xtensa: add support for TLS
The Xtensa architecture provides a global register called THREADPTR for the purpose of Thread Local Storage (TLS) support. This allows us to use a fairly simple implementation, keeping the thread pointer in the regset and simply saving and restoring it upon entering/exiting the from user space. Signed-off-by: Chris Zankel <chris@zankel.net>
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@ -84,7 +84,8 @@ typedef struct {
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elf_greg_t sar;
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elf_greg_t windowstart;
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elf_greg_t windowbase;
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elf_greg_t reserved[8+48];
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elf_greg_t threadptr;
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elf_greg_t reserved[7+48];
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elf_greg_t a[64];
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} xtensa_gregset_t;
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@ -38,6 +38,7 @@ struct pt_regs {
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unsigned long syscall; /* 56 */
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unsigned long icountlevel; /* 60 */
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unsigned long scompare1; /* 64 */
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unsigned long threadptr; /* 68 */
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/* Additional configurable registers that are used by the compiler. */
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xtregs_opt_t xtregs_opt;
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@ -48,7 +49,7 @@ struct pt_regs {
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/* current register frame.
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* Note: The ESF for kernel exceptions ends after 16 registers!
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*/
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unsigned long areg[16]; /* 128 (64) */
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unsigned long areg[16];
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};
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#include <variant/core.h>
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@ -42,6 +42,7 @@ int main(void)
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DEFINE(PT_ICOUNTLEVEL, offsetof (struct pt_regs, icountlevel));
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DEFINE(PT_SYSCALL, offsetof (struct pt_regs, syscall));
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DEFINE(PT_SCOMPARE1, offsetof(struct pt_regs, scompare1));
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DEFINE(PT_THREADPTR, offsetof(struct pt_regs, threadptr));
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DEFINE(PT_AREG, offsetof (struct pt_regs, areg[0]));
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DEFINE(PT_AREG0, offsetof (struct pt_regs, areg[0]));
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DEFINE(PT_AREG1, offsetof (struct pt_regs, areg[1]));
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@ -130,6 +130,11 @@ _user_exception:
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s32i a3, a1, PT_SAR
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s32i a2, a1, PT_ICOUNTLEVEL
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#if XCHAL_HAVE_THREADPTR
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rur a2, threadptr
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s32i a2, a1, PT_THREADPTR
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#endif
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/* Rotate ws so that the current windowbase is at bit0. */
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/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
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@ -510,6 +515,11 @@ user_exception_exit:
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* (if we have restored WSBITS-1 frames).
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*/
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#if XCHAL_HAVE_THREADPTR
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l32i a3, a1, PT_THREADPTR
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wur a3, threadptr
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#endif
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2: j common_exception_exit
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/* This is the kernel exception exit.
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@ -1955,7 +1965,7 @@ ENTRY(_switch_to)
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s32i a6, a3, EXC_TABLE_FIXUP
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s32i a7, a3, EXC_TABLE_KSTK
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/* restore context of the task that 'next' addresses */
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/* restore context of the task 'next' */
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l32i a0, a13, THREAD_RA # restore return address
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l32i a1, a13, THREAD_SP # restore stack pointer
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@ -259,9 +259,10 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
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memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
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®s->areg[XCHAL_NUM_AREGS - len/4], len);
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}
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// FIXME: we need to set THREADPTR in thread_info...
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/* The thread pointer is passed in the '4th argument' (= a5) */
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if (clone_flags & CLONE_SETTLS)
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childregs->areg[2] = childregs->areg[6];
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childregs->threadptr = childregs->areg[5];
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} else {
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p->thread.ra = MAKE_RA_FOR_CALL(
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(unsigned long)ret_from_kernel_thread, 1);
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@ -66,6 +66,7 @@ int ptrace_getregs(struct task_struct *child, void __user *uregs)
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__put_user(regs->lcount, &gregset->lcount);
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__put_user(regs->windowstart, &gregset->windowstart);
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__put_user(regs->windowbase, &gregset->windowbase);
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__put_user(regs->threadptr, &gregset->threadptr);
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for (i = 0; i < XCHAL_NUM_AREGS; i++)
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__put_user(regs->areg[i],
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@ -92,6 +93,7 @@ int ptrace_setregs(struct task_struct *child, void __user *uregs)
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__get_user(regs->lcount, &gregset->lcount);
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__get_user(ws, &gregset->windowstart);
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__get_user(wb, &gregset->windowbase);
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__get_user(regs->threadptr, &gregset->threadptr);
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regs->ps = (regs->ps & ~ps_mask) | (ps & ps_mask) | (1 << PS_EXCM_BIT);
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@ -337,7 +337,7 @@ static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
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struct rt_sigframe *frame;
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int err = 0;
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int signal;
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unsigned long sp, ra;
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unsigned long sp, ra, tp;
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sp = regs->areg[1];
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@ -395,7 +395,8 @@ static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
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* Return context not modified until this point.
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*/
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/* Set up registers for signal handler */
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/* Set up registers for signal handler; preserve the threadptr */
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tp = regs->threadptr;
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start_thread(regs, (unsigned long) ka->sa.sa_handler,
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(unsigned long) frame);
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@ -406,6 +407,7 @@ static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
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regs->areg[6] = (unsigned long) signal;
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regs->areg[7] = (unsigned long) &frame->info;
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regs->areg[8] = (unsigned long) &frame->uc;
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regs->threadptr = tp;
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/* Set access mode to USER_DS. Nomenclature is outdated, but
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* functionality is used in uaccess.h
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