On Mon, May 12, 2025 at 01:31:34PM +1000, Michael Ellerman wrote: > Are you building with pcrel? Otherwise r2 shouldn't be getting used as > an ordinary register.
Yes, CONFIG_PPC_KERNEL_PCREL=y. I'll try with n and see what happens. > Can you show the disassembly of where it's getting used? c00000000000fc50 <__do_IRQ>: c00000000000fc50: a6 02 08 7c mflr r0 c00000000000fc54: f0 ff c1 fb std r30,-16(r1) c00000000000fc58: f8 ff e1 fb std r31,-8(r1) c00000000000fc5c: 26 01 10 06 pla r2,19317860 # c00000000127c0c0 <__irq_regs> c00000000000fc60: 64 c4 40 38 c00000000000fc64: 2e 01 10 06 pla r10,19857060 # c0000000012ffb08 <hardirq_ctx> c00000000000fc68: a4 fe 40 39 c00000000000fc6c: 10 00 01 f8 std r0,16(r1) c00000000000fc70: d1 ff 21 f8 stdu r1,-48(r1) c00000000000fc74: 20 00 0d e9 ld r8,32(r13) c00000000000fc78: 78 13 49 7c mr r9,r2 c00000000000fc7c: 2a 40 c9 7f ldx r30,r9,r8 c00000000000fc80: 2a 49 68 7c stdx r3,r8,r9 c00000000000fc84: 00 00 2d a1 lhz r9,0(r13) c00000000000fc88: 24 1f 29 79 sldi r9,r9,3 c00000000000fc8c: 2a 48 ea 7f ldx r31,r10,r9 c00000000000fc90: 64 04 29 78 clrrdi r9,r1,14 c00000000000fc94: 40 48 3f 7c cmpld r31,r9 c00000000000fc98: 24 00 82 40 bne c00000000000fcbc <__do_IRQ+0x6c> c00000000000fc9c: 78 0b 24 7c mr r4,r1 c00000000000fca0: e5 f9 ff 4b bl c00000000000f684 <__do_irq> c00000000000fca4: 26 01 10 06 pla r2,19317788 # c00000000127c0c0 <__irq_regs> c00000000000fca8: 1c c4 40 38 c00000000000fcac: 20 00 2d e9 ld r9,32(r13) c00000000000fcb0: 30 00 21 38 addi r1,r1,48 c00000000000fcb4: 2a 11 c9 7f stdx r30,r9,r2 c00000000000fcb8: 4c c0 50 48 b c00000000051bd04 <_restgpr0_30> c00000000000fcbc: e1 3f 3f f8 stdu r1,16352(r31) c00000000000fcc0: 78 0b 24 7c mr r4,r1 c00000000000fcc4: 78 fb e1 7f mr r1,r31 c00000000000fcc8: bd f9 ff 4b bl c00000000000f684 <__do_irq> c00000000000fccc: 00 00 21 e8 ld r1,0(r1) c00000000000fcd0: dc ff ff 4b b c00000000000fcac <__do_IRQ+0x5c> That's the whole of __do_IRQ(). It explodes at c00000000000fcb4 after the return from the call to __do_irq() at c00000000000fcc8, which is the one in the inline asm. The compiler does reload r2 after the ordinary call to __do_irq() at c00000000000fca0. > There was a change to r2 handling in GCC 15, but AFAICS it was meant to > only affect pcrel code. > > Still it's likely our bug because we are being weird and calling a > function inside an inline asm block. Yep. Thanks, Paul.
