| Message ID | 20230217174814.1006961-3-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/kexec: ASM improvements | expand |
On 17.02.2023 18:48, Andrew Cooper wrote: > Assemble the GDT base relative to kexec_reloc, and simply add the identity map > base address to relocate. > > Adjust a stale comment, and drop the unused matching label. Only kind of - the comment is referencing call_32_bit, and hence wasn't really stale. And what was (and would remain to be) dead is call_64_bit. May want slightly re-wording. > @@ -81,9 +80,8 @@ ENTRY(kexec_reloc) > /* Setup IDT. */ > lidt compat_mode_idt(%rip) > > - /* Load compat GDT. */ > - leaq compat_mode_gdt(%rip), %rax > - movq %rax, (compat_mode_gdt_desc + 2)(%rip) > + /* Relocate and load compat GDT. */ > + add %rdi, 2 + compat_mode_gdt_desc(%rip) > lgdt compat_mode_gdt_desc(%rip) Where's %rdi being populated for this? At kexec_reloc %rdi points at the code page, but prior to calling relocate_pages the register is overwritten (and the original value is lost). relocate_pages also has normal C calling convention afaict; kind of as a result %rdi is actually being clobbered there. Jan
diff --git a/xen/arch/x86/x86_64/kexec_reloc.S b/xen/arch/x86/x86_64/kexec_reloc.S index 035164e96f38..a81f64146190 100644 --- a/xen/arch/x86/x86_64/kexec_reloc.S +++ b/xen/arch/x86/x86_64/kexec_reloc.S @@ -72,7 +72,6 @@ ENTRY(kexec_reloc) testq $KEXEC_RELOC_FLAG_COMPAT, %r8 jnz .L_call_32_bit -.L_call_64_bit: /* Call the image entry point. This should never return. */ callq *%rbp ud2 @@ -81,9 +80,8 @@ ENTRY(kexec_reloc) /* Setup IDT. */ lidt compat_mode_idt(%rip) - /* Load compat GDT. */ - leaq compat_mode_gdt(%rip), %rax - movq %rax, (compat_mode_gdt_desc + 2)(%rip) + /* Relocate and load compat GDT. */ + add %rdi, 2 + compat_mode_gdt_desc(%rip) lgdt compat_mode_gdt_desc(%rip) /* Enter compatibility mode. */ @@ -172,7 +170,7 @@ compatibility_mode: .align 4 compat_mode_gdt_desc: .word .Lcompat_mode_gdt_end - compat_mode_gdt -1 - .quad 0x0000000000000000 /* set in call_32_bit above */ + .quad . - kexec_reloc /* Relocated before use */ .type compat_mode_gdt_desc, @object .size compat_mode_gdt_desc, . - compat_mode_gdt_desc
Assemble the GDT base relative to kexec_reloc, and simply add the identity map base address to relocate. Adjust a stale comment, and drop the unused matching label. No functional change. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Roger Pau Monné <roger.pau@citrix.com> CC: Wei Liu <wl@xen.org> --- xen/arch/x86/x86_64/kexec_reloc.S | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)