On Tue, Jul 29, 2008 at 11:15:33AM -0400, Vivek Goyal wrote: > On Tue, Jul 29, 2008 at 06:12:37PM +1000, Simon Horman wrote: > > 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 <horms@xxxxxxxxxxxx> > > > > > > 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 <linux/proc_fs.h> > > > > #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; > > +} > > Hi Simon, > > Should above condition be "if(is_kdump_kernel())" instead of > "if(!is_kdump_kernel())? > > I would think that you would like to mark a vmcore unusable only if, to > begin with you were booting after a panic. > > If we being marking vmcore_unusable in case of normal kernel > (!is_kdump_kernel()), then is_kdump_kernel() will start reporting > normal kernel as kdump kernel? Yes, you are correct. Sorry for the silly mistake. I'll repost with if (!is_kdump_kernel()) ... -- Horms -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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