[U-Boot] [PATCH 02/11] x86: bios: Synchronize stack between real and protected mode
From: Jian Luo jian.luo4@boschrexroth.de
PCI option rom may use different SS during its execution, so it is not safe to assume esp pointed to the same location in the protected mode.
Signed-off-by: Jian Luo jian.luo4@boschrexroth.de Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com ---
arch/x86/lib/bios_asm.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/x86/lib/bios_asm.S b/arch/x86/lib/bios_asm.S index 4faa70e..a29fe0e 100644 --- a/arch/x86/lib/bios_asm.S +++ b/arch/x86/lib/bios_asm.S @@ -246,6 +246,8 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) push %fs push %gs
+ movw %ss, %cs:__realmode_ss + /* Clear DF to not break ABI assumptions */ cld
@@ -258,12 +260,22 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
enter_protected_mode
+ movzwl %cs:__realmode_ss, %ecx + shll $4, %ecx + addl %ecx, %esp + /* Call the C interrupt handler */ movl $interrupt_handler, %eax call *%eax
+ movzwl %cs:__realmode_ss, %ecx + shll $4, %ecx + subl %ecx, %esp + enter_real_mode
+ movw %cs:__realmode_ss, %ss + /* * Restore all registers, including those manipulated by the C * handler @@ -276,6 +288,9 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) popal iret
+__realmode_ss = PTR_TO_REAL_MODE(.) + .word 0 + .globl asm_realmode_code_size asm_realmode_code_size: .long . - asm_realmode_code
Hi,
On 1 July 2015 at 02:27, Bin Meng bmeng.cn@gmail.com wrote:
From: Jian Luo jian.luo4@boschrexroth.de
PCI option rom may use different SS during its execution, so it is not safe to assume esp pointed to the same location in the protected mode.
Signed-off-by: Jian Luo jian.luo4@boschrexroth.de Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com
arch/x86/lib/bios_asm.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/x86/lib/bios_asm.S b/arch/x86/lib/bios_asm.S index 4faa70e..a29fe0e 100644 --- a/arch/x86/lib/bios_asm.S +++ b/arch/x86/lib/bios_asm.S @@ -246,6 +246,8 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) push %fs push %gs
movw %ss, %cs:__realmode_ss/* Clear DF to not break ABI assumptions */ cld@@ -258,12 +260,22 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
enter_protected_mode
Please can you add a comment here for the next person who changes this, about what is going on? It looks like it is saving and restoring the real mode SS register?
movzwl %cs:__realmode_ss, %ecxshll $4, %ecxaddl %ecx, %esp/* Call the C interrupt handler */ movl $interrupt_handler, %eax call *%eaxmovzwl %cs:__realmode_ss, %ecxshll $4, %ecxsubl %ecx, %espenter_real_modemovw %cs:__realmode_ss, %ss/* * Restore all registers, including those manipulated by the C * handler@@ -276,6 +288,9 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) popal iret
+__realmode_ss = PTR_TO_REAL_MODE(.)
.word 0.globl asm_realmode_code_sizeasm_realmode_code_size: .long . - asm_realmode_code -- 1.8.2.1
Regards, Simon
Hi Simon,
On Wed, Jul 1, 2015 at 10:58 PM, Simon Glass sjg@chromium.org wrote:
Hi,
On 1 July 2015 at 02:27, Bin Meng bmeng.cn@gmail.com wrote:
From: Jian Luo jian.luo4@boschrexroth.de
PCI option rom may use different SS during its execution, so it is not safe to assume esp pointed to the same location in the protected mode.
Signed-off-by: Jian Luo jian.luo4@boschrexroth.de Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com
arch/x86/lib/bios_asm.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/x86/lib/bios_asm.S b/arch/x86/lib/bios_asm.S index 4faa70e..a29fe0e 100644 --- a/arch/x86/lib/bios_asm.S +++ b/arch/x86/lib/bios_asm.S @@ -246,6 +246,8 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) push %fs push %gs
movw %ss, %cs:__realmode_ss/* Clear DF to not break ABI assumptions */ cld@@ -258,12 +260,22 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.)
enter_protected_modePlease can you add a comment here for the next person who changes this, about what is going on? It looks like it is saving and restoring the real mode SS register?
Will add a comment in v2.
movzwl %cs:__realmode_ss, %ecxshll $4, %ecxaddl %ecx, %esp/* Call the C interrupt handler */ movl $interrupt_handler, %eax call *%eaxmovzwl %cs:__realmode_ss, %ecxshll $4, %ecxsubl %ecx, %espenter_real_modemovw %cs:__realmode_ss, %ss/* * Restore all registers, including those manipulated by the C * handler@@ -276,6 +288,9 @@ __interrupt_handler_16bit = PTR_TO_REAL_MODE(.) popal iret
+__realmode_ss = PTR_TO_REAL_MODE(.)
.word 0.globl asm_realmode_code_sizeasm_realmode_code_size: .long . - asm_realmode_code --
Regards, Bin
participants (2)
-
Bin Meng -
Simon Glass