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vfs: make <rom> fs robust against invalid ROMs 

An invalid ROM dataspace can occur, for example, when requesting a ROM
from the report_rom service before the first report was posted. Such a
<rom> node can still be useful if it's dynamic. E.g., it can be watched.
Hence, the corner case of an invalid ROM dataspace should be gracefully
handled instead of causing an abort.

Issue #3606
This commit is contained in:
Norman Feske 2020-01-14 23:05:30 +01:00 committed by Christian Helmuth
parent c67a0d3dd8
commit 96cde52838
1 changed files with 7 additions and 4 deletions
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11
repos/os/src/lib/vfs/rom_file_system.h
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@ -60,7 +60,10 @@ class Vfs::Rom_file_system : public Single_file_system
Genode::Allocator &alloc,
Genode::Attached_rom_dataspace &rom,
Rom_type type)
: Single_vfs_handle(ds, fs, alloc, 0), _rom(rom), _content_size(_init_content_size(type)) { }
:
Single_vfs_handle(ds, fs, alloc, 0),
_rom(rom), _content_size(_init_content_size(type))
{ }
Read_result read(char *dst, file_size count,
file_size &out_count) override
@ -74,15 +77,15 @@ class Vfs::Rom_file_system : public Single_file_system
/* maximum read offset, clamped to dataspace size */
file_size const end_offset = min(count + read_offset, max_size);
/* source address within the dataspace */
char const *src = _rom.local_addr<char>() + read_offset;
/* check if end of file is reached */
if (read_offset >= end_offset) {
out_count = 0;
return READ_OK;
}
/* source address within the dataspace */
char const *src = _rom.local_addr<char>() + read_offset;
/* copy-out bytes from ROM dataspace */
file_size const num_bytes = end_offset - read_offset;