src: find .text section using dl_iterate_phdr #32244

gabrielschulhof · 2020-03-13T06:48:32Z

Use dl_iterate_phdr(3) to find the mapping containing
__node_text_start instead of parsing /proc/self/maps.

Signed-off-by: @gabrielschulhof

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
commit message follows commit guidelines

nodejs-github-bot · 2020-03-13T06:49:51Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29798/

nodejs-github-bot · 2020-03-13T07:04:22Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29799/

bnoordhuis

LGTM % some minor (mostly style) issues.

src/large_pages/node_large_page.cc

bnoordhuis · 2020-03-13T09:01:01Z

src/large_pages/node_large_page.cc

+          uintptr_t end = start + phdr->p_memsz;
+
+          if (dl_params->reference_sym >= start &&
+              dl_params->reference_sym <= end) {


Just checking, is end inclusive or exclusive?

Aside: it looks like there's no real need for the dl_params->reference_sym field. This also works, wouldn't it?

auto reference_sym = reinterpret_cast<uintptr_t>(&__node_text_start); if (reference_sym >= start && reference_sym <= end) { // ... }

@bnoordhuis the reference_sym field is being used both inside the dl_iterate_phdr callback and outside of it. I thought it best not to assign reinterpret_cast<uintptr_t>(&__node_text_start); to two different variables because, if the symbol changes in the future, they might get out of sync.

bnoordhuis · 2020-03-13T09:03:05Z

src/large_pages/node_large_page.cc

+      }
+    }
+    return 0;
+  }, &dl_params) == 1) {


For legibility, it'd be better to hoist the lambda out of the function call:

auto callback = [](dl_phdr_info* info, size_t, void* data) -> int { // ... }; if (1 == dl_iterate_phdr(callback, &dl_params)) { // ... }

src/large_pages/node_large_page.cc

gabrielschulhof · 2020-03-13T18:20:57Z

src/large_pages/node_large_page.cc

+    if (dl_params.start < dl_params.end) {
+      char* from = reinterpret_cast<char*>(hugepage_align_up(dl_params.start));
+      char* to = reinterpret_cast<char*>(hugepage_align_down(dl_params.end));
+      if (from < to) {
+        size_t pagecount = (to - from) / hps;
+        if (pagecount > 0) {
+          nregion.found_text_region = true;
+          nregion.from = from;
+          nregion.to = to;
+          nregion.total_hugepages = pagecount;
+        }
+      }
+    }


@bnoordhuis I added some more sanity checks to ensure that we create a region that has proper offsets and > 0 page count.

... or rather, that we consider the region to have been found only if it has proper offsets and >0 page count.

gabrielschulhof · 2020-03-13T18:22:25Z

@bnoordhuis I addressed your review comments and added some sanity checks wrt. your comment regarding inclusive/exclusive comparison.

nodejs-github-bot · 2020-03-13T18:23:36Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29817/

nodejs-github-bot · 2020-03-13T20:17:05Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29818/

nodejs-github-bot · 2020-03-13T20:25:24Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29819/

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]>

Co-Authored-By: Ben Noordhuis <[email protected]>

gabrielschulhof · 2020-03-13T21:47:21Z

Rebased in the hope that if fixes the "node ASAN" test.

nodejs-github-bot · 2020-03-13T21:48:15Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29820/

nodejs-github-bot · 2020-03-14T07:06:27Z

CI: https://ci.nodejs.org/job/node-test-pull-request/29827/

gabrielschulhof · 2020-03-15T18:42:25Z

@nodejs/collaborators sorry about the spam! Can this land without the "node ASAN" test? AFAICT it's failing for a lot of PRs.

gabrielschulhof · 2020-03-15T18:43:29Z

https://github.com/nodejs/node/actions?query=workflow%3A%22node+ASAN%22

addaleax · 2020-03-15T18:45:45Z

sorry about the spam! Can this land without the "node ASAN" test? AFAICT it's failing for a lot of PRs.

Yes. 👍

gengjiawen · 2020-03-16T00:28:15Z

@nodejs/collaborators sorry about the spam! Can this land without the "node ASAN" test? AFAICT it's failing for a lot of PRs.

We dealt with Node ASAN fail in #32116. Not sure we should cherrypick the commit to master, since the PR is pretty ready to launch.

Also +1 for this PR to launch.

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]> Co-Authored-By: Ben Noordhuis <[email protected]> PR-URL: #32244 Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: David Carlier <[email protected]>

gabrielschulhof · 2020-03-16T05:42:51Z

Landed in 25cb855.

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]> Co-Authored-By: Ben Noordhuis <[email protected]> PR-URL: #32244 Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: David Carlier <[email protected]>

targos · 2020-04-22T16:01:28Z

Depends on the large pages change to land on v12.x

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]> Co-Authored-By: Ben Noordhuis <[email protected]> PR-URL: nodejs#32244 Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: David Carlier <[email protected]>

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]> Co-Authored-By: Ben Noordhuis <[email protected]> PR-URL: #32244 Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: David Carlier <[email protected]>

gabrielschulhof requested review from bnoordhuis, devnexen and lundibundi March 13, 2020 06:48

nodejs-github-bot added the c++ Issues and PRs that require attention from people who are familiar with C++. label Mar 13, 2020

gabrielschulhof force-pushed the large-pages-use-dl_iterate_phdr branch from efd3932 to b53d3cd Compare March 13, 2020 07:01

bnoordhuis approved these changes Mar 13, 2020

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gabrielschulhof commented Mar 13, 2020

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devnexen approved these changes Mar 13, 2020

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Gabriel Schulhof and others added 6 commits March 13, 2020 14:46

src: find .text section using dl_iterate_phdr

31c03a2

Use `dl_iterate_phdr(3)` to find the mapping containing `__node_text_start` instead of parsing `/proc/self/maps`. Signed-off-by: Gabriel Schulhof <[email protected]>

Update src/large_pages/node_large_page.cc

f6531aa

Co-Authored-By: Ben Noordhuis <[email protected]>

Update src/large_pages/node_large_page.cc

5932d05

Co-Authored-By: Ben Noordhuis <[email protected]>

address review comments

617e601

introduce additional sanity checks on the range

ba539ef

ensure _GNU_SOURCE is defined instead of defining it unconditionally

2d6be5e

gabrielschulhof force-pushed the large-pages-use-dl_iterate_phdr branch from af31134 to 2d6be5e Compare March 13, 2020 21:46

addaleax added the author ready PRs that have at least one approval, no pending requests for changes, and a CI started. label Mar 15, 2020

gabrielschulhof closed this Mar 16, 2020

gabrielschulhof deleted the large-pages-use-dl_iterate_phdr branch March 16, 2020 05:43

MylesBorins mentioned this pull request Mar 19, 2020

v13.12.0 proposal #32376

Merged

targos added the backport-blocked-v12.x label Apr 22, 2020

targos removed author ready PRs that have at least one approval, no pending requests for changes, and a CI started. backport-blocked-v12.x labels Apr 25, 2020

targos mentioned this pull request May 2, 2020

v12.17.0 release proposal #33197

Merged

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src: find .text section using dl_iterate_phdr #32244

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src: find .text section using dl_iterate_phdr #32244

src: find .text section using dl_iterate_phdr #32244

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