[GDB] Add watch and rwatch hardware watchpoints

diff --git a/src/arch/i386/core/gdbidt.S b/src/arch/i386/core/gdbidt.S
index 45d079f..a494923 100644 (file)
--- a/src/arch/i386/core/gdbidt.S
+++ b/src/arch/i386/core/gdbidt.S
@@ -184,7 +184,7 @@ do_interrupt:
        /* Call GDB stub exception handler */
        pushl   %esp
        pushl   (IH_OFFSET_SIGNO + 4)(%esp)
-       call    gdbstub_handler
+       call    gdbmach_handler
        addl    $8, %esp
 
        /* Restore CPU state from GDB register snapshot */

diff --git a/src/arch/i386/core/gdbmach.c b/src/arch/i386/core/gdbmach.c
new file mode 100644 (file)
index 0000000..7cffc9e
--- /dev/null
+++ b/src/arch/i386/core/gdbmach.c
@@ -0,0 +1,126 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <assert.h>
+#include <virtaddr.h>
+#include <gpxe/gdbstub.h>
+#include <gdbmach.h>
+
+enum {
+       DR7_CLEAR = 0x00000400,    /* disable hardware breakpoints */
+       DR6_CLEAR = 0xffff0ff0,    /* clear breakpoint status */
+};
+
+/** Hardware breakpoint, fields stored in x86 bit pattern form */
+struct hwbp {
+       int type;           /* type (1=write watchpoint, 3=access watchpoint) */
+       unsigned long addr; /* linear address */
+       size_t len;         /* length (0=1-byte, 1=2-byte, 3=4-byte) */
+       int enabled;
+};
+
+static struct hwbp hwbps [ 4 ];
+static gdbreg_t dr7 = DR7_CLEAR;
+static gdbreg_t dr6;
+
+static struct hwbp *gdbmach_find_hwbp ( int type, unsigned long addr, size_t len ) {
+       struct hwbp *available = NULL;
+       unsigned int i;
+       for ( i = 0; i < sizeof hwbps / sizeof hwbps [ 0 ]; i++ ) {
+               if ( hwbps [ i ].type == type && hwbps [ i ].addr == addr && hwbps [ i ].len == len ) {
+                       return &hwbps [ i ];
+               }
+               if ( !hwbps [ i ].enabled ) {
+                       available = &hwbps [ i ];
+               }
+       }
+       return available;
+}
+
+static void gdbmach_commit_hwbp ( struct hwbp *bp ) {
+       int regnum = bp - hwbps;
+
+       /* Set breakpoint address */
+       assert ( regnum >= 0 && regnum < sizeof hwbps / sizeof hwbps [ 0 ] );
+       switch ( regnum ) {
+               case 0:
+                       __asm__ __volatile__ ( "movl %0, %%dr0\n" : : "r" ( bp->addr ) );
+                       break;
+               case 1:
+                       __asm__ __volatile__ ( "movl %0, %%dr1\n" : : "r" ( bp->addr ) );
+                       break;
+               case 2:
+                       __asm__ __volatile__ ( "movl %0, %%dr2\n" : : "r" ( bp->addr ) );
+                       break;
+               case 3:
+                       __asm__ __volatile__ ( "movl %0, %%dr3\n" : : "r" ( bp->addr ) );
+                       break;
+       }
+
+       /* Set type */
+       dr7 &= ~( 0x3 << ( 16 + 4 * regnum ) );
+       dr7 |= bp->type << ( 16 + 4 * regnum );
+
+       /* Set length */
+       dr7 &= ~( 0x3 << ( 18 + 4 * regnum ) );
+       dr7 |= bp->len << ( 18 + 4 * regnum );
+
+       /* Set/clear local enable bit */
+       dr7 &= ~( 0x3 << 2 * regnum );
+       dr7 |= bp->enabled << 2 * regnum;
+}
+
+int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len, int enable ) {
+       struct hwbp *bp;
+       
+       /* Check and convert breakpoint type to x86 type */
+       switch ( type ) {
+               case GDBMACH_WATCH:
+                       type = 0x1;
+                       break;
+               case GDBMACH_AWATCH:
+                       type = 0x3;
+                       break;
+               default:
+                       return 0; /* unsupported breakpoint type */
+       }
+
+       /* Only lengths 1, 2, and 4 are supported */
+       if ( len != 2 && len != 4 ) {
+               len = 1;
+       }
+       len--; /* convert to x86 breakpoint length bit pattern */
+
+       /* Calculate linear address by adding segment base */
+       addr += virt_offset;
+
+       /* Set up the breakpoint */
+       bp = gdbmach_find_hwbp ( type, addr, len );
+       if ( !bp ) {
+               return 0; /* ran out of hardware breakpoints */
+       }
+       bp->type = type;
+       bp->addr = addr;
+       bp->len = len;
+       bp->enabled = enable;
+       gdbmach_commit_hwbp ( bp );
+       return 1;
+}
+
+static void gdbmach_disable_hwbps ( void ) {
+       /* Store and clear breakpoint status register */
+       __asm__ __volatile__ ( "movl %%dr6, %0\n" "movl %1, %%dr6\n" : "=r" ( dr6 ) : "r" ( DR6_CLEAR ) );
+
+       /* Store and clear hardware breakpoints */
+       __asm__ __volatile__ ( "movl %0, %%dr7\n" : : "r" ( DR7_CLEAR ) );
+}
+
+static void gdbmach_enable_hwbps ( void ) {
+       /* Restore hardware breakpoints */
+       __asm__ __volatile__ ( "movl %0, %%dr7\n" : : "r" ( dr7 ) );
+}
+
+__cdecl void gdbmach_handler ( int signo, gdbreg_t *regs ) {
+       gdbmach_disable_hwbps();
+       gdbstub_handler ( signo, regs );
+       gdbmach_enable_hwbps();
+}

diff --git a/src/arch/i386/include/gdbmach.h b/src/arch/i386/include/gdbmach.h
index 9f6dc8f..1a38ccd 100644 (file)
--- a/src/arch/i386/include/gdbmach.h
+++ b/src/arch/i386/include/gdbmach.h
@@ -10,6 +10,8 @@
  *
  */
 
+#include <stdint.h>
+
 typedef uint32_t gdbreg_t;
 
 /* The register snapshot, this must be in sync with interrupt handler and the
@@ -35,6 +37,15 @@ enum {
        GDBMACH_SIZEOF_REGS = GDBMACH_NREGS * sizeof ( gdbreg_t )
 };
 
+/* Breakpoint types */
+enum {
+       GDBMACH_BPMEM,
+       GDBMACH_BPHW,
+       GDBMACH_WATCH,
+       GDBMACH_RWATCH,
+       GDBMACH_AWATCH,
+};
+
 static inline void gdbmach_set_pc ( gdbreg_t *regs, gdbreg_t pc ) {
        regs [ GDBMACH_EIP ] = pc;
 }
@@ -48,4 +59,6 @@ static inline void gdbmach_breakpoint ( void ) {
        __asm__ __volatile__ ( "int $3\n" );
 }
 
+extern int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len, int enable );
+
 #endif /* GDBMACH_H */

diff --git a/src/core/gdbstub.c b/src/core/gdbstub.c
index c331b85..8e33877 100644 (file)
--- a/src/core/gdbstub.c
+++ b/src/core/gdbstub.c
@@ -249,6 +249,22 @@ static void gdbstub_continue ( struct gdbstub *stub, int single_step ) {
        /* Reply will be sent when we hit the next breakpoint or interrupt */
 }
 
+static void gdbstub_breakpoint ( struct gdbstub *stub ) {
+       unsigned long args [ 3 ];
+       int enable = stub->payload [ 0 ] == 'Z' ? 1 : 0;
+       if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], NULL ) ) {
+               gdbstub_send_errno ( stub, POSIX_EINVAL );
+               return;
+       }
+       if ( gdbmach_set_breakpoint ( args [ 0 ], args [ 1 ], args [ 2 ], enable ) ) {
+               gdbstub_send_ok ( stub );
+       } else {
+               /* Not supported */
+               stub->len = 0;
+               gdbstub_tx_packet ( stub );
+       }
+}
+
 static void gdbstub_rx_packet ( struct gdbstub *stub ) {
        switch ( stub->payload [ 0 ] ) {
                case '?':
@@ -275,6 +291,10 @@ static void gdbstub_rx_packet ( struct gdbstub *stub ) {
                                gdbstub_send_ok ( stub );
                        }
                        break;
+               case 'Z': /* Insert breakpoint */
+               case 'z': /* Remove breakpoint */
+                       gdbstub_breakpoint ( stub );
+                       break;
                default:
                        stub->len = 0;
                        gdbstub_tx_packet ( stub );
@@ -341,7 +361,7 @@ static struct gdbstub stub = {
        .parse = gdbstub_state_new
 };
 
-__cdecl void gdbstub_handler ( int signo, gdbreg_t *regs ) {
+void gdbstub_handler ( int signo, gdbreg_t *regs ) {
        char packet [ SIZEOF_PAYLOAD + 4 ];
        size_t len, i;
 

diff --git a/src/include/gpxe/gdbstub.h b/src/include/gpxe/gdbstub.h
index adc7e38..bf5d24d 100644 (file)
--- a/src/include/gpxe/gdbstub.h
+++ b/src/include/gpxe/gdbstub.h
@@ -9,6 +9,7 @@
 
 #include <stdint.h>
 #include <gpxe/tables.h>
+#include <gdbmach.h>
 
 /**
  * A transport mechanism for the GDB protocol
@@ -61,4 +62,12 @@ extern struct gdb_transport *find_gdb_transport ( const char *name );
  */
 extern void gdbstub_start ( struct gdb_transport *trans );
 
+/**
+ * Interrupt handler
+ *
+ * @signo POSIX signal number
+ * @regs CPU register snapshot
+ **/
+extern void gdbstub_handler ( int signo, gdbreg_t *regs );
+
 #endif /* _GPXE_GDBSTUB_H */

diff --git a/src/tests/gdbstub_test.S b/src/tests/gdbstub_test.S
index 6478308..bd29383 100644 (file)
--- a/src/tests/gdbstub_test.S
+++ b/src/tests/gdbstub_test.S
@@ -1,4 +1,9 @@
        .arch i386
+
+       .section ".data"
+watch_me:
+       .long 0xfeedbeef
+
        .section ".text"
        .code32
 gdbstub_test:
@@ -29,5 +34,21 @@ gdbstub_test:
        int     $3
        nop
 
+       /* 6. Access watch test */
+       movl    $0x600d0000, %ecx
+       movl    watch_me, %eax
+       movl    $0xbad00000, %ecx
+       int     $3
+       movl    $0x600d0001, %ecx
+       movl    %eax, watch_me
+       movl    $0xbad00001, %ecx
+       int     $3
+
+       /* 7. Write watch test */
+       movl    $0x600d0002, %ecx
+       movl    %eax, watch_me
+       movl    $0xbad00002, %ecx
+       int     $3
+
 1:
        jmp     1b

diff --git a/src/tests/gdbstub_test.gdb b/src/tests/gdbstub_test.gdb
index c86d4f2..191799a 100755 (executable)
--- a/src/tests/gdbstub_test.gdb
+++ b/src/tests/gdbstub_test.gdb
@@ -77,6 +77,34 @@ define gpxe_test_step
        gpxe_assert ({char}($eip-1)) (char)0x90 "gpxe_test_step" # nop = 0x90
 end
 
+define gpxe_test_awatch
+       awatch watch_me
+
+       c
+       gpxe_assert $ecx 0x600d0000 "gpxe_test_awatch"
+       if $ecx == 0x600d0000
+               c
+       end
+
+       c
+       gpxe_assert $ecx 0x600d0001 "gpxe_test_awatch"
+       if $ecx == 0x600d0001
+               c
+       end
+
+       delete
+end
+
+define gpxe_test_watch
+       watch watch_me
+       c
+       gpxe_assert $ecx 0x600d0002 "gpxe_test_watch"
+       if $ecx == 0x600d0002
+               c
+       end
+       delete
+end
+
 gpxe_load_symbols
 gpxe_start_tests
 gpxe_test_regs_read
@@ -84,3 +112,5 @@ gpxe_test_regs_write
 gpxe_test_mem_read
 gpxe_test_mem_write
 gpxe_test_step
+gpxe_test_awatch
+gpxe_test_watch