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Implement swapcontext() and makecontext()

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This change introduces support for Linux-style uc_context manipulation
that's fast and works well on all supported OSes and architectures. It
also integrates with the Cosmpolitan runtime which can show backtraces
comprised of multiple stacks and fibers. See the test and example code
for further details. This will be used by Mold once it's been vendored
This commit is contained in:
Justine Tunney 2023-07-02 03:50:29 -07:00
parent 7ec84655b4
commit 197aa0d465
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
28 changed files with 617 additions and 355 deletions
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134
libc/calls/getcontext.S
View file

@ -20,132 +20,14 @@
// Gets machine state.
//
// @return 0 on success, or -1 w/ errno
// @see makecontext()
// @see swapcontext()
// @see setcontext()
// @threadsafe
.ftrace1
getcontext:
#ifdef __x86_64__
pushf
pop 176(%rdi)
movaps %xmm0,480(%rdi)
movaps %xmm1,496(%rdi)
movaps %xmm2,512(%rdi)
movaps %xmm3,528(%rdi)
movaps %xmm4,544(%rdi)
movaps %xmm5,560(%rdi)
movaps %xmm6,576(%rdi)
movaps %xmm7,592(%rdi)
movaps %xmm8,608(%rdi)
movaps %xmm9,624(%rdi)
movaps %xmm10,640(%rdi)
movaps %xmm11,656(%rdi)
movaps %xmm12,672(%rdi)
movaps %xmm13,688(%rdi)
movaps %xmm14,704(%rdi)
movaps %xmm15,720(%rdi)
mov %r8,40(%rdi)
mov %r9,48(%rdi)
mov %r10,56(%rdi)
mov %r11,64(%rdi)
mov %r12,72(%rdi)
mov %r13,80(%rdi)
mov %r14,88(%rdi)
mov %r15,96(%rdi)
mov %rdi,104(%rdi)
mov %rsi,112(%rdi)
mov %rbp,120(%rdi)
mov %rbx,128(%rdi)
mov %rdx,136(%rdi)
mov %rax,144(%rdi)
mov %rcx,152(%rdi)
lea 320(%rdi),%rax
mov %rax,224(%rdi)
lea 8(%rsp),%rax
mov %rax,160(%rdi)
mov (%rsp),%rax
mov %rax,168(%rdi)
jmp __getcontext
#elif defined(__aarch64__)
stp x0,x1,[x0,184]
stp x2,x3,[x0,200]
stp x4,x5,[x0,216]
stp x6,x7,[x0,232]
stp x8,x9,[x0,248]
stp x10,x11,[x0,264]
stp x12,x13,[x0,280]
stp x14,x15,[x0,296]
stp x16,x17,[x0,312]
stp x18,x19,[x0,328]
stp x20,x21,[x0,344]
stp x22,x23,[x0,360]
stp x24,x25,[x0,376]
stp x26,x27,[x0,392]
stp x28,x29,[x0,408]
str x30,[x0,424]
mov x1,sp
str x1,[x0,432] // sp = caller's sp
str x30,[x0,440] // pc = caller's pc
b __getcontext
#else
#error "unsupported architecture"
#endif
.ftrace2
#include "libc/calls/getcontext.inc"
jmp __getcontextsig
.endfn getcontext,globl
.end
////////////////////////////////////////////////////////////////////////////////
noasan noubsan dontinstrument int getcontext(ucontext_t *uc) {
asm volatile("movaps\t%%xmm0,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[0]));
asm volatile("movaps\t%%xmm1,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[1]));
asm volatile("movaps\t%%xmm2,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[2]));
asm volatile("movaps\t%%xmm3,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[3]));
asm volatile("movaps\t%%xmm4,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[4]));
asm volatile("movaps\t%%xmm5,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[5]));
asm volatile("movaps\t%%xmm6,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[6]));
asm volatile("movaps\t%%xmm7,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[7]));
asm volatile("movaps\t%%xmm8,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[8]));
asm volatile("movaps\t%%xmm9,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[9]));
asm volatile("movaps\t%%xmm10,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[10]));
asm volatile("movaps\t%%xmm11,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[11]));
asm volatile("movaps\t%%xmm12,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[12]));
asm volatile("movaps\t%%xmm13,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[13]));
asm volatile("movaps\t%%xmm14,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[14]));
asm volatile("movaps\t%%xmm15,%0" : /* no outputs */ : "m"(uc->__fpustate.xmm[15]));
asm volatile("mov\t%%r8,%0" : "=m"(uc->uc_mcontext.r8));
asm volatile("mov\t%%r9,%0" : "=m"(uc->uc_mcontext.r9));
asm volatile("mov\t%%r10,%0" : "=m"(uc->uc_mcontext.r10));
asm volatile("mov\t%%r11,%0" : "=m"(uc->uc_mcontext.r11));
asm volatile("mov\t%%r12,%0" : "=m"(uc->uc_mcontext.r12));
asm volatile("mov\t%%r13,%0" : "=m"(uc->uc_mcontext.r13));
asm volatile("mov\t%%r14,%0" : "=m"(uc->uc_mcontext.r14));
asm volatile("mov\t%%r15,%0" : "=m"(uc->uc_mcontext.r15));
asm volatile("mov\t%%rdi,%0" : "=m"(uc->uc_mcontext.rdi));
asm volatile("mov\t%%rsi,%0" : "=m"(uc->uc_mcontext.rsi));
asm volatile("mov\t%%rbp,%0" : "=m"(uc->uc_mcontext.rbp));
asm volatile("mov\t%%rbx,%0" : "=m"(uc->uc_mcontext.rbx));
asm volatile("mov\t%%rdx,%0" : "=m"(uc->uc_mcontext.rdx));
asm volatile("mov\t%%rax,%0" : "=m"(uc->uc_mcontext.rax));
asm volatile("mov\t%%rcx,%0" : "=m"(uc->uc_mcontext.rcx));
uc->uc_mcontext.fpregs = &uc->__fpustate;
asm volatile("lea\t8(%%rsp),%%rax\n\t"
"mov\t%%rax,%0"
: "=m"(uc->uc_mcontext.rsp)
: /* no inputs */
: "rax");
asm volatile("mov\t(%%rsp),%%rax\n\t"
"mov\t%%rax,%0"
: "=m"(uc->uc_mcontext.rip)
: /* no inputs */
: "rax");
return 0;
}
noasan noubsan dontinstrument int getcontext(ucontext_t *uc) {
asm volatile("stp\tx0,x1,%0" : "=m"(uc->uc_mcontext.regs[0]));
asm volatile("stp\tx2,x3,%0" : "=m"(uc->uc_mcontext.regs[2]));
asm volatile("mov\tx1,sp\n\tstr\tx1,%0" : "=m"(uc->uc_mcontext.sp));
asm volatile("str\tx30,%0" : "=m"(uc->uc_mcontext.pc));
return 0;
}