search for: startup_64

...gest some useful objdump flags?) > >Regards, >Dmitry Just want to share latest results of investigation from my side. I traced kernel linked with LLD to find where it fails. LLD linked kernel starts execution and then I came up to protected_mode_jump? function, which intention to jump to startup_64: jmpl *%eax # Jump to the 32-bit entrypoint (https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/arch/x86/boot/pmjump.S#L76) (https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/arch/x86/kernel/head_64.S#L48) It does not happen. Code exec...

...movabsq $INIT_PER_CPU_VAR(irq_stack_union),%rax cdq wrmsr #endif diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S index e1a5fbeae08d..43e234c7c2de 100644 --- a/arch/x86/xen/xen-pvh.S +++ b/arch/x86/xen/xen-pvh.S @@ -101,8 +101,8 @@ ENTRY(pvh_start_xen) call xen_prepare_pvh /* startup_64 expects boot_params in %rsi. */ - mov $_pa(pvh_bootparams), %rsi - mov $_pa(startup_64), %rax + movabs $_pa(pvh_bootparams), %rsi + movabs $_pa(startup_64), %rax jmp *%rax #else /* CONFIG_X86_64 */ @@ -137,10 +137,15 @@ END(pvh_start_xen) .section ".init.data","aw" .b...

From: Joerg Roedel <jroedel at suse.de> When the pre-decompression code loads its first GDT in startup_64, it is still running on the CS value of the previous GDT. In the case of SEV-ES this is the EFI GDT. To make exception handling work (especially IRET) the CPU needs to switch to a CS value in the current GDT, so jump to __KERNEL_CS after the first GDT is loaded. Signed-off-by: Joerg Roedel <jr...

On Tue, Apr 28, 2020 at 05:16:22PM +0200, Joerg Roedel wrote: > From: Joerg Roedel <jroedel at suse.de> > > When the pre-decompression code loads its first GDT in startup_64, it is > still running on the CS value of the previous GDT. In the case of SEV-ES > this is the EFI GDT. > > To make exception handling work (especially IRET) the CPU needs to > switch to a CS value in the current GDT, so jump to __KERNEL_CS after > the first GDT is loaded. >...

From: Joerg Roedel <jroedel at suse.de> When booted through startup_64 the kernel keeps running on the EFI page-table until the KASLR code sets up its own page-table. Without KASLR the pre-decompression boot code never switches off the EFI page-table. Change that by unconditionally switching to a kernel controlled page-table after relocation. This makes sure we can m...

...o that properly :), so inserted infinite loops in asm code: foo: jmp foo And watched for behavior of QEMU. If it just hanged that was fine, I knew I am inside my loop, if QEMU rebooted, I knew it crashed at point I was looking for. So tracing bfd linked kernel and using documentation I found that startup_64 ?is next destination POI, and found that this instruction is the last before QEMU reboots for me. >I think you can also get DSO with -pie I think, but I don't see that either. This is quite mysterious. I also did a quick look at the >linker script and didn't see anything at first gla...

...tr("== 0x1000000"); output[0] = 0xEB; output[1] = 0xFE; return output; And during boot in shows all text from above and enters infinite loop as expected. So, that means it successfully jumps to 0x1000000, but looks something is wrong in decompressed code. Next destination point should be startup_64?. https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/arch/x86/kernel/head_64.S#L50<https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/arch/x86/kernel/head_64.S#L48> Though as I mentioned it does not reach it for me. Next step I probab...

From: Joerg Roedel <jroedel at suse.de> Add code needed to setup an IDT in the early pre-decompression boot-code. The IDT is loaded first in startup_64, which is after EfiExitBootServices() has been called, and later reloaded when the kernel image has been relocated to the end of the decompression area. This allows to setup different IDT handlers before and after the relocation. Signed-off-by: Joerg Roedel <jroedel at suse.de> --- arch/x8...

From: Joerg Roedel <jroedel at suse.de> Add code needed to setup an IDT in the early pre-decompression boot-code. The IDT is loaded first in startup_64, which is after EfiExitBootServices() has been called, and later reloaded when the kernel image has been relocated to the end of the decompression area. This allows to setup different IDT handlers before and after the relocation. Signed-off-by: Joerg Roedel <jroedel at suse.de> --- arch/x8...

On Thu, Feb 2, 2017 at 12:38 AM, George Rimar <grimar at accesssoftek.com> wrote: > >As far as the setup, I would recommend setting up qemu for actually > running the LLD-linked kernel and custom bootloader etc. because then you > can have a single >script that rebuilds the bootloader and kernel and > copies the files to the VM. This reduces iteration time significantly.

...86/kernel/head_64.S | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..5a3cde971cb7 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -72,6 +72,20 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_base(%rip) + lgdt boot_gdt_descr(%rip) + + /* GDT loaded - switch t...

...+++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 4bbc770af632..5a3cde971cb7 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -72,6 +72,20 @@ SYM_CODE_START_NOALIGN(startup_64) > /* Set up the stack for verify_cpu(), similar to initial_stack below */ > leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp > > + /* Setup boot GDT descriptor and load boot GDT */ > + leaq boot_gdt(%rip), %rax > + movq %rax, boot_gdt_...

On Thu, Mar 19, 2020 at 10:13:12AM +0100, Joerg Roedel wrote: > From: Joerg Roedel <jroedel at suse.de> > > When booted through startup_64 the kernel keeps running on the EFI > page-table until the KASLR code sets up its own page-table. Without > KASLR the pre-decompression boot code never switches off the EFI > page-table. Change that by unconditionally switching to our own > page-table once the kernel is relocated. >...

...head_64.S | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..11a28c1fb51f 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -72,6 +72,26 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_base(%rip) + lgdt boot_gdt_descr(%rip) + + /* New GDT is live - rel...

...el/head64.c @@ -36,6 +36,7 @@ #include <asm/microcode.h> #include <asm/kasan.h> #include <asm/fixmap.h> +#include <asm/realmode.h> /* * Manage page tables very early on. @@ -513,6 +514,8 @@ void __init x86_64_start_reservations(char *real_mode_data) */ void __head startup_64_setup_env(unsigned long physbase) { + unsigned long gsbase; + /* Load GDT */ startup_gdt_descr.address = (unsigned long)fixup_pointer(startup_gdt, physbase); native_load_gdt(&startup_gdt_descr); @@ -521,4 +524,8 @@ void __head startup_64_setup_env(unsigned long physbase) asm volatile(&...

...el/head64.c @@ -36,6 +36,7 @@ #include <asm/microcode.h> #include <asm/kasan.h> #include <asm/fixmap.h> +#include <asm/realmode.h> /* * Manage page tables very early on. @@ -513,6 +514,8 @@ void __init x86_64_start_reservations(char *real_mode_data) */ void __head startup_64_setup_env(unsigned long physbase) { + unsigned long gsbase; + /* Load GDT */ startup_gdt_descr.address = (unsigned long)fixup_pointer(startup_gdt, physbase); native_load_gdt(&startup_gdt_descr); @@ -521,4 +524,8 @@ void __head startup_64_setup_env(unsigned long physbase) asm volatile(&...

On Mon, Aug 24, 2020 at 10:54:26AM +0200, Joerg Roedel wrote: > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 2b2e91627221..800053219054 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -78,6 +78,14 @@ SYM_CODE_START_NOALIGN(startup_64) > call startup_64_setup_env > popq %rsi > > + /* > + * Setup %gs here already to make stack-protector work - it needs to be > + * setup again after the switch to kernel addresses. The address read > + * from initial_gs is a kernel address, so it needs to be adjusted f...

Modern hardware relies primarily on memory mapped I/O which is typically at addresses that are not mapped by the kernels initial page tables, which makes using them currently unusable for early debugging print support. So this patch set digs in and fixes the early page tables on both arch/i386 and arch/x86_64 so that set_fixmap works with our initial boot page tables. All that is needed is that

Modern hardware relies primarily on memory mapped I/O which is typically at addresses that are not mapped by the kernels initial page tables, which makes using them currently unusable for early debugging print support. So this patch set digs in and fixes the early page tables on both arch/i386 and arch/x86_64 so that set_fixmap works with our initial boot page tables. All that is needed is that

...on(.head.text) static void __head *fixup_pointer(void *ptr, unsigned long physaddr) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..62513dd1e0e4 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -72,6 +72,26 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_descr+2(%rip) + lgdt boot_gdt_descr(%rip) + + /* New GDT is live -...