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<a href="https://gitlab.rtems.org/ClaudioGrasso">Claudio Grasso</a>
commented on a
discussion on <a href="https://gitlab.rtems.org/rtems/pkg/rtems-lwip/-/merge_requests/37#note_151413">stm32h7/include/lwipbspopts.h</a>:
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cp" style="color: #999999; font-weight: 600;">#define ETH_PAD_SIZE 2</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"></span>
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<td class="new_line diff-line-num new" data-linenumber="15" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cm" style="color: #999988; font-style: italic;">/* Strongly byte-by-byte MEMCPY for STM32H7 to avoid all hardware traps.</span></span>
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<td class="new_line diff-line-num new" data-linenumber="16" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cm" style="color: #999988; font-style: italic;"> * Optimized library versions of memcpy() may use word-aligned instructions (LDR/STR)</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cm" style="color: #999988; font-style: italic;"> * even on byte-access paths, which can trigger usage faults in certain memory regions.</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cm" style="color: #999988; font-style: italic;"> */</span></span>
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<td class="new_line diff-line-num new" data-linenumber="19" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="k" style="font-weight: 600;">static</span> <span class="kr" style="font-weight: 600;">inline</span> <span class="kt" style="color: #445588; font-weight: 600;">void</span> <span class="nf" style="color: #990000; font-weight: 600;">stm32h7_byte_memcpy</span><span class="p">(</span><span class="kt" style="color: #445588; font-weight: 600;">void</span> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">dst</span><span class="p">,</span> <span class="k" style="font-weight: 600;">const</span> <span class="kt" style="color: #445588; font-weight: 600;">void</span> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">src</span><span class="p">,</span> <span class="kt" style="color: #445588; font-weight: 600;">size_t</span> <span class="n" style="color: #333333;">len</span><span class="p">)</span> <span class="p">{</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"> <span class="kt" style="color: #445588; font-weight: 600;">uint8_t</span> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">d</span> <span class="o" style="font-weight: 600;">=</span> <span class="p">(</span><span class="kt" style="color: #445588; font-weight: 600;">uint8_t</span> <span class="o" style="font-weight: 600;">*</span><span class="p">)</span><span class="n" style="color: #333333;">dst</span><span class="p">;</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"> <span class="k" style="font-weight: 600;">const</span> <span class="kt" style="color: #445588; font-weight: 600;">uint8_t</span> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">s</span> <span class="o" style="font-weight: 600;">=</span> <span class="p">(</span><span class="k" style="font-weight: 600;">const</span> <span class="kt" style="color: #445588; font-weight: 600;">uint8_t</span> <span class="o" style="font-weight: 600;">*</span><span class="p">)</span><span class="n" style="color: #333333;">src</span><span class="p">;</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"> <span class="k" style="font-weight: 600;">while</span> <span class="p">(</span><span class="n" style="color: #333333;">len</span><span class="o" style="font-weight: 600;">--</span><span class="p">)</span> <span class="p">{</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">d</span><span class="o" style="font-weight: 600;">++</span> <span class="o" style="font-weight: 600;">=</span> <span class="o" style="font-weight: 600;">*</span><span class="n" style="color: #333333;">s</span><span class="o" style="font-weight: 600;">++</span><span class="p">;</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="p">}</span></span>
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<td class="new_line diff-line-num new" data-linenumber="26" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
26
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cp" style="color: #999999; font-weight: 600;">#define MEMCPY(dst, src, len) stm32h7_byte_memcpy(dst, src, len)</span></span>
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<td class="new_line diff-line-num new" data-linenumber="27" style="width: 35px; color: rgba(5,5,6,.24); border-right-width: 1px; border-right-color: #c7f0d2; border-right-style: solid; padding: inherit;" align="right" bgcolor="#ddfbe6">
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cp" style="color: #999999; font-weight: 600;">#define SMEMCPY(dst, src, len) stm32h7_byte_memcpy(dst, src, len)</span></span>
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<td class="line_content new" style="padding: inherit;" bgcolor="#ecfdf0"><pre style="display: block; font-size: 14px; color: #3a383f; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: inherit; border-radius: 2px; margin: 0; padding: 0; border: inherit solid #dcdcde;">+<span class="line" data-lang="c"><span class="cp" style="color: #999999; font-weight: 600;">#define MEMMOVE(dst, src, len) stm32h7_byte_memcpy(dst, src, len)</span></span>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial"><a href="https://gitlab.rtems.org/-/project/15/uploads/954b7286eda68a32c0e6a469b863a828/memcpy_evidence.txt" data-canonical-src="/uploads/954b7286eda68a32c0e6a469b863a828/memcpy_evidence.txt" data-link="true" class="gfm" style="margin-top: 0;">memcpy_evidence.txt</a></p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">On this BSP the Ethernet Rx/Tx buffers and DMA descriptors live in a non-cacheable MPU region configured as Device memory (for DMA coherency without manual cache maintenance). On Cortex-M7, an <strong style="font-weight: 600; margin-top: 0;">unaligned</strong> word access to Device/Strongly-ordered memory <strong style="font-weight: 600;">always faults</strong>, regardless of <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">CCR.UNALIGN_TRP</code>. With <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ETH_PAD_SIZE = 2</code>, the lwIP payload sits 2 bytes off the word-aligned DMA buffer, so any copy between them has mismatched source/destination alignment.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">The problem is that the optimised library <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">memcpy()</code> issues word-wide (32-bit) accesses on its bulk path. Here is the disassembly straight from the linked image to show this is not hypothetical:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style="display: block; font-size: 90%; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #ffffff; -premailer-cellpadding: 0; -premailer-cellspacing: 0; -premailer-width: 100%; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;"><code style="font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: .25rem; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;"><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;">Toolchain : arm-rtems6-gcc (GCC) 13.3.0, Newlib, -mcpu=cortex-m7</span>
<span id="LC2" class="line" lang="plaintext">Binary : build/arm-rtems6-nucleo-h743zi/stm32h7_test.exe</span></code></pre>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">newlib <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">memcpy()</code> — bulk path is 16× unrolled 32-bit <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ldr.w/str.w</code>:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style="display: block; font-size: 90%; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #ffffff; -premailer-cellpadding: 0; -premailer-cellspacing: 0; -premailer-width: 100%; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;"><code style="font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: .25rem; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;"><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;">0802603c <memcpy>:</span>
<span id="LC2" class="line" lang="plaintext"> 802603e: ea41 0300 orr.w r3, r1, r0 ; src | dst</span>
<span id="LC3" class="line" lang="plaintext"> 8026042: f013 0303 ands.w r3, r3, #3 ; test low 2 bits</span>
<span id="LC4" class="line" lang="plaintext"> 8026046: d16d bne.n 8026124 ; -> "unaligned" entry</span>
<span id="LC5" class="line" lang="plaintext"> ...</span>
<span id="LC6" class="line" lang="plaintext"> 802604c: f851 3b04 ldr.w r3, [r1], #4 ; 32-bit load, +4</span>
<span id="LC7" class="line" lang="plaintext"> 8026050: f840 3b04 str.w r3, [r0], #4 ; 32-bit store, +4 (x16)</span></code></pre>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">The "unaligned" entry only realigns the <strong style="font-weight: 600; margin-top: 0;">head</strong> with byte/half-word copies, then branches <strong style="font-weight: 600;">back into the same 32-bit word loop</strong> — so when src and dst differ in alignment (our <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ETH_PAD_SIZE = 2</code> case) one operand is still misaligned on the word access:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style="display: block; font-size: 90%; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #ffffff; -premailer-cellpadding: 0; -premailer-cellspacing: 0; -premailer-width: 100%; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;"><code style="font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: .25rem; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;"><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;"> 8026146: f831 3b02 ldrh.w r3, [r1], #2 ; head realign only</span>
<span id="LC2" class="line" lang="plaintext"> 802614a: f820 3b02 strh.w r3, [r0], #2</span>
<span id="LC3" class="line" lang="plaintext"> 802614e: e77b b.n 8026048 ; back to the word loop</span></code></pre>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">Our override compiles to byte-only accesses, so the alignment of either operand is irrelevant and no unaligned fault is possible in any region:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style="display: block; font-size: 90%; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #ffffff; -premailer-cellpadding: 0; -premailer-cellspacing: 0; -premailer-width: 100%; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;"><code style="font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: .25rem; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;"><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;">08001c74 <stm32h7_byte_memcpy>:</span>
<span id="LC2" class="line" lang="plaintext"> 8001c96: 7812 ldrb r2, [r2, #0]</span>
<span id="LC3" class="line" lang="plaintext"> 8001c98: 701a strb r2, [r3, #0]</span></code></pre>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">No <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ldr.w</code>/<code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">str.w</code>, no <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ldrh</code>, no <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ldrd</code>, no <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">ldm</code>. That byte-only property is exactly what the STM32H7 Ethernet path needs.</p>
<p dir="auto" style="color: #3a383f; margin: 0;" align="initial">Full annotated objdump attached. Sorry I did not realize before this could help.</p>
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