Try to emulate D language exception state save/restore on W64 context switch. - #279

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nat-goodspeed wants to merge 11 commits into
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nat-goodspeed:nat/exstate
Draft

Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
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nat-goodspeed:nat/exstate

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@nat-goodspeednat-goodspeed commented Jan 2, 2025

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This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.

Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain

  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack

respectively.

This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.

Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.

@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
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@nat-goodspeed
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

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Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
Sign up for freeto join this conversation on GitHub.
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@nat-goodspeed

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

Copy link


Copy Markdown

Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
Sign up for freeto join this conversation on GitHub.
Already have an account?
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1 participant

@nat-goodspeed

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

Copy link


Copy Markdown

Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
Sign up for freeto join this conversation on GitHub.
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@nat-goodspeed

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

Copy link


Copy Markdown

Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
Sign up for freeto join this conversation on GitHub.
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1 participant

@nat-goodspeed

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

Copy link


Copy Markdown

Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
Sign up for freeto join this conversation on GitHub.
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1 participant

@nat-goodspeed

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Try to emulate D language exception state save/restore on W64 context switch. - #279
Draft
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Draft
Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
boostorg:developfrom 
nat-goodspeed:nat/exstate
Conversation
@nat-goodspeed
@nat-goodspeednat-goodspeed
commented
Jan 2, 2025

Copy link


Copy Markdown

Contributor
This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Try to emulate D language exception state save/restore on W64 context switch. - #279
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Try to emulate D language exception state save/restore on W64 context switch.#279
nat-goodspeed wants to merge 11 commits into
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Jan 2, 2025

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This hint about the D language fiber implementation points to this tactic for 32-bit Windows, and apparently to a simpler tactic for 64-bit Windows.
Specifically, it appears that for 64-bit Windows, the D fiber implementation saves and restores a three-pointer block at GS:[0] on every context switch. The root block is initialized to contain
  • 0xFFFF'FFFF'FFFF'FFFF (next block in chain, sentinel value)
  • the high end of the stack and
  • the low end of the stack
respectively.
This PR attempts to adopt the same tactic for the Windows 64 fcontext implementation of Boost.Context.
Sadly, with the Boost.Context built from this PR, thesethreeprograms that switch context during exception handling behave no differently than with unmodified Boost.Context.
@nat-goodspeed
Emulating D language fiber-specific exceptions, step 0
27e9496
Reserve extra space on the fiber stack for saving/restoring the three 64-bit
pointers at GS:[0]; initialize the new slots in each new fiber stack; but do
not yet attempt to save or restore the special GS:[0] block.
@nat-goodspeed
Restore code to1bde50e, with the only changes being comments.
b5a1a03
@nat-goodspeed
Add comment blocks for saving and restoring 3 ptrs at GS:[0].
9cc89ec
@nat-goodspeed
Reserve more space on the stack to save state for context switch.
07d0ff8
@nat-goodspeed
Try adjusting fiber context state data by 32 bytes, not 24.
7647c2a
Unfortunately this also produces immediate segfaults.
@nat-goodspeed
Revert "Try adjusting fiber context state data by 32 bytes, not 24."
1446718
This reverts commit 7647c2a.
@nat-goodspeed
This runs like unmodified Boost.Context, with extra space reserved.
9fff6e2
@nat-goodspeed
Merge branch 'nat/exspace' into nat/exstate to fix space reservation.
e078985
@nat-goodspeed
Initialize the exception chain end block.
a51e879
@nat-goodspeed
Save exception block at GS:[0] in context-switch state block.
a91d3a1
This commit doesn't yet restore it.
@nat-goodspeed
Restore exception block at GS:[0] on every fiber context switch.
8324696
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Already have an account?
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1 participant

@nat-goodspeed