From 6aa01f2d8c9c33bfa08e441c9435ec01a57eb385 Mon Sep 17 00:00:00 2001 From: Daniel Jobson Date: Thu, 14 Nov 2024 14:02:53 +0100 Subject: [PATCH] Automatically control system_mode in hardware MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Raise privilege (go to firmware mode) when a function call occurs to the function set in syscall_addr_reg. Automatically revoke privilege when executing above ROM (go to app mode). Remove the option of writing to system_mode through the API. Co-authored-by: Mikael Ågren --- hw/application_fpga/core/tk1/rtl/tk1.v | 31 +++++++++++++++++++++----- 1 file changed, 25 insertions(+), 6 deletions(-) diff --git a/hw/application_fpga/core/tk1/rtl/tk1.v b/hw/application_fpga/core/tk1/rtl/tk1.v index 80cfc17..7ce3a5e 100644 --- a/hw/application_fpga/core/tk1/rtl/tk1.v +++ b/hw/application_fpga/core/tk1/rtl/tk1.v @@ -106,6 +106,7 @@ module tk1 ( localparam FW_RAM_FIRST = 32'hd0000000; localparam FW_RAM_LAST = 32'hd00007ff; + localparam FW_ROM_LAST = 32'h00001fff; // ILLEGAL_ADDR is outside of the physical memory, and will trap in // the security monitor if accessed. @@ -118,6 +119,7 @@ module tk1 ( reg cdi_mem_we; reg system_mode_reg; + reg system_mode_new; reg system_mode_we; reg [ 2 : 0] led_reg; @@ -297,7 +299,7 @@ module tk1 ( gpio2_reg[1] <= gpio2_reg[0]; if (system_mode_we) begin - system_mode_reg <= 1'h1; + system_mode_reg <= system_mode_new; end if (led_we) begin @@ -422,12 +424,33 @@ module tk1 ( end end + //---------------------------------------------------------------- + // system_mode_ctrl will raise the privilege when the function in + // `syscall_addr_reg` is called. + // + // Automatically lowers the privilege when executing above ROM + // ---------------------------------------------------------------- + always @* begin : system_mode_ctrl + system_mode_new = 1'h0; + system_mode_we = 1'h0; + + if (cpu_valid & cpu_instr) begin + if (cpu_addr == syscall_addr_reg) begin + system_mode_new = 1'h0; + system_mode_we = 1'h1; + end + + if (cpu_addr > FW_ROM_LAST) begin + system_mode_new = 1'h1; + system_mode_we = 1'h1; + end + end + end //---------------------------------------------------------------- // api //---------------------------------------------------------------- always @* begin : api - system_mode_we = 1'h0; led_we = 1'h0; gpio3_we = 1'h0; gpio4_we = 1'h0; @@ -455,10 +478,6 @@ module tk1 ( if (cs) begin tmp_ready = 1'h1; if (we) begin - if (address == ADDR_SYSTEM_MODE_CTRL) begin - system_mode_we = 1'h1; - end - if (address == ADDR_LED) begin led_we = 1'h1; end