Add a fault handler which handles immediate reads in Thumb-2 mode. Install the appropriate handler depending on which mode the kernel has been built. This avoids an "Unhandled fault: external abort on non-linefetch (0x1008) at 0xf0a80000" during boot on a device with a PCIe switch connected. Link: https://lore.kernel.org/linux-pci/20181126161645.8177-1-stefan@xxxxxxxx/ Signed-off-by: Stefan Agner <stefan@xxxxxxxx> --- Changes since v1: - Added Thumb-2 32-bit instruction support (tested by inserting .w instructions in arch/arm/include/asm/io.h) - Avoid dereferencing if fault happened in user mode drivers/pci/controller/dwc/pci-imx6.c | 59 ++++++++++++++++++++++++++- 1 file changed, 58 insertions(+), 1 deletion(-) diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c index 54a29e441303..a9bbbf176c4a 100644 --- a/drivers/pci/controller/dwc/pci-imx6.c +++ b/drivers/pci/controller/dwc/pci-imx6.c @@ -29,6 +29,7 @@ #include <linux/reset.h> #include <linux/pm_domain.h> #include <linux/pm_runtime.h> +#include <asm/opcodes.h> #include "pcie-designware.h" @@ -305,6 +306,59 @@ static int imx6q_pcie_abort_handler(unsigned long addr, return 1; } +static int imx6q_pcie_abort_handler_thumb2(unsigned long addr, + unsigned int fsr, struct pt_regs *regs) +{ + unsigned long pc = instruction_pointer(regs); + unsigned long instr; + + if (user_mode(regs)) + return 1; + + instr = __mem_to_opcode_thumb32(*(unsigned long *)pc); + + if (__opcode_is_thumb32(instr)) { + /* Load word/byte and halfword immediate offset */ + if ((instr & 0xff100000UL) == 0xf8100000UL) { + int reg = (instr >> 12) & 0xf; + unsigned long val; + + if ((instr & 0x00700000UL) == 0x00100000UL) + val = 0xff; + else if ((instr & 0x00700000UL) == 0x00300000UL) + val = 0xffff; + else + val = 0xffffffffUL; + + regs->uregs[reg] = val; + regs->ARM_pc += 4; + return 0; + } + } else { + instr = __mem_to_opcode_thumb16(*(unsigned long *)pc); + + /* Load word/byte and halfword immediate offset */ + if (((instr & 0xe800) == 0x6800) || + ((instr & 0xf800) == 0x8800)) { + int reg = instr & 0x7; + unsigned long val; + + if (instr & 0x1000) + val = 0xff; + else if (instr & 0x8000) + val = 0xffff; + else + val = 0xffffffffUL; + + regs->uregs[reg] = val; + regs->ARM_pc += 2; + return 0; + } + } + + return 1; +} + static int imx6_pcie_attach_pd(struct device *dev) { struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev); @@ -1075,6 +1129,8 @@ static struct platform_driver imx6_pcie_driver = { static int __init imx6_pcie_init(void) { + bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL); + /* * Since probe() can be deferred we need to make sure that * hook_fault_code is not called after __init memory is freed @@ -1082,7 +1138,8 @@ static int __init imx6_pcie_init(void) * we can install the handler here without risking it * accessing some uninitialized driver state. */ - hook_fault_code(8, imx6q_pcie_abort_handler, SIGBUS, 0, + hook_fault_code(8, thumb2 ? imx6q_pcie_abort_handler_thumb2 : + imx6q_pcie_abort_handler, SIGBUS, 0, "external abort on non-linefetch"); return platform_driver_register(&imx6_pcie_driver); -- 2.19.1
