On Mon, 9 Nov 2020 06:07:32 GMT, Nick Gasson <ngas...@openjdk.org> wrote:
>> Maurizio Cimadamore has updated the pull request with a new target base due >> to a merge or a rebase. The pull request now contains 64 commits: >> >> - Merge branch '8254162' into 8254231_linker >> - Fix post-merge issues caused by 8219014 >> - Merge branch 'master' into 8254162 >> - Addess remaining feedback from @AlanBateman and @mrserb >> - Address comments from @AlanBateman >> - Fix typo in upcall helper for aarch64 >> - Merge branch '8254162' into 8254231_linker >> - Merge branch 'master' into 8254162 >> - Fix issues with derived buffers and IO operations >> - More 32-bit fixes for TestLayouts >> - ... and 54 more: >> https://git.openjdk.java.net/jdk/compare/a50fdd54...b38afb3f > > src/hotspot/share/opto/output.cpp line 1697: > >> 1695: current_offset = cb->insts_size(); >> 1696: >> 1697: assert(!is_mcall || (call_returns[block->_pre_order] == (uint) >> current_offset), "ret_addr_offset() did not match size of emitted code"); > > This assertion is too strong: on AArch64 we generate additional instructions > after the BLR (call) instruction for certain types of call. For example > > > 0x0000ffff790f00dc: adr x9, 0x0000ffff790f00f4 > 0x0000ffff790f00e0: mov x8, #0x5714 // #22292 > 0x0000ffff790f00e4: movk x8, #0x8d3d, lsl #16 > 0x0000ffff790f00e8: movk x8, #0xffff, lsl #32 > 0x0000ffff790f00ec: stp xzr, x9, [sp, #-16]! > 0x0000ffff790f00f0: blr x8 > 0x0000ffff790f00f4: add sp, sp, #0x10 <== > ret_addr_offset() is here > 0x0000ffff790f00f8: Address 0x0000ffff790f00f8 is out of bounds. <== > current_offset is here > > I think the `==` should be `<=`. (Although this still fails sometimes on > AArch64, but I believe it exposes a real bug. I've opened JDK-8256025 and > will fix this shortly.) Ok, that seems fine to me. IIRC the problem this was trying to catch is a ret_addr_offset that is too large, which might cause a later call's oop map to be overridden. So, using `<=` should still work. At least if the code between ret_addr_offset and current_offset is guaranteed not to contain any calls or other safepoints. ------------- PR: https://git.openjdk.java.net/jdk/pull/634
