Hi Shuah, now I can't paste the test code, so I could write a demo and paste it:
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#include <stdio.h> #include <stdlib.h>
struct ucontext { struct ucontext *uc_link; unsigned long uc_flags; sigset_t uc_sigmask; struct ucontext *uc_mcontext; }; typedef struct ucontext ucontext_t;
void sigsegv(void *ctx_void) { ucontext_t *ctx = (ucontext_t*)ctx_void; ucontext_t *ctx2 = (int *)ctx_void; ucontext_t *ctx3 = ctx_void; printf("ctx:%p, ctx2:%p, ctx3:%p.\n", ctx, ctx2, ctx3); }
int main() { ucontext_t *test = malloc(sizeof(ucontext_t)); sigsegv(test); return 0; }
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The result is CTX: 0x563D96CE5010, CTX2:0x563D96CE5010, CTx3:0x563D96CE5010. Now force ucontext_t and int pointers are the same as the addresses obtained without forced conversion.
Now I'll paste the assembly code for them:
|0x700 <sigsegv> push %rbp │ │0x701 <sigsegv+1> mov %rsp,%rbp │ │0x704 <sigsegv+4> sub $0x30,%rsp │ │0x708 <sigsegv+8> mov %rdi,-0x28(%rbp) │ │0x70c <sigsegv+12> mov -0x28(%rbp),%rax │ │0x710 <sigsegv+16> mov %rax,-0x8(%rbp) │ │0x714 <sigsegv+20> mov -0x28(%rbp),%rax │ │0x718 <sigsegv+24> mov %rax,-0x10(%rbp) │ │0x71c <sigsegv+28> mov -0x28(%rbp),%rax │ │0x720 <sigsegv+32> mov %rax,-0x18(%rbp) │ │0x724 <sigsegv+36> mov -0x18(%rbp),%rcx │ │0x728 <sigsegv+40> mov -0x10(%rbp),%rdx │ │0x72c <sigsegv+44> mov -0x8(%rbp),%rax │ │0x730 <sigsegv+48> mov %rax,%rsi │ │0x733 <sigsegv+51> lea 0xba(%rip),%rdi # 0x7f4 │ │0x73a <sigsegv+58> mov $0x0,%eax │ │0x73f <sigsegv+63> callq 0x5a0 printf@plt │ │0x744 <sigsegv+68> nop │ │0x745 <sigsegv+69> leaveq │ │0x746 <sigsegv+70> retq