From d1e780507b6ed4b67e5e0e4e4b7c9796dc537210 Mon Sep 17 00:00:00 2001 From: Bhupesh Sharma Date: Tue, 6 Mar 2018 02:13:00 +0900 Subject: [PATCH 2/3] arm64: Add support to read symbols like _stext from '/proc/kallsyms' On ARM64 platforms the VA_BITS supported by a linux kernel being run can be selected by setting 'ARM64_VA_BITS_*' (see 'arch/arm64/Kconfig' for details). Now, to determine the 'info->page_offset' in arm64 makedumpfile context ('arch/arm64.c') we need to determine the VA_BITS which was selected by the underlying linux kernel. There can be several ways to determine the VA_BITS, out of which reading the '_stext' symbol and calculating the 'va_bits' using the same is the simplest yet portable method. For reading the kernel symbols like '_stext', we can read the '/proc/kallsyms' file which contains these symbols and works even in case of KASLR enabled arm64 kernels, as in those cases, the '_stext' symbol will end up being randomized and hence cannot be correctly read from the 'vmlinux' file. Signed-off-by: Bhupesh Sharma --- arch/arm64.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 73 insertions(+), 4 deletions(-) diff --git a/makedumpfile-1.6.2/arch/arm64.c b/makedumpfile-1.6.2/arch/arm64.c index 25d7a1f4db98..c9dab677f2c9 100644 --- a/makedumpfile-1.6.2/arch/arm64.c +++ b/makedumpfile-1.6.2/arch/arm64.c @@ -48,6 +48,12 @@ static unsigned long kimage_voffset; #define SZ_64K (64 * 1024) #define SZ_128M (128 * 1024 * 1024) +#define PAGE_OFFSET_36 ((0xffffffffffffffffUL) << 36) +#define PAGE_OFFSET_39 ((0xffffffffffffffffUL) << 39) +#define PAGE_OFFSET_42 ((0xffffffffffffffffUL) << 42) +#define PAGE_OFFSET_47 ((0xffffffffffffffffUL) << 47) +#define PAGE_OFFSET_48 ((0xffffffffffffffffUL) << 48) + #define pgd_val(x) ((x).pgd) #define pud_val(x) (pgd_val((x).pgd)) #define pmd_val(x) (pud_val((x).pud)) @@ -140,8 +146,6 @@ pud_offset(pgd_t *pgda, pgd_t *pgdv, unsigned long vaddr) static int calculate_plat_config(void) { - va_bits = NUMBER(VA_BITS); - /* derive pgtable_level as per arch/arm64/Kconfig */ if ((PAGESIZE() == SZ_16K && va_bits == 36) || (PAGESIZE() == SZ_64K && va_bits == 42)) { @@ -177,6 +181,44 @@ get_phys_base_arm64(void) return TRUE; } +ulong +get_stext_symbol(void) +{ + int found; + FILE *fp; + char buf[BUFSIZE]; + char *kallsyms[MAXARGS]; + ulong kallsym; + + if (!file_exists("/proc/kallsyms")) { + ERRMSG("(%s) does not exist, will not be able to read symbols. %s\n", + "/proc/kallsyms", strerror(errno)); + return FALSE; + } + + if ((fp = fopen("/proc/kallsyms", "r")) == NULL) { + ERRMSG("Cannot open (%s) to read symbols. %s\n", + "/proc/kallsyms", strerror(errno)); + return FALSE; + } + + found = FALSE; + kallsym = 0; + + while (!found && fgets(buf, BUFSIZE, fp) && + (parse_line(buf, kallsyms) == 3)) { + if (hexadecimal(kallsyms[0], 0) && + STREQ(kallsyms[2], "_stext")) { + kallsym = htol(kallsyms[0], 0); + found = TRUE; + break; + } + } + fclose(fp); + + return(found ? kallsym : FALSE); +} + int get_machdep_info_arm64(void) { @@ -188,12 +230,10 @@ get_machdep_info_arm64(void) kimage_voffset = NUMBER(kimage_voffset); info->max_physmem_bits = PHYS_MASK_SHIFT; info->section_size_bits = SECTIONS_SIZE_BITS; - info->page_offset = 0xffffffffffffffffUL << (va_bits - 1); DEBUG_MSG("kimage_voffset : %lx\n", kimage_voffset); DEBUG_MSG("max_physmem_bits : %lx\n", info->max_physmem_bits); DEBUG_MSG("section_size_bits: %lx\n", info->section_size_bits); - DEBUG_MSG("page_offset : %lx\n", info->page_offset); return TRUE; } @@ -219,6 +259,35 @@ get_xen_info_arm64(void) int get_versiondep_info_arm64(void) { + ulong _stext; + + _stext = get_stext_symbol(); + if (!_stext) { + ERRMSG("Can't get the symbol of _stext.\n"); + return FALSE; + } + + /* Derive va_bits as per arch/arm64/Kconfig */ + if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) { + va_bits = 36; + } else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) { + va_bits = 39; + } else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) { + va_bits = 42; + } else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) { + va_bits = 47; + } else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) { + va_bits = 48; + } else { + ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n"); + return FALSE; + } + + info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1); + + DEBUG_MSG("page_offset=%lx, va_bits=%d\n", info->page_offset, + va_bits); + return TRUE; } -- 2.7.4