[PING] [PATCH v3] gdb: ADI support
Wei-min Pan
weimin.pan@oracle.com
Tue Jul 11 02:56:00 GMT 2017
With your comments like:
* You can't access /proc in *-tdep.c file, because it is also compiled for
cross-debugger (from previous review);
* We can't include "nat.h" in "tdep.c";
* Calling pread64 in -tdep.c makes few sense to me. If you only want to
support native debugging, move them to -nat.c file.
I now believe that the ADI support should be in sparc6 4-linux-nat.c,
not sparc64-tdep.c. Doing so also makes cross gdb build a non-issue.
Our QA team has been working on an ADI test case which they will submit
upstream separately. Hope that's OK.
Will address your other comments in separate emails. Thanks.
On 7/10/2017 3:37 AM, Yao Qi wrote:
> Weimin Pan <weimin.pan@oracle.com> writes:
>
>> Tested in sparc64-linux-gnu. No regressions.
>>
> Did you build a cross gdb on x86-linux? At least it breaks the build
> for all targets, I configure gdb this way,
>
> "../binutils-gdb/configure --enable-sim --disable-binutils
> --disable-gprof --disable-gold --disable-gas --disable-ld
> --enable-targets=all --enable-64-bit-bfd"
>
> sparc64-tdep.o: In function `adi_tag_fd()':
> build-gdb/gdb/../../binutils-gdb/gdb/sparc64-tdep.c:1915: undefined reference to `open_adi_tag_fd(int)'
>
> because sparc64-tdep.o references function defined in sparc64-linux-nat.c.
>
>> gdb/ChangeLog:
>> 2017-06-26 Weimin Pan <weimin.pan@oracle.com>
> A blank line is needed here.
>
>> * sparc64-tdep.h: (adi_normalize_address): New export.
>> * sparc-nat.h: (open_adi_tag_fd): New export.
>> * sparc64-linux-nat.c: (open_adi_tag_fd): New function.
>> * sparc64-linux-tdep.c:
>> (SEGV_ACCADI, SEGV_ADIDERR, SEGV_ADIPERR) New defines.
>> (sparc64_linux_handle_segmentation_fault): New function.
>> (sparc64_linux_init_abi): Register
>> sparc64_linux_handle_segmentation_fault
>> * sparc64-tdep.c: Include cli-utils.h,gdbcmd.h,auxv.h,sparc-nat.h.
>> (sparc64_pstate_type): Replace PID1 with MCDE.
>> (sparc64_addr_bits_remove): New function.
>> (sparc64_init_abi): Register sparc64_addr_bits_remove.
>> (MAX_PROC_NAME_SIZE): New macro.
>> (AT_ADI_BLKSZ, AT_ADI_NBITS, AT_ADI_UEONADI) New defines.
>> (sparc64adilist): New variable.
>> (adi_proc_list): New variable.
>> (find_adi_info): New function.
>> (add_adi_info): New function.
>> (get_adi_info_proc): New function.
>> (get_adi_info): New function.
>> (info_adi_command): New function.
>> (read_maps_entry): New function.
>> (adi_available): New function.
>> (adi_normalize_address): New function.
>> (adi_align_address): New function.
>> (adi_convert_byte_count): New function.
>> (adi_tag_fd): New function.
>> (adi_is_addr_mapped): New function.
>> (adi_read_versions): New function.
>> (adi_write_versions): New function.
>> (adi_print_versions): New function.
>> (do_examine): New function.
>> (do_assign): New function.
>> (adi_examine_command): New function.
>> (adi_assign_command): New function.
>> (_initialize_sparc64_tdep): New function.
>>
>> gdb/doc/ChangeLog:
>> 2017-06-26 Weimin Pan <weimin.pan@oracle.com>
>> * gdb.texinfo (Architectures): Add new Sparc64 section to document
>> ADI support.
>> * NEWS: Add "adi examine" and "adi assign" commands.
> Can you add a test case?
>
>> +
>> +Below is an example of displaying ADI versions of variable "shmaddr".
>> +
>> +@smallexample
>> +(@value{GDBP}) adi x/100 shmaddr
>> + 0xfff800010002c000: 0 0
>> +@end smallexample
> Why "0" is printed twice?
>
>> +void
>> +sparc64_linux_handle_segmentation_fault (struct gdbarch *gdbarch,
>> + struct ui_out *uiout)
>> +{
>> + if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word != 64)
>> + return;
>> +
>> + CORE_ADDR addr = 0;
>> + long si_code = 0;
>> +
>> + TRY
>> + {
>> + /* Evaluate si_code to see if the segfault is ADI related. */
>> + si_code = parse_and_eval_long ("$_siginfo.si_code\n");
>> +
>> + if (si_code >= SEGV_ACCADI && si_code <= SEGV_ADIPERR)
>> + addr = parse_and_eval_long ("$_siginfo._sifields._sigfault.si_addr");
>> + }
>> + CATCH (exception, RETURN_MASK_ALL)
>> + {
>> + return;
>> + }
>> + END_CATCH
>> +
>> + /* Print out ADI event based on sig_code value */
>> + switch (si_code)
>> + {
>> + case SEGV_ACCADI: /* adi not enabled */
>> + uiout->text ("\n");
>> + uiout->field_string ("sigcode-meaning", _("ADI disabled"));
>> + uiout->text (_(" while accessing address "));
>> + uiout->field_fmt ("bound-access", "%s", paddress (gdbarch, addr));
>> + break;
>> + case SEGV_ADIDERR: /* disrupting mismatch */
>> + uiout->text ("\n");
>> + uiout->field_string ("sigcode-meaning", _("ADI deferred mismatch"));
>> + uiout->text (_(" while accessing address "));
>> + uiout->field_fmt ("bound-access", "%s", paddress (gdbarch, addr));
>> + break;
>> + case SEGV_ADIPERR: /* precise mismatch */
>> + uiout->text ("\n");
>> + uiout->field_string ("sigcode-meaning", _("ADI precise mismatch"));
>> + uiout->text (_(" while accessing address "));
>> + uiout->field_fmt ("bound-access", "%s", paddress (gdbarch, addr));
>> + break;
>> + default:
>> + break;
>> + }
> It is good to have a test to check the results and outputs here.
>
>> +}
>> +
>>
>> /* Return the address of a system call's alternative return
>> address. */
>> @@ -338,6 +404,8 @@ sparc64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>> set_xml_syscall_file_name (gdbarch, XML_SYSCALL_FILENAME_SPARC64);
>> set_gdbarch_get_syscall_number (gdbarch,
>> sparc64_linux_get_syscall_number);
>> + set_gdbarch_handle_segmentation_fault (gdbarch,
>> + sparc64_linux_handle_segmentation_fault);
>> }
>>
>>
>> diff --git a/gdb/sparc64-tdep.c b/gdb/sparc64-tdep.c
>> index 9e0e6b5..9fa8e13 100644
>> --- a/gdb/sparc64-tdep.c
>> +++ b/gdb/sparc64-tdep.c
>> @@ -35,7 +35,11 @@
>> #include "target.h"
>> #include "value.h"
>>
>> +#include "cli/cli-utils.h"
>> +#include "gdbcmd.h"
>> +#include "auxv.h"
>> #include "sparc64-tdep.h"
>> +#include "sparc-nat.h"
>>
> We can't include "nat.h" in "tdep.c".
>
>> /* This file implements the SPARC 64-bit ABI as defined by the
>> section "Low-Level System Information" of the SPARC Compliance
>> @@ -165,7 +169,7 @@ sparc64_pstate_type (struct gdbarch *gdbarch)
>> append_flags_type_flag (type, 8, "TLE");
>> append_flags_type_flag (type, 9, "CLE");
>> append_flags_type_flag (type, 10, "PID0");
>> - append_flags_type_flag (type, 11, "PID1");
>> + append_flags_type_flag (type, 11, "MCDE");
>>
> I don't understand your reply regarding to this change,
>
>> This change, which indicated that the TSTATE reigster contained the
>> "mcde" value, was requested by our kernel engineers.
> How is it related to the adi support? If it is not, split it to another
> patch. In any case, we need a technical reason for the change.
>
>> tdep->sparc64_pstate_type = type;
>> }
>> @@ -1290,6 +1294,14 @@ sparc64_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>> }
>> }
>>
>> +/* sparc64_addr_bits_remove - remove useless address bits */
>> +
>> +static CORE_ADDR
>> +sparc64_addr_bits_remove (struct gdbarch *gdbarch, CORE_ADDR addr)
>> +{
>> + return adi_normalize_address (addr);
> adi_normalize_address can be a static function, and other .c file can
> use it via gdbarch_addr_bits_remove.
>
>> +}
>> +
>> void
>> sparc64_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>> {
>> @@ -1342,6 +1354,8 @@ sparc64_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>>
>> frame_unwind_append_unwinder (gdbarch, &sparc64_frame_unwind);
>> frame_base_set_default (gdbarch, &sparc64_frame_base);
>> +
>> + set_gdbarch_addr_bits_remove (gdbarch, sparc64_addr_bits_remove);
>> }
>>
>>
>> @@ -1666,3 +1680,495 @@ const struct sparc_fpregmap sparc64_bsd_fpregmap =
>> 0 * 8, /* %f0 */
>> 32 * 8, /* %fsr */
>> };
>> +
>> +/* The M7 processor supports an Application Data Integrity (ADI) feature
>> + that detects invalid data accesses. When software allocates memory and
>> + enables ADI on the allocated memory, it chooses a 4-bit version number,
>> + sets the version in the upper 4 bits of the 64-bit pointer to that data,
>> + and stores the 4-bit version in every cacheline of the object. Hardware
>> + saves the latter in spare bits in the cache and memory hierarchy. On each
>> + load and store, the processor compares the upper 4 VA (virtual address) bits
>> + to the cacheline's version. If there is a mismatch, the processor generates
>> + a version mismatch trap which can be either precise or disrupting.
>> + The trap is an error condition which the kernel delivers to the process
>> + as a SIGSEGV signal.
>> +
>> + The upper 4 bits of the VA represent a version and are not part of the
>> + true address. The processor clears these bits and sign extends bit 59
>> + to generate the true address.
>> +
>> + Note that 32-bit applications cannot use ADI. */
>> +
>> +
>> +#define MAX_PROC_NAME_SIZE sizeof("/proc/99999/lwp/9999/adi/lstatus")
>> +
>> +/* ELF Auxiliary vectors */
>> +#ifndef AT_ADI_BLKSZ
>> +#define AT_ADI_BLKSZ 34
>> +#endif
>> +#ifndef AT_ADI_NBITS
>> +#define AT_ADI_NBITS 35
>> +#endif
>> +#ifndef AT_ADI_UEONADI
>> +#define AT_ADI_UEONADI 36
>> +#endif
>> +
>> +/* ADI command list. */
>> +static struct cmd_list_element *sparc64adilist = NULL;
>> +
>> +/* ADI stat settings. */
>> +struct adi_stat_t
>> +{
>> + /* The ADI block size. */
>> + unsigned long blksize;
>> +
>> + /* Number of bits used for an ADI version tag which can be
>> + * used together with the shift value for an ADI version tag
>> + * to encode or extract the ADI version value in a pointer. */
>> + unsigned long nbits;
>> +
>> + /* The maximum ADI version tag value supported. */
>> + int max_version;
>> +
>> + /* ADI version tag file. */
>> + int tag_fd;
>> +
>> + /* Last ADI address examined. */
>> + CORE_ADDR last_vaddr;
>> +
>> + /* Last specified examination count. */
>> + int last_cnt;
>> +
>> + /* ADI availability check has been done. */
>> + bool checked_avail;
>> +
>> + /* ADI is available. */
>> + bool is_avail;
>> +
>> +};
>> +
>> +/* Per-process ADI stat info. */
>> +
>> +struct sparc64_adi_info
>> +{
>> + /* The process identifier. */
>> + pid_t pid;
>> +
>> + /* The ADI stat. */
>> + struct adi_stat_t stat;
>> +
>> + /* Linked list. */
>> + struct sparc64_adi_info *next;
> Can you use C++ STL list?
>
>> +};
>> +
>> +static struct sparc64_adi_info *adi_proc_list = NULL;
>> +
>> +/* Find ADI info for process PID. */
>> +
>> +static struct sparc64_adi_info *
>> +find_adi_info (pid_t pid)
>> +{
>> + struct sparc64_adi_info *proc;
>> +
>> + for (proc = adi_proc_list; proc; proc = proc->next)
>> + if (proc->pid == pid)
>> + return proc;
>> +
>> + return NULL;
>> +}
>> +
>> +/* Add ADI info for process PID. Returns newly allocated info
>> + object. */
>> +
>> +static struct sparc64_adi_info *
>> +add_adi_info (pid_t pid)
>> +{
>> + struct sparc64_adi_info *proc = XCNEW (struct sparc64_adi_info);
>> +
>> + proc->pid = pid;
>> + proc->next = adi_proc_list;
>> + adi_proc_list = proc;
>> + proc->stat.is_avail = false;
>> + proc->stat.checked_avail = false;
>> + proc->stat.tag_fd = 0;
>> +
>> + return proc;
>> +}
>> +
>> +/* Get ADI info for process PID, creating one if it doesn't exist. */
>> +
>> +static struct sparc64_adi_info *
>> +get_adi_info_proc (pid_t pid)
>> +{
>> + struct sparc64_adi_info *proc;
>> +
>> + proc = find_adi_info (pid);
>> + if (proc == NULL)
>> + proc = add_adi_info (pid);
>> +
>> + return proc;
>> +}
> I don't see the place you remove elements from adi list. You probably
> need to implement sparc64_forget_process (in which you can delete the
> adi element if the process exits), and hook it on via
> "linux_nat_set_forget_process (t, sparc64_forget_process);".
>
>> +
>> +static struct adi_stat_t
>> +get_adi_info (pid_t pid)
>> +{
>> + struct sparc64_adi_info *proc;
>> +
>> + proc = get_adi_info_proc (pid);
>> + return proc->stat;
>> +}
>> +
>> +static void
>> +info_adi_command (char *args, int from_tty)
>> +{
>> + printf_unfiltered ("\"adi\" must be followed by \"examine\" "
>> + "or \"assign\".\n");
>> + help_list (sparc64adilist, "adi ", all_commands, gdb_stdout);
>> +}
>> +
>> +/* Read attributes of a maps entry in /proc/[pid]/adi/maps. */
>> +
>> +static void
>> +read_maps_entry (const char *line,
>> + ULONGEST *addr, ULONGEST *endaddr)
>> +{
>> + const char *p = line;
>> +
>> + *addr = strtoulst (p, &p, 16);
>> + if (*p == '-')
>> + p++;
>> +
>> + *endaddr = strtoulst (p, &p, 16);
>> +}
>> +
>> +/* Check if ADI is available. */
>> +
>> +static bool
>> +adi_available (void)
>> +{
>> + pid_t pid = ptid_get_pid (inferior_ptid);
>> + struct sparc64_adi_info *proc = get_adi_info_proc (pid);
>> +
>> + if (proc->stat.checked_avail)
>> + return proc->stat.is_avail;
>> +
>> + proc->stat.checked_avail = true;
>> + if (target_auxv_search (¤t_target, AT_ADI_BLKSZ, &proc->stat.blksize) <= 0)
> THis line is too long.
>
>> + return false;
>> + target_auxv_search (¤t_target, AT_ADI_NBITS, &proc->stat.nbits);
>> + proc->stat.max_version = (1 << proc->stat.nbits) - 2;
>> + proc->stat.is_avail = true;
>> +
>> + return proc->stat.is_avail;
>> +}
>> +
>> +/* Normalize a versioned address - a VA with ADI bits (63-60) set. */
>> +
>> +CORE_ADDR
>> +adi_normalize_address (CORE_ADDR addr)
>> +{
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> +
>> + if (adi_stat.nbits)
>> + return ((CORE_ADDR)(((long)addr << adi_stat.nbits) >> adi_stat.nbits));
>> + return addr;
>> +}
>> +
>> +/* Align a normalized address - a VA with bit 59 sign extended into ADI bits. */
>> +
>> +static CORE_ADDR
>> +adi_align_address (CORE_ADDR naddr)
>> +{
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> +
>> + return (naddr - (naddr % adi_stat.blksize)) / adi_stat.blksize;
>> +}
>> +
>> +/* Convert a byte count to count at a ratio of 1:adi_blksz. */
>> +
>> +static int
>> +adi_convert_byte_count (CORE_ADDR naddr, int nbytes, CORE_ADDR locl)
>> +{
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> +
>> + return ((naddr + nbytes + adi_stat.blksize - 1) / adi_stat.blksize) - locl;
>> +}
>> +
>> +/* The /proc/[pid]/adi/tags file, which allows gdb to get/set ADI
>> + version in a target process, maps linearly to the address space
>> + of the target process at a ratio of 1:adi_blksz.
>> +
>> + A read (or write) at offset K in the file returns (or modifies)
>> + the ADI version tag stored in the cacheline containing address
>> + K * adi_blksz, encoded as 1 version tag per byte. The allowed
>> + version tag values are between 0 and adi_stat.max_version. */
>> +
>> +static int
>> +adi_tag_fd (void)
>> +{
>> + pid_t pid = ptid_get_pid (inferior_ptid);
>> + struct sparc64_adi_info *proc = get_adi_info_proc (pid);
>> +
>> + if (proc->stat.tag_fd != 0)
>> + return proc->stat.tag_fd;
>> +
>> + proc->stat.tag_fd = open_adi_tag_fd (pid);
>> + return proc->stat.tag_fd;
>> +}
>> +
>> +/* Check if an address set is ADI enabled, using /proc/[pid]/adi/maps
>> + which was exported by the kernel and contains the currently ADI
>> + mapped memory regions and their access permissions. */
>> +
>> +static bool
>> +adi_is_addr_mapped (CORE_ADDR vaddr, size_t cnt)
>> +{
>> + char filename[MAX_PROC_NAME_SIZE];
>> + size_t i = 0;
>> +
>> + pid_t pid = ptid_get_pid (inferior_ptid);
>> + snprintf (filename, sizeof filename, "/proc/%d/adi/maps", pid);
>> + char *data = target_fileio_read_stralloc (NULL, filename);
>> + if (data)
>> + {
>> + struct cleanup *cleanup = make_cleanup (xfree, data);
>> + struct adi_stat_t adi_stat = get_adi_info (pid);
>> + char *line;
>> + for (line = strtok (data, "\n"); line; line = strtok (NULL, "\n"))
>> + {
>> + ULONGEST addr, endaddr;
>> +
>> + read_maps_entry (line, &addr, &endaddr);
>> +
>> + while (((vaddr + i) * adi_stat.blksize) >= addr
>> + && ((vaddr + i) * adi_stat.blksize) < endaddr)
>> + {
>> + if (++i == cnt)
>> + {
>> + do_cleanups (cleanup);
>> + return true;
>> + }
>> + }
>> + }
>> + do_cleanups (cleanup);
>> + }
>> + else
>> + warning (_("unable to open /proc file '%s'"), filename);
>> +
>> + return false;
>> +}
>> +
>> +/* Read ADI version tag value for memory locations starting at "vaddr"
>> + for "size" number of bytes. */
>> +
>> +static int
>> +adi_read_versions (CORE_ADDR vaddr, size_t size, unsigned char *tags)
>> +{
>> + int fd = adi_tag_fd ();
>> + if (fd == -1)
>> + return -1;
>> +
>> + if (!adi_is_addr_mapped (vaddr, size))
>> + {
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> + error(_("Address at 0x%lx is not in ADI maps"), vaddr*adi_stat.blksize);
>> + }
>> +
>> + return pread64 (fd, tags, size, vaddr);
>> +}
> Calling pread64 in -tdep.c makes few sense to me. If you only want to
> support native debugging, move them to -nat.c file.
>
>> +
>> +/* Write ADI version tag for memory locations starting at "vaddr" for
>> + "size" number of bytes to "tags". */
>> +
>> +static int
>> +adi_write_versions (CORE_ADDR vaddr, size_t size, unsigned char *tags)
>> +{
>> + int fd = adi_tag_fd ();
>> + if (fd == -1)
>> + return -1;
>> +
>> + if (!adi_is_addr_mapped (vaddr, size))
>> + {
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> + error(_("Address at 0x%lx is not in ADI maps"), vaddr*adi_stat.blksize);
>> + }
>> +
>> + return pwrite64 (fd, tags, size, vaddr);
>> +}
>> +
>> +/* Print ADI version tag value in "tags" for memory locations starting
>> + at "vaddr" with number of "cnt". */
>> +
>> +static void
>> +adi_print_versions (CORE_ADDR vaddr, size_t cnt, unsigned char *tags)
>> +{
>> + int v_idx = 0;
>> + const int maxelts = 8; /* # of elements per line */
>> +
>> + struct adi_stat_t adi_stat = get_adi_info (ptid_get_pid (inferior_ptid));
>> +
>> + while (cnt > 0)
>> + {
>> + QUIT;
>> + printf_filtered ("0x%016lx:\t", vaddr * adi_stat.blksize);
>> + for (int i = maxelts; i > 0 && cnt > 0; i--, cnt--)
>> + {
>> + if (tags[v_idx] == 0xff) /* no version tag */
>> + printf_filtered ("- ");
>> + else
>> + printf_filtered ("%1X ", tags[v_idx]);
>> + ++v_idx;
>> + }
>> + printf_filtered ("\n");
>> + gdb_flush (gdb_stdout);
>> + vaddr += maxelts;
>> + }
>> +}
>> +
>> +static void
>> +do_examine (CORE_ADDR start, int bcnt)
>> +{
>> + CORE_ADDR vaddr = adi_normalize_address (start);
>> + struct cleanup *cleanup;
>> +
>> + CORE_ADDR vstart = adi_align_address (vaddr);
>> + int cnt = adi_convert_byte_count (vaddr, bcnt, vstart);
>> + unsigned char *buf = (unsigned char *) xmalloc (cnt);
>> + cleanup = make_cleanup (xfree, buf);
>> + int read_cnt = adi_read_versions (vstart, cnt, buf);
>> + if (read_cnt == -1)
>> + error (_("No ADI information"));
>> + else if (read_cnt < cnt)
>> + error(_("No ADI information at 0x%lx"), vaddr);
>> +
>> + adi_print_versions (vstart, cnt, buf);
>> +
>> + do_cleanups (cleanup);
>> +}
>> +
>> +static void
>> +do_assign (CORE_ADDR start, size_t bcnt, int version)
>> +{
>> + CORE_ADDR vaddr = adi_normalize_address (start);
>> +
>> + CORE_ADDR vstart = adi_align_address (vaddr);
>> + int cnt = adi_convert_byte_count (vaddr, bcnt, vstart);
>> + unsigned char *buf = (unsigned char *) xmalloc (cnt);
> Use std::vector<gdb_byte>? so that you don't need memset and xfree.
>
>> + memset(buf, version, cnt);
>> +
>> + int set_cnt = adi_write_versions (vstart, cnt, buf);
>> + xfree (buf);
>> +
>> + if (set_cnt == -1)
>> + error (_("No ADI information"));
>> + else if (set_cnt < cnt)
>> + error(_("No ADI information at 0x%lx"), vaddr);
>> +
>> +}
>> +
>> +/* ADI examine version tag command.
>> +
>> + Command syntax:
>> +
>> + adi (examine|x)/count <addr> */
>> +
>> +static void
>> +adi_examine_command (char *args, int from_tty)
>> +{
>> + /* make sure program is active and adi is available */
>> + if (!target_has_execution)
>> + error (_("ADI command requires a live process/thread"));
>> +
>> + if (!adi_available ())
>> + error (_("No ADI information"));
>> +
>> + pid_t pid = ptid_get_pid (inferior_ptid);
>> + struct sparc64_adi_info *proc = get_adi_info_proc (pid);
>> + int cnt = proc->stat.last_cnt? proc->stat.last_cnt : 1;
>> + char *p = args;
>> + if (p && *p == '/')
>> + {
>> + p++;
>> + cnt = get_number (&p);
>> + }
>> +
>> + CORE_ADDR next_address = proc->stat.last_vaddr ? proc->stat.last_vaddr : 0;
>> + if (p != 0 && *p != 0)
>> + next_address = parse_and_eval_address (p);
>> + else if (!proc->stat.last_cnt)
>> + error (_("Usage: adi examine|x[/count] <addr>"));
> IIUC, "address" in this command is mandatory, and it makes sense to do
> so. We don't need .last_vaddr. I don't like such variable making the
> command stateful.
>
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