On Sat, Feb 10, 2024 at 10:05:34AM -0800, H.J. Lu wrote: > > I bet it probably doesn't work properly for -mx32 (which defines > > __x86_64__), CCing H.J. on that, but that is a preexisting issue > > (and I don't have any experience with it; I guess one would either > > need to add 4 bytes of padding after the func_ptr so that those > > bits remain zeros as sizeof (void *) is 4, but presumably it would be > > better to just use movl (but into %r10) and maybe the jmpl instead > > of movabsq. > > Are there any testcases to exercise this code on Linux?
Here is an untested attempt to implement it for -mx32 (well, I've compiled it with -mx32 in libgcc by hand after stubbing /usr/include/gnu/stubs-x32.h). Testcase could be something like: /* { dg-do run } */ /* { dg-options "-ftrampoline-impl=heap" } */ __attribute__((noipa)) int bar (int (*fn) (int)) { return fn (42) + 1; } int main () { int a = 0; int foo (int x) { if (x != 42) __builtin_abort (); return ++a; } if (bar (foo) != 2 || a != 1) __builtin_abort (); if (bar (foo) != 3 || a != 2) __builtin_abort (); a = 42; if (bar (foo) != 44 || a != 43) __builtin_abort (); return 0; } but I must say I'm also surprised we have no tests for this in the testsuite. Sure, we'd also need to add some effective target whether -ftrampoline-impl=heap can be used for a link/runtime test or not. 2024-02-13 Jakub Jelinek <ja...@redhat.com> PR target/113855 * config/i386/heap-trampoline.c (trampoline_insns): Use movabsq instead of movabs in comments. Add -mx32 variant. --- libgcc/config/i386/heap-trampoline.c.jj 2024-02-12 18:48:08.548886036 +0100 +++ libgcc/config/i386/heap-trampoline.c 2024-02-13 10:24:06.348020670 +0100 @@ -30,18 +30,34 @@ void __gcc_nested_func_ptr_created (void void __gcc_nested_func_ptr_deleted (void); #if __x86_64__ + +#ifdef __LP64__ static const uint8_t trampoline_insns[] = { - /* movabs $<func>,%r11 */ + /* movabsq $<func>,%r11 */ 0x49, 0xbb, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, - /* movabs $<chain>,%r10 */ + /* movabsq $<chain>,%r10 */ 0x49, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* rex.WB jmpq *%r11 */ 0x41, 0xff, 0xe3 }; +#else +static const uint8_t trampoline_insns[] = { + /* movl $<func>,%r11d */ + 0x41, 0xbb, + 0x00, 0x00, 0x00, 0x00, + + /* movl $<chain>,%r10d */ + 0x41, 0xba, + 0x00, 0x00, 0x00, 0x00, + + /* rex.WB jmpq *%r11 */ + 0x41, 0xff, 0xe3 +}; +#endif union ix86_trampoline { uint8_t insns[sizeof(trampoline_insns)]; Jakub