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dc2cf4ca86
segbase is the address of .eh_frame_hdr and table_data is segbase plus
the header size. find_proc_info computes segbase as `map->start +
segbase - map->pgoff` which is wrong when
* .eh_frame_hdr and .text are in different PT_LOAD program headers
* and their p_vaddr difference does not equal their p_offset difference
Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has
such R and RX PT_LOAD program headers.
ld.lld (default) => perf report fails to unwind `perf record
--call-graph dwarf` recorded data
ld.lld --no-rosegment => ok (trivial, no R PT_LOAD)
ld.lld -z separate-code => ok but by luck: there are two PT_LOAD but
their p_vaddr difference equals p_offset difference
ld.bfd -z noseparate-code => ok (trivial, no R PT_LOAD)
ld.bfd -z separate-code (default for Linux/x86) => ok but by luck:
there are two PT_LOAD but their p_vaddr difference equals p_offset
difference
To fix the issue, compute segbase as dso's base address plus
PT_GNU_EH_FRAME's p_vaddr. The base address is computed by iterating
over all dso-associated maps and then subtract the first PT_LOAD p_vaddr
(the minimum guaranteed by generic ABI) from the minimum address.
In libunwind, find_proc_info transitively called by unw_step is cached,
so the iteration overhead is acceptable.
Reported-by: Sebastian Ullrich <sebasti@nullri.ch>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: llvm@lists.linux.dev
Link: https://github.com/ClangBuiltLinux/linux/issues/1646
Link: https://lore.kernel.org/r/20220527182039.673248-1-maskray@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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| accounting | ||
| arch | ||
| bootconfig | ||
| bpf | ||
| build | ||
| certs | ||
| cgroup | ||
| counter | ||
| debugging | ||
| edid | ||
| firewire | ||
| firmware | ||
| gpio | ||
| hv | ||
| iio | ||
| include | ||
| io_uring | ||
| kvm/kvm_stat | ||
| laptop | ||
| leds | ||
| lib | ||
| memory-model | ||
| objtool | ||
| pci | ||
| pcmcia | ||
| perf | ||
| power | ||
| rcu | ||
| scripts | ||
| spi | ||
| testing | ||
| thermal | ||
| time | ||
| tracing | ||
| usb | ||
| virtio | ||
| vm | ||
| wmi | ||
| Makefile | ||