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ulp patches skip livepatchable libraries #159

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giulianobelinassi opened this issue Feb 22, 2023 · 4 comments
Open

ulp patches skip livepatchable libraries #159

giulianobelinassi opened this issue Feb 22, 2023 · 4 comments

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@giulianobelinassi
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Because of:

libpulp/tools/patches.c

Line 441 in fd16e1b

int len = MIN(obj->num_symbols, 64);

libcrypto.so.1.1 is not being listed as a livepatchable library in SLE-15-SP4. Find another way of finding if a loaded library is livepatchable in the target process.
@giulianobelinassi
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One way of fixing this is by not limiting the number of symbols to 64. But that slows down patchable considerably because glibc is huge.

@giulianobelinassi
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A safe value for this seems to be 8192:
symbols_needed_to_check_if_library_is_livepatchable

@giulianobelinassi
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The above graph was generated by simulating how many symbols patches would have to read to decide if a library is livepatchable or not on all libraries in /usr/lib64/ and its subdirectories.

@giulianobelinassi
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Some libraries have up to 50.000 symbols, so limiting to 8000 may still have some speedups.

giulianobelinassi added a commit to giulianobelinassi/libpulp that referenced this issue Feb 23, 2023
@giulianobelinassi
Fix patches not detecting libcrypto as livepatchable
9ab9ff8 
libcrypto.so.1.1 required to read around 200 symbols in order for
`patch` to detect it as a livepatchable library.  Hence we bump
the number of symbols to read from 64 to 8000.  This value of 8000 is
found by analyzing all libraries found in /usr/lib64 and its subfolders
for how many symbols it would need to be read in order to decide if
the library is livepatchable.

Workarround SUSE#159

Signed-off-by: Giuliano Belinassi <[email protected]>
@giulianobelinassi giulianobelinassi mentioned this issue Feb 23, 2023
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giulianobelinassi added a commit that referenced this issue Feb 23, 2023
@giulianobelinassi
Fix patches not detecting libcrypto as livepatchable
a208967 
libcrypto.so.1.1 required to read around 200 symbols in order for
`patch` to detect it as a livepatchable library.  Hence we bump
the number of symbols to read from 64 to 8000.  This value of 8000 is
found by analyzing all libraries found in /usr/lib64 and its subfolders
for how many symbols it would need to be read in order to decide if
the library is livepatchable.

Workarround #159

Signed-off-by: Giuliano Belinassi <[email protected]>
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@giulianobelinassi