Hi Dave, I resend the email with the patch attached. It’s a bugfix for the determination of the ARM64 SECTION_SIZE_BITS. For some ARM64 arch platforms such as qcom 8150/8250 boards, they define their own section size bits in kernel config to support memory hotplug, which is not same as ARM64 default SECTION_SIZE_BITS value: 30. The SECTION_SIZE_BITS definition in qcom's linux-4.14 code as below: [arch/arm64/include/asm/sparsemem.h] #ifdef CONFIG_SPARSEMEM #define MAX_PHYSMEM_BITS 48 #ifndef CONFIG_MEMORY_HOTPLUG #define SECTION_SIZE_BITS 30 #else #define SECTION_SIZE_BITS CONFIG_HOTPLUG_SIZE_BITS #endif #endif

Without the patch, after load ramdump by crash tool, the warning message maybe displayed: crash> kmem -P 0x80000000 kmem: WARNING: cannot find mem_map page for address: fffffffe80000000 kmem: cannot determine page for 80000000 80000000: physical address not found in mem map So I introduce this patch to fix it, we can determine SECTION_SIZE_BITS either by reading VMCOREINFO or the kernel config, otherwise borrow the 64-bit ARM default definiton. diff --git a/arm64.c b/arm64.c index 6b34b5f..31c03d4 100644 --- a/arm64.c +++ b/arm64.c @@ -32,6 +32,7 @@ static int verify_kimage_voffset(void); static void arm64_calc_kimage_voffset(void); static void arm64_calc_phys_offset(void); static void arm64_calc_virtual_memory_ranges(void); +static void arm64_get_section_size_bits(void); static int arm64_kdump_phys_base(ulong *); static ulong arm64_processor_speed(void); static void arm64_init_kernel_pgd(void); @@ -375,7 +376,11 @@ arm64_init(int when) case POST_GDB: arm64_calc_virtual_memory_ranges(); - machdep->section_size_bits = _SECTION_SIZE_BITS; + arm64_get_section_size_bits(); + if (CRASHDEBUG(1)) { + fprintf(fp, "SECTION_SIZE_BITS: %ld\n", machdep->section_size_bits); + } + if (!machdep->max_physmem_bits) { if ((string = pc->read_vmcoreinfo("NUMBER(MAX_PHYSMEM_BITS)"))) { machdep->max_physmem_bits = atol(string); @@ -1055,6 +1060,32 @@ arm64_calc_phys_offset(void) fprintf(fp, "using %lx as phys_offset\n", ms->phys_offset); } +/* + * Determine SECTION_SIZE_BITS either by reading VMCOREINFO or the kernel + * config, otherwise borrow the 64-bit ARM default definiton. + */ +static void +arm64_get_section_size_bits(void) +{ + int ret; + char *string; + + if ((string = pc->read_vmcoreinfo("NUMBER(SECTION_SIZE_BITS)"))) { + machdep->section_size_bits = atol(string); + free(string); + return; + } + + if ((ret = get_kernel_config("CONFIG_MEMORY_HOTPLUG", NULL)) == IKCONFIG_Y) { + if ((ret = get_kernel_config("CONFIG_HOTPLUG_SIZE_BITS", &string)) == IKCONFIG_STR) { + machdep->section_size_bits = atol(string); + free(string); + return; + } + } + + machdep->section_size_bits = _SECTION_SIZE_BITS; +} Thanks for your review. I’m looking forward to your favourable reply! Best regards, Qiwu -----Original Message----- From: Dave Anderson <anderson(a)redhat.com&gt; Sent: Wednesday, September 18, 2019 9:32 PM To: 陈启武 <chenqiwu(a)xiaomi.com&gt; Cc: crash-utility(a)redhat.com Subject: Re: [External Mail]Re: [PATCH] Fix a segfault in setup_ikconfig. ----- Original Message ----- > Hi Dave, > 1. I'm requesting the arm64.c change as well. Because some chip makers > would like to define their own section size bits in kernel config to > support memory hotplug, which is not same as ARM64 default > SECTION_SIZE_BITS value: > 30, such as QCOM SDM8150 or 8250 borads. Although linux kernel > maintain line still define default SECTION_SIZE_BITS value: 30 as > section_size_bits for sparsemem. The patch has detailed descript in > the email "[PATCH] Fix for the determination of the ARM64 > SECTION_SIZE_BITS". I never received an email with that header. Can you please resend the email with the patch attached (i.e., not inlined)? Thanks, Dave > 2. The output of "sys config" for my dumpfile has been uploaded, which > shows the last line is empty. it occurs a segment fault when add the > last empty line into ikconfig entry. I agree that the use of STRNEQ() > is better than strncmp(). > > Best regards, > Qiwu > > > > -----Original Message----- > From: Dave Anderson <anderson(a)redhat.com&gt; > Sent: Wednesday, September 18, 2019 3:22 AM > To: 陈启武 <chenqiwu(a)xiaomi.com&gt; > Cc: crash-utility(a)redhat.com > Subject: [External Mail]Re: [PATCH] Fix a segfault in setup_ikconfig. > > > > ----- Original Message ----- > > > > Hi Anderson, > > I want to introduce a patch to your crash tool project. It’s a > > bugfix for a segfault in setup_ikconfig. > > We add an ikconfig entry only if ent[0] != '#', it is not an > > advisable condition because there is a potential segfault risk if ent is > > gibberish. > > Using your dumpfile that has the bogus "ent" string, can you show me > what the output of "sys config" looks like? > > Dave > > > I explain the reproducing steps about this segfault case: > > I try to apply the following patch to crash 7.2.6++ code for a test. > > --- a/arm64.c > > +++ b/arm64.c > > @@ -32,6 +32,7 @@ static int verify_kimage_voffset(void); static > > void arm64_calc_kimage_voffset(void); static void > > arm64_calc_phys_offset(void); static void > > arm64_calc_virtual_memory_ranges(void); > > +static void arm64_get_section_size_bits(void); > > static int arm64_kdump_phys_base(ulong *); static ulong > > arm64_processor_speed(void); static void > > arm64_init_kernel_pgd(void); @@ -375,7 +376,11 @@ arm64_init(int > > when) > > > > case POST_GDB: > > arm64_calc_virtual_memory_ranges(); > > - machdep->section_size_bits = _SECTION_SIZE_BITS; > > + arm64_get_section_size_bits(); > > + if (CRASHDEBUG(1)) { > > + fprintf(fp, "SECTION_SIZE_BITS: %ld\n", > > machdep->section_size_bits); > > + } > > + > > if (!machdep->max_physmem_bits) { > > if ((string = > > pc->read_vmcoreinfo("NUMBER(MAX_PHYSMEM_BITS)"))) > > { > > machdep->max_physmem_bits = > > atol(string); @@ -1055,6 +1060,32 @@ arm64_calc_phys_offset(void) > > fprintf(fp, "using %lx as phys_offset\n", > > ms->phys_offset); } > > > > +/* > > + * Determine SECTION_SIZE_BITS either by reading VMCOREINFO or the > > +kernel > > + * config, otherwise borrow the 64-bit ARM default definiton. > > + */ > > +static void > > +arm64_get_section_size_bits(void) > > +{ > > + int ret; > > + char *string; > > + > > + if ((string = pc->read_vmcoreinfo("NUMBER(SECTION_SIZE_BITS)"))) > > { > > + machdep->section_size_bits = atol(string); > > + free(string); > > + return; > > + } > > + > > + if ((ret = get_kernel_config("CONFIG_MEMORY_HOTPLUG", NULL)) > > + == > > IKCONFIG_Y) { > > + if ((ret = > > + get_kernel_config("CONFIG_HOTPLUG_SIZE_BITS", > > &string)) == IKCONFIG_STR) { > > + machdep->section_size_bits = atol(string); > > + free(string); > > + return; > > + } > > + } else { > > + machdep->section_size_bits = _SECTION_SIZE_BITS; > > + } > > +} > > > > Then I make and load the dumpfiles by crash, it occurs a segment > > fault as > > below: > > crash[31000]: segfault at 0 ip 00007f0fb24d98d1 sp 00007fff1703f7e8 > > error 4 in libc-2.26.so[7f0fb235b000+1d6000] > > > > So I add debug to find out the segfault reason, It occurred in > > setup_ikconfig-> add_ikconfig_entry. > > add_ikconfig_entry: ▒▒▒U //The last ent is a gibberish, > > lead > > to segfault > > > > I think the most advisable judgement is if an ikconfig entry start > > with "CONFIG_". I debug by the following patch and never reproduce > > segfault again. > > diff --git a/kernel.c b/kernel.c > > index 7804aef..d023c87 100644 > > --- a/kernel.c > > +++ b/kernel.c > > @@ -10144,7 +10144,7 @@ static int setup_ikconfig(char *config) > > while (whitespace(*ent)) > > ent++; > > > > - if (ent[0] != '#') { > > + if (!strncmp(ent, "CONFIG_", strlen("CONFIG_"))) { > > add_ikconfig_entry(ent, > > &ikconfig_all[kt->ikconfig_ents++]); > > if (kt->ikconfig_ents == IKCONFIG_MAX) { > > > > Thanks for your review. I’m looking forward to your favourable reply! > > > > Best regards, > > Qiwu > > > > > > > > > > #/******本邮件及其附件含有小米公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁止任何其他人以任何形式使用（包括但不限于 > > 全部 > > 或部分地泄露、复制、或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ > > This e-mail and its attachments contain confidential information > > from XIAOMI, which is intended only for the person or entity whose > > address is listed above. 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