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| author | Michael Brown <mcb30@etherboot.org> | 2008-09-23 01:13:28 +0100 |
|---|---|---|
| committer | Michael Brown <mcb30@etherboot.org> | 2008-09-23 01:13:28 +0100 |
| commit | ca0b0f061673b27bb7bfa6f62e99385273c097da (patch) | |
| tree | cf2c06b66558f8f85fbf69e37af1885f189c7d7e | |
| parent | 0fd1e54026d9c941fce041157bb00cb42fdef9dd (diff) | |
| download | ipxe-ca0b0f061673b27bb7bfa6f62e99385273c097da.tar.gz | |
[relocate] Guard against systems that report empty memory regions
If the INT 15,e820 memory map reports a region [0,0), this confuses
the "truncate to even megabytes" logic, which ends up rounding the
region 'down' to [0,fff00000).
Fix by ensuring that the region's end address is at least 1, before we
subtract 1 to obtain the "last byte in region" address.
| -rw-r--r-- | src/arch/i386/core/relocate.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/src/arch/i386/core/relocate.c b/src/arch/i386/core/relocate.c index 39d00b09..aa58ad65 100644 --- a/src/arch/i386/core/relocate.c +++ b/src/arch/i386/core/relocate.c @@ -93,11 +93,16 @@ __cdecl void relocate ( struct i386_all_regs *ix86 ) { /* If last byte that might be used (r_end-1) * is in an odd megabyte, round down r_end to * the top of the next even megabyte. + * + * Make sure that we don't accidentally wrap + * r_end below 0. */ - r_end = ( r_end - 1 ) & ~0xfffff; - DBG ( "...end truncated to %lx " - "(avoid ending in odd megabyte)\n", - r_end ); + if ( r_end >= 1 ) { + r_end = ( r_end - 1 ) & ~0xfffff; + DBG ( "...end truncated to %lx " + "(avoid ending in odd megabyte)\n", + r_end ); + } } else if ( ( r_end - size ) & 0x100000 ) { /* If the last byte that might be used * (r_end-1) is in an even megabyte, but the @@ -108,7 +113,7 @@ __cdecl void relocate ( struct i386_all_regs *ix86 ) { * Make sure that we don't accidentally wrap * r_end below 0. */ - if ( r_end > 0x100000 ) { + if ( r_end >= 0x100000 ) { r_end = ( r_end - 0x100000 ) & ~0xfffff; DBG ( "...end truncated to %lx " "(avoid starting in odd megabyte)\n", |