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Current code could cause a bug in symbol_put_addr() if an arch used
kmalloc module text: we might think the symbol belongs to the core
kernel.
The downside is that this might make backtraces through (discarded)
init functions harder to read on some archs, but we already have that
issue for modules and noone has complained.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Even since a previous patch:
Fix race between CONFIG_DEBUG_SLABALLOC and modules
Sun, 27 Jun 2004 17:55:19 +0000 (17:55 +0000)
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=92b3db26d31cf21b70e3c1eadc56c179506d8fbe
The function symbol_put_addr() will deadlock the kernel.
symbol_put_addr() would acquire modlist_lock, then while holding the lock call
two functions kernel_text_address() and module_text_address() which also try
to acquire the same lock. This deadlocks the kernel of course.
This patch changes symbol_put_addr() to not acquire the modlist_lock, it
doesn't need it since it never looks at the module list directly. Also, it
now uses core_kernel_text() instead of kernel_text_address(). The latter has
an additional check for addr inside a module, but we don't need to do that
since we call module_text_address() (the same function kernel_text_address
uses) ourselves.
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Cc: Zwane Mwaikambo <zwane@fsmlabs.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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store_stackinfo() does an unlocked module list walk during normal runtime
which opens up a race with the module load/unload code. This can be
triggered by simply unloading and loading a module in a loop with
CONFIG_DEBUG_PAGEALLOC resulting in store_stackinfo() tripping over bad
list pointers.
kernel_text_address doesn't take any locks, because during an OOPS we don't
want to deadlock. Rename that to __kernel_text_address, and make
kernel_text_address take the lock.
Signed-off-by: Zwane Mwaikambo <zwane@fsmlabs.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch arranges for the exception tables to be sorted on most
architectures. It sorts the main kernel exception table on startup
and the module exception tables when they get loaded. The main table
is sorted reasonably early - just after kmem_cache_init - but that
could be moved even earlier if necessary.
There is now a lib/extable.c which includes the sort_extable()
function from arch/ppc/mm/extable.c and the search_extable() function
from arch/i386/mm/extable.c, which had been copied to many
architectures. On many architectures, arch/$(ARCH)/mm/extable.c
became empty and so I have removed it.
There are four architectures which do things differently from i386:
alpha, ia64, sparc and sparc64. Alpha and ia64 store the offset from
the offset from the exception table entry to the instruction, and
sparc and sparc64 have range entries in the table. For those
architectures I have added empty sort_extable functions. The
maintainers for those architectures can implement something better if
they care to. As it is they are no worse off than before.
Although it is a moderately sizable patch, it ends up with a net
reduction of 377 lines in the size of the kernel source. :)
I have tested this on x86 and ppc with a module that uses __get_user
in an init function, deliberately laid out to get the exception table
out of order, and it works (whereas it oopsed without this patch).
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Richard Henderson point out a while back that linker generated symbols
should be declared as: "char _text[]" so that the compiler can't make
assumptions about them sitting in small sections, etc.
Centralize these defintions in asm/sections.h (where some already
are on x86).
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From: Rusty Russell <rusty@rustcorp.com.au>
Introduce _sinittext and _einittext (cf. _stext and _etext), so kallsyms
includes __init functions.
TODO: Use huffman name compression and 16-bit offsets (see IDE
oopser patch)
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This removes the extable list, and the struct exception_table, in
favour of just iterating through the modules. Now all iteration is
within kernel/module.c, this is a fairly trivial cleanup.
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By making module_text_address return the module it found, we
simplify symbol_put_addr significantly.
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Various archs (i386, m68k, s390, s390x, m68k, parisc, um, x86_64)
implement kernel_text_address. Put this in kernel/extable.c, and the
module iteration inside module.c.
Other than cleanliness, this finally allows the module list and lock
to be static to kernel/module.c (you didn't think I actually cared
about those archs did you?)
It also drops the module->init_size to zero when it's discarded, so
bounds checking is simplified (and the /proc/modules size statistic
will be more accurate, too).
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This patch combines the common exception table searching functionality
for various architectures, to avoid unneccessary (and currently buggy)
duplication, and so that the exception table list and lock can be kept
private to module.c.
The archs provide "struct exception_table" and "search_extable": the
generic infrastructure drives the rest.
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This implements EXPORT_SYMBOL_GPL and MODULE_LICENSE properly (so
restrictions are enforced). Also fixes "proprietory" spelling.
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was enabled, so split it up into "extable.c"
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