From 1228c4596a0046b3e4e71f62773caa835dfc79df Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 18 Mar 2021 17:48:22 +0000 Subject: hw/core/loader: Add new function rom_ptr_for_as() For accesses to rom blob data before or during reset, we have a function rom_ptr() which looks for a rom blob that would be loaded to the specified address, and returns a pointer into the rom blob data corresponding to that address. This allows board or CPU code to say "what is the data that is going to be loaded to this address?". However, this function does not take account of memory region aliases. If for instance a machine model has RAM at address 0x0000_0000 which is aliased to also appear at 0x1000_0000, a rom_ptr() query for address 0x0000_0000 will only return a match if the guest image provided by the user was loaded at 0x0000_0000 and not if it was loaded at 0x1000_0000, even though they are the same RAM and a run-time guest CPU read of 0x0000_0000 will read the data loaded to 0x1000_0000. Provide a new function rom_ptr_for_as() which takes an AddressSpace argument, so that it can check whether the MemoryRegion corresponding to the address is also mapped anywhere else in the AddressSpace and look for rom blobs that loaded to that alias. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20210318174823.18066-5-peter.maydell@linaro.org --- include/hw/loader.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'include/hw/loader.h') diff --git a/include/hw/loader.h b/include/hw/loader.h index a9eeea3..cbfc184 100644 --- a/include/hw/loader.h +++ b/include/hw/loader.h @@ -290,6 +290,37 @@ void rom_transaction_end(bool commit); int rom_copy(uint8_t *dest, hwaddr addr, size_t size); void *rom_ptr(hwaddr addr, size_t size); +/** + * rom_ptr_for_as: Return a pointer to ROM blob data for the address + * @as: AddressSpace to look for the ROM blob in + * @addr: Address within @as + * @size: size of data required in bytes + * + * Returns: pointer into the data which backs the matching ROM blob, + * or NULL if no blob covers the address range. + * + * This function looks for a ROM blob which covers the specified range + * of bytes of length @size starting at @addr within the address space + * @as. This is useful for code which runs as part of board + * initialization or CPU reset which wants to read data that is part + * of a user-supplied guest image or other guest memory contents, but + * which runs before the ROM loader's reset function has copied the + * blobs into guest memory. + * + * rom_ptr_for_as() will look not just for blobs loaded directly to + * the specified address, but also for blobs which were loaded to an + * alias of the region at a different location in the AddressSpace. + * In other words, if a machine model has RAM at address 0x0000_0000 + * which is aliased to also appear at 0x1000_0000, rom_ptr_for_as() + * will return the correct data whether the guest image was linked and + * loaded at 0x0000_0000 or 0x1000_0000. Contrast rom_ptr(), which + * will only return data if the image load address is an exact match + * with the queried address. + * + * New code should prefer to use rom_ptr_for_as() instead of + * rom_ptr(). + */ +void *rom_ptr_for_as(AddressSpace *as, hwaddr addr, size_t size); void hmp_info_roms(Monitor *mon, const QDict *qdict); #define rom_add_file_fixed(_f, _a, _i) \ -- cgit v1.1