Optionally use orc_header to detect orc version#171
Optionally use orc_header to detect orc version#171nilayvaish wants to merge 1 commit intocrash-utility:masterfrom
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In Linux kernel commit b9f174c811e3ae4ae8959dc57e6adb9990e913f4, a new .orc_header section was introduced. This section holds a version identifier for the ORC types in use. This patch was tested by compiling crash and using it to read coredump of kernel. A temporary print statement was added to check that the if conditions specified are working fine.
| if (try_get_symbol_data("orc_header", sizeof(orc_header), orc_header) && | ||
| memcmp(orc_header, orc_hash_6_4, 20) == 0) { |
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We might want to move these lines since we have checks on lines 6413-6421 that can fail.
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Move to where? Could you please be more specific. In addition the lines 6413-6421 currenty point to code which seems unrelated to this topic, could you please update it too, so we can know the failing checks:
6413
6414 if (!errflag) {
6415 machdep->machspec->page_offset_force = value;
6416 error(NOTE, "setting PAGE_OFFSET to: 0x%lx\n\n",
6417 machdep->machspec->page_offset_force);
6418 continue;
6419 }
6420 }
6421 }
| }; | ||
| struct ORC_data *orc; | ||
| unsigned char orc_header[20]; | ||
| const uint8_t orc_hash_6_4[20] = { |
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The orc_header in hex is hard coded, according to the commit log, is a 20-byte hash. Though I have the same value in my kernel, what if the hash changed in the future, do we still need to hard code those by then? Or will the hash stay unchanged all the time?
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In addition, I would suggest to add code comment of how to get those hex number. E.g. I get those number on my machine by "readelf -x .orc_header vmlinux"
| if (try_get_symbol_data("orc_header", sizeof(orc_header), orc_header) && | ||
| memcmp(orc_header, orc_hash_6_4, 20) == 0) { | ||
| machdep->flags |= ORC_6_4; | ||
| } else if (orc->has_signal && !orc->has_end) |
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I still didn't understand why the previous if (orc->has_signal && !orc->has_end) check is not enough with the introducing of the kernel patch "x86/unwind/orc: Add ELF section with ORC version identifier"? Please add the root cause in the commit message if possible. Thanks!
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Hi, Tao Let's close this PR, feel free to post the patch to crash-utility email list if the patch gets updated. In addition, currently there is a similar checking for the orc version in crash-utility code. Patch review mail list: devel@lists.crash-utility.osci.io Thanks. |
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In Linux kernel commit b9f174c811e3ae4ae8959dc57e6adb9990e913f4, a new .orc_header section was introduced. This section holds a version identifier for the ORC types in use.
This patch was tested by compiling crash and using it to read coredump of kernel. A temporary print statement was added to check that the if conditions specified are working fine.
#169