a2b38e6dfe
* Linux 6.13 support * Support for symbols without debuginfo * Use Python 3.13 enhanced REPL when available * Add a 'stat' subcommand to contrib/cgroup.py * Many bug fixes - API compatibility with libkdumpfile-0.5.5: * libdrgn-kdump-prepare-for-incompatible-changes-in-li.patch * libdrgn-kdump-simplify-getting-the-PRSTATUS-attribut.patch OBS-URL: https://build.opensuse.org/package/show/Kernel:kdump/python-drgn?expand=0&rev=23
87 lines
3.3 KiB
Diff
87 lines
3.3 KiB
Diff
From: Petr Tesarik <ptesarik@suse.com>
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Date: Mon, 2 Dec 2024 17:38:24 +0100
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Subject: libdrgn: kdump: simplify getting the PRSTATUS attributes
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Upstream: merged
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Git-commit: 885a3209f3603593fb89327c1072f94e5862ffbb
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Since libkdumpfile commit 5b044292abe9 ("Clarify and fix attribute data
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lifetime") changes the lifetime of attribute values retrieved with
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kdump_attr_ref_get(), the extra reference would keep the PRSTATUS blob
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around even after kdump_free().
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However, the attribute hierarchy cannot change while iterating over the
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PRSTATUS attributes, so it is not necessary to take an attribute reference
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and we can use kdump_get_typed_attr().
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The attribute blob itself should not change either, but it is a good idea
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to keep its data pinned, because a raw pointer to it is stored in the
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drgn_thread_set hash table. If some code tries to modify the PRSTATUS
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attribute data, the attempt will fail with KDUMP_ERR_BUSY rather than leave
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a dangling pointer in the hash table and possibly cause a UAF bug later.
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The blob pin does not prevent freeing the blob when the blob reference
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count reaches zero.
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Signed-off-by: Petr Tesarik <ptesarik@suse.com>
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---
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libdrgn/kdump.c | 28 ++++++++++------------------
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1 file changed, 10 insertions(+), 18 deletions(-)
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diff --git a/libdrgn/kdump.c b/libdrgn/kdump.c
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index 09efd965..0bb594d1 100644
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--- a/libdrgn/kdump.c
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+++ b/libdrgn/kdump.c
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@@ -299,39 +299,31 @@ struct drgn_error *drgn_program_cache_kdump_threads(struct drgn_program *prog)
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}
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/*
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- * Note that in the following loop we never call kdump_attr_unref() on
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- * prstatus_ref, nor kdump_blob_unpin() on the prstatus blob that we get
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- * from libkdumpfile. Since drgn is completely read-only as a consumer
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- * of that library, we "leak" both the attribute reference and blob pin
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- * until kdump_free() is called which will clean up everything for us.
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+ * Note that in the following loop we never call kdump_blob_unpin() on
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+ * the prstatus blob that we get from libkdumpfile. Since drgn never
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+ * modifies the PRSTATUS attributes (neither directly nor indirectly),
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+ * we "leak" the blob pin until kdump_free() is called, which will
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+ * clean up everything for us.
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*/
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for (i = 0; i < ncpus; i++) {
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- /* Enough for the longest possible PRSTATUS attribute name. */
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- kdump_attr_ref_t prstatus_ref;
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kdump_attr_t prstatus_attr;
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void *prstatus_data;
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size_t prstatus_size;
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#define FORMAT "cpu.%" PRIuFAST64 ".PRSTATUS"
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+ /* Enough for the longest possible PRSTATUS attribute name. */
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char attr_name[sizeof(FORMAT)
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- sizeof("%" PRIuFAST64)
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+ max_decimal_length(uint_fast64_t)
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+ 1];
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snprintf(attr_name, sizeof(attr_name), FORMAT, i);
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#undef FORMAT
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- ks = kdump_attr_ref(prog->kdump_ctx, attr_name, &prstatus_ref);
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- if (ks != KDUMP_OK) {
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- return drgn_error_format(DRGN_ERROR_OTHER,
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- "kdump_attr_ref(%s): %s",
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- attr_name,
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- kdump_get_err(prog->kdump_ctx));
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- }
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-
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- ks = kdump_attr_ref_get(prog->kdump_ctx, &prstatus_ref,
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- &prstatus_attr);
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+ prstatus_attr.type = KDUMP_BLOB;
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+ ks = kdump_get_typed_attr(prog->kdump_ctx, attr_name,
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+ &prstatus_attr);
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if (ks != KDUMP_OK) {
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return drgn_error_format(DRGN_ERROR_OTHER,
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- "kdump_attr_ref_get(%s): %s",
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+ "kdump_get_typed_attr(%s): %s",
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attr_name,
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kdump_get_err(prog->kdump_ctx));
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}
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--
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2.47.1
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