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Diffstat (limited to 'gdb/nat/x86-dregs.c')
| -rw-r--r-- | gdb/nat/x86-dregs.c | 664 |
1 files changed, 664 insertions, 0 deletions
diff --git a/gdb/nat/x86-dregs.c b/gdb/nat/x86-dregs.c new file mode 100644 index 0000000..5381c77 --- /dev/null +++ b/gdb/nat/x86-dregs.c @@ -0,0 +1,664 @@ +/* Debug register code for x86 (i386 and x86-64). + + Copyright (C) 2001-2014 Free Software Foundation, Inc. + + This file is part of GDB. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +#ifdef GDBSERVER +#include "server.h" +#else +#include "defs.h" +#include "inferior.h" +#endif +#include "x86-dregs.h" + +/* Support for hardware watchpoints and breakpoints using the x86 + debug registers. + + This provides several functions for inserting and removing + hardware-assisted breakpoints and watchpoints, testing if one or + more of the watchpoints triggered and at what address, checking + whether a given region can be watched, etc. + + The functions below implement debug registers sharing by reference + counts, and allow to watch regions up to 16 bytes long. */ + +/* Accessor macros for low-level function vector. */ + +/* Can we update the inferior's debug registers? */ +#define x86_dr_low_can_set_addr() (x86_dr_low.set_addr != NULL) + +/* Update the inferior's debug register REGNUM from STATE. */ +#define x86_dr_low_set_addr(new_state, i) \ + (x86_dr_low.set_addr ((i), (new_state)->dr_mirror[(i)])) + +/* Return the inferior's debug register REGNUM. */ +#define x86_dr_low_get_addr(i) (x86_dr_low.get_addr ((i))) + +/* Can we update the inferior's DR7 control register? */ +#define x86_dr_low_can_set_control() (x86_dr_low.set_control != NULL) + +/* Update the inferior's DR7 debug control register from STATE. */ +#define x86_dr_low_set_control(new_state) \ + (x86_dr_low.set_control ((new_state)->dr_control_mirror)) + +/* Return the value of the inferior's DR7 debug control register. */ +#define x86_dr_low_get_control() (x86_dr_low.get_control ()) + +/* Return the value of the inferior's DR6 debug status register. */ +#define x86_dr_low_get_status() (x86_dr_low.get_status ()) + +/* Return the debug register size, in bytes. */ +#define x86_get_debug_register_length() \ + (x86_dr_low.debug_register_length) + +/* Support for 8-byte wide hw watchpoints. */ +#define TARGET_HAS_DR_LEN_8 (x86_get_debug_register_length () == 8) + +/* DR7 Debug Control register fields. */ + +/* How many bits to skip in DR7 to get to R/W and LEN fields. */ +#define DR_CONTROL_SHIFT 16 +/* How many bits in DR7 per R/W and LEN field for each watchpoint. */ +#define DR_CONTROL_SIZE 4 + +/* Watchpoint/breakpoint read/write fields in DR7. */ +#define DR_RW_EXECUTE (0x0) /* Break on instruction execution. */ +#define DR_RW_WRITE (0x1) /* Break on data writes. */ +#define DR_RW_READ (0x3) /* Break on data reads or writes. */ + +/* This is here for completeness. No platform supports this + functionality yet (as of March 2001). Note that the DE flag in the + CR4 register needs to be set to support this. */ +#ifndef DR_RW_IORW +#define DR_RW_IORW (0x2) /* Break on I/O reads or writes. */ +#endif + +/* Watchpoint/breakpoint length fields in DR7. The 2-bit left shift + is so we could OR this with the read/write field defined above. */ +#define DR_LEN_1 (0x0 << 2) /* 1-byte region watch or breakpoint. */ +#define DR_LEN_2 (0x1 << 2) /* 2-byte region watch. */ +#define DR_LEN_4 (0x3 << 2) /* 4-byte region watch. */ +#define DR_LEN_8 (0x2 << 2) /* 8-byte region watch (AMD64). */ + +/* Local and Global Enable flags in DR7. + + When the Local Enable flag is set, the breakpoint/watchpoint is + enabled only for the current task; the processor automatically + clears this flag on every task switch. When the Global Enable flag + is set, the breakpoint/watchpoint is enabled for all tasks; the + processor never clears this flag. + + Currently, all watchpoint are locally enabled. If you need to + enable them globally, read the comment which pertains to this in + x86_insert_aligned_watchpoint below. */ +#define DR_LOCAL_ENABLE_SHIFT 0 /* Extra shift to the local enable bit. */ +#define DR_GLOBAL_ENABLE_SHIFT 1 /* Extra shift to the global enable bit. */ +#define DR_ENABLE_SIZE 2 /* Two enable bits per debug register. */ + +/* Local and global exact breakpoint enable flags (a.k.a. slowdown + flags). These are only required on i386, to allow detection of the + exact instruction which caused a watchpoint to break; i486 and + later processors do that automatically. We set these flags for + backwards compatibility. */ +#define DR_LOCAL_SLOWDOWN (0x100) +#define DR_GLOBAL_SLOWDOWN (0x200) + +/* Fields reserved by Intel. This includes the GD (General Detect + Enable) flag, which causes a debug exception to be generated when a + MOV instruction accesses one of the debug registers. + + FIXME: My Intel manual says we should use 0xF800, not 0xFC00. */ +#define DR_CONTROL_RESERVED (0xFC00) + +/* Auxiliary helper macros. */ + +/* A value that masks all fields in DR7 that are reserved by Intel. */ +#define X86_DR_CONTROL_MASK (~DR_CONTROL_RESERVED) + +/* The I'th debug register is vacant if its Local and Global Enable + bits are reset in the Debug Control register. */ +#define X86_DR_VACANT(state, i) \ + (((state)->dr_control_mirror & (3 << (DR_ENABLE_SIZE * (i)))) == 0) + +/* Locally enable the break/watchpoint in the I'th debug register. */ +#define X86_DR_LOCAL_ENABLE(state, i) \ + do { \ + (state)->dr_control_mirror |= \ + (1 << (DR_LOCAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \ + } while (0) + +/* Globally enable the break/watchpoint in the I'th debug register. */ +#define X86_DR_GLOBAL_ENABLE(state, i) \ + do { \ + (state)->dr_control_mirror |= \ + (1 << (DR_GLOBAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \ + } while (0) + +/* Disable the break/watchpoint in the I'th debug register. */ +#define X86_DR_DISABLE(state, i) \ + do { \ + (state)->dr_control_mirror &= \ + ~(3 << (DR_ENABLE_SIZE * (i))); \ + } while (0) + +/* Set in DR7 the RW and LEN fields for the I'th debug register. */ +#define X86_DR_SET_RW_LEN(state, i, rwlen) \ + do { \ + (state)->dr_control_mirror &= \ + ~(0x0f << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \ + (state)->dr_control_mirror |= \ + ((rwlen) << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \ + } while (0) + +/* Get from DR7 the RW and LEN fields for the I'th debug register. */ +#define X86_DR_GET_RW_LEN(dr7, i) \ + (((dr7) \ + >> (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))) & 0x0f) + +/* Did the watchpoint whose address is in the I'th register break? */ +#define X86_DR_WATCH_HIT(dr6, i) ((dr6) & (1 << (i))) + +/* Types of operations supported by x86_handle_nonaligned_watchpoint. */ +typedef enum { WP_INSERT, WP_REMOVE, WP_COUNT } x86_wp_op_t; + +#ifndef GDBSERVER +/* Whether or not to print the mirrored debug registers. */ +extern int debug_hw_points; +#endif + +/* Print the values of the mirrored debug registers. */ + +static void +x86_show_dr (struct x86_debug_reg_state *state, + const char *func, CORE_ADDR addr, + int len, enum target_hw_bp_type type) +{ + int i; + + debug_printf ("%s", func); + if (addr || len) + debug_printf (" (addr=%s, len=%d, type=%s)", + phex (addr, 8), len, + type == hw_write ? "data-write" + : (type == hw_read ? "data-read" + : (type == hw_access ? "data-read/write" + : (type == hw_execute ? "instruction-execute" + /* FIXME: if/when I/O read/write + watchpoints are supported, add them + here. */ + : "??unknown??")))); + debug_printf (":\n"); + debug_printf ("\tCONTROL (DR7): %s STATUS (DR6): %s\n", + phex (state->dr_control_mirror, 8), + phex (state->dr_status_mirror, 8)); + ALL_DEBUG_REGISTERS (i) + { + debug_printf ("\ +\tDR%d: addr=0x%s, ref.count=%d DR%d: addr=0x%s, ref.count=%d\n", + i, phex (state->dr_mirror[i], + x86_get_debug_register_length ()), + state->dr_ref_count[i], + i + 1, phex (state->dr_mirror[i + 1], + x86_get_debug_register_length ()), + state->dr_ref_count[i + 1]); + i++; + } +} + +/* Return the value of a 4-bit field for DR7 suitable for watching a + region of LEN bytes for accesses of type TYPE. LEN is assumed to + have the value of 1, 2, or 4. */ + +static unsigned +x86_length_and_rw_bits (int len, enum target_hw_bp_type type) +{ + unsigned rw; + + switch (type) + { + case hw_execute: + rw = DR_RW_EXECUTE; + break; + case hw_write: + rw = DR_RW_WRITE; + break; + case hw_read: + internal_error (__FILE__, __LINE__, + _("The i386 doesn't support " + "data-read watchpoints.\n")); + case hw_access: + rw = DR_RW_READ; + break; +#if 0 + /* Not yet supported. */ + case hw_io_access: + rw = DR_RW_IORW; + break; +#endif + default: + internal_error (__FILE__, __LINE__, _("\ +Invalid hardware breakpoint type %d in x86_length_and_rw_bits.\n"), + (int) type); + } + + switch (len) + { + case 1: + return (DR_LEN_1 | rw); + case 2: + return (DR_LEN_2 | rw); + case 4: + return (DR_LEN_4 | rw); + case 8: + if (TARGET_HAS_DR_LEN_8) + return (DR_LEN_8 | rw); + /* ELSE FALL THROUGH */ + default: + internal_error (__FILE__, __LINE__, _("\ +Invalid hardware breakpoint length %d in x86_length_and_rw_bits.\n"), len); + } +} + +/* Insert a watchpoint at address ADDR, which is assumed to be aligned + according to the length of the region to watch. LEN_RW_BITS is the + value of the bits from DR7 which describes the length and access + type of the region to be watched by this watchpoint. Return 0 on + success, -1 on failure. */ + +static int +x86_insert_aligned_watchpoint (struct x86_debug_reg_state *state, + CORE_ADDR addr, unsigned len_rw_bits) +{ + int i; + + if (!x86_dr_low_can_set_addr () || !x86_dr_low_can_set_control ()) + return -1; + + /* First, look for an occupied debug register with the same address + and the same RW and LEN definitions. If we find one, we can + reuse it for this watchpoint as well (and save a register). */ + ALL_DEBUG_REGISTERS (i) + { + if (!X86_DR_VACANT (state, i) + && state->dr_mirror[i] == addr + && X86_DR_GET_RW_LEN (state->dr_control_mirror, i) == len_rw_bits) + { + state->dr_ref_count[i]++; + return 0; + } + } + + /* Next, look for a vacant debug register. */ + ALL_DEBUG_REGISTERS (i) + { + if (X86_DR_VACANT (state, i)) + break; + } + + /* No more debug registers! */ + if (i >= DR_NADDR) + return -1; + + /* Now set up the register I to watch our region. */ + + /* Record the info in our local mirrored array. */ + state->dr_mirror[i] = addr; + state->dr_ref_count[i] = 1; + X86_DR_SET_RW_LEN (state, i, len_rw_bits); + /* Note: we only enable the watchpoint locally, i.e. in the current + task. Currently, no x86 target allows or supports global + watchpoints; however, if any target would want that in the + future, GDB should probably provide a command to control whether + to enable watchpoints globally or locally, and the code below + should use global or local enable and slow-down flags as + appropriate. */ + X86_DR_LOCAL_ENABLE (state, i); + state->dr_control_mirror |= DR_LOCAL_SLOWDOWN; + state->dr_control_mirror &= X86_DR_CONTROL_MASK; + + return 0; +} + +/* Remove a watchpoint at address ADDR, which is assumed to be aligned + according to the length of the region to watch. LEN_RW_BITS is the + value of the bits from DR7 which describes the length and access + type of the region watched by this watchpoint. Return 0 on + success, -1 on failure. */ + +static int +x86_remove_aligned_watchpoint (struct x86_debug_reg_state *state, + CORE_ADDR addr, unsigned len_rw_bits) +{ + int i, retval = -1; + int all_vacant = 1; + + ALL_DEBUG_REGISTERS (i) + { + if (!X86_DR_VACANT (state, i) + && state->dr_mirror[i] == addr + && X86_DR_GET_RW_LEN (state->dr_control_mirror, i) == len_rw_bits) + { + if (--state->dr_ref_count[i] == 0) /* No longer in use? */ + { + /* Reset our mirror. */ + state->dr_mirror[i] = 0; + X86_DR_DISABLE (state, i); + /* Even though not strictly necessary, clear out all + bits in DR_CONTROL related to this debug register. + Debug output is clearer when we don't have stale bits + in place. This also allows the assertion below. */ + X86_DR_SET_RW_LEN (state, i, 0); + } + retval = 0; + } + + if (!X86_DR_VACANT (state, i)) + all_vacant = 0; + } + + if (all_vacant) + { + /* Even though not strictly necessary, clear out all of + DR_CONTROL, so that when we have no debug registers in use, + we end up with DR_CONTROL == 0. The Linux support relies on + this for an optimization. Plus, it makes for clearer debug + output. */ + state->dr_control_mirror &= ~DR_LOCAL_SLOWDOWN; + + gdb_assert (state->dr_control_mirror == 0); + } + return retval; +} + +/* Insert or remove a (possibly non-aligned) watchpoint, or count the + number of debug registers required to watch a region at address + ADDR whose length is LEN for accesses of type TYPE. Return 0 on + successful insertion or removal, a positive number when queried + about the number of registers, or -1 on failure. If WHAT is not a + valid value, bombs through internal_error. */ + +static int +x86_handle_nonaligned_watchpoint (struct x86_debug_reg_state *state, + x86_wp_op_t what, CORE_ADDR addr, int len, + enum target_hw_bp_type type) +{ + int retval = 0; + int max_wp_len = TARGET_HAS_DR_LEN_8 ? 8 : 4; + + static const int size_try_array[8][8] = + { + {1, 1, 1, 1, 1, 1, 1, 1}, /* Trying size one. */ + {2, 1, 2, 1, 2, 1, 2, 1}, /* Trying size two. */ + {2, 1, 2, 1, 2, 1, 2, 1}, /* Trying size three. */ + {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size four. */ + {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size five. */ + {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size six. */ + {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size seven. */ + {8, 1, 2, 1, 4, 1, 2, 1}, /* Trying size eight. */ + }; + + while (len > 0) + { + int align = addr % max_wp_len; + /* Four (eight on AMD64) is the maximum length a debug register + can watch. */ + int try = (len > max_wp_len ? (max_wp_len - 1) : len - 1); + int size = size_try_array[try][align]; + + if (what == WP_COUNT) + { + /* size_try_array[] is defined such that each iteration + through the loop is guaranteed to produce an address and a + size that can be watched with a single debug register. + Thus, for counting the registers required to watch a + region, we simply need to increment the count on each + iteration. */ + retval++; + } + else + { + unsigned len_rw = x86_length_and_rw_bits (size, type); + + if (what == WP_INSERT) + retval = x86_insert_aligned_watchpoint (state, addr, len_rw); + else if (what == WP_REMOVE) + retval = x86_remove_aligned_watchpoint (state, addr, len_rw); + else + internal_error (__FILE__, __LINE__, _("\ +Invalid value %d of operation in x86_handle_nonaligned_watchpoint.\n"), + (int) what); + if (retval) + break; + } + + addr += size; + len -= size; + } + + return retval; +} + +/* Update the inferior debug registers state, in STATE, with the + new debug registers state, in NEW_STATE. */ + +static void +x86_update_inferior_debug_regs (struct x86_debug_reg_state *state, + struct x86_debug_reg_state *new_state) +{ + int i; + + ALL_DEBUG_REGISTERS (i) + { + if (X86_DR_VACANT (new_state, i) != X86_DR_VACANT (state, i)) + x86_dr_low_set_addr (new_state, i); + else + gdb_assert (new_state->dr_mirror[i] == state->dr_mirror[i]); + } + + if (new_state->dr_control_mirror != state->dr_control_mirror) + x86_dr_low_set_control (new_state); + + *state = *new_state; +} + +/* Insert a watchpoint to watch a memory region which starts at + address ADDR and whose length is LEN bytes. Watch memory accesses + of the type TYPE. Return 0 on success, -1 on failure. */ + +int +x86_dr_insert_watchpoint (struct x86_debug_reg_state *state, + enum target_hw_bp_type type, + CORE_ADDR addr, int len) +{ + int retval; + /* Work on a local copy of the debug registers, and on success, + commit the change back to the inferior. */ + struct x86_debug_reg_state local_state = *state; + + if (type == hw_read) + return 1; /* unsupported */ + + if (((len != 1 && len != 2 && len != 4) + && !(TARGET_HAS_DR_LEN_8 && len == 8)) + || addr % len != 0) + { + retval = x86_handle_nonaligned_watchpoint (&local_state, + WP_INSERT, + addr, len, type); + } + else + { + unsigned len_rw = x86_length_and_rw_bits (len, type); + + retval = x86_insert_aligned_watchpoint (&local_state, + addr, len_rw); + } + + if (retval == 0) + x86_update_inferior_debug_regs (state, &local_state); + + if (debug_hw_points) + x86_show_dr (state, "insert_watchpoint", addr, len, type); + + return retval; +} + +/* Remove a watchpoint that watched the memory region which starts at + address ADDR, whose length is LEN bytes, and for accesses of the + type TYPE. Return 0 on success, -1 on failure. */ + +int +x86_dr_remove_watchpoint (struct x86_debug_reg_state *state, + enum target_hw_bp_type type, + CORE_ADDR addr, int len) +{ + int retval; + /* Work on a local copy of the debug registers, and on success, + commit the change back to the inferior. */ + struct x86_debug_reg_state local_state = *state; + + if (((len != 1 && len != 2 && len != 4) + && !(TARGET_HAS_DR_LEN_8 && len == 8)) + || addr % len != 0) + { + retval = x86_handle_nonaligned_watchpoint (&local_state, + WP_REMOVE, + addr, len, type); + } + else + { + unsigned len_rw = x86_length_and_rw_bits (len, type); + + retval = x86_remove_aligned_watchpoint (&local_state, + addr, len_rw); + } + + if (retval == 0) + x86_update_inferior_debug_regs (state, &local_state); + + if (debug_hw_points) + x86_show_dr (state, "remove_watchpoint", addr, len, type); + + return retval; +} + +/* Return non-zero if we can watch a memory region that starts at + address ADDR and whose length is LEN bytes. */ + +int +x86_dr_region_ok_for_watchpoint (struct x86_debug_reg_state *state, + CORE_ADDR addr, int len) +{ + int nregs; + + /* Compute how many aligned watchpoints we would need to cover this + region. */ + nregs = x86_handle_nonaligned_watchpoint (state, WP_COUNT, + addr, len, hw_write); + return nregs <= DR_NADDR ? 1 : 0; +} + +/* If the inferior has some break/watchpoint that triggered, set the + address associated with that break/watchpoint and return non-zero. + Otherwise, return zero. */ + +int +x86_dr_stopped_data_address (struct x86_debug_reg_state *state, + CORE_ADDR *addr_p) +{ + CORE_ADDR addr = 0; + int i; + int rc = 0; + /* The current thread's DR_STATUS. We always need to read this to + check whether some watchpoint caused the trap. */ + unsigned status; + /* We need DR_CONTROL as well, but only iff DR_STATUS indicates a + data breakpoint trap. Only fetch it when necessary, to avoid an + unnecessary extra syscall when no watchpoint triggered. */ + int control_p = 0; + unsigned control = 0; + + /* In non-stop/async, threads can be running while we change the + global dr_mirror (and friends). Say, we set a watchpoint, and + let threads resume. Now, say you delete the watchpoint, or + add/remove watchpoints such that dr_mirror changes while threads + are running. On targets that support non-stop, + inserting/deleting watchpoints updates the global dr_mirror only. + It does not update the real thread's debug registers; that's only + done prior to resume. Instead, if threads are running when the + mirror changes, a temporary and transparent stop on all threads + is forced so they can get their copy of the debug registers + updated on re-resume. Now, say, a thread hit a watchpoint before + having been updated with the new dr_mirror contents, and we + haven't yet handled the corresponding SIGTRAP. If we trusted + dr_mirror below, we'd mistake the real trapped address (from the + last time we had updated debug registers in the thread) with + whatever was currently in dr_mirror. So to fix this, dr_mirror + always represents intention, what we _want_ threads to have in + debug registers. To get at the address and cause of the trap, we + need to read the state the thread still has in its debug + registers. + + In sum, always get the current debug register values the current + thread has, instead of trusting the global mirror. If the thread + was running when we last changed watchpoints, the mirror no + longer represents what was set in this thread's debug + registers. */ + status = x86_dr_low_get_status (); + + ALL_DEBUG_REGISTERS (i) + { + if (!X86_DR_WATCH_HIT (status, i)) + continue; + + if (!control_p) + { + control = x86_dr_low_get_control (); + control_p = 1; + } + + /* This second condition makes sure DRi is set up for a data + watchpoint, not a hardware breakpoint. The reason is that + GDB doesn't call the target_stopped_data_address method + except for data watchpoints. In other words, I'm being + paranoiac. */ + if (X86_DR_GET_RW_LEN (control, i) != 0) + { + addr = x86_dr_low_get_addr (i); + rc = 1; + if (debug_hw_points) + x86_show_dr (state, "watchpoint_hit", addr, -1, hw_write); + } + } + + if (debug_hw_points && addr == 0) + x86_show_dr (state, "stopped_data_addr", 0, 0, hw_write); + + if (rc) + *addr_p = addr; + return rc; +} + +/* Return non-zero if the inferior has some watchpoint that triggered. + Otherwise return zero. */ + +int +x86_dr_stopped_by_watchpoint (struct x86_debug_reg_state *state) +{ + CORE_ADDR addr = 0; + return x86_dr_stopped_data_address (state, &addr); +} |