Hi all, This patch is not for review and a V2 is upcoming.
The current version contains a few known issues that have already been fixed by Igor Podgainoi <[email protected]<mailto:[email protected]>>. Those fixes will be contributed directly by Igor by a V2 patch, which will be posted to this same thread. Notes: Attached is a patch that adds an ARM64 stub for the `stabilize_sig_stack` routine in the gendef script. The changes are documented with inline comments and should be self-explanatory. I would also like to thank Radek BartoĊ <[email protected]<mailto:[email protected]>> for his initial contributions to this effort. Thanks & regards Thirumalai Nagalingam <[email protected]<mailto:[email protected]>> In-lined patch: diff --git a/winsup/cygwin/scripts/gendef b/winsup/cygwin/scripts/gendef index ff13f1daa..0b2d3db9b 100755 --- a/winsup/cygwin/scripts/gendef +++ b/winsup/cygwin/scripts/gendef @@ -464,7 +464,83 @@ _sigbe: sigdelayed: _sigdelayed_end: .global _sigdelayed_end + .seh_proc stabilize_sig_stack stabilize_sig_stack: + // prologue + stp fp, lr, [sp, #-0x10]! // save FP and LR registers + .seh_save_fplr_x 0x10 + mov fp, sp // set frame pointer for unwinder + .seh_set_fp + .seh_endprologue + + ldr x10, [x18, #0x8] // load TLS block base pointer into x10 + + // try to acquire the lock + mov w9, #1 // value to store (1 == locked) + ldr x11, =_cygtls.stacklock // load the symbol offset + add x12, x10, x11 // x12 = tls_base + &stacklock +1: + ldaxr w13, [x12] // load old lock value + stlxr w14, w9, [x12] // attempt to store 1 + cbnz w14, 1b // if store failed, retry + cbz w13, 2f // if lock was acquired, continue + yield // yield to allow other threads to run + b 1b // retry acquiring the lock + +2: + // lock acquired, increment incyg counter + ldr x11, =_cygtls.incyg // load the symbol offset + add x12, x10, x11 // x12 = tls_base + &incyg + ldr w9, [x12] // load current value of incyg + add w9, w9, #1 // increment incyg counter + str w9, [x12] // store back incremented value + + // check current_sig + ldr x11, =_cygtls.current_sig // load the symbol offset + ldr w9, [x10, x11] // load current value of current_sig + cbz w9, 3f // if no current signal, jump to cleanup + + // release lock before calling signal handler + ldr x11, =_cygtls.stacklock // load the symbol offset + add x12, x10, x11 // x12 = tls_base + &stacklock + ldr w9, [x12] // load current value of stacklock + sub w9, w9, #1 // decrement stacklock + stlr w9, [x12] // store with release semantics + + // prepare arg and call handler + ldr x0, =_cygtls.start_offset // load the symbol offset + add x0, x10, x0 // x0 = tls_base + &start_offset + bl _ZN7_cygtls19call_signal_handlerEv + + // call may clobber x10, restore TLS base + ldr x10, [x18, #0x8] // reload tls_base + + // decrement incyg + ldr x11, =_cygtls.incyg + add x12, x10, x11 + ldr w9, [x12] + sub w9, w9, #1 + str w9, [x12] + + // loop to handle another signal + b 1b + +3: + // no signal to handle, decrement incyg counter + ldr x11, =_cygtls.incyg + add x12, x10, x11 + ldr w9, [x12] + sub w9, w9, #1 + str w9, [x12] + + mov x0, x10 // return TLS address in x0 (return register) + + // epilogue + .seh_startepilogue + ldp fp, lr, [sp], #0x10 + .seh_endepilogue + ret + .seh_endproc EOF } }
Cygwin-gendef-Implement-stabilize_sig_stack-for-aarc.patch
Description: Cygwin-gendef-Implement-stabilize_sig_stack-for-aarc.patch
