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authorDanny Holman <dholman@gymli.org>2024-06-21 23:32:18 -0500
committerDanny Holman <dholman@gymli.org>2024-06-21 23:32:18 -0500
commit0e8081d8e9db8b9482da7e92a72194bfa927223d (patch)
treea8250c2071b1af527d896b718827ff7081cb5b56 /arch/i386
parent2f224cdeadc380037cb74c10fc65d17aac05b730 (diff)
libk: use a random value for the stack protector
Don't hardcode the __stack_chk_guard value, generate a random value (using RDRAND on x86) before running any C code. Signed-off-by: Danny Holman <dholman@gymli.org>
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/boot/boot.s29
1 files changed, 29 insertions, 0 deletions
diff --git a/arch/i386/boot/boot.s b/arch/i386/boot/boot.s
index 29a3575..f861699 100644
--- a/arch/i386/boot/boot.s
+++ b/arch/i386/boot/boot.s
@@ -78,6 +78,8 @@ _start:
4: movl $stack_top, %esp
and $-16, %esp
+ call setup_stack_guard
+
pushl %ebx
pushl %eax
call i386_entry
@@ -86,6 +88,33 @@ _start:
1: hlt
jmp 1b
+.global setup_stack_guard
+.type setup_stack_guard, @function
+setup_stack_guard:
+ pushl %eax
+ pushl %ebx
+ pushl %ecx
+
+ movl $1, %eax
+ movl $0, %ecx
+ cpuid
+ shrl $30, %ecx
+ andl $1, %ecx
+ jnz start_loop
+ jmp fail
+start_loop:
+ rdrand %eax
+ jc done
+ loop start_loop
+fail:
+ movl $-1, %eax
+done:
+ movl %eax, __stack_chk_guard
+ popl %ecx
+ popl %ebx
+ popl %eax
+ ret
+
.global enable_paging
.type enable_paging, @function
enable_paging: