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Document new "x" and "print" memory tagging extensions

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Document the changes to the "print" and "x" commands to support memory
tagging.

gdb/doc/ChangeLog:

2021-03-24  Luis Machado  <luis.machado@linaro.org>

	* gdb.texinfo (Data): Document memory tagging changes to the "print"
	command.
	(Examining Memory): Document memory tagging changes to the "x"
	command.
	(Memory Tagging): Update with more information on changes to the "x"
	and "print" commands.
This commit is contained in:
Luis Machado 2020-06-15 15:51:21 -03:00
parent bef382e61a
commit a668276c18
2 changed files with 48 additions and 3 deletions
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9
gdb/doc/ChangeLog
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@ -1,3 +1,12 @@
2021-03-24 Luis Machado <luis.machado@linaro.org>
* gdb.texinfo (Data): Document memory tagging changes to the "print"
command.
(Examining Memory): Document memory tagging changes to the "x"
command.
(Memory Tagging): Update with more information on changes to the "x"
and "print" commands.
2021-03-24 Luis Machado <luis.machado@linaro.org>
* gdb.texinfo (Memory Tagging): New subsection and node.

42
gdb/doc/gdb.texinfo
View File

@ -9951,6 +9951,10 @@ If you omit @var{expr}, @value{GDBN} displays the last value again (from the
conveniently inspect the same value in an alternative format.
@end table
If the architecture supports memory tagging, the @code{print} command will
display pointer/memory tag mismatches if what is being printed is a pointer
or reference type. @xref{Memory Tagging}.
A more low-level way of examining data is with the @code{x} command.
It examines data in memory at a specified address and prints it in a
specified format. @xref{Memory, ,Examining Memory}.
@ -10718,7 +10722,8 @@ number is specified, memory is examined backward from @var{addr}.
@item @var{f}, the display format
The display format is one of the formats used by @code{print}
(@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
@samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
@samp{f}, @samp{s}), @samp{i} (for machine instructions) and
@samp{m} (for displaying memory tags).
The default is @samp{x} (hexadecimal) initially. The default changes
each time you use either @code{x} or @code{print}.
@ -10813,6 +10818,22 @@ counter is shown with a @code{=>} marker. For example:
0x804838c <main+24>: call 0x80482d4 <puts@@plt>
@end smallexample
If the architecture supports memory tagging, the tags can be displayed by
using @samp{m}. @xref{Memory Tagging}.
The information will be displayed once per granule size
(the amount of bytes a particular memory tag covers). For example, AArch64
has a granule size of 16 bytes, so it will display a tag every 16 bytes.
Due to the way @value{GDBN} prints information with the @code{x} command (not
aligned to a particular boundary), the tag information will refer to the
initial address displayed on a particular line. If a memory tag boundary
is crossed in the middle of a line displayed by the @code{x} command, it
will be displayed on the next line.
The @samp{m} format doesn't affect any other specified formats that were
passed to the @code{x} command.
@cindex @code{$_}, @code{$__}, and value history
The addresses and contents printed by the @code{x} command are not saved
in the value history because there is often too much of them and they
@ -10890,8 +10911,9 @@ If the underlying architecture supports memory tagging, like AArch64 MTE
or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
against memory allocation tags.
A command prefix of @code{memory-tag} gives access to the various memory tagging
commands.
The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
display tag information when appropriate, and a command prefix of
@code{memory-tag} gives access to the various memory tagging commands.
The @code{memory-tag} commands are the following:
@ -11527,6 +11549,20 @@ language, for most languages @code{@{...@}} is used, but Fortran uses
Display the current threshold after which nested structures are
replaces with ellipsis.
@anchor{set print memory-tag-violations}
@cindex printing memory tag violation information
@item set print memory-tag-violations
@itemx set print memory-tag-violations on
Cause @value{GDBN} to display additional information about memory tag violations
when printing pointers and addresses.
@item set print memory-tag-violations off
Stop printing memory tag violation information.
@item show print memory-tag-violations
Show whether memory tag violation information is displayed when printing
pointers and addresses.
@anchor{set print null-stop}
@item set print null-stop
@cindex @sc{null} elements in arrays