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https://github.com/cirosantilli/linux-kernel-module-cheat.git
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a90271c6af
Split userland/arch/<arch>/c/ into inline_asm and intrinsics, and move programs that don't match either up.
39 lines
1.1 KiB
C
39 lines
1.1 KiB
C
/* https://github.com/cirosantilli/linux-kernel-module-cheat#gcc-inline-assembly-register-variables */
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#include <assert.h>
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#include <inttypes.h>
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int main(void) {
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register uint32_t r0 __asm__ ("r0");
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register uint32_t r1 __asm__ ("r1");
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uint32_t new_r0;
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uint32_t new_r1;
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{
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/* We must set the registers immediately before calling,
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* without making any function calls in between.
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*/
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r0 = 1;
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r1 = 2;
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__asm__ (
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/* We intentionally use an explicit r0 and r1 here,
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* just to illustrate that we are certain that the
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* r0 variable will go in r0. Real code would never do this.
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*/
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"add %[r0], r0, #1;"
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"add %[r1], r1, #1;"
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/* We have to specify r0 in the constraints.*/
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: [r0] "+r" (r0),
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[r1] "+r" (r1)
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:
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:
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);
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/* When we are done, we must immediatly assign
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* the register variables to regular variables.
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*/
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new_r0 = r0;
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new_r1 = r1;
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}
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assert(new_r0 == 2);
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assert(new_r1 == 3);
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}
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