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| author | Damien Zammit via Bug reports for the GNU Hurd <bug-hurd@gnu.org> | 2024-12-21 23:55:17 +0000 |
|---|---|---|
| committer | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2024-12-22 01:23:24 +0100 |
| commit | 8fcabe224198a5c9697fb9a48cc966a50ccedbda (patch) | |
| tree | f728c58275052ff7b40fe6ef995a595ac291cd02 | |
| parent | 7b578f3794dbf1c9cde6bb92f1fc5799a287bd1a (diff) | |
| download | gnumach-8fcabe224198a5c9697fb9a48cc966a50ccedbda.tar.gz gnumach-8fcabe224198a5c9697fb9a48cc966a50ccedbda.tar.bz2 gnumach-8fcabe224198a5c9697fb9a48cc966a50ccedbda.zip | |
cpuboot: Fix percpu apboot_gdt for early gs
This allocates a constant space for percpu gdts
and copies the first entry to the nth entry on each cpu,
then patches its own copy of the gdt so it can function
independently.
Message-ID: <20241221235456.423860-2-damien@zamaudio.com>
| -rw-r--r-- | i386/i386/cpuboot.S | 63 |
1 files changed, 53 insertions, 10 deletions
diff --git a/i386/i386/cpuboot.S b/i386/i386/cpuboot.S index f93e0387..76ed907d 100644 --- a/i386/i386/cpuboot.S +++ b/i386/i386/cpuboot.S @@ -31,15 +31,19 @@ #define BOOT_CS 0x8 #define BOOT_DS 0x10 +#define GDT_DESCR_M32 4 +#define GDT_TABLE_M32 (14*2) + .data .align 16 apboot_idt_ptr: .long 0 .align 16 +apboot_gdt_top: .word 0 apboot_gdt_descr: - .word 14*8-1 + .word (GDT_TABLE_M32 * 4) - 1 .long apboot_gdt - KERNELBASE .align 16 apboot_gdt: @@ -101,6 +105,9 @@ apboot_percpu_med: apboot_percpu_high: .byte 0 +/* Empty space for per-cpu gdt descriptor and gdt */ +.space (NCPUS-1) * (GDT_DESCR_M32 + GDT_TABLE_M32) * 4, 0x0 + .globl apboot, apbootend, gdt_descr_tmp, apboot_jmp_offset .align 16 .code16 @@ -159,28 +166,62 @@ apboot_jmp_offset: movw %ax, %gs movw %ax, %ss - /* Get CPU number */ + /* Get CPU number into ebp */ movl $1, %eax cpuid shrl $24, %ebx - movl %cs:CX(cpu_id_lut, %ebx), %ecx + movl %cs:CX(cpu_id_lut, %ebx), %ebp + + /* Copy first gdt descriptor and gdt to cpu-th area */ + movl $(GDT_DESCR_M32 + GDT_TABLE_M32), %ecx + movl $apboot_gdt_top, %esi + movl %esi, %edi + movl $((GDT_DESCR_M32 + GDT_TABLE_M32) * 4), %eax + mul %ebp + addl %eax, %edi + rep movsl /* Access per_cpu area */ - movl %ecx,%eax + movl %ebp, %eax movl $PC_SIZE,%ebx mul %ebx addl $percpu_array, %eax /* Record our cpu number */ - movl %ecx, (PERCPU_CPU_ID)(%eax) + movl %ebp, (PERCPU_CPU_ID)(%eax) /* Set up temporary percpu descriptor */ addl $(-KERNELBASE), %eax - movw %ax, apboot_percpu_low - shr $16, %eax - movb %al, apboot_percpu_med - shr $8, %ax - movb %al, apboot_percpu_high + movl %eax, %ebx + + /* Make eax hold offset to my cpus gdt */ + movl $((GDT_DESCR_M32 + GDT_TABLE_M32) * 4), %eax + mul %ebp + + /* Patch only our own copy of gdt */ + movl $apboot_percpu_low, %ecx + addl %eax, %ecx + movw %bx, (%ecx) + shr $16, %ebx + addl $2, %ecx + movb %bl, (%ecx) + shr $8, %bx + addl $3, %ecx + movb %bl, (%ecx) + + /* Patch only our own copy of gdt descriptor */ + movl $apboot_gdt_descr, %ecx + addl %eax, %ecx + movl %ecx, %edx + addl $2, %edx + movl (%edx), %ebx + addl %eax, %ebx + movl %ebx, (%edx) + + /* Reload our copy of gdt */ + lgdtl (%ecx) + ljmpl $KERNEL_CS, $2f +2: movw $PERCPU_DS, %ax movw %ax, %gs @@ -213,8 +254,10 @@ apboot_jmp_offset: /* Finish the cpu configuration */ call EXT(cpu_ap_main) +3: /* NOT REACHED */ hlt + jmp 3b .align 16 .word 0 |