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[libc] fix sysconf test for rv32 #162685

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Merged
merged 3 commits into from
Oct 9, 2025
Merged

[libc] fix sysconf test for rv32 #162685

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06b1f11
[libc] fix sysconf test for rv32
SchrodingerZhu Oct 9, 2025
88d0f00
[libc] address CRs
SchrodingerZhu Oct 9, 2025
6f99a06
[libc] address CRs
SchrodingerZhu Oct 9, 2025
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3 changes: 2 additions & 1 deletion libc/src/__support/OSUtil/linux/auxv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@

#include <linux/auxvec.h> // For AT_ macros
#include <linux/mman.h> // For mmap flags
#include <linux/param.h> // For EXEC_PAGESIZE
#include <linux/prctl.h> // For prctl
#include <sys/syscall.h> // For syscall numbers

Expand Down Expand Up @@ -90,7 +91,7 @@ LIBC_INLINE void Vector::fallback_initialize_unsync() {
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
// We do not proceed if mmap fails.
if (mmap_ret <= 0)
if (mmap_ret <= 0 && mmap_ret > -EXEC_PAGESIZE)
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I think we should restrict this extra condition to RV32 only, and add comments to explain the reason.

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@SchrodingerZhu SchrodingerZhu Oct 9, 2025 •
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llvm-project/libc/src/sys/mman/linux/mmap.cpp

Line 59 in ec15cdf

if (ret < 0 && ret > -EXEC_PAGESIZE) {

So the original mmap.cpp always have this check logic.

However, I read the comment again and the argument looks suspicious. EXEC_PAGESIZE is not always the page size in general.

Inside linux kernel, the logic is defined in https://elixir.bootlin.com/linux/v6.17.1/source/tools/include/linux/err.h#L33.

I think the checking logic should be provided as a common function and used in both cases.

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Having a common check function and link to the linux kernel would be great.

return;

// Initialize the auxv array with AT_NULL entries.
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