[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(a)suse.cz&gt; --- 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;