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[Crash-utility] [PATCH] Make the __per_cpu_offset symbol available



Hi,

the code in xen_hyper_init() tries to determine the per-cpu shift from the 
__per_cpu_shift symbol if available. This doesn't work because the symbol's 
value is outside the kernel text address range. This patch makes a special 
case for this symbol on Xen targets, so it can be used later.

Without this patch, crash initialization fails on SLES11 Xen hypervisor dumps, 
because on incorrect per-cpu offset is assumed. The failure can't be fixed 
simply by adding a version check, because SLES11 Xen is patched to increase 
the per-cpu shift in order to support more CPUs.

It is also important not to try to relocate ABSOLUTE symbol (such as this 
one), so add this condition in store_symbols().

Signed-off-by: Petr Tesarik <ptesarik suse cz>
---
 ia64.c    |   22 ++++++++++++++++++++--
 symbols.c |    3 ++-
 x86.c     |   22 ++++++++++++++++++++--
 x86_64.c  |   22 ++++++++++++++++++++--
 4 files changed, 62 insertions(+), 7 deletions(-)

--- a/ia64.c
+++ b/ia64.c
@@ -20,6 +20,7 @@
 #include <sys/prctl.h>
 
 static int ia64_verify_symbol(const char *, ulong, char);
+static int ia64_hyper_verify_symbol(const char *, ulong, char);
 static int ia64_eframe_search(struct bt_info *);
 static void ia64_back_trace_cmd(struct bt_info *);
 static void ia64_old_unwind(struct bt_info *);
@@ -571,7 +572,12 @@ ia64_dump_machdep_table(ulong arg)
         fprintf(fp, "        memory_size: generic_memory_size()\n");
         fprintf(fp, "      vmalloc_start: ia64_vmalloc_start()\n");
         fprintf(fp, "       is_task_addr: ia64_is_task_addr()\n");
-        fprintf(fp, "      verify_symbol: ia64_verify_symbol()\n");
+	if (machdep->verify_symbol == ia64_verify_symbol)
+		fprintf(fp, "      verify_symbol: ia64_verify_symbol()\n");
+	else if (machdep->verify_symbol == ia64_hyper_verify_symbol)
+		fprintf(fp, "      verify_symbol: ia64_hyper_verify_symbol()\n");
+	else
+		fprintf(fp, "      verify_symbol: %lx\n", (ulong)machdep->verify_symbol);
         fprintf(fp, "         dis_filter: ia64_dis_filter()\n");
         fprintf(fp, "           cmd_mach: ia64_cmd_mach()\n");
         fprintf(fp, "       get_smp_cpus: ia64_get_smp_cpus()\n");
@@ -724,6 +730,18 @@ ia64_verify_symbol(const char *name, ulo
 		 (region == KERNEL_VMALLOC_REGION)));
 }
 
+static int
+ia64_hyper_verify_symbol(const char *name, ulong value, char type)
+{
+	if (ia64_verify_symbol(name, value, type))
+		return TRUE;
+
+	if (STREQ(name, "__per_cpu_shift"))
+		return TRUE;
+
+	return FALSE;
+}
+
 
 /*
  *   Look for likely exception frames in a stack.
@@ -4225,7 +4243,7 @@ ia64_init_hyper(int when)
 		break;
 
         case PRE_SYMTAB:
-                machdep->verify_symbol = ia64_verify_symbol;
+                machdep->verify_symbol = ia64_hyper_verify_symbol;
 		machdep->machspec = &ia64_machine_specific;
 		if (pc->flags & KERNEL_DEBUG_QUERY)
 			return;
--- a/symbols.c
+++ b/symbols.c
@@ -568,7 +568,8 @@ store_symbols(bfd *abfd, int dynamic, vo
       		bfd_get_symbol_info(abfd, sym, &syminfo);
 		if (machdep->verify_symbol(syminfo.name, syminfo.value, 
 		    syminfo.type)) {
-			if (kt->flags & (RELOC_SET|RELOC_FORCE))
+			if ((kt->flags & (RELOC_SET|RELOC_FORCE)) &&
+			    sym->section != &bfd_abs_section)
 				sp->value = relocate(syminfo.value,
 					(char *)syminfo.name, !(first++));
 			else
--- a/x86.c
+++ b/x86.c
@@ -986,6 +986,7 @@ static void eframe_init(void);
 static char *extract_idt_function(ulong *, char *, ulong *);
 static int x86_is_task_addr(ulong);
 static int x86_verify_symbol(const char *, ulong, char);
+static int x86_hyper_verify_symbol(const char *, ulong, char);
 static int x86_eframe_search(struct bt_info *);
 static ulong x86_in_irqstack(ulong);
 static int x86_dis_filter(ulong, char *);
@@ -3254,7 +3255,12 @@ x86_dump_machdep_table(ulong arg)
 	fprintf(fp, "        memory_size: x86_memory_size()\n");
 	fprintf(fp, "      vmalloc_start: x86_vmalloc_start()\n");
 	fprintf(fp, "       is_task_addr: x86_is_task_addr()\n");
-	fprintf(fp, "      verify_symbol: x86_verify_symbol()\n");
+	if (machdep->verify_symbol == x86_verify_symbol)
+		fprintf(fp, "      verify_symbol: x86_verify_symbol()\n");
+	else if (machdep->verify_symbol == x86_hyper_verify_symbol)
+		fprintf(fp, "      verify_symbol: x86_hyper_verify_symbol()\n");
+	else
+		fprintf(fp, "      verify_symbol: %lx\n", (ulong)machdep->verify_symbol);
 	fprintf(fp, "         dis_filter: x86_dis_filter()\n");
 	fprintf(fp, "           cmd_mach: x86_cmd_mach()\n");
 	fprintf(fp, "       get_smp_cpus: x86_get_smp_cpus()\n");
@@ -3789,6 +3795,18 @@ x86_verify_symbol(const char *name, ulon
 	return TRUE;
 }
 
+static int
+x86_hyper_verify_symbol(const char *name, ulong value, char type)
+{
+	if (x86_verify_symbol(name, value, type))
+		return TRUE;
+
+	if (STREQ(name, "__per_cpu_shift"))
+		return TRUE;
+
+	return FALSE;
+}
+
 /*
  *  Filter disassembly output if the output radix is not gdb's default 10
  */
@@ -4967,7 +4985,7 @@ x86_init_hyper(int when)
 	switch (when)
 	{
 	case PRE_SYMTAB:
-		machdep->verify_symbol = x86_verify_symbol;
+		machdep->verify_symbol = x86_hyper_verify_symbol;
                 if (pc->flags & KERNEL_DEBUG_QUERY)
                         return;
                 machdep->pagesize = memory_page_size();
--- a/x86_64.c
+++ b/x86_64.c
@@ -27,6 +27,7 @@ static int x86_64_uvtop_level4_rhel4_xen
 static ulong x86_64_vmalloc_start(void);
 static int x86_64_is_task_addr(ulong);
 static int x86_64_verify_symbol(const char *, ulong, char);
+static int x86_64_hyper_verify_symbol(const char *, ulong, char);
 static ulong x86_64_get_task_pgd(ulong);
 static int x86_64_translate_pte(ulong, void *, ulonglong);
 static ulong x86_64_processor_speed(void);
@@ -491,7 +492,12 @@ x86_64_dump_machdep_table(ulong arg)
 	fprintf(fp, "        memory_size: generic_memory_size()\n");
 	fprintf(fp, "      vmalloc_start: x86_64_vmalloc_start()\n");
 	fprintf(fp, "       is_task_addr: x86_64_is_task_addr()\n");
-	fprintf(fp, "      verify_symbol: x86_64_verify_symbol()\n");
+	if (machdep->verify_symbol == x86_64_verify_symbol)
+		fprintf(fp, "      verify_symbol: x86_64_verify_symbol()\n");
+	else if (machdep->verify_symbol == x86_64_hyper_verify_symbol)
+		fprintf(fp, "      verify_symbol: x86_64_hyper_verify_symbol()\n");
+	else
+		fprintf(fp, "      verify_symbol: %lx\n", (ulong)machdep->verify_symbol);
 	fprintf(fp, "         dis_filter: x86_64_dis_filter()\n");
 	fprintf(fp, "           cmd_mach: x86_64_cmd_mach()\n");
 	fprintf(fp, "       get_smp_cpus: x86_64_get_smp_cpus()\n");
@@ -1978,6 +1984,18 @@ x86_64_verify_symbol(const char *name, u
 	return TRUE;
 }
 
+static int
+x86_64_hyper_verify_symbol(const char *name, ulong value, char type)
+{
+	if (x86_64_verify_symbol(name, value, type))
+		return TRUE;
+
+	if (STREQ(name, "__per_cpu_shift"))
+		return TRUE;
+
+	return FALSE;
+}
+
 
 /*
  *  Get the relevant page directory pointer from a task structure.
@@ -5949,7 +5967,7 @@ x86_64_init_hyper(int when)
 	switch (when)
 	{
 	case PRE_SYMTAB:
-		machdep->verify_symbol = x86_64_verify_symbol;
+		machdep->verify_symbol = x86_64_hyper_verify_symbol;
                 machdep->machspec = &x86_64_machine_specific;
                 if (pc->flags & KERNEL_DEBUG_QUERY)
                         return;


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