Crash encounters a bug like the following: ... SECTION_SIZE_BITS: 30 CONFIG_ARM64_VA_BITS: 52 VA_BITS_ACTUAL: 48 (calculated) VA_BITS: 48 PAGE_OFFSET: ffff000000000000 VA_START: ffff800000000000 modules: ffff800008000000 - ffff80000fffffff vmalloc: ffff800010000000 - ffffffdfdffeffff kernel image: ffff800010000000 - ffff800012750000 vmemmap: ffffffdfffe00000 - ffffffffffffffff <readmem: ffff800011c53bc8, KVADDR, "nr_irqs", 4, (FOE), b47bdc> <read_kdump: addr: ffff800011c53bc8 paddr: eb453bc8 cnt: 4> read_netdump: addr: ffff800011c53bc8 paddr: eb453bc8 cnt: 4 offset: 1c73bc8 irq_stack_ptr: type: 1, TYPE_CODE_PTR target_typecode: 8, TYPE_CODE_INT target_length: 8 length: 8 GNU_GET_DATATYPE[thread_union]: returned via gdb_error_hook <readmem: ffff000b779c0050, KVADDR, "IRQ stack pointer", 8, (ROE), 3a37bea0> <read_kdump: addr: ffff000b779c0050 paddr: fff1000bf79c0050 cnt: 8> read_netdump: READ_ERROR: offset not found for paddr: fff1000bf79c0050 crash: read error: kernel virtual address: ffff000b779c0050 type: "IRQ stack pointer" <readmem: ffff000b77a60050, KVADDR, "IRQ stack pointer", 8, (ROE), 3a37bea8> <read_kdump: addr: ffff000b77a60050 paddr: fff1000bf7a60050 cnt: 8> read_netdump: READ_ERROR: offset not found for paddr: fff1000bf7a60050 ... Apparently, for a normal system, the 'paddr: fff1000bf79c0050' is unreasonable. This bug connects with kernel commit 7bc1a0f9e176 ("arm64: mm: use single quantity to represent the PA to VA translation"), memstart_addr can be negative, which makes it different from real phys_offset. If using memstart_addr to calculate the real paddr, the unreasonable paddr will be got. Furthermore, in crash utility, PTOV() needs memstart_addr to calculate VA from PA, while getting PFN offset in a dumpfile, phys_offset is required. To serve the different purpose, using phys_offset_nominal and phys_offset to store them. Signed-off-by: Pingfan Liu <piliu(a)redhat.com&gt; Cc: HAGIO KAZUHITO <k-hagio-ab(a)nec.com&gt; Cc: Lianbo Jiang <lijiang(a)redhat.com&gt; Cc: Bhupesh Sharma <bhupesh.sharma(a)linaro.org&gt; To: crash-utility(a)redhat.com --- v3 -> v4: use _PAGE_OFFSET(va) to define MEMSTART_ADDR_OFFSET and use the formula "#define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)" for arm64_VTOP() v2 -> v3: rename ms->memstart_addr as ms->phys_offset_nominal ( I keep the name as phys_offset* since it is in accordance with other platform conventions) --- arm64.c | 45 ++++++++++++++++++++++++++++++++++++++++----- defs.h | 3 +++ 2 files changed, 43 insertions(+), 5 deletions(-) diff --git a/arm64.c b/arm64.c index 4787fa6..84addde 100644 --- a/arm64.c +++ b/arm64.c @@ -23,6 +23,10 @@ #include <sys/ioctl.h> #define NOT_IMPLEMENTED(X) error((X), "%s: function not implemented\n", __func__) +/* + * _PAGE_OFFSET() refers to arch/arm64/include/asm/memory.h + */ +#define _PAGE_OFFSET(va) (-1UL << (va)) static struct machine_specific arm64_machine_specific = { 0 }; static int arm64_verify_symbol(const char *, ulong, char); @@ -687,6 +691,7 @@ arm64_dump_machdep_table(ulong arg) fprintf(fp, " kimage_voffset: %016lx\n", ms->kimage_voffset); } fprintf(fp, " phys_offset: %lx\n", ms->phys_offset); + fprintf(fp, " phys_offset_nominal: %lx\n", ms->phys_offset_nominal); fprintf(fp, "__exception_text_start: %lx\n", ms->__exception_text_start); fprintf(fp, " __exception_text_end: %lx\n", ms->__exception_text_end); fprintf(fp, " __irqentry_text_start: %lx\n", ms->__irqentry_text_start); @@ -987,7 +992,12 @@ arm64_calc_physvirt_offset(void) ulong physvirt_offset; struct syment *sp; - ms->physvirt_offset = ms->phys_offset - ms->page_offset; + /* + * source arch/arm64/include/asm/memory.h + * #define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) + * the part "addr & ~PAGE_OFFSET" is done in arm64_VTOP() + */ + ms->physvirt_offset = ms->phys_offset_nominal; if ((sp = kernel_symbol_search("physvirt_offset")) && machdep->machspec->kimage_voffset) { @@ -1002,6 +1012,8 @@ arm64_calc_physvirt_offset(void) static void arm64_calc_phys_offset(void) { +#define MEMSTART_ADDR_OFFSET _PAGE_OFFSET(48) - _PAGE_OFFSET(52) + struct machine_specific *ms = machdep->machspec; ulong phys_offset; @@ -1028,7 +1040,11 @@ arm64_calc_phys_offset(void) ms->kimage_voffset && (sp = kernel_symbol_search("memstart_addr"))) { if (pc->flags & PROC_KCORE) { if ((string = pc->read_vmcoreinfo("NUMBER(PHYS_OFFSET)"))) { - ms->phys_offset = htol(string, QUIET, NULL); + ms->phys_offset_nominal = htol(string, QUIET, NULL); + if (ms->phys_offset_nominal < 0) + ms->phys_offset = ms->phys_offset_nominal + MEMSTART_ADDR_OFFSET; + else + ms->phys_offset = ms->phys_offset_nominal; free(string); return; } @@ -1080,7 +1096,18 @@ arm64_calc_phys_offset(void) } else if (DISKDUMP_DUMPFILE() && diskdump_phys_base(&phys_offset)) { ms->phys_offset = phys_offset; } else if (KDUMP_DUMPFILE() && arm64_kdump_phys_base(&phys_offset)) { - ms->phys_offset = phys_offset; + /* + * When running a 52bits kernel on 48bits hardware. Kernel plays a trick: + * if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) + * memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52); + * + * In crash, this should be detected to get a real physical start address. + */ + ms->phys_offset_nominal = phys_offset; + if ((long)phys_offset < 0) + ms->phys_offset = phys_offset + MEMSTART_ADDR_OFFSET; + else + ms->phys_offset = phys_offset; } else { error(WARNING, "phys_offset cannot be determined from the dumpfile.\n"); @@ -1180,8 +1207,16 @@ arm64_VTOP(ulong addr) return addr - machdep->machspec->kimage_voffset; } - if (addr >= machdep->machspec->page_offset) - return addr + machdep->machspec->physvirt_offset; + if (addr >= machdep->machspec->page_offset) { + ulong paddr; + + /* + * #define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) + */ + paddr = addr & ~ _PAGE_OFFSET(machdep->machspec->CONFIG_ARM64_VA_BITS); + paddr += machdep->machspec->physvirt_offset; + return paddr; + } else if (machdep->machspec->kimage_voffset) return addr - machdep->machspec->kimage_voffset; else /* no randomness */ diff --git a/defs.h b/defs.h index f9c711c..0a152f1 100644 --- a/defs.h +++ b/defs.h @@ -3289,7 +3289,10 @@ struct machine_specific { ulong vmemmap_end; ulong modules_vaddr; ulong modules_end; + /* real physical offset */ ulong phys_offset; + /* read from kernel symbol memstart_addr */ + long phys_offset_nominal; ulong __exception_text_start; ulong __exception_text_end; struct arm64_pt_regs *panic_task_regs; -- 2.29.2