diff options
Diffstat (limited to 'print.html')
| -rw-r--r-- | print.html | 619 |
1 files changed, 591 insertions, 28 deletions
@@ -32,10 +32,11 @@ <!-- Custom theme stylesheets --> - <!-- Provide site root to javascript --> + <!-- Provide site root and default themes to javascript --> <script> - var path_to_root = ""; - var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light"; + const path_to_root = ""; + const default_light_theme = "light"; + const default_dark_theme = "navy"; </script> <!-- Start loading toc.js asap --> <script src="toc.js"></script> @@ -45,8 +46,8 @@ <!-- Work around some values being stored in localStorage wrapped in quotes --> <script> try { - var theme = localStorage.getItem('mdbook-theme'); - var sidebar = localStorage.getItem('mdbook-sidebar'); + let theme = localStorage.getItem('mdbook-theme'); + let sidebar = localStorage.getItem('mdbook-sidebar'); if (theme.startsWith('"') && theme.endsWith('"')) { localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1)); @@ -60,7 +61,8 @@ <!-- Set the theme before any content is loaded, prevents flash --> <script> - var theme; + const default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? default_dark_theme : default_light_theme; + let theme; try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { } if (theme === null || theme === undefined) { theme = default_theme; } const html = document.documentElement; @@ -73,8 +75,8 @@ <!-- Hide / unhide sidebar before it is displayed --> <script> - var sidebar = null; - var sidebar_toggle = document.getElementById("sidebar-toggle-anchor"); + let sidebar = null; + const sidebar_toggle = document.getElementById("sidebar-toggle-anchor"); if (document.body.clientWidth >= 1080) { try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { } sidebar = sidebar || 'visible'; @@ -110,6 +112,7 @@ <i class="fa fa-paint-brush"></i> </button> <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu"> + <li role="none"><button role="menuitem" class="theme" id="default_theme">Auto</button></li> <li role="none"><button role="menuitem" class="theme" id="light">Light</button></li> <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li> <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li> @@ -1426,7 +1429,7 @@ eval strace -f (find /dev -name 'std*' | xargs -I {} echo -P {}) ls # eval strace -f -P /dev/stdin -P /dev/stdout -P /dev/stderr ls </code></pre> <div style="break-before: page; page-break-before: always;"></div><h1 id="grep1"><a class="header" href="#grep1">grep(1)</a></h1> -<pre><code>sort [opts] [pattern] [files] +<pre><code>grep [opts] [pattern] [files] -e <pattern> pattern to search for (can be supplied multiple times) -i ignore case in patterns -v invert match @@ -2829,6 +2832,7 @@ renice -n 5 -p PID <li><a href="trace_profile/./callgrind.html">callgrind</a></li> <li><a href="trace_profile/./valgrind.html">valgrind</a></li> <li><a href="trace_profile/./vtune.html">vtune</a></li> +<li><a href="trace_profile/./tracy.html">tracy</a></li> </ul> <div style="break-before: page; page-break-before: always;"></div><h1 id="usrbintime1"><a class="header" href="#usrbintime1">/usr/bin/time(1)</a></h1> <pre><code class="language-markdown"># statistics of process run @@ -3276,6 +3280,231 @@ main: main.c vtune: main $(VTUNE)/bin64/vtune -collect hotspots -start-paused -- ./main </code></pre> +<div style="break-before: page; page-break-before: always;"></div><h1 id="tracy1"><a class="header" href="#tracy1">tracy(1)</a></h1> +<p><a href="https://github.com/wolfpld/tracy">Tracy</a> is a frame profiler, supporting manual code instrumentation +and providing a sampling profiler.</p> +<p>One can either record and visualize the profiling data live using +<code>tracy-profiler</code> or record the profiling data to a file using <code>tracy-capture</code>.</p> +<pre><code>tracy-profiler [file] [-p port] + +tracy-capture -o file [-f] [-p port] + -f overwrite <file> if it exists +</code></pre> +<h2 id="example-7"><a class="header" href="#example-7">Example</a></h2> +<p>The example showcases different cases:</p> +<ol> +<li>Use tracy from a single binary. In that case the <code>TracyClient.cpp</code> can be +directly linked / included in the instrumented binary.</li> +<li>Use tracy from different binaries (eg main executable + shared library). In +this case the <code>TracyClient.cpp</code> should be compiled into its own shared +library, such that there is a single tracy client.</li> +<li>Use tracy from different binaries on windows. In this case the +<code>TracyClient.cpp</code> must be compiled again into a separate shared library, +while defining <code>TRACY_EXPORTS</code>. The code being instrumented must be compiled +with <code>TRACY_IMPORTS</code> defined.</li> +</ol> +<p>An instrumented <code>c++</code> example:</p> +<pre><code class="language-cpp">#include <chrono> +#include <thread> + +#include <tracy/Tracy.hpp> + +#ifdef USE_FOO +extern "C" void foo_comp_hook(int64_t); +#endif + +void init() { + // Create a named zone (active for the current scope). + // Name will be used when rendering the zone in the thread timeline. + ZoneScopedN("init()"); + // Set explicit color for the rendered zone. + ZoneColor(0xff0000); + + std::this_thread::sleep_for(std::chrono::seconds(1)); +} + +void comp(const char* name) { + // Track call count. + static int64_t ccnt = 0; + ccnt += 1; + + // Create an unnamed zone for the current scope. + ZoneScoped; + // Name the zone by formatting the name dynamically. + // This name is shown for the zone in the thread timeline, however + // in the zone statistics they are all accounted under one common + // zone "comp". + ZoneNameF("comp(%s)", name); + // Additional text to attach to the zone. + ZoneTextF("text(%s)", name); + // Additional value to attach to the zone measurement. + ZoneValue(ccnt); + + // Statistics for dynamic names, text and values can be looked at in the zone + // statistics.There measurements can be grouped by different categories. + + // Add a simple plot. + TracyPlot("comp-plot", ccnt % 4); + + std::this_thread::sleep_for(std::chrono::milliseconds(100)); + +#ifdef USE_FOO + foo_comp_hook(ccnt); +#endif +} + +void post_comp() { + // Create an unnamed zone for the current scope and capture callstack (max + // depth 10). Capturing callstack requires platform with TRACY_HAS_CALLSTACK + // support. + ZoneScopedS(10); + // Name the zone, w/o formatting. + const char name[] = "post_comp()"; + ZoneName(name, sizeof(name)); + + // Add trace messages to the timeline. + TracyMessageL("start sleep in post_comp()"); + std::this_thread::sleep_for(std::chrono::milliseconds(50)); + TracyMessageL("end sleep in post_comp()"); +} + +void fini() { + // Create a named zone with an explicit color. + ZoneScopedNC("fini()", 0x00ff00); + std::this_thread::sleep_for(std::chrono::seconds(1)); +} + +int main() { + // Create a named zone. + ZoneScopedN("main()"); + + init(); + + int step = 0; + while (step++ < 10) { + // Create a frame message, this start a new frame with the name + // "step" and end the previous frame with the name "step". + FrameMarkNamed("step"); + // Create a named scope. + ZoneScopedN("step()"); + comp("a"); + comp("b"); + comp("c"); + post_comp(); + } + + fini(); +} +</code></pre> +<p>An instrumented <code>c</code> example:</p> +<pre><code class="language-c">#include <stdint.h> +#include <inttypes.h> +#include <stdio.h> + +#include <tracy/TracyC.h> + +static void comp_helper(int64_t i) { + char buf[64]; + int cnt = snprintf(buf, sizeof(buf), "helper(%" PRId64 ")", i); + + // Create an active unnamed zone. + TracyCZone(ctx, 1); + + // Name the zone. + TracyCZoneName(ctx, buf, cnt); + // Add custom text to the zone measurement. + TracyCZoneText(ctx, buf, cnt); + // Add custom value to the zone measurement. + TracyCZoneValue(ctx, i); + + for (int ii = 0; ii < i * 100000; ++ii) { + /* fake work */ + } + + // End the zone measurement. + TracyCZoneEnd(ctx); +} + +void foo_comp_hook(int64_t cnt) { + // Create an active named zone. + TracyCZoneN(ctx, "foo", 1); + + for (int i = 0; i < cnt; ++i) { + // Plot value. + TracyCPlot("foo_comp_hook", cnt + i); + + comp_helper(i); + } + + // Configure plot "foo", probably best done once during initialization.. + TracyCPlotConfig("foo", TracyPlotFormatNumber, 1 /* step */, 1 /* fill */, + 0xff0000); + // Plot value. + TracyCPlot("foo", cnt); + + // End the zone measurement. + TracyCZoneEnd(ctx); +} +</code></pre> +<p>Raw build commands to demonstrate compiling tracy w/o <code>cmake</code>, in case we need +to integrate it into a different build system.</p> +<pre><code class="language-makefile">B := BUILD + +main: $(B)/main-static $(B)/main-dynamic $(B)/main-dynamic-win +tracy: $(B)/tracy +.PHONY: main tracy + +# -- TRACY STATIC --------------------------------------------------------------- + +$(B)/main-static: main.cpp | $(B) + clang++ -DTRACY_ENABLE -I$(B)/tracy/public -o $@ $^ $(B)/tracy/public/TracyClient.cpp + +# -- TRACY DYNAMIC -------------------------------------------------------------- + +$(B)/main-dynamic: main.cpp $(B)/foo.so $(B)/TracyClient.so | $(B) + clang++ -DTRACY_ENABLE -I$(B)/tracy/public -DUSE_FOO -o $@ $^ + +$(B)/foo.so: foo.c $(B)/TracyClient.so + clang -DTRACY_ENABLE -I$(B)/tracy/public -fPIC -shared -o $@ $^ + +$(B)/TracyClient.so: $(B)/tracy/public/TracyClient.cpp + clang++ -DTRACY_ENABLE -I$(B)/tracy/public -fPIC -shared -o $@ $^ + +# -- TRACY DYNAMIC WINDOWS ------------------------------------------------------ + +$(B)/main-dynamic-win: main.cpp $(B)/foo.dll $(B)/TracyClient.dll + @# eg run with wine + zig c++ -target x86_64-windows -DTRACY_ENABLE -DTRACY_IMPORTS -DUSE_FOO -o $@ $^ -I $(B)/tracy/public + +$(B)/foo.dll: foo.c $(B)/TracyClient.dll + zig c++ -target x86_64-windows -DTRACY_ENABLE -DTRACY_IMPORTS -fPIC -shared -o $@ $^ -I $(B)/tracy/public + +$(B)/TracyClient.dll: $(B)/tracy/public/TracyClient.cpp + @# win libs from 'pragma comment(lib, ..)' + zig c++ -target x86_64-windows -DTRACY_ENABLE -DTRACY_EXPORTS -fPIC -shared -o $@ $^ -lws2_32 -ldbghelp -ladvapi32 -luser32 + +# -- TRACY ---------------------------------------------------------------------- + +# Get latest tracy and build profiler. +$(B)/tracy: $(B) + cd $(B); bash $(CURDIR)/get-tracy.sh +.PHONY: $(B)/tracy + +$B: + mkdir -p $(B) +.PHONY: $(B) + +# -- CLEAN ---------------------------------------------------------------------- + +clean: + $(RM) $(B)/*.so $(B)/*.dll $(B)/*.pdb $(B)/*.lib $(B)/main* + +distclean: + rm -rf $(B) +</code></pre> +<blockquote> +<p>Find <code>get-tracy.sh</code> <a href="https://github.com/johannst/notes/blob/master/src/trace_profile/tracy/get-tracy.sh">here</a>.</p> +</blockquote> <div style="break-before: page; page-break-before: always;"></div><h1 id="debug-1"><a class="header" href="#debug-1">Debug</a></h1> <ul> <li><a href="debug/./gdb.html">gdb</a></li> @@ -3774,7 +4003,7 @@ $MOOSE=moose host:port tty </code></pre> -<h2 id="example-7"><a class="header" href="#example-7">Example</a></h2> +<h2 id="example-8"><a class="header" href="#example-8">Example</a></h2> <pre><code class="language-markdown"># Start gdbserver. gdbserver localhost:1234 /bin/ls @@ -3941,6 +4170,8 @@ objdump -C --disassemble=foo::bar <bin> <li><a href="development/./c++.html">c++</a></li> <li><a href="development/./glibc.html">glibc</a></li> <li><a href="development/./gcc.html">gcc</a></li> +<li><a href="development/./gas.html">gas</a></li> +<li><a href="development/./ld.html">ld</a></li> <li><a href="development/./git.html">git</a></li> <li><a href="development/./cmake.html">cmake</a></li> <li><a href="development/./make.html">make</a></li> @@ -5015,6 +5246,287 @@ run1: <li>C ABI (x86_64) - <a href="https://gitlab.com/x86-psABIs/x86-64-ABI">SystemV ABI</a></li> <li>C++ ABI - <a href="https://itanium-cxx-abi.github.io/cxx-abi">C++ Itanium ABI</a></li> </ul> +<div style="break-before: page; page-break-before: always;"></div><h1 id="gas"><a class="header" href="#gas">gas</a></h1> +<h2 id="frequently-used-directives"><a class="header" href="#frequently-used-directives">Frequently used directives</a></h2> +<ul> +<li><code>.section</code> to define a section (elf files) +<pre><code class="language-x86asm">.section .text.foo, "ax", @progbits +; defines section named .text.foo with alloc+exec perms + +.section .data.foo, "aw", @progbits +; defines section named .data.foo with alloc+write perms + +.section .rodata.foo, "a", @progbits +; defines section named .rodata.foo with alloc perms +</code></pre> +</li> +<li><code>.byte</code>, <code>.2byte</code>, <code>.4byte</code>, <code>.8byte</code> to define a N byte value +<pre><code class="language-x86asm">.byte 0xaa +.2byte 0xaabb +.2byte 0xaa, 0xbb +.4byte 0xaabbccdd +.8byte 0xaabbccdd11223344 +</code></pre> +</li> +<li><code>.ascii</code> to define an ascii string +<pre><code class="language-x86asm">.ascii "foo" ; allocates 3 bytes +</code></pre> +</li> +<li><code>.asciz</code> to define an ascii string with <code>'\0'</code> terminator +<pre><code class="language-x86asm">.asciz "foo" ; allocates 4 bytes (str + \0) +</code></pre> +</li> +<li><code>.macro</code> to define assembler macros. Arguments are accessed with the +<code>\arg</code> syntax. +<pre><code class="language-x86asm">.macro defstr name str +\name: + .ascii "\str" +\name\()_len: + .8byte . - \name +.endm + +; use as +defstr foo, "foobar" +</code></pre> +<blockquote> +<p>Use <code>\()</code> to concatenate macro argument and literal.</p> +</blockquote> +</li> +<li><code>.rept</code> to repeat a sequence of lines between <code>.rept</code> and <code>.endr</code>. +<pre><code class="language-x86asm">.rept 4 +.4byte 123 +.endr +</code></pre> +</li> +<li><code>.fill cnt, elem_size, val</code> write <code>cnt</code> times <code>val</code> with element size <code>elem_size</code>. For example one can use it to create a mbr boot record (magic number 0xaa55 at byte 511, 512). +<pre><code class="language-x86asm">.section .boot, "ax", @progbits +; some code .. +.4byte 0xff + +.fill 510 - (. - .boot), 1, 0x00 +.2byte 0xaa55 + +; as foo.s && objdump -j .boot -s +; Contents of section .boot: +; 0000 ff000000 00000000 00000000 00000000 +; .. +; 01f0 00000000 00000000 00000000 000055aa +</code></pre> +<blockquote> +<p>Here <code>.</code> stands for the current location counter.</p> +</blockquote> +</li> +</ul> +<h2 id="references-4"><a class="header" href="#references-4">References</a></h2> +<ul> +<li><a href="https://sourceware.org/binutils/docs/as">GNU Assembler</a></li> +<li><a href="https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops">GNU Assembler Directives</a></li> +<li><a href="https://sourceware.org/binutils/docs/as/i386_002dDependent.html">GNU Assembler <code>x86_64</code> dependent features</a></li> +</ul> +<div style="break-before: page; page-break-before: always;"></div><h1 id="ld1"><a class="header" href="#ld1">ld(1)</a></h1> +<pre><code>ld [opts] files... + -T <script> use <script> as linker script + --trace report each file the linker touches + --start-group archives --end-group + search archives repearepeatedly until no new + undefined references are created + (eg helpfull with list of static libraries) +</code></pre> +<h2 id="linker-script"><a class="header" href="#linker-script">Linker Script</a></h2> +<p><code>output</code> sections are defined as follows (full description at <a href="https://sourceware.org/binutils/docs/ld/Output-Section-Attributes.html">output +section</a> and <a href="https://sourceware.org/binutils/docs/ld/Input-Section.html">input section</a>).</p> +<pre><code>section_name [vaddr] : [AT(paddr)] { + file_pattern (section_pattern) +} +</code></pre> +<p>The following gives an example of an <code>output</code> section with two <code>input</code> section rules.</p> +<pre><code>.foo : { + abc.o (.foo) + *.o (.foo.*) +} +</code></pre> +<h3 id="example-virtual-vs-physical-load-address"><a class="header" href="#example-virtual-vs-physical-load-address">Example: virtual vs physical (load) address</a></h3> +<p>Sometimes code is initially located at a different location as when being run. +For example in embedded cases, where code may initially resides in a <em>rom</em> and +startup code will copy a section with writable <em>data</em> into <em>ram</em>. Code accessing +the writable data accesses the data in the <em>ram</em>.</p> +<p>In this case we need different addresses for the same data.</p> +<ul> +<li>The <code>virtual</code> or <em>runtime</em> address, this is the address used when the linker +resolves accesses to the data. Hence, this is the address the data will have +when the code is running.</li> +<li>The <code>physical</code> or <em>load</em> address, this is the address the data is stored at +initially. Startup code typically copies the initial values from the +<code>physical</code> to the <code>virtual</code> address.</li> +</ul> +<p>The following shows an example linker script which uses <em>virtual</em> and <em>physical</em> +addresses. The full source files can be found <a href="https://github.com/johannst/notes/tree/master/src/development/ld">here</a>.</p> +<pre><code>OUTPUT_FORMAT(elf64-x86-64) +ENTRY(_entry) + +SECTIONS { + /* Set the initial location counter (vaddr) */ + . = 0x00800000; + + /* Create .text output section at current vaddr */ + .text : { + *(.text*) + } + + ASSERT(. == 0x00800000 + SIZEOF(.text), "inc loc counter automatically") + + /* Create .data section at location counter aligned to the next 0x100 (vaddr) */ + /* Set the load address to 0x00100000 (paddr) */ + .data ALIGN(0x100) : AT(0x00100000) { + HIDDEN(_data_vaddr = .); + HIDDEN(_data_paddr = LOADADDR(.data)); + *(.data*) + } + + /* Create .rodata with explicit vaddr */ + /* Re-adjust the paddr location counter */ + .rodata 0x00804000 : AT(ADDR(.rodata)) { + *(.rodata*) + } + + ASSERT(. == 0x00804000 + SIZEOF(.rodata), "inc loc counter automatically") + + .stack ALIGN (0x1000) : { + . += 0x1000; + HIDDEN(_stack_top = .); + } + + /DISCARD/ : { + *(.*) + } +} + +/* Some example assertions */ +ASSERT(ADDR(.data) != LOADADDR(.data), "DATA vaddr and paddr must be different") +ASSERT(SIZEOF(.stack) == 0x1000, "STACK section must be 0x1000") +</code></pre> +<p>We can use the following assembly snippet to explore the linker script.</p> +<pre><code class="language-x86asm">.section .text, "ax", @progbits +.global _entry +_entry: + mov $_stack_top, %rsp + mov $asm_array, %rax + mov (asm_len), %eax + + hlt + jmp _entry + +.section .data.asm, "aw", @progbits +asm_array: + .4byte 0xa + .4byte 0xb + .4byte 0xc + .4byte 0xd +.rept 4 + .4byte 0xff +.endr + +.section .rodata.asm, "a", @progbits +asm_len: + .4byte 8 +</code></pre> +<blockquote> +<p><code>gcc -c data.S && ld -o link-nomem -T link-nomem.ld data.o</code></p> +</blockquote> +<p>The elf load segments show the difference in <em>physical</em> and <em>virtual</em> address +for the segment containing the <code>.data</code> section.</p> +<pre><code class="language-sh">> readelf -W -l link-nomem +# There are 4 program headers, starting at offset 64 +# +# Program Headers: +# Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align +# LOAD 0x001100 0x0000000000800100 0x0000000000100000 0x000020 0x000020 RW 0x1000 +# LOAD 0x002000 0x0000000000800000 0x0000000000800000 0x000018 0x000018 R E 0x1000 +# LOAD 0x003000 0x0000000000804000 0x0000000000804000 0x000004 0x000004 R 0x1000 +# LOAD 0x000000 0x0000000000805000 0x0000000000805000 0x000000 0x001000 RW 0x1000 +# +# Section to Segment mapping: +# Segment Sections... +# 00 .data +# 01 .text +# 02 .rodata +# 03 .stack +</code></pre> +<p>Startup code could copy data from <code>_data_paddr</code> to <code>_data_vaddr</code>.</p> +<pre><code class="language-sh">> nm link-nomem +# 0000000000800100 d asm_array +# 0000000000804000 r asm_len +# 0000000000100000 a _data_paddr +# 0000000000800100 d _data_vaddr +# 0000000000800000 T _entry +# 0000000000806000 b _stack_top +</code></pre> +<p>The linker resolves symbols to their <em>virtual</em> address, this can be seen by the +access to the <code>asm_array</code> variable.</p> +<pre><code class="language-sh">> objdump -d link-nomem +# Disassembly of section .text: +# +# 0000000000800000 <_entry>: +# 800000: 48 c7 c4 00 60 80 00 mov $0x806000,%rsp +# 800007: 48 c7 c0 00 01 80 00 mov $0x800100,%rax ;; mov $asm_array, %rax +# 80000e: 8b 04 25 00 40 80 00 mov 0x804000,%eax +# 800015: f4 hlt +# 800016: eb e8 jmp 800000 <_entry> +</code></pre> +<p>The following linker script shows an example with the <code>MEMORY</code> command.</p> +<pre><code>OUTPUT_FORMAT(elf64-x86-64) +ENTRY(_entry) + +MEMORY { + ROM : ORIGIN = 0x00100000, LENGTH = 0x4000 + RAM : ORIGIN = 0x00800000, LENGTH = 0x4000 +} + +SECTIONS { + /* Create .text output section at ROM (vaddr) */ + .text : { + *(.text*) + } > ROM + + ASSERT(. == ORIGIN(ROM) + SIZEOF(.text), "inc loc counter automatically") + + /* Create .data output section at RAM (vaddr) */ + /* Set load addr to ROM, right after .text (paddr) */ + .data : { + HIDDEN(_data_vaddr = .); + HIDDEN(_data_paddr = LOADADDR(.data)); + *(.data*) + } > RAM AT > ROM + + /* Append .rodata output section at ROM (vaddr) */ + .rodata : { + *(.rodata*) + } > ROM + + /* Append .stack output section at RAM (vaddr) aligned up to next 0x1000 */ + .stack : ALIGN (0x1000) { + . += 0x1000; + HIDDEN(_stack_top = .); + } > RAM + + /DISCARD/ : { + *(.*) + } +} + +/* Some example assertions */ +ASSERT(ADDR(.data) != LOADADDR(.data), "DATA vaddr and paddr must be different") +ASSERT(ADDR(.rodata) == LOADADDR(.rodata), "RODATA vaddr and paddr must be euqal") +ASSERT(ADDR(.stack) == ORIGIN(RAM) + 0x1000, "STACK section must aligned to 0x1000") +ASSERT(SIZEOF(.stack) == 0x1000, "STACK section must be 0x1000") +</code></pre> +<h2 id="references-5"><a class="header" href="#references-5">References</a></h2> +<ul> +<li><a href="https://sourceware.org/binutils/docs/ld/">ld manual</a></li> +<li><a href="https://sourceware.org/binutils/docs/ld/Input-Section.html">ld script: input sections</a></li> +<li><a href="https://sourceware.org/binutils/docs/ld/Output-Section-Attributes.html">ld script: output sections</a></li> +<li><a href="https://github.com/johannst/notes/tree/master/src/development/ld">notes/ld example files</a></li> +</ul> <div style="break-before: page; page-break-before: always;"></div><h1 id="git1"><a class="header" href="#git1">git(1)</a></h1> <h2 id="working-areas"><a class="header" href="#working-areas">Working areas</a></h2> <pre><code class="language-text">+-------------------+ --- stash -----> +-------+ @@ -5968,7 +6480,7 @@ func_v0 func_v1 func_v2 </code></pre> -<h2 id="references-4"><a class="header" href="#references-4">References</a></h2> +<h2 id="references-6"><a class="header" href="#references-6">References</a></h2> <ul> <li><a href="https://akkadia.org/drepper/symbol-versioning">ELF Symbol Versioning</a></li> <li><a href="https://sourceware.org/binutils/docs/ld/VERSION.html">Binutils ld: Symbol Versioning</a></li> @@ -6091,7 +6603,7 @@ link time <code>-lgcov</code>.</p> generated for a single file for example such as</p> <pre><code class="language-shell">gcov <SRC FILE | OBJ FILE> </code></pre> -<h2 id="example-8"><a class="header" href="#example-8">Example</a></h2> +<h2 id="example-9"><a class="header" href="#example-9">Example</a></h2> <pre><code class="language-cpp">#include <cstdio> void tell_me(int desc) { @@ -6372,7 +6884,7 @@ journalctl --user -u test -n 5 --disk-usage Show current disk usage --vacuum-size=<size> Reduce journal log to <size> (K/M/G) </code></pre> -<h2 id="references-5"><a class="header" href="#references-5">References</a></h2> +<h2 id="references-7"><a class="header" href="#references-7">References</a></h2> <ul> <li><a href="https://www.man7.org/linux/man-pages/man5/systemd.unit.5.html">man systemd.unit(5)</a></li> <li><a href="https://www.man7.org/linux/man-pages/man5/systemd.service.5.html">man systemd.service(5)</a></li> @@ -6755,7 +7267,7 @@ group::r-x mask::r-x other::rwx </code></pre> -<h2 id="references-6"><a class="header" href="#references-6">References</a></h2> +<h2 id="references-8"><a class="header" href="#references-8">References</a></h2> <ul> <li><a href="https://www.man7.org/linux/man-pages/man5/acl.5.html">acl(5)</a></li> <li><a href="https://www.man7.org/linux/man-pages/man1/getfacl.1.html">getfacl(1)</a></li> @@ -6997,7 +7509,7 @@ cpupower -c all frequency-info -g # Change frequency governor to POWERSAVE (eg). cpupower -c all frequency-set -g powersave </code></pre> -<h2 id="example-9"><a class="header" href="#example-9">Example</a></h2> +<h2 id="example-10"><a class="header" href="#example-10">Example</a></h2> <p>Watch cpu frequency.</p> <pre><code class="language-sh">watch -n1 "cpupower -c all frequency-info -f -m | xargs -n2 -d'\n'" </code></pre> @@ -7052,6 +7564,9 @@ lp -d PRINTER FILE -o sides=one-sided print front-page only -o sides=two-sided-long-edge print duplex +# Show job queue +lpq -P PRINTER + # Remove pending print job. lprm JOOBID </code></pre> @@ -7112,7 +7627,7 @@ locally and <code>-R</code> means that requests are issued remotely.</p> drop into shell)</li> <li><code>-f</code> run <code>ssh</code> command in the background</li> </ul> -<h3 id="example-10"><a class="header" href="#example-10">Example</a></h3> +<h3 id="example-11"><a class="header" href="#example-11">Example</a></h3> <pre><code class="language-sh"># Forward requests on localhost:8080 to moose:1234 and keep ssh in forground # but dont drop into a shell. ssh -N -L 8080:1234 moose @@ -7290,7 +7805,7 @@ firewall-cmd --remove-port 8000/tcp # Remove rich rule. firewall-cmd --remove-rich-rule 'rule family="ipv4" forward-port port="80" protocol="tcp" to-port="8080"' </code></pre> -<h2 id="references-7"><a class="header" href="#references-7">References</a></h2> +<h2 id="references-9"><a class="header" href="#references-9">References</a></h2> <ul> <li>man <a href="https://firewalld.org/documentation/man-pages/firewall-cmd.html">firewall-cmd(1)</a></li> <li>man <a href="https://firewalld.org/documentation/man-pages/firewalld.html">firewalld(1)</a></li> @@ -8307,6 +8822,41 @@ wrmsr // Write MSR register, effectively does MSR[ECX] <- EDX:EAX <blockquote> <p>See <a href="https://github.com/johannst/mini-kvm-rs/blob/main/guest/guest64-msr.S">guest64-msr.S</a> as an example.</p> </blockquote> +<h4 id="some-interesting-msrs"><a class="header" href="#some-interesting-msrs">Some interesting MSRs</a></h4> +<ul> +<li><code>C000_0082: IA32_LSTAR</code> target address for <a href="https://www.felixcloutier.com/x86/syscall"><code>syscall</code></a> instruction +in <strong>IA-32e</strong> (64 bit) mode.</li> +<li><code>C000_0100: IA32_FS_BASE</code> storage for <strong>%fs</strong> segment base address.</li> +<li><code>C000_0101: IA32_GS_BASE</code> storage for <strong>%gs</strong> segment base address.</li> +<li><code>C000_0102: IA32_KERNEL_GS_BASE</code> additional register, <a href="https://www.felixcloutier.com/x86/swapgs"><code>swapgs</code></a> +swaps <strong>GS_BASE</strong> and <strong>KERNEL_GS_BASE</strong>, without altering any register state. +Can be used to swap in a pointer to a kernel data structure on syscall entry, +as for example in <a href="https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/entry/entry_64.S?h=v6.13#n87"><code>entry_SYSCALL_64</code></a>.</li> +</ul> +<h2 id="current-privilege-level"><a class="header" href="#current-privilege-level">Current privilege level</a></h2> +<p>The current privilege level can be found at any time in the last two bits of the +code segment selector <code>cs</code>. The following shows an example debugging an entry +and exit of a syscall in x86_64-linux.</p> +<pre><code>Breakpoint 1, entry_SYSCALL_64 () at arch/x86/entry/entry_64.S:90 +90 swapgs +(gdb) info r rax rcx cs +rax 0x0 0 ; syscall nr +rcx 0x7feb16399e56 140647666916950 ; ret addr +cs 0x10 16 ; cs & 0x3 -> 0 (ring0,kernel) + +(gdb) c +Breakpoint 2, entry_SYSCALL_64 () at arch/x86/entry/entry_64.S:217 +217 sysretq +(gdb) info r rcx cs +rcx 0x7feb16399e56 140647666916950 ; ret addr +cs 0x10 16 ; cs & 0x3 -> 0 (ring0,kernel) + +(gdb) b *$rcx +(gdb) s +Breakpoint 3, 0x00007feb16399e56 in ?? () +(gdb) info r cs +cs 0x33 51 ; cs & 0x3 -> 3 (ring3,user) +</code></pre> <h2 id="size-directives"><a class="header" href="#size-directives">Size directives</a></h2> <p>Explicitly specify size of the operation.</p> <pre><code class="language-x86asm">mov byte ptr [rax], 0xff // save 1 byte(s) at [rax] @@ -8373,6 +8923,18 @@ mov al, 0xaa mov cx, 0x10 rep stosb </code></pre> +<h2 id="att-syntax-for-intel-syntax-users"><a class="header" href="#att-syntax-for-intel-syntax-users">AT&T syntax for intel syntax users</a></h2> +<pre><code class="language-x86asm">mov %rax, %rbx // mov rbx, rax +mov $12, %rax // mov rax, 12 + +mov (%rsp), %rax // mov rax, [rsp] +mov 8(%rsp), %rax // mov rax, [rsp + 8] +mov (%rsp,%rcx,4), %rax // mov rax, [rsp + 8 * rcx] +mov 0x100, %rax // mov rax, [0x100] +mov (0x100), %rax // mov rax, [0x100] + +mov %gs:8, %rax // mov rax, gs:8 +</code></pre> <h2 id="time-stamp-counter---rdtsc"><a class="header" href="#time-stamp-counter---rdtsc">Time stamp counter - <code>rdtsc</code></a></h2> <pre><code class="language-c">static inline uint64_t rdtsc() { uint32_t eax, edx; @@ -8566,34 +9128,35 @@ must must save these registers in case they are used.</p> <li>gnu assembler <a href="https://sourceware.org/binutils/docs/as"><code>gas</code></a></li> <li>intel syntax</li> </ul> -<pre><code class="language-x86asm"># file: greet.s +<pre><code class="language-x86asm">// file: greet.S +#include <asm/unistd.h> .intel_syntax noprefix .section .text, "ax", @progbits .global _start _start: - mov rdi, 1 # fd + mov rdi, 1 # fd (stdout) lea rsi, [rip + greeting] # buf mov rdx, [rip + greeting_len] # count - mov rax, 1 # write(2) syscall nr + mov rax, __NR_write # write(2) syscall nr syscall - mov rdi, 0 # exit code + mov rdi, __NR_exit # exit code mov rax, 60 # exit(2) syscall nr syscall .section .rdonly, "a", @progbits greeting: - .asciz "Hi ASM-World!\n" + .ascii "Hi ASM-World!\n" greeting_len: .int .-greeting </code></pre> <blockquote> -<p>Syscall numbers are defined in <code>/usr/include/asm/unistd.h</code>.</p> +<p>Files with <code>.S</code> suffix are pre-processed, while files with <code>.s</code> suffix are not.</p> </blockquote> <p>To compile and run:</p> -<pre><code class="language-bash">> gcc -o greet greet.s -nostartfiles -nostdlib && ./greet +<pre><code class="language-bash">> gcc -o greet greet.S -nostartfiles -nostdlib && ./greet Hi ASM-World! </code></pre> <h2 id="mbr-boot-sectors-example"><a class="header" href="#mbr-boot-sectors-example">MBR boot sectors example</a></h2> @@ -8785,7 +9348,7 @@ address translation.</p> <p>The example in <a href="arch/x86/seg/seg.c">seg.c</a> shows how to set the <code>gs</code> base address and to relative accesses.</p> </blockquote> -<h2 id="references-8"><a class="header" href="#references-8">References</a></h2> +<h2 id="references-10"><a class="header" href="#references-10">References</a></h2> <ul> <li><a href="https://gitlab.com/x86-psABIs/x86-64-ABI">SystemV AMD64 ABI</a></li> <li><a href="https://www.amd.com/system/files/TechDocs/24592.pdf">AMD64 Vol1: Application Programming</a></li> @@ -9058,7 +9621,7 @@ Hi ASM-World! distributions. Explicitly specifying the dynamic linker should not be required when compiling natively on arm64.</p> </blockquote> -<h2 id="references-9"><a class="header" href="#references-9">References</a></h2> +<h2 id="references-11"><a class="header" href="#references-11">References</a></h2> <ul> <li><a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst">Procedure Call Standard ARM64</a></li> <li><a href="https://developer.arm.com/documentation/den0024/latest">ARMv8-A Programmer's Guide</a></li> @@ -9303,7 +9866,7 @@ Hi ASM-World! distributions. Explicitly specifying the dynamic linker should not be required when compiling natively on arm.</p> </blockquote> -<h2 id="references-10"><a class="header" href="#references-10">References</a></h2> +<h2 id="references-12"><a class="header" href="#references-12">References</a></h2> <ul> <li><a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs32/aapcs32.rst">Procedure Call Standard ARM</a></li> <li><a href="https://developer.arm.com/documentation/den0013/latest">ARMv7-A Programmer's Guide</a></li> @@ -9384,7 +9947,7 @@ distributions. Explicitly specifying the dynamic linker should not be required when compiling natively on riscv.</p> <p>Select dynamic linker according to abi used during compile & link.</p> </blockquote> -<h2 id="references-11"><a class="header" href="#references-11">References</a></h2> +<h2 id="references-13"><a class="header" href="#references-13">References</a></h2> <ul> <li><a href="https://sourceware.org/binutils/docs/as">GNU Assembler</a></li> <li><a href="https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops">GNU Assembler Directives</a></li> |