| Message ID | 20240821133224.198923-1-frediano.ziglio@cloud.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Restore memory used for IP computation | expand |
On 21/08/2024 2:32 pm, Frediano Ziglio wrote: > We need to write in some location but no reasons to not > trying to restore what we potentially overwrote. > > Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com> Please follow how Linux does this. e.g. https://lore.kernel.org/xen-devel/20240814195053.5564-3-jason.andryuk@amd.com/ Specifically, ... > --- > xen/arch/x86/boot/head.S | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S > index d8ac0f0494..3e1e9e05b6 100644 > --- a/xen/arch/x86/boot/head.S > +++ b/xen/arch/x86/boot/head.S > @@ -418,13 +418,17 @@ __pvh_start: > * absolute stack address as the native path, for lack of a better > * alternative. > */ ... the reasoning in this comment here is incorrect for non-BIOS systems, and causes memory corruption for Coreboot based boot. I've been meaning to fix it for ages, but seeing as you're changing it... :) The first field under %ebx in a boot ABI we recognise is a much better choice that an arbitrary location in the first page of memory. ~Andrew
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S index d8ac0f0494..3e1e9e05b6 100644 --- a/xen/arch/x86/boot/head.S +++ b/xen/arch/x86/boot/head.S @@ -418,13 +418,17 @@ __pvh_start: * absolute stack address as the native path, for lack of a better * alternative. */ - mov $0x1000, %esp + mov $0xffc, %esp + pop %edx /* Calculate the load base address. */ call 1f 1: pop %esi sub $sym_offs(1b), %esi + /* Restore clobbered stack */ + push %edx + /* Set up stack. */ lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp @@ -468,13 +472,17 @@ __start: * this page for a temporary stack, being one of the safest locations * to clobber. */ - mov $0x1000, %esp + mov $0xffc, %esp + pop %edx /* Calculate the load base address. */ call 1f 1: pop %esi sub $sym_offs(1b), %esi + /* Restore clobbered stack */ + push %edx + /* Set up stack. */ lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp
We need to write in some location but no reasons to not trying to restore what we potentially overwrote. Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com> --- xen/arch/x86/boot/head.S | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)