From a668276c18948280cdaa548aa2b8da7293b21e10 Mon Sep 17 00:00:00 2001 From: Luis Machado Date: Mon, 15 Jun 2020 15:51:21 -0300 Subject: [PATCH] Document new "x" and "print" memory tagging extensions Document the changes to the "print" and "x" commands to support memory tagging. gdb/doc/ChangeLog: 2021-03-24 Luis Machado * 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. --- gdb/doc/ChangeLog | 9 +++++++++ gdb/doc/gdb.texinfo | 42 +++++++++++++++++++++++++++++++++++++++--- 2 files changed, 48 insertions(+), 3 deletions(-) diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index 674a2a2f6a6..cbacf184712 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,12 @@ +2021-03-24 Luis Machado + + * 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 * gdb.texinfo (Memory Tagging): New subsection and node. diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index d976325e695..dbf878cdbc3 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -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 : call 0x80482d4 @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 -- 2.30.2