https://github.com/torvalds/linux
Revision dc2cf4ca866f571590b65f5e4de06b8c9a302808 authored by Fangrui Song on 27 May 2022, 18:20:39 UTC, committed by Arnaldo Carvalho de Melo on 03 June 2022, 19:20:25 UTC
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>
1 parent 4f52ca1
Tip revision: dc2cf4ca866f571590b65f5e4de06b8c9a302808 authored by Fangrui Song on 27 May 2022, 18:20:39 UTC
perf unwind: Fix segbase for ld.lld linked objects
perf unwind: Fix segbase for ld.lld linked objects
Tip revision: dc2cf4c
File | Mode | Size |
---|---|---|
Documentation | ||
LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | -rw-r--r-- | 19.8 KB |
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.9 KB |
.mailmap | -rw-r--r-- | 22.5 KB |
COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 98.9 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 555 bytes |
MAINTAINERS | -rw-r--r-- | 648.7 KB |
Makefile | -rw-r--r-- | 63.9 KB |
README | -rw-r--r-- | 727 bytes |
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