* [PATCH] added the inpsect block command ('xb') to print the contents within a block device to the monitor.
@ 2026-07-27 2:47 Tripp R
2026-08-01 17:17 ` Dr. David Alan Gilbert
0 siblings, 1 reply; 2+ messages in thread
From: Tripp R @ 2026-07-27 2:47 UTC (permalink / raw)
To: qemu-devel; +Cc: Dr. David Alan Gilbert, Tripp R
'xb' (examine block) is almost identical in usage to 'x' and 'xp', having the same targuments for those commands , albeit preceded by a drive name.
---
Implemented the xb (examine block) command to print the contents of a block device to the console.
It is effectively a clone of the x/xp commands (examine memory / examine physical memory), having the same arguments for those commands, albeit preceded by the name of a block driver.
e.g. usage
xd floppy0 /510c 0
Signed-off-by: Tripp R <tripprobins@gmail.com>
---
hmp-commands.hx | 14 +++++++
include/monitor/hmp.h | 1 +
monitor/hmp-cmds.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 119 insertions(+)
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 7ae2468a3d..db63b58a47 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -472,6 +472,20 @@ ERST
.cmd = hmp_memory_dump,
},
+SRST
+``xb/``\ *fmt* *addr*
+ Block memory dump starting at *addr*.
+ERST
+
+ {
+ .name = "xb",
+ .args_type = "device:s, fmt:/,addr:l",
+ .params = "device /fmt addr",
+ .help = "block memory dump starting at 'addr'",
+ .cmd = hmp_block_dump,
+ },
+
+
SRST
``x/``\ *fmt* *addr*
Virtual memory dump starting at *addr*.
diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
index 9258a049bf..0c3e8a30c2 100644
--- a/include/monitor/hmp.h
+++ b/include/monitor/hmp.h
@@ -182,6 +182,7 @@ void hmp_info_local_apic(Monitor *mon, const QDict *qdict);
void hmp_info_sev(Monitor *mon, const QDict *qdict);
void hmp_info_sgx(Monitor *mon, const QDict *qdict);
void hmp_info_via(Monitor *mon, const QDict *qdict);
+void hmp_block_dump(Monitor *mon, const QDict *qdict);
void hmp_memory_dump(Monitor *mon, const QDict *qdict);
void hmp_physical_memory_dump(Monitor *mon, const QDict *qdict);
void hmp_info_registers(Monitor *mon, const QDict *qdict);
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index e9fb8d827a..5d4a6c6a78 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -39,8 +39,12 @@
#include "system/hw_accel.h"
#include "system/memory.h"
#include "system/system.h"
+#include "system/block-backend-common.h"
+#include "system/block-backend-io.h"
+#include "system/block-backend-global-state.h"
#include "disas/disas.h"
+
/* Please update hmp-commands.hx when adding or changing commands */
static HMPCommand hmp_info_cmds[] = {
#include "hmp-commands-info.h"
@@ -584,6 +588,89 @@ void hmp_info_registers(Monitor *mon, const QDict *qdict)
}
}
+
+static void block_dump(Monitor *mon, BlockBackend* blk, int count, int format,
+ int wsize, int64_t offset)
+{
+ uint8_t buf[16];
+
+ uint16_t max_digits = 0;
+
+ switch (format) {
+ case 'o':
+ max_digits = DIV_ROUND_UP(wsize * 8, 3);
+ break;
+ default:
+ case 'x':
+ max_digits = (wsize * 8) / 4;
+ break;
+ case 'u':
+ case 'd':
+ max_digits = DIV_ROUND_UP(wsize * 8 * 10, 33);
+ break;
+ case 'c':
+ wsize = 1;
+ break;
+ }
+
+
+ while (count > 0) {
+ int bytes = MIN(16, count * wsize);
+
+ if (blk_pread(blk, offset, bytes, buf, 0) < 0) {
+ monitor_printf(mon,
+ "Read failed at 0x%" PRIx64 "\n",
+ offset);
+ return;
+ }
+
+ monitor_printf(mon, "%08" PRIx64 ": ", offset);
+
+ for (int i = 0; i < bytes; i += wsize) {
+ uint64_t v;
+
+ switch (wsize) {
+ case 1:
+ v = buf[i];
+ break;
+ case 2:
+ v = lduw_le_p(buf + i);
+ break;
+ case 4:
+ v = ldl_le_p(buf + i);
+ break;
+ case 8:
+ v = ldq_le_p(buf + i);
+ break;
+ default:
+ v=0;
+ }
+ switch (format) {
+ case 'o':
+ monitor_printf(mon, "0%*" PRIo64, max_digits, v);
+ break;
+ case 'x':
+ monitor_printf(mon, "0x%0*" PRIx64, max_digits, v);
+ break;
+ case 'u':
+ monitor_printf(mon, "%*" PRIu64, max_digits, v);
+ break;
+ case 'd':
+ monitor_printf(mon, "%*" PRId64, max_digits, v);
+ break;
+ case 'c':
+ monitor_printc(mon, v);
+ break;
+ }
+ }
+
+ monitor_printf(mon, "\n");
+
+ offset += bytes;
+ count -= bytes / wsize;
+ }
+}
+
static void memory_dump(Monitor *mon, int count, int format, int wsize,
uint64_t addr, bool is_physical)
{
@@ -692,6 +779,23 @@ static void memory_dump(Monitor *mon, int count, int format, int wsize,
}
}
+void hmp_block_dump(Monitor *mon, const QDict *qdict)
+{
+ int count = qdict_get_int(qdict, "count");
+ int format = qdict_get_int(qdict, "format");
+ int size = qdict_get_int(qdict, "size");
+ vaddr addr = qdict_get_int(qdict, "addr");
+ const char* dblock = qdict_get_str(qdict, "device");
+
+ BlockBackend *blk = blk_by_name(dblock);
+
+ if (!blk) {
+ monitor_printf(mon, "Invalid block device name '%s'.\n\r", dblock);
+ return;
+ }
+ block_dump(mon,blk, count, format, size, addr);
+}
+
void hmp_memory_dump(Monitor *mon, const QDict *qdict)
{
int count = qdict_get_int(qdict, "count");
---
base-commit: 443e02410695b35a27fad18217424b6370358be7
change-id: 20260726-xbcmd-7fa889067f15
Best regards,
--
Tripp R <tripprobins@gmail.com>
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] added the inpsect block command ('xb') to print the contents within a block device to the monitor.
2026-07-27 2:47 [PATCH] added the inpsect block command ('xb') to print the contents within a block device to the monitor Tripp R
@ 2026-08-01 17:17 ` Dr. David Alan Gilbert
0 siblings, 0 replies; 2+ messages in thread
From: Dr. David Alan Gilbert @ 2026-08-01 17:17 UTC (permalink / raw)
To: Tripp R, hreitz, kwolf; +Cc: qemu-devel
* Tripp R (tripprobins@gmail.com) wrote:
> 'xb' (examine block) is almost identical in usage to 'x' and 'xp', having the same targuments for those commands , albeit preceded by a drive name.
Hi Tripp,
Thanks for resending this. Note that normally you'd mark this as being a 'v2' version.
I'm copying in Kevin and Hanna from the Block layer; although there's still
some work to do here.
> ---
> Implemented the xb (examine block) command to print the contents of a block device to the console.
>
> It is effectively a clone of the x/xp commands (examine memory / examine physical memory), having the same arguments for those commands, albeit preceded by the name of a block driver.
OK, these are still a bit weirdly formatted; you seem to have spaces added between 'block device'
and 'examine physical' rather than the line actually being broken into two lines.
>
> e.g. usage
> xd floppy0 /510c 0
Remember to include the explanation.
Also, I'd shorten the subject, something like
[PATCH] Add the inspect block command ('xb')
> Signed-off-by: Tripp R <tripprobins@gmail.com>
> ---
> hmp-commands.hx | 14 +++++++
> include/monitor/hmp.h | 1 +
> monitor/hmp-cmds.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 119 insertions(+)
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 7ae2468a3d..db63b58a47 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -472,6 +472,20 @@ ERST
> .cmd = hmp_memory_dump,
> },
>
> +SRST
> +``xb/``\ *fmt* *addr*
> + Block memory dump starting at *addr*.
Block *device* not memory - or just 'Block dump'
> +ERST
> +
> + {
> + .name = "xb",
> + .args_type = "device:s, fmt:/,addr:l",
> + .params = "device /fmt addr",
> + .help = "block memory dump starting at 'addr'",
again not 'block memory'
> + .cmd = hmp_block_dump,
> + },
> +
> +
> SRST
> ``x/``\ *fmt* *addr*
> Virtual memory dump starting at *addr*.
> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
> index 9258a049bf..0c3e8a30c2 100644
> --- a/include/monitor/hmp.h
> +++ b/include/monitor/hmp.h
> @@ -182,6 +182,7 @@ void hmp_info_local_apic(Monitor *mon, const QDict *qdict);
> void hmp_info_sev(Monitor *mon, const QDict *qdict);
> void hmp_info_sgx(Monitor *mon, const QDict *qdict);
> void hmp_info_via(Monitor *mon, const QDict *qdict);
> +void hmp_block_dump(Monitor *mon, const QDict *qdict);
> void hmp_memory_dump(Monitor *mon, const QDict *qdict);
> void hmp_physical_memory_dump(Monitor *mon, const QDict *qdict);
> void hmp_info_registers(Monitor *mon, const QDict *qdict);
> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> index e9fb8d827a..5d4a6c6a78 100644
> --- a/monitor/hmp-cmds.c
> +++ b/monitor/hmp-cmds.c
> @@ -39,8 +39,12 @@
> #include "system/hw_accel.h"
> #include "system/memory.h"
> #include "system/system.h"
> +#include "system/block-backend-common.h"
> +#include "system/block-backend-io.h"
> +#include "system/block-backend-global-state.h"
> #include "disas/disas.h"
>
> +
Stray extra line
> /* Please update hmp-commands.hx when adding or changing commands */
> static HMPCommand hmp_info_cmds[] = {
> #include "hmp-commands-info.h"
> @@ -584,6 +588,89 @@ void hmp_info_registers(Monitor *mon, const QDict *qdict)
> }
> }
>
> +
> +static void block_dump(Monitor *mon, BlockBackend* blk, int count, int format,
> + int wsize, int64_t offset)
> +{
> + uint8_t buf[16];
> +
> + uint16_t max_digits = 0;
> +
> + switch (format) {
> + case 'o':
> + max_digits = DIV_ROUND_UP(wsize * 8, 3);
> + break;
> + default:
> + case 'x':
> + max_digits = (wsize * 8) / 4;
> + break;
> + case 'u':
> + case 'd':
> + max_digits = DIV_ROUND_UP(wsize * 8 * 10, 33);
> + break;
> + case 'c':
> + wsize = 1;
> + break;
> + }
This code is a copy/paste out of memory_dump; it's always best
to avoid copy paste - so if you can move this code out of memory_dump
into a function - e.g. digits_for_format say, and then just call
it from both places it would be best.
> + while (count > 0) {
> + int bytes = MIN(16, count * wsize);
> +
> + if (blk_pread(blk, offset, bytes, buf, 0) < 0) {
> + monitor_printf(mon,
> + "Read failed at 0x%" PRIx64 "\n",
> + offset);
> + return;
> + }
> +
> + monitor_printf(mon, "%08" PRIx64 ": ", offset);
> +
> + for (int i = 0; i < bytes; i += wsize) {
> + uint64_t v;
> +
> + switch (wsize) {
> + case 1:
> + v = buf[i];
> + break;
> + case 2:
> + v = lduw_le_p(buf + i);
> + break;
> + case 4:
> + v = ldl_le_p(buf + i);
> + break;
> + case 8:
> + v = ldq_le_p(buf + i);
> + break;
I don't think you need to use the magic ld*_le_p functions here - those
are normally used for access to guest ram, which the 'x' command does;
you can use normal C casts etc here.
> + default:
> + v=0;
> + }
> + switch (format) {
> + case 'o':
> + monitor_printf(mon, "0%*" PRIo64, max_digits, v);
> + break;
> + case 'x':
> + monitor_printf(mon, "0x%0*" PRIx64, max_digits, v);
> + break;
> + case 'u':
> + monitor_printf(mon, "%*" PRIu64, max_digits, v);
> + break;
> + case 'd':
> + monitor_printf(mon, "%*" PRId64, max_digits, v);
> + break;
> + case 'c':
> + monitor_printc(mon, v);
> + break;
> + }
> + }
Again this is a block of code copied from memory_dump; so better
to share a function rather than copy.
> + monitor_printf(mon, "\n");
> +
> + offset += bytes;
> + count -= bytes / wsize;
OK, so you're printing one entry per line rather than memory_dump's
fancier trick of printing a few on a line; I prefer memory_dumps way
of doing it - your example dump of 510 bytes must be annoying to scroll
through!
Dave
> + }
> +}
> +
> static void memory_dump(Monitor *mon, int count, int format, int wsize,
> uint64_t addr, bool is_physical)
> {
> @@ -692,6 +779,23 @@ static void memory_dump(Monitor *mon, int count, int format, int wsize,
> }
> }
>
> +void hmp_block_dump(Monitor *mon, const QDict *qdict)
> +{
> + int count = qdict_get_int(qdict, "count");
> + int format = qdict_get_int(qdict, "format");
> + int size = qdict_get_int(qdict, "size");
> + vaddr addr = qdict_get_int(qdict, "addr");
> + const char* dblock = qdict_get_str(qdict, "device");
> +
> + BlockBackend *blk = blk_by_name(dblock);
> +
> + if (!blk) {
> + monitor_printf(mon, "Invalid block device name '%s'.\n\r", dblock);
> + return;
> + }
> + block_dump(mon,blk, count, format, size, addr);
> +}
> +
> void hmp_memory_dump(Monitor *mon, const QDict *qdict)
> {
> int count = qdict_get_int(qdict, "count");
>
> ---
> base-commit: 443e02410695b35a27fad18217424b6370358be7
> change-id: 20260726-xbcmd-7fa889067f15
>
> Best regards,
> --
> Tripp R <tripprobins@gmail.com>
>
>
--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
\ _________________________|_____ http://www.treblig.org |_______/
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2026-07-27 2:47 [PATCH] added the inpsect block command ('xb') to print the contents within a block device to the monitor Tripp R
2026-08-01 17:17 ` Dr. David Alan Gilbert
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