Attachment 513288 Details for Bug 717136 – Fix SDT relocations in prelinked modules

[patch] Fix SDT relocations in prelinked modules

rhbz717136-Fix-SDT-relocations-in-prelinked-modules.patch (text/plain), 2.45 KB, created by Josh Stone on 2011-07-14 23:05:30 UTC

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Creator: Josh Stone

Created: 2011-07-14 23:05:30 UTC

Size: 2.45 KB

patch

obsolete

>From 9829768104cba372c4f0a1870fdfe0cf89d0d15d Mon Sep 17 00:00:00 2001
>From: Josh Stone <jistone@redhat.com>
>Date: Thu, 14 Jul 2011 15:32:42 -0700
>Subject: [PATCH] rhbz717136: Fix SDT relocations in prelinked modules
>
>* tapsets.cxx (sdt_query::handle_probe_entry): The debuginfoless SDT
>  addresses are relative to the ELF file, so get only that bias.  The
>  DWARF bias is not interesting here.
>  (sdt_query::setup_note_probe_entry): Add the ELF bias to the semaphore
>  address too, so record_semaphore can completely relocate it.
>  (sdt_query::record_semaphore): SDT V3 semaphores need relocation too,
>  now removing both the bias and prelinking effects.
>---
> tapsets.cxx |   14 ++++++++++----
> 1 files changed, 10 insertions(+), 4 deletions(-)
>
>diff --git a/tapsets.cxx b/tapsets.cxx
>index 8c66f00..a8e4cba 100644
>--- a/tapsets.cxx
>+++ b/tapsets.cxx
>@@ -5508,9 +5508,12 @@ sdt_query::handle_probe_entry()
> 
>   bool need_debug_info = false;
> 
>+  // We could get the Elf* from either dwarf_getelf(dwfl_module_getdwarf(...))
>+  // or dwfl_module_getelf(...).  We only need it for the machine type, which
>+  // should be the same.  The bias is used for relocating debuginfoless probes,
>+  // though, so that must come from the possibly-prelinked ELF file, not DWARF.
>   Dwarf_Addr bias;
>-  Elf* elf = (dwarf_getelf (dwfl_module_getdwarf (dw.mod_info->mod, &bias))
>-	      ?: dwfl_module_getelf (dw.mod_info->mod, &bias));
>+  Elf* elf = dwfl_module_getelf (dw.mod_info->mod, &bias);
> 
>   if (have_kprobe())
>     {
>@@ -5732,6 +5735,10 @@ sdt_query::setup_note_probe_entry (int type, const char *data, size_t len)
>   semaphore += base - base_ref;
>   pc += base - base_ref;
> 
>+  // The semaphore also needs the ELF bias added now, so
>+  // record_semaphore can properly relocate it later.
>+  semaphore += bias;
>+
>   if (sess.verbose > 4)
>     clog << _F(" saw .note.stapsdt %s%s ", probe_name.c_str(), (provider_name != "" ? _(" (provider ")+provider_name+") " : "").c_str()) << "@0x" << hex << pc << dec << endl;
> 
>@@ -5824,8 +5831,7 @@ sdt_query::record_semaphore (vector<derived_probe *> & results, unsigned start)
>       addr  = lookup_symbol_address(dw.module, semaphore.c_str());
>     if (addr)
>       {
>-        if (probe_type != uprobe3_type
>-	    && dwfl_module_relocations (dw.module) > 0)
>+        if (dwfl_module_relocations (dw.module) > 0)
>           dwfl_module_relocate_address (dw.module, &addr);
>         // XXX: relocation basis?
>         for (unsigned i = start; i < results.size(); ++i)
>-- 
>1.7.6
>

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Attachments on bug 717136: 511947 | 511948 | 513288