note: allow notes with alignment 0 #52
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On an aarch64 machine running Debian the notes section of a core dump is generated with p_align=0 in the program header, while in the notes section both name and description are aligned to 4 bytes. The manpage for elf(5) suggests that padding is inserted after name and description to always end on a 4 byte boundary, and that p_align values of 0 and 1 mean no alignment is required. Commit 3713bb2 observes that a p_align value of 8 has been seen in the wild, though the test case doesn't confirm if the 8 byte alignment was applied to name, description, each note or the section as a whole. The pdf linked from the added comment suggests that each note is aligned to p_align, but doesn't say anything about the alignment of name and description. To allow the p_align=0 core file seen in the wild without potentially breaking p_align=8 files regardless of where the alignment is applied this patch only adjusts the actual alignment when p_align is 0 to four bytes. The added test is a stripped down version of the aarch64 core file that only retains one note.
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Using coredump_filter=0 I got the full core dump down to 16K, so it could be included in sample-objects/ as well if you want. |
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On an aarch64 machine running Debian the notes section of a core dump is generated with p_align=0 in the program header, while in the notes section both name and description are aligned to 4 bytes.
The manpage for elf(5) suggests that padding is inserted after name and description to always end on a 4 byte boundary, and that p_align values of 0 and 1 mean no alignment is required. Commit 3713bb2 observes that a p_align value of 8 has been seen in the wild, though the test case doesn't confirm if the 8 byte alignment was applied to name, description, each note or the section as a whole. The pdf linked from the added comment suggests that each note is aligned to p_align, but doesn't say anything about the alignment of name and description.
To allow the p_align=0 core file seen in the wild without potentially breaking p_align=8 files regardless of where the alignment is applied this patch only adjusts the actual alignment when p_align is 0 to four bytes.
The added test is a stripped down version of the aarch64 core file that only retains one note.