_sysfs_init(void)
{
- memconsole_bin_attr.size = memconsole_length;
return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
}
EXPORT_SYMBOL(memconsole_sysfs_init);
diff --git a/drivers/firmware/google/memconsole.h b/drivers/firmware/google/memconsole.h
index 190fc03a51ae..ff1592dc7d1a 100644
--- a/drivers/firmware/google/memconsole.h
+++ b/drivers/firmware/google/memconsole.h
@@ -18,13 +18,14 @@
#ifndef __FIRMWARE_GOOGLE_MEMCONSOLE_H
#define __FIRMWARE_GOOGLE_MEMCONSOLE_H
+#include <linux/types.h>
+
/*
* memconsole_setup
*
- * Initialize the memory console from raw (virtual) base
- * address and length.
+ * Initialize the memory console, passing the function to handle read accesses.
*/
-void memconsole_setup(void *baseaddr, size_t length);
+void memconsole_setup(ssize_t (*read_func)(char *, loff_t, size_t));
/*
* memconsole_sysfs_init
--
2.12.2
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH 2/2] firmware: google: memconsole: Adapt to new coreboot ring buffer format
2017-05-02 22:16 [PATCH v3 0/2] Memconsole changes for new coreboot format Julius Werner
2017-05-02 22:16 ` [PATCH 1/2] firmware: google: memconsole: Make memconsole interface more flexible Julius Werner
@ 2017-05-02 22:16 ` Julius Werner
1 sibling, 0 replies; 3+ messages in thread
From: Julius Werner @ 2017-05-02 22:16 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: linux-kernel, Thierry Escande, Dmitry Torokhov, Aaron Durbin,
Julius Werner
The upstream coreboot implementation of memconsole was enhanced from a
single-boot console to a persistent ring buffer
(https://review.coreboot.org/#/c/18301). This patch changes the kernel
memconsole driver to be able to read the new format in all cases.
Signed-off-by: Julius Werner <jwerner@chromium.org>
---
drivers/firmware/google/memconsole-coreboot.c | 47 ++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 8 deletions(-)
diff --git a/drivers/firmware/google/memconsole-coreboot.c b/drivers/firmware/google/memconsole-coreboot.c
index b6234e61004d..23dc363b8519 100644
--- a/drivers/firmware/google/memconsole-coreboot.c
+++ b/drivers/firmware/google/memconsole-coreboot.c
@@ -26,19 +26,50 @@
/* CBMEM firmware console log descriptor. */
struct cbmem_cons {
- u32 buffer_size;
- u32 buffer_cursor;
- u8 buffer_body[0];
+ u32 size;
+ u32 cursor;
+ u8 body[0];
} __packed;
+#define CURSOR_MASK ((1 << 28) - 1)
+#define OVERFLOW (1 << 31)
+
static struct cbmem_cons __iomem *cbmem_console;
+/*
+ * The cbmem_console structure is read again on every access because it may
+ * change at any time if runtime firmware logs new messages. This may rarely
+ * lead to race conditions where the firmware overwrites the beginning of the
+ * ring buffer with more lines after we have already read |cursor|. It should be
+ * rare and harmless enough that we don't spend extra effort working around it.
+ */
static ssize_t memconsole_coreboot_read(char *buf, loff_t pos, size_t count)
{
- return memory_read_from_buffer(buf, count, &pos,
- cbmem_console->buffer_body,
- min(cbmem_console->buffer_cursor,
- cbmem_console->buffer_size));
+ u32 cursor = cbmem_console->cursor & CURSOR_MASK;
+ u32 flags = cbmem_console->cursor & ~CURSOR_MASK;
+ u32 size = cbmem_console->size;
+ struct seg { /* describes ring buffer segments in logical order */
+ u32 phys; /* physical offset from start of mem buffer */
+ u32 len; /* length of segment */
+ } seg[2] = { {0}, {0} };
+ size_t done = 0;
+ int i;
+
+ if (flags & OVERFLOW) {
+ if (cursor > size) /* Shouldn't really happen, but... */
+ cursor = 0;
+ seg[0] = (struct seg){.phys = cursor, .len = size - cursor};
+ seg[1] = (struct seg){.phys = 0, .len = cursor};
+ } else {
+ seg[0] = (struct seg){.phys = 0, .len = min(cursor, size)};
+ }
+
+ for (i = 0; i < ARRAY_SIZE(seg) && count > done; i++) {
+ done += memory_read_from_buffer(buf + done, count - done, &pos,
+ cbmem_console->body + seg[i].phys, seg[i].len);
+ pos -= seg[i].len;
+ }
+ return done;
}
static int memconsole_coreboot_init(phys_addr_t physaddr)
@@ -51,7 +82,7 @@ static int memconsole_coreboot_init(phys_addr_t physaddr)
return -ENOMEM;
cbmem_console = memremap(physaddr,
- tmp_cbmc->buffer_size + sizeof(*cbmem_console),
+ tmp_cbmc->size + sizeof(*cbmem_console),
MEMREMAP_WB);
memunmap(tmp_cbmc);
--
2.12.2
^ permalink raw reply [flat|nested] 3+ messages in thread