coreboot-kgpe-d16/util/cbfstool/linux_trampoline.S

/* linux_trampoline */
/* SPDX-License-Identifier: GPL-2.0-only */

/* NOTE: THIS CODE MUST REMAIN POSITION INDEPENDENT
 *       IT SHOULDN'T USE THE STACK
 *       AND IN GENERAL EXPECT NOTHING BUT RAM TO WORK
 */
.code32
.data

#include "linux_trampoline.h"
#define HEADER_SIG 0x4f49424c // LBIO little endian
#define CB_TAG_FORWARD 0x11
#define CB_TAG_MEMORY 0x1
#define CB_TAG_FRAMEBUFFER 0x12

#define E820_NR_OFFSET 0x1e8
#define LINUX_ENTRY_OFFSET 0x214
#define E820_OFFSET 0x2d0

.trampoline_start:
cld
xor %edx, %edx
mov $0, %ecx

.headerSearch:
mov $0x10000, %ebx
add %ecx, %ebx
mov (%ecx), %eax
cmp $HEADER_SIG, %eax
je .headerSearchDone // found the header
add $16, %ecx
cmp %ecx, %ebx
jne .headerSearch

.headerSearchDone:
cmp %ecx, %ebx // reached the end == not found anything?
je 2f // give up

// we assume the checksum is okay, no test
mov 4(%ecx), %ebx
add %ecx, %ebx // ebx = cb_header + header_bytes
mov 20(%ecx), %ecx // ecx = table_entries

.tableScan:
cmp $CB_TAG_FORWARD, (%ebx)
jne .testMemory

/* forward tag: assume 32bit pointer */
mov 8(%ebx), %ecx
jmp .headerSearch

.testMemory:
cmp $CB_TAG_MEMORY, (%ebx)
jne .testFramebuffer

/* memory tag: copy e820 map and entry count. also determine alt_mem_k */
mov 4(%ebx), %eax
sub $8, %eax
shr $2, %eax /* eax = number of dwords of e820 data */
cmp $(32 * 5), %eax /* linux wants at most 32 entries of 5 dwords */
jng 1f
mov $(32 * 5), %eax /* only copy 32 entries */
1:
mov %eax, %esi
mov $5, %edi
div %edi
mov %eax, (LINUX_PARAM_LOC + E820_NR_OFFSET)
mov %esi, %eax
xchg %eax, %ecx
lea 8(%ebx), %esi /* e820 data source */
mov $(LINUX_PARAM_LOC + E820_OFFSET), %edi
rep movsl
xchg %eax, %ecx
jmp .endScan

.testFramebuffer:
cmp $CB_TAG_FRAMEBUFFER, (%ebx)
jne .endScan
/* TODO: handle framebuffer tag */

.endScan:
add 4(%ebx), %ebx
dec %ecx
jnz .tableScan

/* Setup basic code and data segment selectors for Linux
**
** Flat code segment descriptor:
**   selector: 0x10
**   base    : 0x00000000
**   limit   : 0xFFFFFFFF
**   type    : code, execute, read
**
** Flat data segment descriptor:
**   selector: 0x18
**   base    : 0x00000000
**   limit   : 0xFFFFFFFF
**   type    : data, read/write
**
** Use TRAMPOLINE_ENTRY_LOC as a scratchpad.
*/
mov  $TRAMPOLINE_ENTRY_LOC, %eax
movl  $0x0000ffff, 16(%eax)		// Set up the 2 new descriptors
movl  $0x00cf9b00, 20(%eax)
movl  $0x0000ffff, 24(%eax)
movl  $0x00cf9300, 28(%eax)
movb $0x2b, 0(%eax)			// Set the size
movl %eax, 2(%eax)			// Set pointer to new GDT
lgdt (%eax)				// Load it

/* finally: jump to kernel */
mov $LINUX_PARAM_LOC, %esi
jmp *(LINUX_PARAM_LOC + LINUX_ENTRY_OFFSET)


2:
hlt
jmp 2b
.trampoline_end:
AUTHORS, util/: Drop individual copyright notices We have the git history which is a more reliable librarian. Change-Id: Idbcc5ceeb33804204e56d62491cb58146f7c9f37 Signed-off-by: Patrick Georgi <pgeorgi@google.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/41175 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: ron minnich <rminnich@gmail.com> 2020-05-08 19:28:13 +02:00			`/* linux_trampoline */`
util/: Replace GPLv2 boiler plate with SPDX header Used commands: perl -i -p0e 's\|\/\[\s].is free software[:;][\s]you[\s]can[\s]redistribute[\s]it[\s]and\/or[\s]modify[\s]it[\s]under[\s]the[\s]terms[\s]of[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]as[\s]published[\s]by[\s]the[\s]Free[\s]Software[\s]Foundation[;,][\s]version[\s]2[\s]of[\s]the[\s]License.[\s]This[\s]program[\s]is[\s]distributed[\s]in[\s]the[\s]hope[\s]that[\s]it[\s]will[\s]be[\s]useful,[\s]but[\s]WITHOUT[\s]ANY[\s]WARRANTY;[\s]without[\s]even[\s]the[\s]implied[\s]warranty[\s]of[\s]MERCHANTABILITY[\s]or[\s]FITNESS[\s]FOR[\s]A[\s]PARTICULAR[\s]PURPOSE.[\s]See[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]for[\s]more[\s]details.[\s]\\/\|/ SPDX-License-Identifier: GPL-2.0-only /\|' $(cat filelist) perl -i -p0e 's\|This[\s]program[\s]is[\s]free[\s]software[:;][\s]you[\s]can[\s]redistribute[\s]it[\s]and/or[\s]modify[\s]it[\s]under[\s]the[\s]terms[\s]of[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]as[\s]published[\s]by[\s]the[\s]Free[\s]Software[\s]Foundation[;,][\s]either[\s]version[\s]2[\s]of[\s]the[\s]License,[\s]or[\s].at[\s]your[\s]option.[\s]any[\s]later[\s]version.[\s]This[\s]program[\s]is[\s]distributed[\s]in[\s]the[\s]hope[\s]that[\s]it[\s]will[\s]be[\s]useful,[\s]but[\s]WITHOUT[\s]ANY[\s]WARRANTY;[\s]without[\s]even[\s]the[\s]implied[\s]warranty[\s]of[\s]MERCHANTABILITY[\s]or[\s]FITNESS[\s]FOR[\s]A[\s]PARTICULAR[\s]PURPOSE.[\s]See[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]for[\s]more[\s]details.[\s]\\/\|/ SPDX-License-Identifier: GPL-2.0-or-later /\|' $(cat filelist) perl -i -p0e 's\|\/\[\s].This[\s#]program[\s#]is[\s#]free[\s#]software[;:,][\s#]you[\s#]can[\s#]redistribute[\s#]it[\s#]and/or[\s#]modify[\s#]it[\s#]under[\s#]the[\s#]terms[\s#]of[\s#]the[\s#]GNU[\s#]General[\s#]Public[\s#]License[\s#]as[\s#]published[\s#]by[\s#]the[\s#]Free[\s#]Software[\s#]Foundation[;:,][\s#]either[\s#]version[\s#]3[\s#]of[\s#]the[\s#]License[;:,][\s#]or[\s#].at[\s#]your[\s#]option.[\s#]any[\s#]later[\s#]version.[\s#]This[\s#]program[\s#]is[\s#]distributed[\s#]in[\s#]the[\s#]hope[\s#]that[\s#]it[\s#]will[\s#]be[\s#]useful[;:,][\s#]but[\s#]WITHOUT[\s#]ANY[\s#]WARRANTY[;:,][\s#]without[\s#]even[\s#]the[\s#]implied[\s#]warranty[\s#]of[\s#]MERCHANTABILITY[\s#]or[\s#]FITNESS[\s#]FOR[\s#]A[\s#]PARTICULAR[\s#]PURPOSE.[\s#]See[\s#]the[\s#]GNU[\s#]General[\s#]Public[\s#]License[\s#]for[\s#]more[\s#]details.[\s]\\/\|/ SPDX-License-Identifier: GPL-3.0-or-later /\|' $(cat filelist) perl -i -p0e 's\|(\#\#)[\w].is free software[:;][\#\s]you[\#\s]can[\#\s]redistribute[\#\s]it[\#\s]and\/or[\#\s]modify[\#\s]it[\s\#]under[\s \#]the[\s\#]terms[\s\#]of[\s\#]the[\s\#]GNU[\s\#]General[\s\#]Public[\s\#]License[\s\#]as[\s\#]published[\s\#]by[\s\#]the[\s\#]Free[\s\#]Software[\s\#]Foundation[;,][\s\#]version[\s\#]2[\s\#]of[\s\#]the[\s\#]License.[\s\#]This[\s\#]program[\s\#]is[\s\#]distributed[\s\#]in[\s\#]the[\s\#]hope[\s\#]that[\s\#]it[\s\#]will[\#\s]be[\#\s]useful,[\#\s]but[\#\s]WITHOUT[\#\s]ANY[\#\s]WARRANTY;[\#\s]without[\#\s]even[\#\s]the[\#\s]implied[\#\s]warranty[\#\s]of[\#\s]MERCHANTABILITY[\#\s]or[\#\s]FITNESS[\#\s]FOR[\#\s]A[\#\s]PARTICULAR[\#\s]PURPOSE.[\#\s]See[\#\s]the[\#\s]GNU[\#\s]General[\#\s]Public[\#\s]License[\#\s]for[\#\s]more[\#\s]details.\s(# \n)\|\1 SPDX-License-Identifier: GPL-2.0-only\n\n\|' $(cat filelist) perl -i -p0e 's\|(\#\#)[\w].is free software[:;][\s]you[\s]can[\s]redistribute[\s]it[\s]and\/or[\s]modify[\s]it[\s]under[\s]the[\s]terms[\s]of[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]as[\s]published[\s]by[\s]the[\s]Free[\s]Software[\s]Foundation[;,][\s]version[\s]2[\s]of[\s]the[\s]License.[\s]This[\s]program[\s]is[\s]distributed[\s]in[\s]the[\s]hope[\s]that[\s]it[\s]will[\s]be[\s]useful,[\s]but[\s]WITHOUT[\s]ANY[\s]WARRANTY;[\s]without[\s]even[\s]the[\s]implied[\s]warranty[\s]of[\s]MERCHANTABILITY[\s]or[\s]FITNESS[\s]FOR[\s]A[\s]PARTICULAR[\s]PURPOSE.[\s]See[\s]the[\s]GNU[\s]General[\s]Public[\s]License[\s]for[\s]more[\s]details.\s(#* \n)\|\1 SPDX-License-Identifier: GPL-2.0-only\n\n\|' $(cat filelist) Change-Id: I1008a63b804f355a916221ac994701d7584f60ff Signed-off-by: Patrick Georgi <pgeorgi@google.com> Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr> Reviewed-on: https://review.coreboot.org/c/coreboot/+/41177 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> 2020-05-08 20:48:04 +02:00			`/* SPDX-License-Identifier: GPL-2.0-only */`
cbfstool: autocreate trampoline Add the code necessary to create the linux trampoline blob. Don't enforce this for the in-coreboot build or use objcopy to produce linux_trampoline.o as it is a bit trickier to get all the details right than I had hoped: - you have to know the elf architecture of the host machine - you might have to have more tools (xxd, perl, etc) installed Change-Id: I9b7877c58d90f9fb21d16e0061a31e19fffa2470 Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org> Reviewed-on: https://review.coreboot.org/12505 Tested-by: build bot (Jenkins) Reviewed-by: Martin Roth <martinroth@google.com> 2015-11-20 17:58:59 +01:00
			`/* NOTE: THIS CODE MUST REMAIN POSITION INDEPENDENT`
			`* IT SHOULDN'T USE THE STACK`
			`* AND IN GENERAL EXPECT NOTHING BUT RAM TO WORK`
			`*/`
			`.code32`
			`.data`

			`#include "linux_trampoline.h"`
			`#define HEADER_SIG 0x4f49424c // LBIO little endian`
			`#define CB_TAG_FORWARD 0x11`
			`#define CB_TAG_MEMORY 0x1`
			`#define CB_TAG_FRAMEBUFFER 0x12`

			`#define E820_NR_OFFSET 0x1e8`
			`#define LINUX_ENTRY_OFFSET 0x214`
			`#define E820_OFFSET 0x2d0`

			`.trampoline_start:`
			`cld`
			`xor %edx, %edx`
			`mov $0, %ecx`

			`.headerSearch:`
			`mov $0x10000, %ebx`
			`add %ecx, %ebx`
			`mov (%ecx), %eax`
			`cmp $HEADER_SIG, %eax`
			`je .headerSearchDone // found the header`
			`add $16, %ecx`
			`cmp %ecx, %ebx`
			`jne .headerSearch`

			`.headerSearchDone:`
			`cmp %ecx, %ebx // reached the end == not found anything?`
			`je 2f // give up`

			`// we assume the checksum is okay, no test`
			`mov 4(%ecx), %ebx`
			`add %ecx, %ebx // ebx = cb_header + header_bytes`
			`mov 20(%ecx), %ecx // ecx = table_entries`

			`.tableScan:`
			`cmp $CB_TAG_FORWARD, (%ebx)`
			`jne .testMemory`

			`/* forward tag: assume 32bit pointer */`
			`mov 8(%ebx), %ecx`
			`jmp .headerSearch`

			`.testMemory:`
			`cmp $CB_TAG_MEMORY, (%ebx)`
			`jne .testFramebuffer`

			`/* memory tag: copy e820 map and entry count. also determine alt_mem_k */`
			`mov 4(%ebx), %eax`
			`sub $8, %eax`
			`shr $2, %eax /* eax = number of dwords of e820 data */`
			`cmp $(32 * 5), %eax /* linux wants at most 32 entries of 5 dwords */`
			`jng 1f`
			`mov $(32 * 5), %eax /* only copy 32 entries */`
			`1:`
			`mov %eax, %esi`
			`mov $5, %edi`
			`div %edi`
			`mov %eax, (LINUX_PARAM_LOC + E820_NR_OFFSET)`
			`mov %esi, %eax`
			`xchg %eax, %ecx`
			`lea 8(%ebx), %esi /* e820 data source */`
			`mov $(LINUX_PARAM_LOC + E820_OFFSET), %edi`
			`rep movsl`
			`xchg %eax, %ecx`
			`jmp .endScan`

			`.testFramebuffer:`
			`cmp $CB_TAG_FRAMEBUFFER, (%ebx)`
			`jne .endScan`
			`/* TODO: handle framebuffer tag */`

			`.endScan:`
			`add 4(%ebx), %ebx`
			`dec %ecx`
			`jnz .tableScan`

			`/* Setup basic code and data segment selectors for Linux`
			`**`
			`** Flat code segment descriptor:`
			`** selector: 0x10`
			`** base : 0x00000000`
			`** limit : 0xFFFFFFFF`
			`** type : code, execute, read`
			`**`
			`** Flat data segment descriptor:`
			`** selector: 0x18`
			`** base : 0x00000000`
			`** limit : 0xFFFFFFFF`
			`** type : data, read/write`
			`**`
			`** Use TRAMPOLINE_ENTRY_LOC as a scratchpad.`
			`*/`
			`mov $TRAMPOLINE_ENTRY_LOC, %eax`
linux_trampoline: use trampoline RAM for the GDT The linux trampoline was modifying the existing GDT to add the 0x10 and 0x18 descriptors for Linux. This will not work when the existing GDT is in ROM. Change the code to set up a new GDT in what we know to be RAM. Tested by booting a linux payload. The main reason this works is that Linux almost immediately loads its own GDT and then segment registers. This GDT is a very temporary bridge. Note that none of this change used to be necessary; the coreboot GDT was originally compatible with Linux (ca 2000); then Linux changed. Change-Id: I13990052fbfd6a500adab8a2db8f7aead1d24fa6 Signed-off-by: Ronald G. Minnich <rminnich@gmail.com> Reviewed-on: https://review.coreboot.org/27529 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com> 2018-07-18 16:19:30 +02:00			`movl $0x0000ffff, 16(%eax) // Set up the 2 new descriptors`
			`movl $0x00cf9b00, 20(%eax)`
			`movl $0x0000ffff, 24(%eax)`
			`movl $0x00cf9300, 28(%eax)`
			`movb $0x2b, 0(%eax) // Set the size`
			`movl %eax, 2(%eax) // Set pointer to new GDT`
			`lgdt (%eax) // Load it`
cbfstool: autocreate trampoline Add the code necessary to create the linux trampoline blob. Don't enforce this for the in-coreboot build or use objcopy to produce linux_trampoline.o as it is a bit trickier to get all the details right than I had hoped: - you have to know the elf architecture of the host machine - you might have to have more tools (xxd, perl, etc) installed Change-Id: I9b7877c58d90f9fb21d16e0061a31e19fffa2470 Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org> Reviewed-on: https://review.coreboot.org/12505 Tested-by: build bot (Jenkins) Reviewed-by: Martin Roth <martinroth@google.com> 2015-11-20 17:58:59 +01:00
			`/* finally: jump to kernel */`
			`mov $LINUX_PARAM_LOC, %esi`
			`jmp *(LINUX_PARAM_LOC + LINUX_ENTRY_OFFSET)`


			`2:`
			`hlt`
			`jmp 2b`
			`.trampoline_end:`