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6e3092d788
uprobe_write_opcode() does some pretty low-level things that really, it shouldn't be doing: for example, manually breaking COW by allocating anonymous folios and replacing mapped pages. Further, it does seem to do some shaky things: for example, writing to possible COW-shared anonymous pages or zapping anonymous pages that might be pinned. We're also not taking care of uffd, uffd-wp, softdirty ... although rather corner cases here. Let's just get it right like ordinary ptrace writes would. Let's rewrite the code, leaving COW-breaking to core-MM, triggered by FOLL_FORCE|FOLL_WRITE (note that the code was already using FOLL_FORCE). We'll use GUP to lookup/faultin the page and break COW if required. Then, we'll walk the page tables using a folio_walk to perform our page modification atomically by temporarily unmap the PTE + flushing the TLB. Likely, we could avoid the temporary unmap in case we can just atomically write the instruction, but that will be a separate project. Unfortunately, we still have to implement the zapping logic manually, because we only want to zap in specific circumstances (e.g., page content identical). Note that we can now handle large folios (compound pages) and the shared zeropage just fine, so drop these checks. Link: https://lkml.kernel.org/r/20250321113713.204682-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <olsajiri@gmail.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Namhyung kim <namhyung@kernel.org> Cc: Russel King <linux@armlinux.org.uk> Cc: tongtiangen <tongtiangen@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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