From a5061d028594a31dbf70f4554e0b7d83e5ce770f Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Tue, 2 May 2017 15:16:30 -0700 Subject: firmware: google: memconsole: Adapt to new coreboot ring buffer format 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 Signed-off-by: Greg Kroah-Hartman --- drivers/firmware/google/memconsole-coreboot.c | 47 ++++++++++++++++++++++----- 1 file changed, 39 insertions(+), 8 deletions(-) (limited to 'drivers/firmware/google') diff --git a/drivers/firmware/google/memconsole-coreboot.c b/drivers/firmware/google/memconsole-coreboot.c index d48a80c3042d..7d39f4ef5d9e 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); -- cgit v1.2.3