From 85a0ee342e0c06c19d78fdf48307211c6cf18fcb Mon Sep 17 00:00:00 2001 From: Simon Horman Date: Sat, 18 Oct 2008 20:28:29 -0700 Subject: [PATCH] kdump: add is_vmcore_usable() and vmcore_unusable() 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 Cc: Vivek Goyal Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/ia64/kernel/setup.c | 4 ++-- fs/proc/vmcore.c | 2 +- include/linux/crash_dump.h | 24 ++++++++++++++++++++++++ 3 files changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c index a0286be6c235..60286522d54a 100644 --- a/arch/ia64/kernel/setup.c +++ b/arch/ia64/kernel/setup.c @@ -509,11 +509,11 @@ int __init reserve_elfcorehdr(unsigned long *start, unsigned long *end) * to work properly. */ - if (elfcorehdr_addr >= ELFCORE_ADDR_MAX) + if (!is_vmcore_usable()) return -EINVAL; if ((length = vmcore_find_descriptor_size(elfcorehdr_addr)) == 0) { - elfcorehdr_addr = ELFCORE_ADDR_MAX; + vmcore_unusable(); return -EINVAL; } diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index 4c65ca432d30..cd9ca67f841b 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -644,7 +644,7 @@ 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) { diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h index de027d1db745..0acf3b737e2e 100644 --- a/include/linux/crash_dump.h +++ b/include/linux/crash_dump.h @@ -8,6 +8,7 @@ #include #define ELFCORE_ADDR_MAX (-1ULL) +#define ELFCORE_ADDR_ERR (-2ULL) extern unsigned long long elfcorehdr_addr; @@ -38,6 +39,29 @@ static inline int is_kdump_kernel(void) { return (elfcorehdr_addr != ELFCORE_ADDR_MAX) ? 1 : 0; } + +/* 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 -2ULL 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; +} #else /* !CONFIG_CRASH_DUMP */ static inline int is_kdump_kernel(void) { return 0; } #endif /* CONFIG_CRASH_DUMP */ -- GitLab