Messages in this thread Patch in this message | | | Date | Tue, 28 Aug 2007 11:44:31 +0100 | From | "Jan Beulich" <> | Subject | [PATCH] x86: optionally show last exception from/to register contents (v2) |
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.. when dumping register state. This is particularly useful when gcc managed to tail-call optimize an indirect call which happens to hit a NULL (or otherwise invalid) pointer.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Documentation/kernel-parameters.txt | 3 +++ arch/i386/kernel/cpu/amd.c | 4 ++++ arch/i386/kernel/cpu/common.c | 2 ++ arch/i386/kernel/cpu/intel.c | 20 ++++++++++++++------ arch/i386/kernel/traps.c | 35 +++++++++++++++++++++++++++++++++++ arch/x86_64/kernel/setup.c | 23 ++++++++++++++++++----- arch/x86_64/kernel/traps.c | 34 ++++++++++++++++++++++++++++++++++ include/asm-i386/msr-index.h | 3 +++ include/asm-i386/processor.h | 4 ++++ include/asm-x86_64/msr.h | 6 ++++++ include/asm-x86_64/processor.h | 3 +++ 11 files changed, 126 insertions(+), 11 deletions(-)
--- linux-2.6.23-rc4/Documentation/kernel-parameters.txt 2007-08-28 09:41:55.000000000 +0200 +++ 2.6.23-rc4-x86-ler/Documentation/kernel-parameters.txt 2007-08-17 09:58:55.000000000 +0200 @@ -1155,6 +1155,9 @@ and is between 256 and 4096 characters. nolapic_timer [X86-32,APIC] Do not use the local APIC timer. + noler [X86-32/X86-64] Do not print last exception records + with kernel register dumps. + noltlbs [PPC] Do not use large page/tlb entries for kernel lowmem mapping on PPC40x. --- linux-2.6.23-rc4/arch/i386/kernel/cpu/amd.c 2007-08-28 09:41:58.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/i386/kernel/cpu/amd.c 2007-08-17 10:02:17.000000000 +0200 @@ -238,9 +238,13 @@ static void __cpuinit init_amd(struct cp case 0x10: case 0x11: set_bit(X86_FEATURE_K8, c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_IA32_LASTINTFROMIP; break; case 6: set_bit(X86_FEATURE_K7, c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_IA32_LASTINTFROMIP; break; } if (c->x86 >= 6) --- linux-2.6.23-rc4/arch/i386/kernel/cpu/common.c 2007-08-28 09:41:58.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/i386/kernel/cpu/common.c 2007-08-07 10:42:55.000000000 +0200 @@ -503,6 +503,8 @@ static void __cpuinit identify_cpu(struc /* Init Machine Check Exception if available. */ mcheck_init(c); + + ler_enable(); } void __init identify_boot_cpu(void) --- linux-2.6.23-rc4/arch/i386/kernel/cpu/intel.c 2007-07-09 01:32:17.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/i386/kernel/cpu/intel.c 2007-08-07 10:42:55.000000000 +0200 @@ -188,15 +188,23 @@ static void __cpuinit init_intel(struct } #endif - if (c->x86 == 15) { + switch (c->x86) { + case 15: set_bit(X86_FEATURE_P4, c->x86_capability); set_bit(X86_FEATURE_SYNC_RDTSC, c->x86_capability); - } - if (c->x86 == 6) + if (c->x86_model >= 0x03) + set_bit(X86_FEATURE_CONSTANT_TSC, c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_P4_LER_FROM_LIP; + break; + case 6: set_bit(X86_FEATURE_P3, c->x86_capability); - if ((c->x86 == 0xf && c->x86_model >= 0x03) || - (c->x86 == 0x6 && c->x86_model >= 0x0e)) - set_bit(X86_FEATURE_CONSTANT_TSC, c->x86_capability); + if (c->x86_model >= 0x0e) + set_bit(X86_FEATURE_CONSTANT_TSC, c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_IA32_LASTINTFROMIP; + break; + } if (cpu_has_ds) { unsigned int l1; --- linux-2.6.23-rc4/arch/i386/kernel/traps.c 2007-08-28 09:41:58.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/i386/kernel/traps.c 2007-08-17 14:26:08.000000000 +0200 @@ -321,6 +321,20 @@ void show_registers(struct pt_regs *regs unsigned int code_len = code_bytes; unsigned char c; + if (oops_in_progress && __get_cpu_var(ler_msr)) { + u32 from, to, hi; + + if (rdmsr_safe(__get_cpu_var(ler_msr), &from, &hi) == 0 + && rdmsr_safe(__get_cpu_var(ler_msr) + 1, &to, &hi) == 0) { + printk("\n" KERN_EMERG + "last branch before last exception/interrupt\n"); + printk(KERN_EMERG " from %08x", from); + print_symbol(" (%s)\n", from); + printk(KERN_EMERG " to %08x", to); + print_symbol(" (%s)", to); + } else + __get_cpu_var(ler_msr) = 0; + } printk("\n" KERN_EMERG "Stack: "); show_stack_log_lvl(NULL, regs, (unsigned long *)esp, KERN_EMERG); @@ -360,6 +374,19 @@ int is_valid_bugaddr(unsigned long eip) return ud2 == 0x0b0f; } +DEFINE_PER_CPU(u32, ler_msr); +int ler_enabled = 1; + +void ler_enable(void) { + if (__get_cpu_var(ler_msr)) { + u32 lo, hi; + + if (rdmsr_safe(MSR_IA32_DEBUGCTLMSR, &lo, &hi) < 0 + || wrmsr_safe(MSR_IA32_DEBUGCTLMSR, lo | 1, hi) < 0) + __get_cpu_var(ler_msr) = 0; + } +} + /* * This is gone through when something in the kernel has done something bad and * is about to be terminated. @@ -846,6 +873,7 @@ fastcall void __kprobes do_debug(struct struct task_struct *tsk = current; get_debugreg(condition, 6); + ler_enable(); if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code, SIGTRAP) == NOTIFY_STOP) @@ -1239,3 +1267,10 @@ static int __init code_bytes_setup(char return 1; } __setup("code_bytes=", code_bytes_setup); + +static int __init ler_setup(char *s) +{ + ler_enabled = 0; + return 1; +} +__setup("noler", ler_setup); --- linux-2.6.23-rc4/arch/x86_64/kernel/setup.c 2007-08-28 09:42:04.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/x86_64/kernel/setup.c 2007-08-17 10:00:41.000000000 +0200 @@ -617,6 +617,9 @@ static void __cpuinit init_amd(struct cp /* Family 10 doesn't support C states in MWAIT so don't use it */ if (c->x86 == 0x10 && !force_mwait) clear_bit(X86_FEATURE_MWAIT, &c->x86_capability); + + if (ler_enabled && c->x86 <= 17) + __get_cpu_var(ler_msr) = MSR_IA32_LASTINTFROMIP; } static void __cpuinit detect_ht(struct cpuinfo_x86 *c) @@ -736,13 +739,22 @@ static void __cpuinit init_intel(struct c->x86_phys_bits = 36; } - if (c->x86 == 15) + switch (c->x86) { + case 15: c->x86_cache_alignment = c->x86_clflush_size * 2; - if ((c->x86 == 0xf && c->x86_model >= 0x03) || - (c->x86 == 0x6 && c->x86_model >= 0x0e)) - set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability); - if (c->x86 == 6) + if (c->x86_model >= 0x03) + set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_P4_LER_FROM_LIP; + break; + case 6: + if (c->x86_model >= 0x0e) + set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability); set_bit(X86_FEATURE_REP_GOOD, &c->x86_capability); + if (ler_enabled) + __get_cpu_var(ler_msr) = MSR_IA32_LASTINTFROMIP; + break; + } if (c->x86 == 15) set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability); else @@ -906,6 +918,7 @@ void __cpuinit identify_cpu(struct cpuin #ifdef CONFIG_NUMA numa_add_cpu(smp_processor_id()); #endif + ler_enable(); } --- linux-2.6.23-rc4/arch/x86_64/kernel/traps.c 2007-08-28 09:42:05.000000000 +0200 +++ 2.6.23-rc4-x86-ler/arch/x86_64/kernel/traps.c 2007-08-17 14:26:31.000000000 +0200 @@ -426,6 +426,19 @@ void show_registers(struct pt_regs *regs * time of the fault.. */ if (in_kernel) { + if (oops_in_progress && __get_cpu_var(ler_msr)) { + u64 from, to; + + if (checking_rdmsrl(__get_cpu_var(ler_msr), from) == 0 + && checking_rdmsrl(__get_cpu_var(ler_msr) + 1, to) == 0) { + printk("last branch before last exception/interrupt\n"); + printk(" from "); + printk_address(from); + printk(" to "); + printk_address(to); + } else + __get_cpu_var(ler_msr) = 0; + } printk("Stack: "); _show_stack(NULL, regs, (unsigned long*)rsp); @@ -464,6 +477,19 @@ void out_of_line_bug(void) EXPORT_SYMBOL(out_of_line_bug); #endif +DEFINE_PER_CPU(u32, ler_msr); +int ler_enabled = 1; + +void ler_enable(void) { + if (__get_cpu_var(ler_msr)) { + u32 lo, hi; + + if (rdmsr_safe(MSR_IA32_DEBUGCTLMSR, &lo, &hi) < 0 + || wrmsr_safe(MSR_IA32_DEBUGCTLMSR, lo | 1, hi) < 0) + __get_cpu_var(ler_msr) = 0; + } +} + static DEFINE_SPINLOCK(die_lock); static int die_owner = -1; static unsigned int die_nest_count; @@ -849,6 +875,7 @@ asmlinkage void __kprobes do_debug(struc siginfo_t info; get_debugreg(condition, 6); + ler_enable(); if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code, SIGTRAP) == NOTIFY_STOP) @@ -1136,3 +1163,10 @@ static int __init kstack_setup(char *s) return 0; } early_param("kstack", kstack_setup); + +static int __init ler_setup(char *s) +{ + ler_enabled = 0; + return 1; +} +__setup("noler", ler_setup); --- linux-2.6.23-rc4/include/asm-i386/msr-index.h 2007-07-09 01:32:17.000000000 +0200 +++ 2.6.23-rc4-x86-ler/include/asm-i386/msr-index.h 2007-08-07 10:42:55.000000000 +0200 @@ -63,6 +63,9 @@ #define MSR_IA32_LASTINTFROMIP 0x000001dd #define MSR_IA32_LASTINTTOIP 0x000001de +#define MSR_P4_LER_FROM_LIP 0x000001d7 +#define MSR_P4_LER_TO_LIP 0x000001d8 + #define MSR_IA32_MC0_CTL 0x00000400 #define MSR_IA32_MC0_STATUS 0x00000401 #define MSR_IA32_MC0_ADDR 0x00000402 --- linux-2.6.23-rc4/include/asm-i386/processor.h 2007-08-28 09:42:34.000000000 +0200 +++ 2.6.23-rc4-x86-ler/include/asm-i386/processor.h 2007-08-07 10:42:55.000000000 +0200 @@ -643,6 +643,10 @@ static inline unsigned int cpuid_edx(uns return edx; } +DECLARE_PER_CPU(u32, ler_msr); +extern int ler_enabled; +void ler_enable(void); + /* generic versions from gas */ #define GENERIC_NOP1 ".byte 0x90\n" #define GENERIC_NOP2 ".byte 0x89,0xf6\n" --- linux-2.6.23-rc4/include/asm-x86_64/msr.h 2007-07-09 01:32:17.000000000 +0200 +++ 2.6.23-rc4-x86-ler/include/asm-x86_64/msr.h 2007-08-17 14:45:14.000000000 +0200 @@ -63,6 +63,12 @@ :"c"(msr), "i"(-EIO), "0"(0)); \ ret__; }) +#define checking_rdmsrl(msr,val) ({ \ + u32 lo__, hi__; \ + int rc__ = rdmsr_safe(msr, &lo__, &hi__); \ + val = lo__ | ((u64)hi__ << 32); \ + rc__; }) + #define rdtsc(low,high) \ __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high)) --- linux-2.6.23-rc4/include/asm-x86_64/processor.h 2007-08-28 09:42:36.000000000 +0200 +++ 2.6.23-rc4-x86-ler/include/asm-x86_64/processor.h 2007-08-07 10:42:55.000000000 +0200 @@ -333,6 +333,9 @@ struct extended_sigtable { struct extended_signature sigs[0]; }; +DECLARE_PER_CPU(u32, ler_msr); +extern int ler_enabled; +void ler_enable(void); #define ASM_NOP1 K8_NOP1 #define ASM_NOP2 K8_NOP2
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