Mon, 14 Jan 2013 09:22:12 +0000
More bus error fixes for FreeBee
I have fixed two more bus error handling bugs in FreeBee. First, the CPU core was executing the instruction regardless of whether a bus error occurs when fetching the opcode (which caused it to execute a bogus instruction in such cases). The other one was related to one of my previous fixes - the jump to the bus error vector was at the beginning of the main loop, so it wouldn't be called immediately after the bus error occurred if the timeslot expired, causing the return address to be off.
With these fixes, Unix now runs enough to get into userspace and run the install script (it is also possible to break out and get a shell prompt). However, many commands segfault semi-randomly (or more specifically, it seems that some child processes forked by the shell might be segfaulting before they can exec the command program), so installing the system isn't possible yet. I am not sure exactly what the bug is, but it seems to be related to some function in the shell returning null when the code calling it is assuming that it won't. What the function is, or why it is returning null, I'm not sure (the shell is built without the shared libc and is stripped, making identifying the function harder). I suspect that the function might be in libc, but that is hard to tell.
Author: Andrew Warkentin <andreww591 gmail com>
| philpem@112 | 1 | #ifndef _WD2010_H |
| philpem@112 | 2 | #define _WD2010_H |
| philpem@112 | 3 | |
| philpem@112 | 4 | #include <stdbool.h> |
| philpem@112 | 5 | #include <stddef.h> |
| philpem@112 | 6 | #include <stdint.h> |
| philpem@112 | 7 | #include <stdio.h> |
| philpem@112 | 8 | |
| philpem@112 | 9 | /// WD2010 registers |
| philpem@112 | 10 | typedef enum { |
| philpem@116 | 11 | WD2010_REG_ERROR = 1, ///< Error register |
| philpem@116 | 12 | WD2010_REG_WRITE_PRECOMP_CYLINDER = 1, ///< Write precompensation cylinder register |
| philpem@116 | 13 | WD2010_REG_SECTOR_COUNT = 2, ///< Sector count register |
| philpem@116 | 14 | WD2010_REG_SECTOR_NUMBER = 3, ///< Sector number register |
| philpem@116 | 15 | WD2010_REG_CYLINDER_LOW = 4, ///< Low byte of cylinder |
| philpem@116 | 16 | WD2010_REG_CYLINDER_HIGH = 5, ///< High byte of cylinder |
| philpem@116 | 17 | WD2010_REG_SDH = 6, ///< Sector size, drive, and head |
| philpem@116 | 18 | WD2010_REG_STATUS = 7, ///< Status register |
| philpem@116 | 19 | WD2010_REG_COMMAND = 7, ///< Command register |
| philpem@116 | 20 | UNIXPC_REG_MCR2 = 255 ///< UNIX-PC MCR2 register (special!) |
| philpem@112 | 21 | } WD2010_REG; |
| philpem@112 | 22 | |
| philpem@112 | 23 | /// WD2010 emulator error codes |
| philpem@112 | 24 | typedef enum { |
| philpem@112 | 25 | WD2010_ERR_OK = 0, ///< Operation succeeded |
| philpem@112 | 26 | WD2010_ERR_BAD_GEOM = -1, ///< Bad geometry, or image file too small |
| philpem@112 | 27 | WD2010_ERR_NO_MEMORY = -2 ///< Out of memory |
| philpem@112 | 28 | } WD2010_ERR; |
| philpem@112 | 29 | |
| philpem@112 | 30 | typedef struct { |
| philpem@112 | 31 | // Current track, head and sector |
| philpem@112 | 32 | int track, head, sector; |
| philpem@112 | 33 | // Geometry of current disc |
| philpem@112 | 34 | int geom_secsz, geom_spt, geom_heads, geom_tracks; |
| philpem@112 | 35 | // IRQ status |
| philpem@112 | 36 | bool irq; |
| philpem@112 | 37 | // Status of last command |
| philpem@112 | 38 | uint8_t status; |
| philpem@112 | 39 | // Error resgister |
| philpem@112 | 40 | uint8_t error_reg; |
| philpem@112 | 41 | // Cylinder number registers |
| philpem@112 | 42 | uint8_t cylinder_high_reg, cylinder_low_reg; |
| philpem@112 | 43 | // SDH register (sets sector size, drive number, and head number) |
| philpem@112 | 44 | uint8_t sdh; |
| philpem@116 | 45 | // MCR2 register (LSB is HDSEL3 - head select bit 3) |
| philpem@116 | 46 | bool mcr2_hdsel3, mcr2_ddrive1; |
| philpem@112 | 47 | // Sector number and count registers |
| philpem@112 | 48 | int sector_number, sector_count; |
| philpem@112 | 49 | // Last command has the multiple sector flag set? |
| philpem@112 | 50 | bool multi_sector; |
| philpem@112 | 51 | // Last command uses DRQ bit? |
| philpem@112 | 52 | bool cmd_has_drq; |
| philpem@112 | 53 | // Current write is a format? |
| philpem@112 | 54 | bool formatting; |
| philpem@112 | 55 | // Data buffer, current DRQ pointer and length |
| philpem@112 | 56 | uint8_t *data; |
| philpem@112 | 57 | size_t data_pos, data_len; |
| philpem@112 | 58 | // Current disc image file |
| philpem@112 | 59 | FILE *disc_image; |
| philpem@112 | 60 | // LBA at which to start writing |
| philpem@112 | 61 | int write_pos; |
| philpem@112 | 62 | // Flag to allow delaying DRQ |
| philpem@112 | 63 | bool drq; |
| philpem@112 | 64 | } WD2010_CTX; |
| philpem@112 | 65 | |
| philpem@112 | 66 | /** |
| philpem@112 | 67 | * @brief Initialise a WD2010 context. |
| philpem@112 | 68 | * @param ctx WD2010 context. |
| philpem@112 | 69 | * |
| philpem@112 | 70 | * This must be run once when the context is created. |
| philpem@112 | 71 | */ |
| philpem@112 | 72 | int wd2010_init(WD2010_CTX *ctx, FILE *fp, int secsz, int spt, int heads); |
| philpem@112 | 73 | |
| philpem@112 | 74 | /** |
| philpem@112 | 75 | * @brief Reset a WD2010 context. |
| philpem@112 | 76 | * @param ctx WD2010 context. |
| philpem@112 | 77 | * |
| philpem@112 | 78 | * This should be run if the WD2010 needs to be reset (MR/ line toggled). |
| philpem@112 | 79 | */ |
| philpem@112 | 80 | void wd2010_reset(WD2010_CTX *ctx); |
| philpem@112 | 81 | |
| philpem@112 | 82 | /** |
| philpem@112 | 83 | * Deinitialise a WD2010 context. |
| philpem@112 | 84 | * @param ctx WD2010 context. |
| philpem@112 | 85 | */ |
| philpem@112 | 86 | void wd2010_done(WD2010_CTX *ctx); |
| philpem@112 | 87 | |
| philpem@112 | 88 | /** |
| philpem@112 | 89 | * @brief Read IRQ Rising Edge status. |
| philpem@112 | 90 | * @param ctx WD2010 context. |
| philpem@112 | 91 | */ |
| philpem@112 | 92 | bool wd2010_get_irq(WD2010_CTX *ctx); |
| philpem@112 | 93 | |
| philpem@112 | 94 | /** |
| philpem@112 | 95 | * @brief Read DRQ status. |
| philpem@112 | 96 | * @param ctx WD2010 context. |
| philpem@112 | 97 | */ |
| philpem@112 | 98 | bool wd2010_get_drq(WD2010_CTX *ctx); |
| philpem@112 | 99 | |
| philpem@112 | 100 | /** |
| philpem@112 | 101 | * @brief Read WD2010 register. |
| philpem@112 | 102 | * @param ctx WD2010 context |
| philpem@112 | 103 | * @param addr Register address (0, 1, 2, 3, 4, 5, 6, 7, or 8) |
| philpem@112 | 104 | */ |
| philpem@112 | 105 | uint8_t wd2010_read_reg(WD2010_CTX *ctx, uint8_t addr); |
| philpem@112 | 106 | |
| philpem@112 | 107 | /** |
| philpem@112 | 108 | * @brief Write WD2010 register |
| philpem@112 | 109 | * @param ctx WD2010 context |
| philpem@112 | 110 | * @param addr Register address (0, 1, 2, 3, 4, 5, 6, 7, or 8) |
| philpem@112 | 111 | * @param val Value to write |
| philpem@112 | 112 | */ |
| philpem@112 | 113 | void wd2010_write_reg(WD2010_CTX *ctx, uint8_t addr, uint8_t val); |
| philpem@112 | 114 | |
| philpem@112 | 115 | /** |
| philpem@112 | 116 | * @brief Read a data byte from the data buffer |
| philpem@112 | 117 | * @param ctx WD2010 context |
| philpem@112 | 118 | */ |
| philpem@112 | 119 | uint8_t wd2010_read_data(WD2010_CTX *ctx); |
| philpem@112 | 120 | |
| philpem@112 | 121 | /** |
| philpem@112 | 122 | * @brief Write a value to the data buffer |
| philpem@112 | 123 | * @param ctx WD2010 context |
| philpem@112 | 124 | * @param val Value to write |
| philpem@112 | 125 | */ |
| philpem@112 | 126 | void wd2010_write_data(WD2010_CTX *ctx, uint8_t val); |
| philpem@112 | 127 | |
| philpem@112 | 128 | void wd2010_dma_miss(WD2010_CTX *ctx); |
| philpem@112 | 129 | #endif |