Bug 194933
| Summary: | DTrace: Stack() command does not print function name if it is from a kernel module for i386. | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Shrikanth R K <shrikanth07> |
| Component: | bin | Assignee: | Mark Johnston <markj> |
| Status: | Closed FIXED | ||
| Severity: | Affects Many People | CC: | howard0su, markj |
| Priority: | --- | ||
| Version: | 10.0-STABLE | ||
| Hardware: | i386 | ||
| OS: | Any | ||
This is resolved by r275011 based on the thread: https://lists.freebsd.org/pipermail/freebsd-hackers/2014-November/046585.html This was fixed in r275011 in HEAD and r276265 in stable/10. |
I verified this on a FreeBSD 10.0 STABLE, the stack() feature does not appear to print functions from kernel modules. I believe there is a glitch in libdtrace in the function "dt_module_update" (cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c). The section header address computation which is currently being done in the function dt_module_update for elf type ET_REL, a similar computation needs to be done for the ET_DYN maybe. I lack background on the elf types but for experiment sakes I changed the line @@ -948,7 +948,7 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_fil #if defined(__FreeBSD__) mapbase = (uintptr_t)k_stat->address; gelf_getehdr(dmp->dm_elf, &ehdr); - is_elf_obj = (ehdr.e_type == ET_REL); + is_elf_obj = (ehdr.e_type == ET_REL) || (ehdr.e_type == ET_DYN); if (is_elf_obj) { dmp->dm_sec_offsets = malloc(ehdr.e_shnum * sizeof(*dmp->dm_sec_offsets)); So from a previous run where I was running a dtrace one liner %dtrace -n 'fbt:hwpmc:: { stack(); }' The output without the above change shows a sample as 0 50825 pmc_find_process_descriptor:entry 0xc3c35bf5 <-- Address not matched to symbol kernel`syscall+0x48b kernel`0xc0fd2121 whereas with the above nit change to include ET_DYN for section offset adjustment I get the complete stack trace as 0 50825 pmc_find_process_descriptor:entry hwpmc.ko`pmc_hook_handler+0x6a5 <-- Address matched to symbol kernel`syscall+0x48b kernel`0xc0fd2121 I believe without the correct section offset adjustment the following check in the function "dtrace_lookup_by_addr" fails to match the address to the correct symbol if (addr - dmp->dm_text_va < dmp->dm_text_size || addr - dmp->dm_data_va < dmp->dm_data_size || addr - dmp->dm_bss_va < dmp->dm_bss_size) because dml->dm_text_va was not setup correctly in dt_module_update. Filing a bug report after discussion on freebsd-hackers, please refer the following thread https://lists.freebsd.org/pipermail/freebsd-hackers/2014-November/046435.html Reference: commit revision 210425. And also the related thread https://lists.freebsd.org/pipermail/freebsd-amd64/2010-June/013034.html Note that this is not an issue on amd64.