From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Date: Tue, 29 Jul 2008 08:12:37 +0000 Subject: [patch 2/3] kdump: add is_vmcore_usable() and vmcore_unusable() Message-Id: <20080729081629.522008269@vergenet.net> List-Id: References: <20080729081235.293361145@vergenet.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org, linux-ia64@vger.kernel.org, lkml@vger.kernel.org Cc: Vivek Goyal The usage of elfcorehdr_addr has changed recently such that being set to ELFCORE_ADDR_MAX is used by is_kdump_kernel() to indicate if the code is executing in a kernel executed as a crash kernel. However, arch/ia64/kernel/setup.c:reserve_elfcorehdr will rest elfcorehdr_addr to ELFCORE_ADDR_MAX on error, which means any subsequent calls to is_kdump_kernel() will return 0, even though they should return 1. Ok, at this point in time there are no subsequent calls, but I think its fair to say that there is ample scope for error or at the very least confusion. This patch add an extra state, ELFCORE_ADDR_ERR, which indicates that elfcorehdr_addr was passed on the command line, and thus execution is taking place in a crashdump kernel, but vmcore can't be used for some reason. This is tested for using is_vmcore_usable() and set using vmcore_unusable(). A subsequent patch makes use of this new code. To summarise, the states that elfcorehdr_addr can now be in are as follows: ELFCORE_ADDR_MAX: not a crashdump kernel ELFCORE_ADDR_ERR: crashdump kernel but vmcore is unusable any other value: crash dump kernel and vmcore is usable Signed-off-by: Simon Horman Index: linux-2.6/include/linux/crash_dump.h =================================--- linux-2.6.orig/include/linux/crash_dump.h 2008-07-29 17:27:43.000000000 +1000 +++ linux-2.6/include/linux/crash_dump.h 2008-07-29 17:53:13.000000000 +1000 @@ -8,6 +8,7 @@ #include #define ELFCORE_ADDR_MAX (-1ULL) +#define ELFCORE_ADDR_ERR (-2ULL) #ifdef CONFIG_PROC_VMCORE extern unsigned long long elfcorehdr_addr; @@ -36,5 +37,30 @@ static inline int is_kdump_kernel(void) static inline int is_kdump_kernel(void) { return 0; } #endif /* CONFIG_CRASH_DUMP */ +#ifdef CONFIG_PROC_VMCORE +/* is_vmcore_usable() checks if the kernel is booting after a panic and + * the vmcore region is usable. + * + * This makes use of the fact that due to alignment 1 is not + * a valid pointer, much in the vain of IS_ERR(), except + * dealing directly with an unsigned long long rather than a pointer. + */ + +static inline int is_vmcore_usable(void) +{ + return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0; +} + +/* vmcore_unusable() marks the vmcore as unusable, without disturbing + * the logic of is_kdump_kernel() + */ + +static inline void vmcore_unusable(void) +{ + if (!is_kdump_kernel()) + elfcorehdr_addr = ELFCORE_ADDR_ERR; +} +#endif /* CONFIG_PROC_VMCORE */ + extern unsigned long saved_max_pfn; #endif /* LINUX_CRASHDUMP_H */ Index: linux-2.6/fs/proc/vmcore.c =================================--- linux-2.6.orig/fs/proc/vmcore.c 2008-07-29 17:27:43.000000000 +1000 +++ linux-2.6/fs/proc/vmcore.c 2008-07-29 17:39:32.000000000 +1000 @@ -653,7 +653,7 @@ static int __init vmcore_init(void) int rc = 0; /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/ - if (!(elfcorehdr_addr < ELFCORE_ADDR_MAX)) + if (!(is_vmcore_usable())) return rc; rc = parse_crash_elf_headers(); if (rc) { -- -- Horms