mirror of
https://github.com/Motorhead1991/qemu.git
synced 2025-12-26 01:18:36 -07:00
43c64a093d
The function's stated contract is simple enough: "round down to the nearest power of 2". Suggests the domain is the representable numbers >= 1, because that's the smallest power of two. The implementation doesn't check for domain errors, but returns garbage instead: * For negative arguments, pow2floor() returns -2^63, which is not even a power of two, let alone the nearest one. What sort of works is passing *unsigned* arguments >= 2^63. The implicit conversion to signed is implementation defined, but commonly yields the (negative) two's complement. pow2floor() then returns -2^63. Callers that convert that back to unsigned get the correct value 2^63. * For a zero argument, pow2floor() shifts right by 64. Undefined behavior. Common actual behavior is to shift by 0, yielding -2^63. Fix by switching from int64_t to uint64_t and amending the contract to map zero to zero. Callers are fine with that: * memory_access_size() This function makes no sense unless the argument is positive and the return value fits into int. * raw_refresh_limits() Passes an int between 1 and BDRV_REQUEST_MAX_BYTES. * iscsi_refresh_limits() Passes an integer between 0 and INT_MAX, converts the result to uint32_t. Passing zero would be undefined behavior, but commonly yield zero. The patch gives us the zero without the undefined behavior. * cache_init() Passes a positive int64_t argument. * xbzrle_cache_resize() Passes a positive int64_t argument (>= TARGET_PAGE_SIZE, actually). * spapr_node0_size() Passes a positive uint64_t argument, and converts the result to hwaddr, i.e. uint64_t. * spapr_populate_memory() Passes a positive hwaddr argument, and converts the result to hwaddr. Cc: Juan Quintela <quintela@redhat.com> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com> Cc: Eric Blake <eblake@redhat.com> Cc: Peter Maydell <peter.maydell@linaro.org> Cc: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <1501148776-16890-3-git-send-email-armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> |
||
|---|---|---|
| .. | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| standard-headers | ||
| sysemu | ||
| ui | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-common.h | ||
| qemu-io.h | ||
| trace-tcg.h | ||