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| author | David Woodhouse <dwmw@amazon.co.uk> | 2025-03-26 14:16:02 +0000 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-04-10 12:17:14 +0200 |
| commit | 7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed (patch) | |
| tree | b35df9d0213d84e88ca2221f97c72eef1be0dfa3 /arch/x86/kernel/relocate_kernel_64.S | |
| parent | d358b45120cc8da9f10d8c1e8ec3559f72525147 (diff) | |
| download | linux-next-7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed.tar.gz linux-next-7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed.zip | |
x86/kexec: Add 8250 MMIO serial port output
This supports the same 32-bit MMIO-mapped 8250 as the early_printk code.
It's not clear why the early_printk code supports this form and only this
form; the actual runtime 8250_pci doesn't seem to support it. But having
hacked up QEMU to expose such a device, early_printk does work with it,
and now so does the kexec debug code.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250326142404.256980-3-dwmw2@infradead.org
Diffstat (limited to 'arch/x86/kernel/relocate_kernel_64.S')
| -rw-r--r-- | arch/x86/kernel/relocate_kernel_64.S | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 21011cd19c48..8808cfca6322 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -39,6 +39,7 @@ SYM_DATA(kexec_va_control_page, .quad 0) SYM_DATA(kexec_pa_table_page, .quad 0) SYM_DATA(kexec_pa_swap_page, .quad 0) SYM_DATA_LOCAL(pa_backup_pages_map, .quad 0) +SYM_DATA(kexec_debug_8250_mmio32, .quad 0) SYM_DATA(kexec_debug_8250_port, .word 0) .balign 16 @@ -413,6 +414,22 @@ pr_char_null: ret SYM_CODE_END(pr_char_8250) +SYM_CODE_START_LOCAL_NOALIGN(pr_char_8250_mmio32) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR +.Lxmtrdy_loop_mmio: + movb (LSR*4)(%rdx), %ah + testb $XMTRDY, %ah + jnz .Lready_mmio + rep nop + jmp .Lxmtrdy_loop_mmio + +.Lready_mmio: + movb %al, (%rdx) + ANNOTATE_UNRET_SAFE + ret +SYM_CODE_END(pr_char_8250_mmio32) + /* * Load pr_char function pointer into %rsi and load %rdx with whatever * that function wants to see there (typically port/MMIO address). @@ -423,6 +440,11 @@ SYM_CODE_END(pr_char_8250) testw %dx, %dx jnz 1f + leaq pr_char_8250_mmio32(%rip), %rsi + movq kexec_debug_8250_mmio32(%rip), %rdx + testq %rdx, %rdx + jnz 1f + leaq pr_char_null(%rip), %rsi 1: .endm |