Mathias Krause (minipli@googlemail.com) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/18336
-gerrit
commit 12ad262ee22173fc32de216909af9192b29ddf8c Author: Mathias Krause minipli@googlemail.com Date: Sat Feb 11 22:47:04 2017 +0100
libpayload: x86/head - implement argc/argv handling
Implement the argc/argv passing as described in [1].
While at it, give the code some love by not needlessly trashing register values.
[1] http://www.coreboot.org/Payload_API
Change-Id: Ib830f2c67b631b7216843203cefd55d9bb780d83 Signed-off-by: Mathias Krause minipli@googlemail.com --- payloads/libpayload/arch/x86/head.S | 43 +++++++++++++++++++++---------------- 1 file changed, 25 insertions(+), 18 deletions(-)
diff --git a/payloads/libpayload/arch/x86/head.S b/payloads/libpayload/arch/x86/head.S index fa9bb73..37798f3 100644 --- a/payloads/libpayload/arch/x86/head.S +++ b/payloads/libpayload/arch/x86/head.S @@ -28,7 +28,7 @@ */
.code32 - .global _entry, _leave + .global _entry .text .align 4
@@ -55,6 +55,11 @@ mb_header: .long _end .long _init
+#define CB_MAGIC_VALUE 0x12345678 +#define CB_MAGIC 0x04 +#define CB_ARGV 0x08 +#define CB_ARGC 0x10 + /* * This function saves off the previous stack and switches us to our * own execution environment. @@ -63,34 +68,36 @@ _init: /* No interrupts, please. */ cli
- /* There is a bunch of stuff missing here to take arguments on the stack - * See http://www.coreboot.org/Payload_API and exec.S. - */ - /* Store current stack pointer. */ - movl %esp, %esi - /* Store EAX and EBX */ - movl %eax,loader_eax - movl %ebx,loader_ebx + movl %eax, loader_eax + movl %ebx, loader_ebx
- /* Setup new stack. */ - movl $_stack, %ebx + movl CB_MAGIC(%esp), %eax + movl %eax, magic
- movl %ebx, %esp + /* Copy argv[] and argc as demanded by the Payload API, + * see http://www.coreboot.org/Payload_API and exec.S. + */ + cmpl $CB_MAGIC_VALUE, CB_MAGIC(%esp) + jne 1f + + movl CB_ARGV(%esp), %eax + movl %eax, main_argv
- /* Save old stack pointer. */ - pushl %esi + movl CB_ARGC(%esp), %eax + movl %eax, main_argc +1: + /* Store current stack pointer and set up new stack. */ + movl %esp, _stack + movl $(_stack - 4), %esp
/* Let's rock. */ call start_main
/* %eax has the return value - pass it on unmolested */ _leave: - /* Get old stack pointer. */ - popl %ebx - /* Restore old stack. */ - movl %ebx, %esp + movl 4(%esp), %esp
/* Return to the original context. */ ret