[U-Boot] [RFC PATCH v1 1/2] kgdb: add breakpoint support

Simon Glass sjg at chromium.org
Tue Nov 4 07:46:45 CET 2014


Hi Peng,

On 31 October 2014 23:12, Peng Fan <Peng.Fan at freescale.com> wrote:
> Add Z/z protocal support for breakpoint set/remove.
>
> Signed-off-by: Peng Fan <Peng.Fan at freescale.com>

This looks good to me - I just have a few bits below.

> ---
>  common/kgdb.c  | 273 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/kgdb.h |  35 ++++++++
>  2 files changed, 308 insertions(+)
>
> diff --git a/common/kgdb.c b/common/kgdb.c
> index d357463..fd83ccd 100644
> --- a/common/kgdb.c
> +++ b/common/kgdb.c
> @@ -92,6 +92,8 @@
>  #include <kgdb.h>
>  #include <command.h>
>
> +#include <asm-generic/errno.h>

#include <errno.h> would do

> +
>  #undef KGDB_DEBUG

Where is this used?

>
>  /*
> @@ -111,6 +113,17 @@ static int longjmp_on_fault = 0;
>  static int kdebug = 1;
>  #endif
>
> +struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
> +       [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
> +};
> +
> +#ifdef CONFIG_ARM
> +unsigned char gdb_bpt_instr[4] = {0xfe, 0xde, 0xff, 0xe7};
> +#else
> +#error "Please implement gdb_bpt_instr!"
> +#endif
> +
> +
>  static const char hexchars[]="0123456789abcdef";
>
>  /* Convert ch from a hex digit to an int */
> @@ -309,6 +322,200 @@ putpacket(unsigned char *buffer)
>         } while ((recv & 0x7f) != '+');
>  }
>
> +int kgdb_validate_break_address(unsigned addr)
> +{
> +       /* Need More */

?

> +       return 0;
> +}
> +
> +static int probe_kernel_read(unsigned char *dst, void *src, size_t size)
> +{
> +       int i;
> +       unsigned char *dst_ptr = dst;
> +       unsigned char *src_ptr = src;
> +
> +       for (i = 0; i < size; i++)
> +               *dst_ptr++ = *src_ptr++;
> +
> +       return 0;
> +}
> +
> +static int probe_kernel_write(char *dst, void *src, size_t size)

These two above are strange function names - why 'kernel' - what does
it mean in this context? Also could you must use memcpy(), either in
the functions or instead of them?

> +{
> +       int i;
> +       char *dst_ptr = dst;
> +       char *src_ptr = src;
> +
> +       for (i = 0; i < size; i++)
> +               *dst_ptr++ = *src_ptr++;
> +
> +       return 0;
> +}
> +
> +__weak int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
> +{
> +       int err;
> +
> +       err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
> +                               BREAK_INSTR_SIZE);
> +       if (err)
> +               return err;
> +
> +       err = probe_kernel_write((char *)bpt->bpt_addr, gdb_bpt_instr,
> +                                BREAK_INSTR_SIZE);
> +
> +       return err;
> +}
> +
> +/*
> + * Set the breakpoints whose state is BP_SET to BP_ACTIVE
> + */
> +int kgdb_active_sw_breakpoints(void)
> +{
> +       int err;
> +       int ret = 0;
> +       int i;
> +
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               if (kgdb_break[i].state != BP_SET)
> +                       continue;
> +
> +               err = kgdb_arch_set_breakpoint(&kgdb_break[i]);
> +               if (err) {
> +                       ret = err;
> +                       printf("KGDB: BP install failed: %lx\n",
> +                              kgdb_break[i].bpt_addr);
> +                       continue;
> +               }
> +
> +               kgdb_break[i].state = BP_ACTIVE;
> +
> +               /*
> +                * kgdb_arch_set_breakpoint touched dcache and memory.
> +                * cache should be flushed to let icache can see the updated
> +                * inst.

instruction

> +                */
> +               /* flush work is done in do_exit */
> +               kgdb_flush_cache_all();
> +       }
> +
> +       return ret;
> +}
> +
> +/*
> + * Set state from BP_SET to BP_REMOVED
> + */
> +int kgdb_remove_sw_breakpoint(unsigned int addr)
> +{
> +       int i;
> +
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               if ((kgdb_break[i].state == BP_SET) &&
> +                   (kgdb_break[i].bpt_addr == addr)) {
> +                       kgdb_break[i].state = BP_REMOVED;
> +                       return 0;
> +               }
> +       }
> +
> +       return -ENOENT;
> +}
> +
> +int kgdb_set_sw_breakpoint(unsigned int addr)
> +{
> +       int err = kgdb_validate_break_address(addr);
> +       int breakno = -1;
> +       int i;
> +
> +       if (err)
> +               return err;
> +
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               if ((kgdb_break[i].state == BP_SET) &&
> +                   (kgdb_break[i].bpt_addr == addr))
> +                       return -EEXIST;
> +       }
> +
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               /* removed or unused, use it */
> +               if ((kgdb_break[i].state == BP_REMOVED) ||
> +                   (kgdb_break[i].state == BP_UNDEFINED)) {
> +                       breakno = i;
> +                       break;
> +               }
> +       }
> +
> +       if (breakno == -1)
> +               return -E2BIG;
> +
> +       kgdb_break[breakno].state = BP_SET;
> +       kgdb_break[breakno].type = BP_BREAKPOINT;
> +       kgdb_break[breakno].bpt_addr = addr;
> +
> +       return 0;
> +}
> +
> +__weak int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
> +{
> +       return probe_kernel_write((char *)bpt->bpt_addr,
> +                                 (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
> +}
> +
> +/*
> + * set breakpoints whose state is BP_ACTIVE to BP_SET
> + */
> +int kgdb_deactivate_sw_breakpoints(void)
> +{
> +       int err;
> +       int ret = 0;
> +       int i;
> +
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               if (kgdb_break[i].state != BP_ACTIVE)
> +                       continue;
> +
> +               err = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
> +               if (err) {
> +                       printf("KGDB: BP remove failed: %lx\n",
> +                              kgdb_break[i].bpt_addr);
> +                       ret = err;
> +               }
> +
> +               kgdb_break[i].state = BP_SET;
> +
> +               /*
> +                * kgdb_arch_remove_breakpoint touched dcache and memory.
> +                * cache should be flushed to let icache can see the updated
> +                * inst.
> +                */
> +               kgdb_flush_cache_all();
> +       }
> +
> +       return ret;
> +}
> +
> +static int kgdb_remove_all_break(void)

kgdb_remove_all_breakpoints() to be consistent?

> +{
> +       int err;
> +       int i;
> +
> +       /* Clear memory breakpoints. */
> +       for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> +               if (kgdb_break[i].state != BP_ACTIVE)
> +                       goto setundefined;
> +               err = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
> +               if (err)
> +                       printf("KGDB: breakpoint remove failed: %lx\n",
> +                              kgdb_break[i].bpt_addr);
> +setundefined:
> +               kgdb_break[i].state = BP_UNDEFINED;
> +       }
> +
> +       /* clear hardware breakpoints. */
> +       /* ToDo in future. */

/* TODO: clear hardware breakpoints. */

> +
> +       return 0;
> +}
> +
>  /*
>   * This function does all command processing for interfacing to gdb.
>   */
> @@ -318,6 +525,7 @@ handle_exception (struct pt_regs *regs)
>         int addr;
>         int length;
>         char *ptr;
> +       char *bpt_type;
>         kgdb_data kd;
>         int i;
>
> @@ -376,6 +584,12 @@ handle_exception (struct pt_regs *regs)
>
>         putpacket((unsigned char *)&remcomOutBuffer);
>
> +       /*
> +        * Each time trigger a kgdb break, first deactive all active
> +        * breakpoints.
> +        */
> +       kgdb_deactivate_sw_breakpoints();
> +
>         while (1) {
>                 volatile int errnum;
>
> @@ -394,6 +608,8 @@ handle_exception (struct pt_regs *regs)
>                 if (errnum == 0) switch (remcomInBuffer[0]) {
>
>                 case '?':               /* report most recent signal */
> +                       kgdb_remove_all_break();
> +
>                         remcomOutBuffer[0] = 'S';
>                         remcomOutBuffer[1] = hexchars[kd.sigval >> 4];
>                         remcomOutBuffer[2] = hexchars[kd.sigval & 0xf];
> @@ -465,6 +681,8 @@ handle_exception (struct pt_regs *regs)
>                                 kd.extype |= KGDBEXIT_WITHADDR;
>                         }
>
> +                       kgdb_active_sw_breakpoints();
> +
>                         goto doexit;
>
>                 case 'S':    /* SSS  single step with signal SS */
> @@ -479,6 +697,8 @@ handle_exception (struct pt_regs *regs)
>                                 kd.extype |= KGDBEXIT_WITHADDR;
>                         }
>
> +                       kgdb_active_sw_breakpoints();
> +
>                 doexit:
>  /* Need to flush the instruction cache here, as we may have deposited a
>   * breakpoint, and the icache probably has no way of knowing that a data ref to
> @@ -506,6 +726,59 @@ handle_exception (struct pt_regs *regs)
>                                 kgdb_error(KGDBERR_BADPARAMS);
>                         }
>                         break;
> +               case 'z':
> +                       /*
> +                        * Break point remove
> +                        * packet: zt,addr,length
> +                        */
> +               case 'Z':
> +                       /*
> +                        * Break point set
> +                        * packet: Zt,addr,length
> +                        *
> +                        * t is type: `0' - software breakpoint,
> +                        * `1' - hardware breakpoint, `2' - write watchpoint,
> +                        * `3' - read watchpoint, `4' - access watchpoint;
> +                        * addr is address; length is in bytes. For a software
> +                        * breakpoint, length specifies the size of the
> +                        * instruction to be patched. For hardware breakpoints
> +                        * and watchpoints length specifies the memory region
> +                        * to be monitored. To avoid potential problems with
> +                        * duplicate packets, the operations should be
> +                        * implemented in an idempotent way.
> +                        */
> +                       bpt_type = &remcomInBuffer[1];
> +                       ptr = &remcomInBuffer[2];
> +
> +                       if (*(ptr++) != ',') {
> +                               errnum = -EINVAL;
> +                               break;
> +                       }
> +
> +                       if (!hexToInt(&ptr, &addr)) {
> +                               errnum = -EINVAL;
> +                               break;
> +                       }
> +
> +                       if (*ptr++ != ',') {
> +                               errnum = -EINVAL;
> +                               break;
> +                       }
> +
> +                       /* only software breakpoint is implemented */
> +                       if ((remcomInBuffer[0] == 'Z') && (*bpt_type == '0')) {
> +                               errnum = kgdb_set_sw_breakpoint(addr);
> +                       } else if ((remcomInBuffer[0] == 'z') &&
> +                                (*bpt_type == '0')) {
> +                               errnum = kgdb_remove_sw_breakpoint(addr);
> +                       } else {
> +                               /* Unsupported */
> +                               errnum = -EINVAL;
> +                       }
> +
> +                       if (errnum == 0)
> +                               strcpy(remcomOutBuffer, "OK");
> +                       break;
>                 }                       /* switch */
>
>                 if (errnum != 0)
> diff --git a/include/kgdb.h b/include/kgdb.h
> index b6ba742..f9152b5 100644
> --- a/include/kgdb.h
> +++ b/include/kgdb.h
> @@ -20,6 +20,12 @@
>
>  #define KGDBEXIT_WITHADDR      0x100
>
> +#if defined(CONFIG_ARM)
> +#define BREAK_INSTR_SIZE       4
> +#else
> +#error "BREAK_INSTR_SIZE not set"
> +#endif
> +
>  typedef
>         struct {
>                 int num;
> @@ -38,6 +44,29 @@ typedef
>         }
>  kgdb_data;
>
> +enum kgdb_bptype {
> +       BP_BREAKPOINT = 0,
> +       BP_HARDWARE_BREAKPOINT,
> +       BP_WRITE_WATCHPOINT,
> +       BP_READ_WATCHPOINT,
> +       BP_ACCESS_WATCHPOINT,
> +       BP_POKE_BREAKPOINT,
> +};
> +
> +enum kgdb_bpstate {
> +       BP_UNDEFINED = 0,
> +       BP_REMOVED,
> +       BP_SET,
> +       BP_ACTIVE
> +};
> +
> +struct kgdb_bkpt {
> +       unsigned long           bpt_addr;
> +       unsigned char           saved_instr[BREAK_INSTR_SIZE];
> +       enum kgdb_bptype        type;
> +       enum kgdb_bpstate       state;
> +};
> +
>  /* these functions are provided by the generic kgdb support */
>  extern void kgdb_init(void);
>  extern void kgdb_error(int);
> @@ -67,4 +96,10 @@ extern void kgdb_interruptible(int);
>  /* this is referenced in the trap handler for the platform */
>  extern int (*debugger_exception_handler)(struct pt_regs *);
>
> +int kgdb_set_sw_break(unsigned int addr);
> +int kgdb_remove_sw_break(unsigned int addr);
> +int kgdb_validate_break_address(unsigned int addr);
> +
> +#define KGDB_MAX_BREAKPOINTS   32
> +
>  #endif /* __KGDB_H__ */
> --
> 1.8.4.5
>

Regards,
Simon


More information about the U-Boot mailing list