From 47016b341fc3b3fd4909e058c6fa38f165b53646 Mon Sep 17 00:00:00 2001 From: Thor Thayer Date: Mon, 23 Apr 2018 12:45:11 -0500 Subject: [PATCH] mtd: spi-nor: cadence-quadspi: Fix page fault kernel panic The current Cadence QSPI driver caused a kernel panic when loading a Root Filesystem from QSPI. The problem was caused by reading more bytes than needed because the QSPI operated on 4 bytes at a time. [ 7.947754] spi_nor_read[1048]:from 0x037cad74, len 1 [bfe07fff] [ 7.956247] cqspi_read[910]:offset 0x58502516, buffer=bfe07fff [ 7.956247] [ 7.966046] Unable to handle kernel paging request at virtual address bfe08002 [ 7.973239] pgd = eebfc000 [ 7.975931] [bfe08002] *pgd=2fffb811, *pte=00000000, *ppte=00000000 Notice above how only 1 byte needed to be read but by reading 4 bytes into the end of a mapped page, an unrecoverable page fault occurred. This patch uses a temporary buffer to hold the 4 bytes read and then copies only the bytes required into the buffer. A min() function is used to limit the length to prevent buffer overflows. Request testing of this patch on other platforms. This was tested on the Intel Arria10 SoCFPGA DevKit. Fixes: 0cf1725676a97fc8 ("mtd: spi-nor: cqspi: Fix build on arches missing readsl/writesl") Signed-off-by: Thor Thayer Cc: Reviewed-by: Marek Vasut Signed-off-by: Boris Brezillon --- drivers/mtd/spi-nor/cadence-quadspi.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c index 4b8e918..5872f31 100644 --- a/drivers/mtd/spi-nor/cadence-quadspi.c +++ b/drivers/mtd/spi-nor/cadence-quadspi.c @@ -501,7 +501,9 @@ static int cqspi_indirect_read_execute(struct spi_nor *nor, u8 *rxbuf, void __iomem *reg_base = cqspi->iobase; void __iomem *ahb_base = cqspi->ahb_base; unsigned int remaining = n_rx; + unsigned int mod_bytes = n_rx % 4; unsigned int bytes_to_read = 0; + u8 *rxbuf_end = rxbuf + n_rx; int ret = 0; writel(from_addr, reg_base + CQSPI_REG_INDIRECTRDSTARTADDR); @@ -530,11 +532,24 @@ static int cqspi_indirect_read_execute(struct spi_nor *nor, u8 *rxbuf, } while (bytes_to_read != 0) { + unsigned int word_remain = round_down(remaining, 4); + bytes_to_read *= cqspi->fifo_width; bytes_to_read = bytes_to_read > remaining ? remaining : bytes_to_read; - ioread32_rep(ahb_base, rxbuf, - DIV_ROUND_UP(bytes_to_read, 4)); + bytes_to_read = round_down(bytes_to_read, 4); + /* Read 4 byte word chunks then single bytes */ + if (bytes_to_read) { + ioread32_rep(ahb_base, rxbuf, + (bytes_to_read / 4)); + } else if (!word_remain && mod_bytes) { + unsigned int temp = ioread32(ahb_base); + + bytes_to_read = mod_bytes; + memcpy(rxbuf, &temp, min((unsigned int) + (rxbuf_end - rxbuf), + bytes_to_read)); + } rxbuf += bytes_to_read; remaining -= bytes_to_read; bytes_to_read = cqspi_get_rd_sram_level(cqspi); -- 2.7.4