bcc/syms: Fix shared lib module offset <-> global addr conversion #4089
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`bcc` does various conversions of "global address" to "module offset" and vice versa. Previous work (iovisor#1670) modified the "global address" -> "module offset" calculation in `ProcSyms::Module::contains` to account for differences between the file offset a section is loading bytes from and the requested start address (relative to the base address of the `.so`). Unfortunately that change didn't also modify "module offset" -> "global address" calculations, such as the one in bcc_resolve_global_addr. Update that calculation to account for the same. This calculation discrepancy was most apparent for us in production when trying to attach USDTs to a shared lib with differing requested start address and file offset. This patch also adds a test w/ comments describing our specific situation and demonstrating how the patch fixes the issue. Signed-off-by: Dave Marchevsky <[email protected]>
davemarchevsky
requested review from
drzaeus77,
yonghong-song and
4ast
as code owners
fengjixuchui
added a commit
to fengjixuchui/bcc
that referenced
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Jul 5, 2022
Merge pull request iovisor#4089 from davemarchevsky/davemarchevsky_fi…
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bccdoes various conversions of "global address" to "module offset" andvice versa. Previous work (#1670) modified the "global address" ->
"module offset" calculation in
ProcSyms::Module::containsto accountfor differences between the file offset a section is loading bytes from
and the requested start address (relative to the base address of the
.so). Unfortunately that change didn't also modify "module offset" ->"global address" calculations, such as the one in
bcc_resolve_global_addr. Update that calculation to account for the
same.
This calculation discrepancy was most apparent for us in production when
trying to attach USDTs to a shared lib with differing requested start
address and file offset. This patch also adds a test w/ comments
describing our specific situation and demonstrating how the patch fixes
the issue.
Signed-off-by: Dave Marchevsky [email protected]