| Message ID | E1axXS0-0004gz-5a@e0050434b2927.dyn.arm.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, May 3, 2016 at 3:51 PM, Russell King <rmk@arm.linux.org.uk> wrote: > The man page for mmap() and munmap() says that mmap() and munmap() > only works for page-aligned addresses, sizes and offsets. Arrange > to give these interfaces what they want. > If I read correctly, it talks only offsets to be page aligned. > Signed-off-by: Russell King <rmk@arm.linux.org.uk> Anyway, changes looks good to me. Reviewed-by: Pratyush Anand <panand@redhat.com> > --- > kdump/kdump.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/kdump/kdump.c b/kdump/kdump.c > index 821ee7c..3247a54 100644 > --- a/kdump/kdump.c > +++ b/kdump/kdump.c > @@ -25,22 +25,35 @@ > #define MAP_WINDOW_SIZE (64*1024*1024) > #define DEV_MEM "/dev/mem" > > +#define ALIGN_MASK(x,y) (((x) + (y)) & ~(y)) > +#define ALIGN(x,y) ALIGN_MASK(x, (y) - 1) > + > static void *map_addr(int fd, unsigned long size, off_t offset) > { > + unsigned long page_size = getpagesize(); > + unsigned long map_offset = offset & (page_size - 1); > + size_t len = ALIGN(size + map_offset, page_size); > void *result; > - result = mmap(0, size, PROT_READ, MAP_SHARED, fd, offset); > + > + result = mmap(0, len, PROT_READ, MAP_SHARED, fd, offset - map_offset); > if (result == MAP_FAILED) { > fprintf(stderr, "Cannot mmap " DEV_MEM " offset: %llu size: %lu: %s\n", > (unsigned long long)offset, size, strerror(errno)); > exit(5); > } > - return result; > + return result + map_offset; > } > > static void unmap_addr(void *addr, unsigned long size) > { > + unsigned long page_size = getpagesize(); > + unsigned long map_offset = (uintptr_t)addr & (page_size - 1); > + size_t len = ALIGN(size + map_offset, page_size); > int ret; > - ret = munmap(addr, size); > + > + addr -= map_offset; > + > + ret = munmap(addr, len); > if (ret < 0) { > fprintf(stderr, "munmap failed: %s\n", > strerror(errno)); > -- > 1.9.1 >
On Wed, May 25, 2016 at 11:46:08AM +0530, Pratyush Anand wrote: > On Tue, May 3, 2016 at 3:51 PM, Russell King <rmk@arm.linux.org.uk> wrote: > > The man page for mmap() and munmap() says that mmap() and munmap() > > only works for page-aligned addresses, sizes and offsets. Arrange > > to give these interfaces what they want. > > > > If I read correctly, it talks only offsets to be page aligned. Yes, it's not really needed, but as we have to adjust the size anyway to compensate for the reduced file offset, it makes little difference whether we align the size or not.
diff --git a/kdump/kdump.c b/kdump/kdump.c index 821ee7c..3247a54 100644 --- a/kdump/kdump.c +++ b/kdump/kdump.c @@ -25,22 +25,35 @@ #define MAP_WINDOW_SIZE (64*1024*1024) #define DEV_MEM "/dev/mem" +#define ALIGN_MASK(x,y) (((x) + (y)) & ~(y)) +#define ALIGN(x,y) ALIGN_MASK(x, (y) - 1) + static void *map_addr(int fd, unsigned long size, off_t offset) { + unsigned long page_size = getpagesize(); + unsigned long map_offset = offset & (page_size - 1); + size_t len = ALIGN(size + map_offset, page_size); void *result; - result = mmap(0, size, PROT_READ, MAP_SHARED, fd, offset); + + result = mmap(0, len, PROT_READ, MAP_SHARED, fd, offset - map_offset); if (result == MAP_FAILED) { fprintf(stderr, "Cannot mmap " DEV_MEM " offset: %llu size: %lu: %s\n", (unsigned long long)offset, size, strerror(errno)); exit(5); } - return result; + return result + map_offset; } static void unmap_addr(void *addr, unsigned long size) { + unsigned long page_size = getpagesize(); + unsigned long map_offset = (uintptr_t)addr & (page_size - 1); + size_t len = ALIGN(size + map_offset, page_size); int ret; - ret = munmap(addr, size); + + addr -= map_offset; + + ret = munmap(addr, len); if (ret < 0) { fprintf(stderr, "munmap failed: %s\n", strerror(errno));
The man page for mmap() and munmap() says that mmap() and munmap() only works for page-aligned addresses, sizes and offsets. Arrange to give these interfaces what they want. Signed-off-by: Russell King <rmk@arm.linux.org.uk> --- kdump/kdump.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)