Fix how the location of the realmode and bios blobs are calculated
PATCH 1/1 Fix how the location of the realmode and bios blobs are calculated
There are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are realmode_setup and bios_setup functions which prepare those blobs by copying them into the location they're supposed to run from, among other things.
During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called __bios_start and __bios_size which are defined to be the start and size of the blob in the ROM.
In the bios_setup function, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to __bios_start which implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the __bios_start reference in bios_setup so that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.
The net effect is that for both blobs, a + needs to be changed to a -.
--- arch/x86/lib/bios_setup.c | 6 +++++- arch/x86/lib/realmode.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-)
arch/x86/lib/bios_setup.c +5 -1
@@ -140,7 +140,11 @@ static void setvector(int vector, u16 segment, void *handler)int bios_setup (void ) { -ulong bios_start = (ulong )&__bios_start + gd->reloc_off; +/* +* The BIOS section is not relocated and still in the ROM. The +* __bios_start symbol was adjusted, though, so adjust it back. +*/ +ulong bios_start = (ulong )&__bios_start - gd->reloc_off;ulong bios_size = (ulong)&__bios_size;static int done=0 ;
arch/x86/lib/realmode.c +5 -1
@@ -34,7 +34,11 @@ extern char realmode_enter;int realmode_setup (void ) { -ulong realmode_start = (ulong )&__realmode_start + gd->reloc_off; +/* +* The realmode section is not relocated and still in the ROM. The +* __realmode_start symbol was adjusted, though, so adjust it back. +*/ +ulong realmode_start = (ulong )&__realmode_start - gd->reloc_off;ulong realmode_size = (ulong)&__realmode_size;/* copy the realmode switch code */
Signature · 1 line
1.7.3.1
PATCH 1/1 Fix how the location of the realmode and bios blobs are calculated
Gabe,
Can you please change your prefix from '[x86]' to 'x86:'
Thanks,
Graeme
PATCH v2 1/1 x86: Fix how the location of the realmode and bios blobs are calculated
In reply to Gabe BlackThere are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are realmode_setup and bios_setup functions which prepare those blobs by copying them into the location they're supposed to run from, among other things.
During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called __bios_start and __bios_size which are defined to be the start and size of the blob in the ROM.
In the bios_setup function, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to __bios_start which implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the __bios_start reference in bios_setup so that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.
The net effect is that for both blobs, a + needs to be changed to a -.
---
Changes in v2:
Update x86 tag.
arch/x86/lib/bios_setup.c | 6 +++++- arch/x86/lib/realmode.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-)
arch/x86/lib/bios_setup.c +5 -1
@@ -140,7 +140,11 @@ static void setvector(int vector, u16 segment, void *handler)int bios_setup (void ) { -ulong bios_start = (ulong )&__bios_start + gd->reloc_off; +/* +* The BIOS section is not relocated and still in the ROM. The +* __bios_start symbol was adjusted, though, so adjust it back. +*/ +ulong bios_start = (ulong )&__bios_start - gd->reloc_off;ulong bios_size = (ulong)&__bios_size;static int done=0 ;
arch/x86/lib/realmode.c +5 -1
@@ -34,7 +34,11 @@ extern char realmode_enter;int realmode_setup (void ) { -ulong realmode_start = (ulong )&__realmode_start + gd->reloc_off; +/* +* The realmode section is not relocated and still in the ROM. The +* __realmode_start symbol was adjusted, though, so adjust it back. +*/ +ulong realmode_start = (ulong )&__realmode_start - gd->reloc_off;ulong realmode_size = (ulong)&__realmode_size;/* copy the realmode switch code */
Signature · 1 line
1.7.3.1
PATCH v2 1/1 x86: Fix how the location of the realmode and bios blobs are calculated
Quoted 23 lines · Gabe Black
There are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are
realmode_setupandbios_setupfunctions which prepare those blobs by copying them into the location they're supposed to run from, among other things.During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called
__bios_startand__bios_sizewhich are defined to be the start and size of the blob in the ROM.In the
bios_setupfunction, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to__bios_startwhich implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the__bios_startreference inbios_setupso that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.
Quoted 3 lines
The net effect is that for both blobs, a + needs to be changed to a -.
Signed-off-by Gabe Black <[email protected]>
Fixes breakage introduced by commit 5fed8211... 'x86: Fix incorrect usage of relocation offset'
PATCH v2 1/1 x86: Fix how the location of the realmode and bios blobs are calculated
In reply to Gabe BlackHi Gabe,
Quoted 25 lines · Gabe Black
There are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are
realmode_setupandbios_setupfunctions which prepare those blobs by copying them into the location they're supposed to run from, among other things.During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called
__bios_startand__bios_sizewhich are defined to be the start and size of the blob in the ROM.In the
bios_setupfunction, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to__bios_startwhich implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the__bios_startreference inbios_setupso that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.The net effect is that for both blobs, a + needs to be changed to a -.
Quoted 8 lines
Signed-off-by Gabe Black <[email protected]>---
Changes in v2:
Update x86 tag.arch/x86/lib/bios_setup.c | 6 +++++- arch/x86/lib/realmode.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-)
Can you please rebase against u-boot-x86/master and re-submit
Thanks,
Graeme
PATCH v3 1/1 x86: Fix how the location of the realmode and bios blobs are calculated
From: Gabe Black <[email protected]>
There are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are realmode_setup and bios_setup functions which prepare those blobs by copying them into the location they're supposed to run from, among other things.
During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called __bios_start and __bios_size which are defined to be the start and size of the blob in the ROM.
In the bios_setup function, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to __bios_start which implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the __bios_start reference in bios_setup so that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.
The net effect is that for both blobs, a + needs to be changed to a -.
---
Changes in v2:
Update x86 tag.
Changes in v3:
Rebase onto the x86 repository.
arch/x86/lib/bios_setup.c | 6 +++++- arch/x86/lib/realmode.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-)
arch/x86/lib/bios_setup.c +5 -1
@@ -78,7 +78,11 @@ static void setvector(int vector, u16 segment, void *handler)int bios_setup (void ) { -ulong bios_start = (ulong )&__bios_start + gd->reloc_off; +/* +* The BIOS section is not relocated and still in the ROM. The +* __bios_start symbol was adjusted, though, so adjust it back. +*/ +ulong bios_start = (ulong )&__bios_start - gd->reloc_off;ulong bios_size = (ulong)&__bios_size;static int done;
arch/x86/lib/realmode.c +5 -1
@@ -30,7 +30,11 @@int realmode_setup (void ) { -ulong realmode_start = (ulong )&__realmode_start + gd->reloc_off; +/* +* The realmode section is not relocated and still in the ROM. The +* __realmode_start symbol was adjusted, though, so adjust it back. +*/ +ulong realmode_start = (ulong )&__realmode_start - gd->reloc_off;ulong realmode_size = (ulong)&__realmode_size;/* copy the realmode switch code */
Signature · 1 line
1.7.3.1
PATCH v3 1/1 x86: Fix how the location of the realmode and bios blobs are calculated
Quoted 25 lines · Gabe Black
From: Gabe Black <[email protected]>
There are two blobs embedded into the u-boot image which are linked to run at an address which is different from where they actually end up in the ROM, one called "realmode" and one called "bios". There are
realmode_setupandbios_setupfunctions which prepare those blobs by copying them into the location they're supposed to run from, among other things.During u-boot relocation from ROM to RAM, the text and a few data segments are copied over. The realmode and bios sections are not copied, and so the only place they can be read from is their original location in the ROM. Looking specifically at the bios blob, there are symbols defined in the linker script called
__bios_startand__bios_sizewhich are defined to be the start and size of the blob in the ROM.In the
bios_setupfunction, there seem to be two mistakes happening. First, the offset from ROM to RAM is being added to__bios_startwhich implies that this code expects to use the copy moved to RAM. No such copy is made, so that's wrong. More subtly, when u-boot relocates itself, it goes through all of the relocations stored in .rel.dyn and fixes them up. This has the effect of transforming the__bios_startreference inbios_setupso that it refers to the version in RAM (if one existed) instead of the one in ROM. To correct for that, the offset actually needs to be subtracted out again to translate the address back into the ROM.
Quoted 4 lines
The net effect is that for both blobs, a + needs to be changed to a -.
Signed-off-by Gabe Black <[email protected]>---
Applied to u-boot-x86/master
Thanks,
Graeme